Category Archives: Underwater Photography

The Impact of APSC DSLR Phase-Out on Underwater photography

This post will be a bit surprising for those that think I am an MFT partisan and despise any other format, as you probably imagine that is far from truth. This post will look at the strength of the APSC DSLR segment.

If you follow the rumours and announcements of Canon and Nikon you are probably aware that Nikon is not planning any new professional APSC DSLR and Canon just released the last model with the 90D and will not be releasing a new 5D camera having just released the 1DX Mark III.

This is going to be a significant blow to underwater photographers around the world as today most of competition winners shoot an APSC DSLR camera, in particular the Nikon D500 is probably the most popular camera of serious underwater shooters.

What makes APSC DSLR Unique for Underwater Photography?

In an image we can understand what has made this format such a great option

The Tokina Fisheye zoom 10-17 f3.5-4.5 DX lens

The Tokina zoom fisheye is simply the best native option for wide angle underwater photography. It is cost effective and despite the apparent low quality on land it takes some amazing underwater pictures.

What makes this lens even more interesting is that it produces decent results with a small 4.33″ dome.

Nauticam 4.33 Acrylic dome for Tokina 10-17

There are several option acrylic and glass and if you want even better quality you can go for larger dimensions.

Today you can get the Tokina 10-17mm with his port for £1000 which is less than the cost of a Nauticam WWL-1 and much less than any WACP or Nikkor Nikonos vintage lenses.

Nauticam D500

Another extremely popular choice but this time for macro is the Sigma 105mm F2.8 EX DG OS HSM Macro Lens or otherwise the OEM Canon 100mm and Nikon 105mm macro lenses. Those have been taking some amazing super macro shots in the last 10 years plus thanks to 150+mm equivalent focal length.

APSC Mirrorless Cameras

Both Nikon and Canon have launched new mirrorless APSC and with that a new lens format. Sadly the Tokina 10-17mm autofocus will no longer work. This is a major blow and we need to understand if Tokina will delivery a Z mount version of their mythical lens.

Mirrorless cropped format has been the domain of Sony and Micro Four Thirds due Olympus and Panasonic for the last 5 years and it looks like there are no benefits at sensor level between 1.5, 1.6 and 2.0 crop that are meaningful.

Sony APSC and Micro Four Third beat or match latest APSC mirrorless offering from Canon and Nikon

The other issue is that Canon and Nikon mirrorless are also behind in terms of autofocus compared to MFT, while they already are matching or beating Sony.

As a new user would you buy an APSC camera from Nikon or Canon or prefer Sony? Would you just get a micro four thirds that at least has commitment from two brands and a complete set of lenses and ports for underwater use? Nikon themselves have branded their Z50 camera as a non professional unit and make self limiting design choices that are evidence that their commitment is for full frame, this is the only segment where they are making profits currently.

Future of Full Frame DSLR

Canon is definitely abandoning the DSLR ship and has some good mirrorless penetration with their 5DSR and have just announced the EOS R5 that will be the first unit with IBIS and have 8K video.

Nikon is still hanging to their upper range D series for full frame DSLR but it has been also moving strongly into full frame mirroless.

Both Canon and Nikon are no longer developing their DSLR lenses mounts.

Considering the domination of Nikon in the full frame underwater photography segment the full decline of DSLR will not happen for at least another 2 or 3 years but the time will come.


The extinction of APSC DSLR is not good news for underwater photography as currently no other format can match the choice of ports and lenses available to those shooters. There is a risk that a camera like a Nikon D500 becomes a precious 2nd hand commodity however shutters do wear out so this is not a sustainable path.

A few years ago we witnessed the death of compact cameras to phones and this was a first blow to entry level underwater photographers.

The upcoming death of APSC DSLR is going to hit deeper in the semipro user group however alternatives are available thought not matching the same flexibility of lenses and ports.

Our passion is getting increasingly more expensive as the digital camera market focusses on full frame and also more bulky and difficult to carry around.

Autofocus Systems for Underwater Photography

You will notice that the featured image is actually a bird in flight. When we think about fast autofocus birds in flights is what is really going to test performance.

This image was taken by my wife with a Nikon D7100 and a Sigma 70-200mm lens in the Galapagos Islands.

I also shoot birds with my Panasonic G9 and have a direct experience of focus systems for moving subjects and I can comfortably say that today AI has become more important than anything else for those kind of shots. Artificial intelligence predicts movement and ensures that once the camera has reached focus the first time it reacts automatically to movement without the need to refocus.

Let’s start from the basics first.

Types of Autofocus

There are two types of systems for auto focus in digital cameras:

  • Phase Detection
  • Contrast Detection

Both systems need contrast to focus despite the naming convention, so phase detection works on contrast too.

In situation of low light low contrast EVERY camera switches to contrast detection without exceptions.

Contrast Detection AF

This is the simplest and cheapest way to obtain focus and is what is typically implemented in compact cameras. Contrast detection moves the focus back and forth to find the maximum contrast and then locks on subject. This is sometimes perceived as hunting by the user when the camera fails to find focus.

Contrast detection is the most accurate method of autofocus as it looks for perfection without prioritising time. With exception of Panasonic no other major brands use contrast detection AF on high end or semipro models.

Phase Detection AF

With this technique the image goes through a prism and it is split then when the two parts match the subject is in focus and the focus locked.

Phase detection is less accurate than contrast detection in particular there are instances in which focus is achieved in front or behind the subject. This is the system implemented by Nikon, Canon, Olympus and Canon.

Hybrid AF

This system combines both methods, it starts with phase detect to determine the focus start and then uses contrast detect to make sure the focus is accurate. Sony is the main driver of this technology.

Low Light Focus

All autofocus methods need light to function without exception, when the scene is really dark cameras have some methods to achieve focus, this includes:

  • Using the lens widest aperture to focus
  • Bump the ISO and then adjust later
  • Auto focus illuminator and modelling lights

Generally low light is less than 1.25 Lux or candela per square meter representing a really dark scene.

Pro and Cons of Each System

If we look at the three systems each one has positive and negatives and depending on the subject this are more or less important.

Phase DetectFasterLess accurate
Contrast detectSlowerMore accurate
HybridSlowestMore Accurate
AF comparison Table

Performance Requirement for Underwater Photography

Many underwater photographer think that they need a system that focus fast, can track moving objects and work well in the dark, this system of course does not exist.

In particular considering the availability of focus lights the performance in low light is definitely not a show stopper. More important are speed and accuracy. For the purpose of a comparison I have included here some models from Sony, Panasonic, Olympus, Nikon and Canon with a variety of formats representing some popular choices among underwater photographers.

I have included 3 performance metrics for comparison:

  • AF time
  • Low Light Low Contrast Ev
  • Low Light High Contrast Ev

The first measure tells you how quick the camera focuses in normal conditions, this is in my opinion the most important parameter as generally underwater photography is not below 1 Ev.

The second measure is the number of Ev of low light the camera can still focus with a low contrast subject, and finally the third is still a low light scenario with a high contrast subject. Let’s look at the results that are build using test data from imaging resource.

AF comparison table

I have used conditional formatting so green is good amber is average and red is bad for each category.

AF Time

First observation is that hybrid AF is very slow, second contrast AF as implemented by Panasonic is faster than most of DSLR peers in this table. If we consider 0.2 seconds as acceptable the full frame mirrorless Sony A7RIII has unacceptable performance. While the Nikon D850 AF is in another league both MFT Olympus and Panasonic are faster than other APSC and even the canon full frame.

Low Light Low Contrast AF

Mirrorless cameras dominate this category, the Panasonic GH5 can reach focus at -4.5 Ev that is practically dark on a low contrast subject, second is the Sony A7 RIII and third the Olympus OMD-EM1MKII.

In a low light scenario phase detection fails sooner so some of those cameras switch to contrast detection to achieve focus.

Low Light High Contrast AF

All cameras are able to work at least at -3 Ev so this is not a distinctive category, it is worth nothing that some phase detect system that failed in the low contrast target scenario perform well in this category but generally performance is pretty decent.

Why are your shot blurred?

Some people that have the camera in the table still struggle to get shots, why is that? I have found that for most users do not read instruction manuals and to make it worse modern camera have far too many AF settings. My GH5 for example has 6 options of AF area, 4 options for AF Mode, 3 parameters for tuning the AI (artificial intelligence) engine, plus additional custom modes to select the 225 focus points in any random shape you like. The average person will skip all of this and select one option and then fail the shots.


Surprisingly for some if we look overall at the camera that has green in all categories we find two mirrorless micro four thirds. Even more surprisingly both those cameras are faster to focus than APSC DSLR from Canon and Nikon although it is not really a great distance.

Typically when it comes to comparison between camera there is someone that says but camera X gets the shots blurred so speed does not matter. I talk by direct experience with outdoor and birds not just fish and I can tell you that each system will miss shots in burst mode but more importantly underwater photography is nowhere near requirements for birds in flight.

I have performed tests with a light meter at less than 1 candela per square meter with my GH5 with a 60mm macro lens and with my surprise it focuses just fine without the AF illuminator. I have to admit I do not really trust auto-focus so in most situation I use back button and peaking however based on my recent findings I need to trust autofocus a bit more it seems!

Choosing a Camera Format for Macro Underwater Photography

Following from my previous post I wanted to further investigate the implications of formats and megapixels on Macro Underwater Photography.

I also want to stress that my posts are not guides on which camera to choose. For Macro for example some people rely on autofocus so there is no point talking about sensors if your camera does not focus on the shot!

Macro underwater photography and fish portraits in general is easier than wide angle because is totally managed with artificial illumination, although some real masterpieces take advantage also of ambient light.

There are a number of misconceptions also here but probably on the opposite side of wide angle there is a school of thinking that smaller cameras are better for macro but is that really the case?

Myth 1: Wide angle lens -> More Depth of field than Macro

Depth of field depends on a number of factors you can find the full description on sites like Cambridge in Colour a good read is here.

A common misconception without even starting with sensor size is that depth of field is related to focal length and therefore a macro lens that is long has less depth of field than a wide angle lens.

If we look at a DOF formula we can see that the effect of focal length and aperture cancel themselvers

Depth of field approximation

A long lens will have a smaller field of view of a wide lens so the distance u will increase and cancel the effect of the focal length f.

The other variables in this formula are the circle of confusion c and the F-number N. As we are looking at the same sensor the c number is invariant and therefore at equal magnification the depth of field depends only on F number.

Example: we have a macro lens 60mm and a wide angle lens 12mm, and a subject at 1 meter with the 60mm lens. In order to have the same size subject (magnification) we need to shoot at 20cm with the 12mm lens at that point the depth of field will be the same at the same f-number.

So a wide angle lens does not give more depth of field but it gets you closer to a subject. At some point this gets too close and that is why macro lenses are long focal so you can have good magnification and decent working distance.

Myth 2: Smaller Sensor has more depth of field

We have already seen that sensor size is not in the depth of field formula so clearly sensor size is not related to depth of field so why is there such misconception?

Primarily because people do not understand depth of field equivalence and they compare the same f-number on two different formats.

Due to crop factor f/8 on a 2x crop sensor is equivalent to f/16 on a full frame and therefore as long as the larger sensor camera has smaller possible aperture there is no benefit on a smaller sensor for macro until there are available apertures.

So typically the smaller sensor is an advantage only at f/22 on a 2x MFT body or f/32 on a APSC compared to a DSLR. At this small aperture diffraction becomes significant so in real life even in the extreme cases there is no benefit.

Myth 3: Larger Sensor Means I can crop more

The high level of magnification of macro photography create a strain on resolution due to the effects of diffraction this has a real impact on macro photography.

We have two cases first case is camera with same megapixel count and different pixel size.

In our example we can compare a 20.3 MFT 2x crop camera with a 20.8 APSC 1.5x crop and a 20.8 full frame Nikon D5.

Those cameras will have different diffraction limits as they have pixels of 3.33, 4.2 and 6.4 microns respectively those sensor will reach diffraction at f/6.3, f/7.1 and f/11 respectively so in practical terms the smaller camera format have no benefit on larger sensor as even if there is higher depth of field at same f-number the equivalent depth of field and diffraction soon destroy the resolution cancelling the apparent benefit and confirming that sensor size does not matter.

Finally we examine the case of same pixel size and different sensor size.

This is the case for example of Nikon D500 vs D850 the two cameras have the same pixel size and therefore similar circle of confusion. This means that they will be diffraction limited at the same f-number despite the larger sensor. So the 45.7 megapixels of the D850 will not look any different from the 20.7 megapixels of the D500 and none will actually resolve 20.8 megapixels.

So what is the actual real resolution we can resolve?

Using this calculator you can enter parameters in megapixels for the various sensor size.

In macro photography depth of field is essential otherwise the shot is not in focus, for this exercise I have assumed comparable aperture and calculated the number of megapixels until diffraction destroys resolution

MFT 2xf/117.1*
APSC 1.5xf/145.6
Full Framef/226.3
Resolution in Megapixels at constrained DOF

Note that the apparent benefit of MFT does not actually exist as the aspect ratio is 4:3 so once this is normalised to 3:2 we are back to the same 6.3 megapixels of full frame. APSC that has the strong reputation for macro comes last in this comparison.

So although you can crop more with more megapixels the resolution that you can achieve is dropping because of diffraction and therefore your macro image will always look worse when you crop even on screen as now most screens are 4K or 8 megapixels.

Other Considerations

For a macro image depth of field is of course essential to have a sharp shot however we have seen that sensor size is not actually a consideration and therefore everything is level.

Color depth is important in portrait work and provided we have the correct illumination full frame cameras are able to resolve more colours. We are probably not likely to see them anyway if we are diffraction limited but for mid size portraits there will be a difference between a full frame and any cropped format. In this graph you can see that there is nothing in between APSC and MFT but full frame has a benefit of 2.5 Ev and this will show.

The D850 has a clear benefit in color resolution compared to top range APSC and MFT


Surprisingly for most the format that has an edge for macro is actually full frame because it can resolve more colours. The common belief that smaller formats are better is not actually true however some of those rigs will definitely be more portable and able to access awkward and narrow spaces to what extent this is an advantage we will have to wait and see. It may be worth noting that macro competitions are typically dominated by APSC shooters whose crop factor is actually the worst looking at diffraction figures.

Choosing a Camera Format for Underwater Photography

The objective of this post is not to determine what is the best camera for underwater photography, as that is simply the best camera with the best housing and the best strobes and lenses. All needs to be seen as a system in order to take stunning images.

The purpose of this article is to provide some clarity and eliminate common misconceptions that seem to be hindering the decision making of a person wanting to take underwater photos. There is always a vested interested of camera manufacturers to drive sales as well as underwater photography equipment shops to push users to upgrade their gear as frequently as possible as that generates value to them, however this will not necessarily generate value to you the consumer, the only person injecting cash in this network.

I recently posted on WetPixel a discussion that to generate a debate about the gap between APSC and MFT cameras. This in turn made me do some more research on camera sensor and I found some information that is very insightful and confirms some of my suspicions I had years ago when I attended a workshop in the Red Sea with Alex Mustard. In that occasion I was the only user on the boat with a compact camera but managed to pull some decent shots and this made me realise that there are circumstances that equalise your equipment and make the gap in the image quality smaller to the point that a compact camera picture in some cases looks similar to a much larger sensor camera. Although I shoot micro four thirds underwater I have owned and shot DSLR full frame and cropped, film and digital, I have also had an array of compact cameras, so what you are going to read is not focused on one format being better than another.

Let’s discuss some of those misconceptions in more detail.

For those that do not understand optics of dome ports underwater the reason you need to stop down the aperture is NOT because you are looking for depth of field, in fact on land you would shoot a wide angle lens wide open and it would have plenty of depth of field. The reason to stop down the lens is the field of curvature of the dome which makes the areas off centre and on the edges soft this can only be fixed by stopping down the lens. So before you think I can shoot at f/4 on a APSC so what think that your pictures will be mostly blurry on the side and besides each format has got fast lenses so this is not a main consideration for what you are going to read.

Myth 1: Larger Sensor -> Better SNR

Signal to Noise ratio is an important factor in electronics as it allows to distinguish information from noise. Contrary to what most people think SNR is not related to sensor size.

There is an in depth demonstration on this website

The comprehension of some of the concept may be too hard for many so I will attempt a simplification. What R.J.Clark says is that you need to balance the amount of light hitting the sensor before drawing conclusion on SNR. For example assume a camera with a lens of 16mm on a full frame sensor and compare this with a camera with a lens of 8mm on micro four thirds, I am using MFT as crop factor is two and makes examples easier.

An exposure of f/8 on a 16mm lens on Full frame camera is equivalent to an exposure of f/4 on a 8mm lens on MFT. Those will send the same amount of light to the sensor at equivalent exposure. However the smaller sensor will have the same amount of light distributed on a surface that is 1/4 of the larger sensor and therefore if we equalise everything we have a situation whereby the exposure value are balanced and the SNR is pretty much identical because the gain or ISO value necessary was 1/4 of the larger sensor. This SNR 18% graph on DxOMark gives an idea. I have chosen 3 cameras with the same megapixel count to remove megapixels from the discussion.

The dotted line highlights that once ISO values are equalised sensor size has no impact on SNR

Once exposure is equalised the larger sensor has no longer a benefit this is due to the fact that the components of noise shot noise and read noise do not depend on sensor size.

However an important consideration is that ISO 100 does not actually mean the same gain in all systems and in fact a larger camera will have more photons than a smaller one at the same ISO level, this means that at the so called base ISO the larger sensor camera will have an advantage as the smaller sensor can’t decrease the ISO anymore and will need to close aperture. It also means that ISO 100 does not mean the same SNR amongst different formats. So when we compare two shots at the same ISO larger sensors will have more signal than smaller ones. This is the reason sometimes you hear things like why is my shot on my compact camera so noisy at ISO 400 compared to a full frame that looks so clean at ISO 400 but those ISO are not actually the same thing and the smaller sensor has much less photons at that identical ISO number.

Another consequence of this is that as the camera in questions have the same megapixel size larger pixels do not yield better SNR.

However with larger pixels holding more signal it is possible to extend the range of an amplifier to higher value of gain therefore larger pixel camera (less megapixel on the same size) will be able to work at higher ISO levels. This is the reason why MFT camera have a lower maximum ISO than full frame at same megapixel count.

Underwater we use strobes to counter colour absorption and never reach those high ISO levels. If you were shooting at night on land without a flash you may easily reach high ISO value like ISO 25800 or 64000 with strobes however we rarely reach even values like 1600.

Myth 2: Larger Sensor -> Better Dynamic Range

The characteristic that drives dynamic range is not actually sensor size but pixel size however at some point DR no longer grows with very large pixels.

This graph shows that the Panasonic GH5 has a respectable DR at low ISO however it drops faster than the D500 and 1DX MkII. Surprisingly for some the D500 has more DR than the larger pixel 1Dx MKII.

Dotted line for DOF equalisation purposes

If we look at the maximum possible DR and the ISO at which we would still have 7 bits colour and at least 10 stops of DR we have the following values:

CameraMax DRHighest Usable ISO
Canon 1DX MKII13.5 Ev3207
Nikon D50014 Ev1324
Panasonic GH513 Ev807
The larger pixel size makes usable DR go to higher ISO

Although the larger pixel camera does not hold the highest DR it is able to shoot at higher ISO and still keep a decent DR and color tone.

If we calculate the Ev between the ISO value we see that the MFT sensor is 2 Ev away and the APSC is 1.3 Ev away from full frame, this is pretty much in line with the crop factor and therefore once we equalise Depth of field there is no benefit between the various formats at same megapixel count, though the Nikon D500 is the camera that has the highest DR in absolute value. So if you have an extremely high amount of light the D500 would be able to product a high DR image. Underwater however this is rarely the case underwater so the conclusion is that if you are after a 20 Megapixel camera there is no material difference among the various formats in practical underwater use.

Myth 3: Larger Pixels are Better at equal sensor size

Although larger pixels are better at sustained dynamic range, for example in low light, evidence shows that as long as the camera is not limited by diffraction more megapixels are better.

I am comparing here 3 Nikon full frame cameras that have respectively 24, 36 and 47.8 Megapixels.

SNR is not impacted by pixel size

SNR is not impacted by the sensor resolution and this is due mostly to the fact that at similar size downsampling equalises the smaller pixels.

Dynamic range is also unaffected with more megapixels having better results

Looking at Dynamic range the situation is the same and actually the camera with more megapixels has an edge until ISO value become very high.

Color Sensitivity appears to benefit from Pixel Count

Finally the graph for color sensitivity, an important metric for shots with strobes and portrait work, confirms that more megapixels also bear better results.

Please note that this data is limited to sensor analysis and does not take into account the effect of very small pixels on diffraction and sharpness that is a topic on its own.

Choosing a Camera for Social Media

Today majority of people do not print their images and post them on social media or website. Those typically have a low resolution frequently less than 4 megapixels. Screens usually have low dynamic range, and JPEG images are generally limited to 12 Ev Dynamic Range this is a value that is at reach of any camera today starting from 1″ compact cameras but is unreachable to majority of computer screens or phones.

My suggestion for users that post on social media is to find the best camera that fits their budget and ergonomics and worry less about sensors, invest in optics either wet or lenses and port and strobes, as those will yield a higher return.

Today most cameras have a port system anyway so an advanced compact such as the Sony RX100 series or a Micro Four Third camera of small factor (Panasonic GX9 for example) are more than enough.

Choosing a Camera for Medium Size Print

I print my images typically on 16″x12″ or 18″x12″ paper or canvas.

Generally I want to have around 300 dpi so that means I need a 20 Megapixel camera as a minimum. This cuts out a large part of the smaller MFT cameras and also the compacts because the real life resolution is far from the declared pixels.

In my opinion, if you are a user that prints medium formats, a pro grade MFT or an APSC camera is all you need, besides the latest winner of UPY shoots an APSC with a Tokina lens and plenty of winners don’t use full frame.

For those who just want the Best

The best image quality today is produced by high megapixel full frame cameras there is no doubt about it. Full frame cameras however are subject to depth of field issues and as we have seen once you shoot at equal depth of field the benefit is for most eroded.

To get the best outcome of a high megapixel full frame camera you need to be able to shoot at the lowest possible ISO, this is almost impossible if you are shooting a fisheye lens behind a dome as your aperture of f/11 means very little light is hitting the sensor so your ISO will most likely hit 400 many times and at that point the benefit of full frame is gone.

I have looked at all technical details of Alex Mustard images on his book and nearly all shots taken with a full frame camera have at least ISO 400 or higher, with very few exceptions at 200 or lower.

So how to do you manage to shoot at the lowest possible ISO on full frame? You need to be able to shoot at wider aperture and this today means optics like the Nauticam WACP that have two stops benefit on a wide angle lens and three on a rectilinear lens behind a dome on full frame.

WACP retails at $4,500 plus sales tax

The WACP however has a field of view of 130 degrees and therefore is not as wide as a fisheye and unsuitable for close focus wide angle, recently Nauticam has released the WACP-2 that retails at $7,460 and can cover 140 degrees.

My consideration is that, if you are not prepared to spend money for a WACP like solution, then there is no point investing in a full frame system as the benefit goes away once you equalise depth of field.

The Nikon D850 once DOF is equalised performs worse than the old 7200 APSC


Underwater photography is an expensive hobby and every time I am on a boat and see how much money goes into equipment to product average photos this saddens me. While improving technique is only a matter of practice and learning, making the right choice is something we can all do once we have the correct data and information at hand.

I hope this post is useful and helps your decision making going forward.

Announcing New 2020 Offering

Dear readers in 2020 I will be adding some services to the blog to reflect some requirements that have been developing in the last few years.

It happens at times that people get in touch either through comments or directly by email to ask about their current challenges so I thought why not to address this with a bespoke service. Here are my current ideas:

  • Equipment selection – this is generally to do with port lenses, strobes, lights, accessories more than with camera and housing
  • Photo editing clinic – people seem to struggle to handle the editing of their images. While some are definitely skilled majority aren’t and editing an image is almost as important as shooting a good image
  • Video editing clinic – like above but for video that is sometimes even more complex

Those will be offered at the symbolic price of a few beers at UK prices £10 donation using the link on the left hand side.

Other topics that are also becoming interesting are discussions around issues like focus, framing, lens quality. For those I welcome input material by email send me your images or videos with problems and I will use them to build an article for yours and other benefits.

Currently am working on a feature on focus in video so I am looking for your blurred videos (sorry) as I don’t have many myself I need some help from you guys.

Thank you for reading this short post!

Canon 8 – 15 mm Fisheye on the Panasonic GH5 Pool Tests

It was time to get wet and test the Canon 8 – 15 mm fisheye on the GH5 in the pool so I made my way to Luton Aspire with the help of Rec2Tec Bletchley.

I had the change to try a few things first of all to understand the store coverage of the fisheye frame, this is something I had not tested before but I had built a little model.

In purple the ideal rectangle built with the maximum width and height of the fisheye frame

This model ignores the corners the red circle are 90 degrees light beams and the amber is the 120 degrees angle. A strobe does not have a sharp fall off when you use diffusers so this model assumes your strobe can keep within 1 Ev loss around 90 degrees and then drop down to – 4 Ev at 120 degrees. I do not want to dig too deep into this topic anyway this is what I expected and this is the frame.

Shot at 1.5 meters from pool wall

You can see a tiny reflection of the strobes together with a mask falling on the left hand side… In order to test my theory I run this through false colour on my field monitor, at first glance it looks well lit and this is the false colour.

False colour diagram of previous shot

As you can see the strobes drop below 50 at the green colour band and therefore the nominal width of those strobes is probably 100 degrees. In the deep corners you see the drop to 20 % 10% and then 0 %.

Time to take some shots

Divers hovering @ 8 mm

The lens is absolutely pin sharp across the frame, I was shooting at f/5.6 in the 140 mm glass dome.

Happy divers @ 9 mm
BCD removal @ 10 mm
Gliding @ 11 mm
Open Water class @ 12mm
Divers couple @ 13 mm
Hover @ 15 mm

Performance remains stunning across the zoom range. I also tried few shots at f/4

9 mm f/4

There is no reef background but looks pretty good to me.

The pool gives a strong blue cast so the shots are white balanced.

If you want details of the rig and lens mount are in a previous post

Panasonic GH5 zoom fisheye rig

Fisheye Zoom for Micro Four Thirds

Looking at Nauticam port chart the only option for a fisheye zoom is to combine the Panasonic PZ 14-42 with a fisheye add on lens. This is a solution that is not that popular due to low optical quality.

So micro four thirds users have been left with a prime fisheye lens from Panasonic or Olympus…until now!

Looking at Nauticam port chart we can see that there is an option to use the Speedbooster Metabones adapter and with this you convert your MFT camera to a 1.42x crop allowing you to use Canon EF-M lenses for cropped sensor including the Tokina 10-17mm fisheye. This is certainly an option and can be combined with a Kenko 1.4x teleconverter giving you a range of 14.2 to 33.8 mm in full frame equivalent or 7.1 to 16.9 mm in MFT terms fisheye zoom of which the usable range is 8 -16.9 mm after removing vignetting.

A further issue is that the Speedbooster gives you another stop of light limiting the aperture to f/16 while this is generally a bonus for land shooting in low light underwater we want to use all apertures all the way to f/22 for sunbursts even if this means diffraction problems.

Wolfgang Shreibmayer started a trend time ago in WetPixel to use full frame lenses and in this post I want to do a deep dive on what is for me the most interesting lens option the Canon 8-15mm fisheye.

This lens on full frame can be used for a circular and diagonal fisheye but Wolfgang has devised a method to use it as an 8-15mm fisheye zoom on MFT.

Part list – missing the zoom gear

What you need are the following:

  • Canon EF 8-15mm f/4L fisheye USM
  • Metabones Smart Adapter MB_EF_m43_BT2 or Viltrox EF-M1 Adapter
  • A 3D printed gear extension ring
  • Nauticam C-815Z zoom gear
  • Nauticam 36064 N85 to N120 34.7mm port adapter with knob
  • Nauticam 21135 35mm extension ring with lock
  • Nauticam 18810 N120 140mm optical glass fisheye port

The assembly is quite complicated as the lens won’t fit through the N85 port. It starts with inserting the camera with no lens in the housing.

GH5 body only assembly
Camera in housing without port

The next step is to fit the port adapter

Attach N85 N120 Metabones adapter

Then we need to prepare the lens with the smart adapter once removed the tripod mount part.

Canon 8-15 on Metabones Smart Adapter IV

As the port is designed for the speed booster the lens will be few mm off therefore the gear will not grip. Wolfgang has devised a simple adapter to make it work.

gear extension ring
Zoom gear on lens

This shifts the gear backwards allowing to grip on the knob.

3D design is here

Lens inserted on housing

Looking at nauticam port chart an extension ring of 30mm is recommended for the speedbooster and now we have extra 5mm in length Wolfgang uses a 35mm extension. however looking at the lens entrance pupil I have concluded that 30mm will be actually better positioned. Nauticam have confirmed there won’t be performance differences. You need to secure the ring on the dome before final assembly.

Fisheye dome and extension
Full assembly top view
Side front view

The rig looks bigger than the 4.33 dome but the size of the GH5 housing is quite proportionate. It will look bigger on a traditional small size non clam style housing.

The disassembly will be made again in 3 steps.


I am not particularly interested in the 1.4x teleconverter version consider that once zoomed in to 15mm the lens is horizontally narrower than a 12mm native lens so there is no requirement for the teleconverter at all.

This table gives you an idea of the working range compared to a rectilinear lens along the horizontal axis as diagonal is not a fair comparison. The lens is very effective at 8-10mm where any rectilinear would do bad then overlaps with an 8-18mm lens. The choice of lens would be dictated by the need to have or not straight lines. The range from 13mm is particularly useful for sharks and fish that do not come that close.

Focal lengthHorizontalVerticalDiagonalHorizontal Linear EqWidthHeightDiagonal

Wolfgang has provided me with some shots that illustrate how versatile is this set up.

8mm end surface shot
Caves 8mm
15mm end close up
Dolphins at 15mm
Diver close up at 8mm
Snell windows 8mm
Robust ghost pipefish @15mm

As you can see you can even shoot a robust ghost pipefish!

The contrast of the glass dome is great and the optical quality is excellent. On my GH5 body there is uncorrected chromatic aberration that you can remove in one click. Furthermore lens profiles are available to de-fish images and make them rectilinear should you want to do so.

I would like to thank Wolfgang for being available for questions for providing the 3D print and the images that are featured here on this post.

If you can’t print 3D and need an adapter ring I can sell you one for £7 plus shipping contact me for arrangements.

Amazon links UK

Canon EF 8-15 mm f/4 fisheye USM lens

Viltrox EF-M1 Mount Adapter

Note: it is possible to use a Metabones Speed Booster Ultra in combination with a Tokina 10-17mm zoom fisheye and a smaller 4.33″ acrylic dome.

UK Cost of the canon option: £3,076

Uk Cost of the Tokina option: £2,111

However if you add the glass dome back

UK Cost of Tokina with glass dome: £2,615

The gap is £461 and if you go for a Vitrox adapter (would not recommend for the speedbooster) the difference on a comparable basis is £176 which for me does not make sense as the Canon optics are far superior.

So I would say either Tokina in acrylic for the cost conscious or Canon in glass for those looking for the ultimate optical quality.

Using Rectilinear Wide Lenses Underwater

I was checking the technical details of Alex Mustard Underwater Photography Master Class and the majority of wide angle pictures are taken with a fisheye lens. In the section about shooting sharks Alex says that he prefers to shoot sharks with a fisheye otherwise they look ‘skinny’.

If you look online on underwater video forums you frequently see comments on problems with wide angle lenses connected with the use of a rectilinear wide angle lens in a dome.

The two most common complaints are soft corners and distortion.

Soft corners are due to a combination of lens optical issues and dome port optics. In short any lens is to some extent curved and therefore if you shoot a flat surface the image may be sharp in the centre and softer as you move to the corners. Issues with field of curvature are corrected stopping down the lens. The issue with field of curvature happens everywhere not just underwater.

Right now there are four wide angle lens that can be housed for a micro four third camera:

Olympus 9-18mm

This lens has a nice working range that allows to capture 100 degrees diagonal at widest setting and still has a 35mm equivalent at the tele end. This is a pretty little lens at $699 is the most affordable option that can be put in a housing. You will need a wide angle port and the zoom gear. The whole combination for your Nauticam housing comes at $1,399. This lens can also be combined with a glass dome but this will make the whole combination much more expensive and you may want to think about getting a better lens instead.

Olympus 7-14mm

This is an outstanding lens especially on land due to the fast f/2.8 aperture. It is expensive at $1,299.99 and very heavy and bulky. The lens does not fit through the N85 port opening and requires a port adapter this gives the extra benefit of a focus know but with such a wide lens is not really useful due to high depth of field. You will need a 180mm glass dome and the zoom gear for the lens to complete the set up ending at a whopping $3159.99.

Panasonic 7-14mm

I have owned this lens and I have to say that at $799 is the right compromise between wide field of view and price. Furthermore once you get the zoom gear you have the option of a cost effective acrylic dome that will give you a very wide set up for $1589.99. There are reports of poor performance with this lens and it is true that is not as sharp in corners but the results are perfectly acceptable if you stop at f/8 in close shots.

Steering Wheel Truck
Panasonic 7-14mm with acrylic dome 9mm f/8
Exploring the Chrisoula
Panasonic 7-14mm with acrylic dome 7mm f/5

This lens is prone to reflections and flare however once you add the N120 port adapter and the 180mm glass dome this will get you to $2819 at that point you may want to consider the Olympus combination instead.

Panasonic Leica 8-18mm

This is my favourite lens is sharp does not suffer from field of curvature issues and has a very useful zoom range 16-35mm in 35mm equivalent. The zoom gear and the 7″ acrylic dome will take you to 1889.99 that is an excellent price point. The lens is not prone to reflection or flare and as the 7″ dome has the same curvature radius than the 180mm dome it will produce very similar results.

Panasonic 8-18mm in 7 acrylic dome f/8
Sunset Neat
Panasonic 8-18mm at 8mm f/10

The significant size of the acrylic port and the fact it floats make it ideal for split shots and this is the lens that gives me the best results.

This lens can also take port adapter that allows you to use the 180mm glass dome. This adds up to $2919.99 if you experience bad reflections and shoot frequently in the sun it may be worth it but I have not had any issue so far with this lens probably because of its nano coating.

I have found the 7mm focal length too problematic for dome ports and the amount of perspective distortion excessive generally it would be preferred to shoot at 9mm and narrower however this maybe insufficient for wreck interiors if you want a rectilinear look.

Perspective Distortion

One of the regular complaints of video shooters especially in wrecks or caves is that the edges look horrible and distorted and that there is an issue with the corners pulling. This is in fact not an issue but a problem with perspective as you shoot very wide angle. The following test shots will illustrate that the issue happens on land and has nothing to do with dome ports.

Shot at f/2.8 with Panasonic 8-18mm at 8mm shows sharp corners
Image with objects in edges at 8mm

As we can see the football looks like an oval and the chair is pulled. This is due to a perspective issue and is not a lens problem. When you shoot underwater video the objects on the edges of the frame change shape creating this pull effect that most people dislike.

Same scene at 9mm

At 9mm the amount of perspective distortion is reduced and this is the reason why 18mm on 35mm equivalent is one of the favourite focal length for rectilinear video and the maximum angle that should be used in small spaces to avoid the pulling edges.

One of the reason why a lens like the Nauticam WWL-1 is preferred for video is because the corners look sharp but is that really true?

Not really let’s apply some barrel distortion to simulate the WWL-1 to the image that looked badly distorted.

Barrel distortion applied -60 8mm

Now the football looks circular as we have applied -60 barrel distortion, obviously the rest of the image is now bent but this seems not to be of a concern to most people!

Barrel distortion -30 9mm

It needs much less correction to bring the 9mm shot into shape and for sure between the 8mm and 9mm the 9mm is the dimension that produces the most acceptable results.

It has to be said that in video with 16:9 aspect ratio most of the issue will be cropped away at the edges but the distortion in the middle of the frame will remain. For the same reason the 9mm image will appear practically rectilinear with no issues

16:9 crop still showing the edge ‘pulling’ at 8mm

16:9 crop looks straight at 9mm

I hope this post was useful there are four options for micro four thirds shooters to use rectilinear lenses I have settled for the Panasonic 8-18mm as in most cases it is still possible to control the perspective issue, I found this impossible at 7mm.

Bike on Hold 2
Bike in hold 2 on SS Thistlegorm Panasonic 8-18 at 8mm
Bubbling Bike
Shot at 7mm showing the front tyre pulling outside the frame

Obviously if you shoot in the blue this problem will not be visible however rectilinear lenses are popular with wreck shooters and I think this posts gives an idea of the challenges at play.

Finally I would discourage the use of the 7-8mm focal length range for video to those that want to have a rectilinear look.

From this post I started supporting Bluewater Photo in US for my links because it still provides multi brand and choice and because I learnt a lot from Scott Gietler Underwater photography guide back in the days where there was no internet resource to learn from.

interceptor121’s cut – Nauticam n85 Panasonic Olympus and BMPCC port chart

I thought of adding a little stickie post of what I use for my Panasonic GH5 in terms of lenses ports so I made some edits on the official port chart v7.19 please find the google drive link here

There is an addition that I will cover in future posts and relates to using the Canon 8-15 mm Fisheye zoom lens on the GH5 body using a Smartbones Smart Adapter or Vitrox EF-M1.

I have already written about choice of Macro lenses fisheye and wet lenses for video and wide and for macro video.

My latest post is on rectilinear wide angle lenses that is a tricky subject for most.

CREATIVE strobe filters for wide angle

When people think about creating lighting technique for underwater photography a few things come to mind and usually it is about tools. Snoots for example have become very popular and help the underwater photographer to increase separation of the subject from the background. I have seen some people jumping in the water with a black slate to create an artificial black background, clearly is much easier to do that for macro as everything is at end and typically the subjects are not fast moving or the diver is not fast moving.

Then of course there is strobe positioning, classic, inward, crossed, rabbit ears, backlighting etcetera here goes a long list of options.

At the end however some pictures just seem to “pop” more than others, and this usually has to do with the colours and the contrast and with the blue.

It is not a coincidence that the term Mustard Blue is what has made some shots from Alex Mustard re-known and if you read his underwater photography masterclass there is a whole section ‘The sea is blue’ where Dr. Mustard goes on about the importance of exposure and background blue.

His suggestions are to:

  1. Dial in an underexposure (for the water) around -2/3 to -1 1/3 Ev
  2. Using warm strobes

It is worth stressing out that the primary reason why the camera gets fooled by the conditions underwater is because colours gets absorbed and blue lights gets scattered instead creating that milky glare at times when the water has lots of suspended particles.

If shoot an auto mode with exposure compensation at zero your pictures will for most part come out washed out and lacking contrast underwater and this is one the primary reasons photographer like Dr Mustard do not follow the expose to the right rules.

Underexposure for the water is obtained by keeping the aperture and ISO constant as they are aligned to the strobes and changing the shutter speed accordingly. Obviously if you are shooting video your shutter speed is most likely fixed so you need to find alternative ways to get your blue as you want it but generally you would still underexpose probably not as much.

With regards to warm strobes this is a fairly subtle point linked to the camera auto white balance mechanism.

Most flash strobes have colour temperatures between 5500 and 6500 K and therefore are not at all particularly warm.

Inon Z240 Standard and Warm diffuser

Inon has developed warming diffusers for their Z240 range and I believe also for the most recent Z330 range. They are available in 4600K and 4900K temperature. I definitely recommend the 4600K version over the 4900K as it has a stronger effect.

So how does a warm strobe work in order to get a richer blue?

Table of light sources – Olympus education

When we shoot with strobes the camera is set to auto white balance, and will average for most the subject we hit with our strobes to calculate the average colour temperature and tint.

The camera auto white balance operates between 2500K and 7500K typically so a warm strobe is likely to set the colour to 4600K instead of the typical 5500K the ‘extra’ 900K do not really do anything to the subject that will anyway we white balance but give an extra kick to the blue background. Underwater colour temperature is usually higher than 9000K and easily reaches 14000K (purple tone in the water) at depth. So the warm strobes are particularly effective in shallower and clearer water as they push the blue to a darker tint like in this example taken around 12 meters.

f/8 1/125 ISO 125

You can see how deep is the blue other example taken on the Barge at less than 10 meters.

Portrait in deep blue…

So what happens if you don’t have a warm strobe or if there aren’t warm diffusers for the strobe you have, or maybe you don’t want to spend the money for them?

Amazon comes to the rescue

If your strobe is around 5250 with diffusers (like Sea and Sea YS-D2 or Inon S2000/Z240/D200) get a 1/8 CTO

Rosco Cinegel sun 1/8 CTO, 20×24″ Color Correction Lighting Filter

You can find this filter also under Lee on colour 231, with a little amount you can get a half sheet that is enough for a few strobes.

This filter has a negligible -0.3 Ev light loss and will bring your strobe down to around 4600K .

If you have a fairly cool strobe you need a 1/4 CTO

Rosco un 1/4 CTO 20X24 Amber – Rosco RS340911

If you have something different you can try a mired shift calculator here

Be careful not to exceed with this technique or subject will turn too warm.

An alternative and perhaps counterintuitive approach is to use cooling filters.

In this case the strobe light will become colder to emulate the water colour and the camera will need to be set to custom white balance.

In almost all cameras except Olympus that reach 14000K colour temperatures are limited to 10000K however they can be further enhanced to reach 11000K if you have an adjustment panel like the Panasonic or Sony cameras. Pushing the adjustment to the A gives extra 1K. This technique with a bare lens has however a limitation as when the custom white balance caps the colours go completely off.

In order to see what can the colour temperature setting do we can compare a normal grey card shot with one where the colour temp is 11000K and magenta is pushed to the max.

Grey card bare lens
Maxed out Custom White balance on Panasonic GH5

In order to cool down the strobes you need a cyan filter, the custom white balance can correct up to 2 stops Cyan but no more. You can trim a sheet of Rosco 4360 to fit into your diffuser as below. This takes around 1 stop Ev off the strobe.

Sea and Sea diffuser with a Cyan 60 gel

It important to stress that the predominant colour in blue and blue water is cyan not blue and this is what gives the washed out scattering. We want to keep the deep blues and get rid of light blue and green which ultimately is cyan the colour of water.

So the strobe will emulate the water and the camera custom white balance will set the colour restoring what was lost and giving us a full correct spectrum. This however only works until the water colour temperature gets to 11000K and this is not as deep as you may think it could be a low as 9-10 meters. A cyan 60 filter is approximately 9500K. You can see the colour in the image below.

Cyan 2 Stop results in Colour Temperature around 9500K

In this technique the strobe is not used to give colour but to eliminate shadows the custom white balance is going to give a deep colour that penetrates the whole frame so any subject in the distance will be colourful as well.

The benefit of this technique is that you may use wider apertures and even slower shutter speeds like in this 1/60 example here.

batfish formation 1/60 f/5.6 ISO 200

You can clearly see the orange colours of the anthias far behind in the frame.

The ultimate stretch of this technique is to combine a filter like the magic filter this can be used with both a Cyan 2 stops and also a Cyan 3 stops in deeper water. This technique is taxing on exposure as your strobes are half power and your exposure has 1 2/3 stops less however this is easily recovered as you tend to shoot at slower shutter speeds of 1/30 to 1/60 instead of 1/125 to 1/200 because the filter will give you the deeper blues.

Magic filters on WB slate

The magic filter adds around 3000K to you camera custom white balance ability reaching the 14000K where the water starts turning purple blue. To that regards due to the amount of red I do not recommend going to deep with the magic and keep it to a max of 13 meters as recommended on their website.

The magic filter is almost a perfect match for the Cyan 60 filter if you overlap them over the lens you get almost a neutral grey card the temperature is only 150K off while the tint is around 5 notches toward green in Lightroom.

Magic Filter + Cyan 60 results in almost neutral grey card

This cave shot I believe gives an idea and is taken with filter on lens and strobes.

Magic filter plus Cyan 60

I have also tried the magic filter with Cyan 90 however there are some side effect to consider. Firstly you get Cyan cast on the image at shallower depths. Second the magic filter has a tendency to turn purple below a certain depth so I recommend to use the magic with the Cyan 60 as you are certain that the foreground subject and the strobe filter will give you a neutral colour. If you are in deeper water and the temperature is above 10000K this will only result in a deeper blue and a warmer light on the subject that once RAW corrected will look just fine.


In this post I have tried to give you some tips on how to use gels to give deeper blue or richer colours to your wide angle. I would recommend to start with warming diffusers and then move to cyan filters and finally to magic filter and cyan filter in combination.

I will be demonstrating extensively this techniques during my 2020 Red Sea Liveaboard

A final word for video shooters. I am not aware of any add on warming diffusers for video lights and generally I have not seen LED warmer than 5000K therefore unless you shoot at 60p 1/125 it will be very hard to get deep blue at shallow depths without a lens filter.

See my other post for video specific tips.

Full size images are available on my flickr pages all images here are reduced to 1600 pixels for storage purposes.