Category Archives: Wet lenses

Fisheye lens, Full Frame, Sony A1, Tamron 17-28mm, Underwater Photography, Wet lenses, wide angle

Wide Angle Rectilinear Lenses for Underwater Imaging myths vs reality

March 25, 2023 interceptor121 1 Comment

The subject of rectilinear wide angle lenses and underwater optical performance has been beaten to death.

Most recently some photographers and videographers have done without rectilinear lenses altogether citing the horrible performance at the edge of the frame as the primary reason to shoot lenses with barrel distortion being those fisheye or standard lenses with an added water contact optic.

Is it all justified? Should you stay away from rectilinear lenses altogether?

Of course not. Rectilinear lenses have a place in underwater imaging that is there to stay but…

There are many many buts so let’s dive into some demistification and general considerations.

Topside Performance of Wide angle lenses 17mm use case

The vast majority of underwater shooters do not perform any type of topside imaging being that photo or video and use their set up only underwater with the exception of the odd event or those that like to shoot macro above and below this is where we stand in most cases.

In order to ascertain if the performance of the wide angle lens in water deteriorates it is appropriate to determine the performance of said lens topside. This is something that not many people are in fact able to ascertain. You can read equipment review but it is never the same thing.

I have recently invested in a Sony A1 and underwater housing and I decided to purchase a rectilinear wide angle lens. I always try to buy lenses that are good topside and underwater and my choice has fallen on the Tamron 17-28mm F /2.8 Di III RXD.

Several reasons for buying this lens I will list the most important are:

Close minimum focus distance (19 cm wide – 26 cm tele)
Lens does not extend when zooming
Reasonably compact (99 mm and 420 grams)
Not too wide

Items 1,2 above are important underwater and 3,4 are also important topside when you use the lens on a gimbal or when you shoot interiors or close up and you do not want apparent perspective distortion.

I have been shooting the Tamron topside on trips and I have been very pleased with it. Before taking it underwater I wanted to understand what to expect.

I built my scene using my underwater props on a table top and started taking a series of shots from f/8 to f/22 to see the results. What follows are a set of images taken on land with the focus on the eye of the chick.

At f/8 the first row of props is blurry and also the leaves behind are not sharp. The edges are soft.

This is due to lack of depth of field not to the bad performance of the lens.

At f/11 we have more depth of field however the props at the edges and the nearest part is still soft.

By f/16 all the props are in focus, the edges of the math are a tad soft but overall this is the right place to be.

By f/22 pretty much everything is in focus but the image quality has dropped considerably.

In conclusion topside we need to close down to f/16 to have all the props in focus on this scene.

Just so we are clear there is not an issue of edges or else there is simply lack of depth of field as we are shooting a close up.

Underwater Performance of Wide angle lenses 17mm use case

After rigging my camera and lens with the Nauticam 180mm dome it was time to hit the pool and try underwater.

What follows are a series of shots from f/8 to f/16 with focus on the chick as the topside shot.

The image at f/8 looks very much like topside and lacks depth of field, however interestingly the bush behind the chick is relatively sharper to the topside scene. The dome port is increasing the depth of field behind the subject.

By f/11 there is a considerable improvement all across the frame the items at the edges are still soft pretty much like the topside image.

By f/16 we are where we should be. Note how the entire set of props is in focus exactly like the topside image and only a slight deterioration on the very left of the frame prop.

Move your focus…

Dome ports increase the depth of field of the lens as infinity becomes nearer however they also shift the depth of field of the lens because the virtual image is closer and most of the depth of field shifts behind.

With that in mind I focussed on the first prop to see what happens.

At f/8 the first line is sharper even the props at the edges are substantially better and I would say acceptable however the leaves behind are out of focus.

At f/11 the edges are good and so are the props behind the chick with the exception of those really further back where we are running out of depth of field.

By f/16 focussing on the near prop we have pretty much everything in focus.

As final example this is a shot at f/11 with focus just behind the fake coral red and yellow on the right.

With the exception of the very very edge of the right frame which is bordering the dome edge the image is sharp throughout.

Why are the images not blurry?!?

You are now starting to ask why some images you see on the web look horrible and mine don’t? This is a legitimate question to which there are at least five answers.

Lens working distance

The Tamron 17-18mm has a working distance of 19 cm and is 9.9 cm long. From my calculation the entrance pupil is around 26mm from the front of the lens. This means that a dome radius of 10cm is sufficient to be able to focus right on the port. All other lenses for the Sony E-mount have working distance of 25 to 28 cm and would need extremely large radius to be able to focus on the glass.

Wrong Extension Ring

The Nauticam 18809 wide angle dome port is not a classic dome but has design without a flat base. The port has 11cm radius of curvature and is 83mm deep 180mm wide this means the entrance pupil needs to be 27mm behind the extension.

Nauticam 18809 180mm Wide angle dome port

Nauticam recommended extension is 40mm when combined with the 35.5mm N120 to N120 port adapter. Due to the shape of the lens this cannot be used with the N100 port as the zoom is close to the front of the lens.

Underwater housing manufactures unfortunately do not apply any science to the selection of domes and extension for a lens but out of pure coincidence the 40mm extension ring is what this lens requires.

Tamron 17-28mm 35.5 adapter and 40mm extension

Nauticam criteria for the 180mm port seems to be the lens needs to be more or less flush with the extension ring. In our case the entrance pupil is 26mm behind and the extension ring is a few mm over so we are more or less spot on. THIS IS ENTIRELY A COINCIDENCE!

With the 40mm extension the glass port will be exactly 11 cm from the entrance pupil and focus right on the surface.

Unfortunately the principles applied by manufacturers which are either to be flush with the ring or the dome mount or to extend until it vignettes generate loss of angle of view and distortion.

One of the worst offender is the Nauticam 230mm glass dome, where the rule of extend until you can generates pincushion distortion (edge pulling) effect.

Software Correction of Distortion

The lens correction has a warping effect on the edges even when the dome is correctly placed.

Exteme edge at f/11 with distortion correction off

Extreme edge at f/11 with distortion correction on

If you have a full frame camera or a camera where you can disable the correction make sure this is set that way.

For systems where lens correction is baked in the lens profile (micro four thirds) ensure to use a program that can disable the correction such as DxO Photolab for best results.

Constant Autofocus with subject tracking

As we have seen in most cases it is better not to focus bang on the subject but to focus closer or even at the side of the frame and work out the depth of field.

Many users use subject tracking that may seem a wonderful idea and works very well with a flat port however underwater results in blurred edges due to the depth of field distribution of the dome port unless you close the aperture until you can care less.

If you want to ensure the edges of your rectilinear wide angle shots are sharper use single autofocus and position the focus strategically in the frame the dome compression will do the rest.

Superwide lenses (<16mm)

When your lens is superwide you may have all effects on top of each other: pincushion distortion because your extension is calculated with the ‘go until vignette’ method, distortion correction in software, subject tracking, lens with long working distance and to make it worse perspective distortion and spherical aberration which occur when the lens is very very wide.

Choosing your rectilinear wide angle lens

I have computed all lenses avaialble for my A1 and calculated the ideal radius of a dome in this table. Unfortunately while the 230 port has a wider angle of view it has a radius of 12 cm which is only 1 cm more than the 180mm port. The choice of port is therefore driven by angle of view and not radius as 1 cm does not change much. Most lenses would need 15 or 16 cm radius to be able to focus close to the glass.

Brand	Model	Working Distance	Field of View	Radius Required	Port
Sony	SEL1224GM	280	122	152	230
Sony	SEL1224G	280	122	152	230
Sony	FE14 1.8 GM	250	114	157	230
Sony	SEL1635GM	280	107	169	180
Sony	SEL1635Z	280	107	169	180
Sony	PZ1635G	280	107	169	180
Sigma	1424DGDN	280	114	164	230
Tamron	1728RXDIII	190	104	99	180
Zeiss	18mm	250	100	177	250

Sony e-mount rectilinear lenses and ports

You can easily see that the Tamron 17-28mm has much better design characteristics to go into a dome port and this is the lens to buy.

From my tests there is no need of any field flatteners and correction lenses it works fine out of the box as the lens has minimal field of curvature and zero spherical aberrations.

Pool Session

If you are not happy with the CFWA studio scene here are some images from a recent pool session. Many f/8 and f/11 images no need to close the aperture more if you don’t have anything close and shot in single autofocus.

Quite interesting to see the fins at the edges of the f/8 shots.

If there is one challenge of rectilinear lenses is that you need strobe power. The narrower field of view compared to a fisheye means that you are standing further back that in turn means more strobe power and more particles between you and the subject.

Should I buy a rectilinear wide angle lens for underwater use?

My answer is definitely yes but each system will have the special lens, the one that focuses close, does not require a large radius and is not too wide and not too narrow (16-18 is ideal) however examine carefully images of others and check the lens construction as your suggested extension may be wrong.

But when your lens is fit for purpose using the correct size dome and the proper extension you will get high quality images that match or beat fisheye like lenses and water contact optics.

As example here an image shot with a canon 8-15mm at close range f/11. Does it have much better edges?

And here a WWL-1 image at f/8

I cannot see any advantages of the fisheye like lenses at the edges at the same aperture in fact in both cases but judge for yourself.

Phil Rudin reviewed the Tamron 17-28mm on uwpmag you can find here some open water images https://www.uwpmag.com/?p=uwp-back-issues&issue=119

Unfortunately Phil used the Sea and Sea correction lens an expensive accessory that this lens does not require but as soon as I am in open water I will post images myself.

Full Frame, Sony A1, Underwater Photography, UNDERWATER VIDEO, Wet lenses, wide angle

Nauticam WWL-1 on Sony Full Frame what to expect

March 11, 2023 interceptor121 1 Comment

It has been almost 9 years since my first review of the Nauticam WWL-1 and five years ago I revisited this lens on micro four thirds.

Since the very first release I was told by Nauticam that the WWL-1 had been tested on Sony full frame with the 28mm f/2 lens and since then more lenses have been added to the compatibility list and the WWL-1 itself has had a redesign called WWL-1B, this lens has an integrated float collar and I do not know if there is any difference in the optics but I assume there is none.

Nauticam has since released a number of other water contact optics with dry mount and today you have a choice of at least 3 flavours for your Sony full frame camera that provide the 130 degrees diagonal field of view.

Model	Price (€)	Weight (kg)	Diameter (mm)	Depth (mm)	Max Filter size (mm)
WWL-1	1424	1.35	156	97	52
WACP-C	2930	2.24	170	145.5	72
WACP-1	4604	3.90	194	176	82

Summary Table Nauticam 0.36x Water Contact Optics

The three lenses provide the same field of view but they are different in size and mount. A useful way to see is that as the lens physical size grows you require a larger underwater optic.

The Sony E-Mount is still the only full frame format compatible with the WWL-1 in virtue of some really small and compact lenses. As you can see from the table above the WWL-1 rear element is large enough for 28mm lenses that have a maximum filter size of 52mm.

Two E-mount full frame lenses the 28/2mm prime and the 28-60mm zoom are compatible with the WWL-1.

As you move towards the WACP-C you can also use the 28-70mm lens which is one of the worst kit lenses on the market but will give you a longer tele end and finally the WACP-1 gives access to the Tamron 28-75mm and Sigma 24-70mm two lenses that have much higher quality than the smaller Sony lenses but have some restriction in terms of zoom range.

Underwater Performance Context

There are quite long discussions about which water contact optic to get for your Sony full frame once you have the 28-60mm zoom and some comparison in terms of sharpness.

In simple terms you can think of the following equation:

Underwater Performance = Land performance X Port Factor

Port Factor is always less than 1 which means a lens will never do in water as well than it does on land. Looking at my analysis of the 28-60mm corroborated by other test you know before buying any water contact lens that the lens has its own limitations and no matter how good is the port performance will only go down. However this may still be a better option compared to a standard dome port.

I do not have access (yet) to the other two water contact optics however I have a good idea of how the WWL-1 perform and how the Sony 28-60mm performs topside. If you want a refresh look at this article.

To understand how a water contact optic works you can go back all the way to the Inon UWL-100.

The idea of this lens designed for compact cameras is to demagnify the camera master lens to enlarge the field of view. You could then get an optional dome that will enable the lens to expand the underwater field of view from 100 to 131 degrees.

Back in 2015 I compared the Inon UWL-H100 with dome with the WWL-1 and concluded that the WWL-1 was giving better results when used on the same camera. It is now time to see if the WWL-1 can be used also on a full frame system.

Sony A1 WWL-1 Rig

The WWL-1 requires the flat port 45 to be used on a Sony full frame underwater housing. The lens will be attached using the same bayonet adapter that has been available for several years now.

I have removed the focus knob from the port as I found it inconvenient. The focus knob may be useful with the flat port but for the WWL-1 that is afocal is definitely not required.

Once you add the flat port the overall length is very much the same of the WACP-C but this will require an extension ring resulting in overall 30mm additional length.

Overall the rig is very similar in weight to the Canon 8-15mm with the Acrylic Dome Port 5.5″.

Pool Tests

With the rig assembled I went for a pool session with the objective of finding out what was the overall performance of the system.

What follows are a series of test shots of divers.

In general I found the lens to be sharper in the centre at f/8 but closing down to f/11 was required if there was something in the corners.

Edge Sharpness

I was intrigued by a number of discussions on edge sharpness and after several exchanges with Shane Smith he was clear that the lens needs to be stopped down to f/11 for best results.

After the session in the pool I would agree with Shane however I was curious if this was an issue of the WWL-1 or the 28-60mm lens itself.

This image quite simple has something at the edges and has focus in the centre at f/8.

You will notice that the part of the frame closer to the camera is fairly blurry.

So I did another experiment placing the slate on the edge.

The edges were quite fuzzy. I wanted to exclude this was an issue of depth of field so I focussed right on the corner.

This is the resulting image and is still soft on the edge.

I then took the same shot at f/11 with focus on centre.

The image at the edges is better. Then moved the slate to the edge.

The image improved overall regardless of the focus point indicating this is not a depth of field issue but some other defect of the lens, most likely as the lens meridional and sagittal resolution are different we have an example of astigmatism.

The sharpness improves closing down the lens regardless of where the lens is focussing consistent to the MTF charts.

Looking back at land test shots we can see something very similar.

In conclusion it is not about the WWL-1 but about the lens itself.

Comparison to Rectilinear lenses

While the WWL-1 can offer a diagonal feld of view of 130 degrees the image is distorted and the lens can only offer 107 degrees horizontally and 70 vertically. Is like saying that the horizontal field of view is similar to a 13mm rectilinear lens while the vertical is is more like 17mm. A fair comparison is probably a 14mm rectilinear lens but as the WWL-1 is a fisheye like optic a direct comparison is not entirely possible. In my opinion as the image is distorted is more appropriate to compare the WWL-1 with a fisheye with teleconverter and when I look at what the canon 8-15mm with kenko 1.4 tc can produce for me the results are very similar, I would say the Canon has in fact an edge however the field of view are not comparable except when the WWL-1 is at the widest and the canon with the tc at the maximum zoom. I would go as far as to say that the canon + TC at f/8 is as good as the WWL-1 at f/11.

Conclusion

If you have the WWL-1 from your previous rig it makes absolutely sense to get the Sony 28-60mm and flat port. This combination will give you decent (but not sensational) shots and work very well for 4K video at reduced resolution. I do not believe that this lens can resolve the full 50 or 60 megapixels of the A1 or A7R4 or A7R5 even topside.

If you are starting from scratch I would recommend to think careful at your intended use case. If you want angles wider than 130 degrees and already have the Canon 8-15mm you may want to check the kenko telecovenverter before you buy a new port as all you need is a 20mm extension ring and a zoom gear.

If you really like the field of view range of 69-130 degrees you need to consider which water contact optic you need.

I am still looking for a test WACP-C but until then my general guidance would be to consider simply if you prefer a dry or wet mount.

A dry mount has the benefit of being ready to go as you hit the water, without the need to remove bubbles between the wet lens and the port. As photographer a dry mount may be the best way forward.

If you intend to use your camera for video and insert filters between the lens and the flat port or you require the lens to be removed in water then go for the WWL-1.

Rigorous comparisons between WACP-C and WWL-1 are not yet available but the first indications are that the difference in image quality is very small therefore I would not loose my sleep there and look more at overall ergonomics.

The final consideration is should you get the WACP-1 instead? Based on my assessment of the Sony 28-60mm I would think this is not particularly wise even if this choice is very popular. Personally I always believe that the master lens needs to be good enough to justify the cost of the water optic so I would like to see how the Tamron 28-75mm performs however no test images are available so I am not in a position to conclude.

In my case having seen what the Sony 28-60mm lens can do I am not planning to invest in a WACP-C but I would be very interested in testing one.

The WWL-1 gets my approval also on full frame but it is not going to give me the same resolution than the Canon 8-15mm or the Sony 90mm macro will give. I look forward to testing some rectilinear lenses to see how those compare and this will happen in a week from now so stay tuned.

Costs to get one for your Sony full frame excluding lens:

WWL-1B €1,424
Bayonet adapter €102
N100 45 flat port €494

Total €2,020 vs WACP-C + N100 Extension Ring 30 €3,333

Underwater Photography, UNDERWATER VIDEO, Wet lenses

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

October 12, 2019 interceptor121 1 Comment

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.

close up lens, diopters, Fish Portraits, Flat Port, macro, MFT Lenses, Micro 4:3, Panasonic GH5, Underwater Photography, UNDERWATER VIDEO, Wet lenses

which macro lens to pick for your gh5 or micro four third

September 14, 2019 interceptor121 1 Comment

I see many posts on line debating which macro lens is best for your micro four third system.

If I refer to the Nauticam system we have 4 macro lenses:

Olympus 30mm
Panasonic 30mm
Panasonic 45mm
Olympus 60mm

For the purpose of this article I will skip the Olympus 30mm as the Panasonic lens is known to be sharper and will focus on the other 3 lenses.

DxOMark is a popular tool for comparison as it gives you the results on one page. I have run it for the Oly 60 and the Pana 30 and 45 on the 20 Mpix OMD E-M1 MKII

DxOMark Comparison on Olympus OMD E-M1 MKII

Surprisingly the much more expensive Leica performs worse than the other cheaper models, this is confirmed on all internet sites running other type of tests.

What we can see is that there is little difference between the Panasonic 30mm and Olympus 60mm when it comes to image quality so whichever lens you choose your subject at the same level of magnification and aperture will have more or less the same detail.

Common Misconception: Shorter focal length give more depth of field

Many people think that using a longer lens is harder because there is less depth of field this is actually incorrect conceptually.

Let see why

Using an online calculatore like Dofmaster https://www.dofmaster.com/dofjs.html

Enter for the Panasonic GH5 the following parameters

Circle of confusion: 0.015 mm

Focal length 30mm

Distance 10.5 cm (minimum distance of the 30mm Macro)

Aperture f/11

Result Total depth of field 0.3cm

Now enter

Focal Length 60mm

Distance 21 cm (as it achieves the same magnification)

Aperture f/11

Result Total depth of field 0.3cm

So depth of field is not a consideration when choosing a macro lens…

Shooting a subject close to the background

In the following 3 shots am taking an image of a widget at f/11 at 29-44-60 mm on a Leica 12-60 (it is just easier it makes no difference to the outcomes)

At the same aperture you can clearly see that there are no difference whatsoever in the detail and actually overall in the picture you don’t notice anything.

Shooting a subject far from the background

For the second shot I have moved the widget away from the wall.

Again there is no difference in the level of detail of the widget however looking at the background we can see that

The 60mm shot reveals one brick and less than one quarter
The 44mm shot reveals one brick and a half
The 29mm shot reveals two bricks

So while the subject is exactly the same as the 60mm lens has a narrower field of view we see much less of the background.

This means that if you are shooting a nudibranch on the sand or something flat on a rock you won’t notice anything however if there is space behind the subject you will capture much more of that resulting in less subject isolation.

Underwater Comparison 30 vs 60 mm

In the first shot the Rhinopia is taken with a 60mm lens

In the second shot the same Rhinopia with the 30mm (in a different place to be fair)

I have marked up with red the areas that with a longer focal length would have been minimised.

Which Lens to choose?

Now that we have clarified that depth of field is not a consideration and as each macro lens will have the same magnification there are only two factors that matter:

Working distance
Isolation from background

The 60 mm will have a longer working distance and at the same magnification will isolate the subject better from busy backgrounds, the 60 mm is also better for skittish subject because of the longer working distance. I have this lens and I have borrowed the 30mm in couple of occasions but do not have the 30mm yet.

There are however situations where longer working distance is not a benefit, specifically when the visibility is poor and there are suspended particles or the subject is really large.

In the example below I was at one meter from the two frogfish, a 30mm would have been better however the shot came OK.

Conclusion

I believe the Olympus 60mm is a must lens to have. To date I have not felt the need for the Panasonic 30mm that is indeed a very sharp lens because I have always managed to pull out the shots. However for someone diving in murky water and focussing on nudibranches or subject laying flat on the seabed the Panasonic 30mm could be a better choice. I also want to say that using the 14-42mm at 42mm for me is actually a better choice for portraits and with a close up lens works very well with small subject not super macro and therefore as I already own the 14-42mm and various diopter for me the 30mm is not on the shopping list.

ambient light, filter, Micro 4:3, Panasonic GH5, Underwater Photography, UNDERWATER VIDEO, Video Lights, Wet lenses, White Balance, wide angle

Getting the best colors in your underwater video with the panasonic gh5

August 3, 2019 interceptor121 26 Comments

There is no doubt that the Panasonic GH5 is a very capable camera and in given conditions the video performance you can get is truly impressive.

Broadly speaking a video clip needs to be:

Sharp
Colorful
Contrasty
Clean

Those 4 characteristics are tightly related to:

Resolution
Color depth
Dynamic range
Low Noise

Resolution

Today everyone shoots 4K and after all resolution is well supported by almost any camera, broadly is unaffected by other factors and unless the noise is really high sharpness of your frame is not going to be a real issue shooting at 4K.

Color depth

In normal conditions and not underwater a camera can resolve many colors. However underwater due to the diffraction of light and selective absorption of colours the starting point is very different from land. So generally is not the camera that cannot resolve the colors but the colors that are missing to start with. This post will focus specifically on this aspect. The Panasonic GH5 can resolve 23.8 bits in RAW and therefore technically has less than 8 bits color depth – do not confuse this with the 8 or 10 bit recording setting.

Dynamic Range

Underwater scenes tend to have limited dynamic range, with the exception of sunbursts or shooting against the light this is going to be an issue only in specific circumstances of very bright scenes with shadows. In all scenes taken with video lights dynamic range is not an issue at all. The GH5 has 13 stops of dynamic range but rarely this is an important consideration.

Noise

Noise is an important consideration as when the noise goes up the camera looses the other characteristics, color, dynamic range and resolution will be affected when the camera is outside the sweet spot. Broadly speaking the Panasonic GH5 does not do well once you pass the ISO 1600 setting and I tend to cap the ISO in video at 800 in most cases.

Diving Conditions

To understand how those variables play we can see how the same set up reacts very differently in scene where there is less light and therefore the camera uses high ISO like this one.

The same camera with exactly the same equipment in brighter water produces this

So the reason for the above is that with less light there are less colours and the clip looks what it is really.

OK moving on to the main subject of this post how do I get the colors right? It is a combination of techniques and the trick is to use the right one in the right conditions.

Generally every site has specific conditions that change depending on weather, time of the day, visibility and other factors. So in broad terms a site will have more or less light and therefore more or less colours. It is therefore impossible to categorically define what to do at a given depth but is more about typical values. With this in mind we have typically 3 scenarios:

Ambient light shots
Artificial light shots
Balanced light shots

Close up Shots

In general close up shots especially of small subject fall within the scenario 2 for which a video light with high color rendering is important as this will define the colours you see. With a lot of power it is possible to extend artificial lighting to larger subjects but eventually you run out of power due to distance or size of the subject.

Wide angle shots and seascapes

True wide angle shots are generally ambient light shots which also means when it gets too dark the colors will be missing and it will look blue not matter the equipment.

In order to make the most of ambient light shots for wide angle it is essential to balance the colours in water even when you use a RAW format on a still image because RAW files are not as RAW as you think and are actually compressed.

Custom White Balance

Using Custom White balance with a grey card it is possible to obtain decent results until the camera hits the maximum color temperature in the case of the Panasonic GH5 this is 9900K. Depending on conditions you may get to 10-12 meters and this still works, in darker water this stops working much sooner.

Chrisoula K Bow — Chrisoula K Ambient Light 5 meters

Color Filters

Color filters push the limit of custom white balance further down. Some add more or less 4 meters others up to 6-8 meters at the expense of an overall loss of light. Filters are useful when there is a lot of light because also help to keep the Panasonic Gh5 in the best aperture range (not smaller than f/11)

Filter in action at 10 meters

Right now there are predominantly 3 filters on the market:

UR PRO
Magic filter
Keldan Spectrum

All those filters will improve the performance and color rendering of your footage, under the conditions that the loss of light is not pushing the camera above reasonable ISO values.

In terms of depth range the magic filter and the Keldan Spectrum -2 version can be pushed to 15 meters depth on a bright day in clear water. The URPRO is capable of getting a few meters more down to around 17-18 meters although it does generate an orange cast (as there is no red left) it is still workable.

Filter	Light Loss	Typical Max Depth
Magic Filter	1 2/3 Ev	15 meters
Keldan Spectrum -2	2 stop (WWL)	15 meters
URPRO	1 2/3 Ev	18 meters

This image gives an idea of the 3 filters as you can see they are very different one from the other.

Balanced Wide Angle Shots

This is an entirely new technique that has started with the Keldan Ambient light filters. I wrote a whole piece on wetpixel

The principle is to use custom white balance with or without filter to obtain color rendering and then put filters on the video light so that the color of the light emulates the ambient light and therefore it only gives texture not color.

Keldan has developed a whole range of filters for various situation that match their light and therefore are not applicable to any other light.

As I do not own a set of Keldan I have done some tests and found that a gel of Cyan filter 2 or 3 stops makes my divepro G18+ practically ambient light in the conditions I dive into.

Filter	Cyan Strength
Magic Filter	2 stops
Keldan Spectrum	2 stops
URPRO	3 stops

The above value are based on my experience use at your own risk especially with different lights.

To give an idea I overlapped the filter to my iPhone lens

This is the shot without any filters

This example shows that the two filters cancel themselves the result is almost daylight with no cast which means in water if you use a video light or a strobe you will not see a red or orange spots on the image.

For those taking pictures the same combination remains true with Inon Z240 and Sea and Sea YS-D2

Example picture here

five in a row — My own filter and Cyan 3 stop note that the light is coming from the other side

One thing to take into account is that you need to find a way to hold the gel on the video light or the strobes. The flat surface strobe diffusers make this process easy, finding something you can use with your video lights is not easy and also the gels may melt after continuous use.

Artificial lights

It comes a point and a depth where filters stop working, this could be as shallow as 8 meters in green water. As the scene is dark using lights is what is required. There is nothing specific about this technique except making sure you don’t get burned highlights or backscatter. As it happens in photography using long arms (maybe not as long as for stills) is key to get good lighting on your subject.

My Camera Settings

I use CineLike D with saturation, sharpness and noise reduction to -5. I shoot at 24/25p AVCI 400 mbps and follow the 180 rules, it is entirely possible to shoot at 1/100 if you like more crisp look.

Clearly there are people out there that do not like filters and think white balance is best etc but I think a good read on magic filters explains it all.

http://www.magic-filters.com/need.html

Micro 4:3, Panasonic GH5, Underwater Photography, UNDERWATER VIDEO, Wet lenses, wide angle

NAUTICAM WWL-1:THE BEST WIDE ANGLE LENS FOR UNDERWATER VIDEO (ON THE GH5 AND OTHER MICRO FOUR THIRDS)

May 12, 2019 interceptor121 8 Comments

It has been almost 4 years since my first review of the Nauticam WWL-1 wet wide angle lens and a few accessories later this lens is definitely my all time favourite for underwater video with my GH5.

I do not want to repeat myself and beat to death the topic of sharpness in corners I would rather recap on the other benefits of this lens that really make it unique for underwater video. Obviously this lens is very valid also for still images because of the ability to zoom through but this is not the focus of this post.

So let’s have a look at the three killer features of this lens that make it really special

Field of view

The WWL-1 once combined with the Panasonic 14-42mm MKII (the best lens to combine with the WWL-1 in my view) offers a field of view of 130 degrees diagonal. But what does that really mean?

First the WWL-1 does not compare with a rectilinear lens in fact it is almost a fisheye lens as we can see from those shots of a pool wall.

The barrel distortion is evident correcting the image in lightroom gives an idea although not 100% correct of what is the real field of view of the lens.

WWl-1 at 14mm with distortion correction at 100

What is interesting to see is that the WWL-1 like a fisheye lens offers a much wider diagonal field of view than on the other dimensions.

I have compared the WWL-1 with other rectilinear lenses and with the 8mm fisheye.


Horizontal	25	50	100	200	FOV	Linear Ratio to FE
7-14mm@7	62	124	248	496	102	57%
8-18mm@8	54	108	216	432	94	50%
12-60mm@12	36	72	144	288	72	33%
WWL-1	61	122	244	488	102	56%
Fisheye 8mm	109	218	436	872	130	100%

Vertical	25	50	100	200	FOV
7-14mm@7	46	92	184	368	86	84%
8-18mm@8	41	82	164	328	78	75%
12-60mm@12	27	54	108	216	57	49%
WWL-1	39	78	156	312	75	71%
Fisheye 8mm	55	110	220	440	96	100%

Diagonal	25	50	100	200	FOV
7-14mm@7	77	154	308	616	114	13%
8-18mm@8	68	136	272	544	107	12%
12-60mm@12	45	90	180	360	84	8%
WWL-1	107	214	428	856	130	18%
Fisheye 8mm	583	1166	2332	4664	170	100%

The table I have prepared uses the equisolid equation for a fisheye lens to map the WWL-1 I have verified the values and I can confirm the WWL-1 is somehow equivalent to 10.06mm fisheye lens.

There are two things that are worth noting, the first is that on the horizontal and vertical axis the WWL-1 is not wider than the Panasonic 7-14mm at 7mm. The other consideration is that with the WWL-1 the 4:3 format frame starts to become a classic 3:2 as the ration width/height is 1.56.

When we work in video at 16:9 we crop out most of the diagonal part leaving the rest of the field of view intact this means that in video mode the lens is much more rectilinear and the barrel distortion more contained.

If we look at a frame at 25mm we can see that at 4:3 the level of distortion is reduced but still present.

.The corrected frame shows the residual distortion.

The level of residual distortion in video mode is pretty negligible at 25mm. At 35mm even in 4:3 mode the WWL-1 is practically straight.

The benefit of the distortion of the WWL-1 is such that if you are shooting large sharks for example the barrel distortion makes those sharks look large in the centre of the frame and when they go out of the frame you don’t have the pull effect of a classic rectilinear lens behind a dome. At the same time if you need to shoot some divers or lines that are straight you can zoom in and still cover a pretty wide field of view.

Stabilization

The other benefit of the WWL-1 is that allows you to use lenses that are stabilised, today any lens at the 7-8mm range on micro four third has no stabilisation which means you need to use the in body stabiliser if available with your camera. For the GH5 this means that choosing a lens like the 14-42 MkII gives you access to Dual IS combining body and lens stabiliser and IS lock that really is useful when finning around. I just want to make sure that I am clear I am talking of this lens

https://www.panasonic.com/uk/consumer/cameras-camcorders/lumix-camera-lenses/lumix-g-lenses/h-fs1442ae.html

The Panasonic 14-42PZ power zoom is NOT compatible with dual IS so if you use this lens you either have in body or lens stabiliser not both. Obviously if you have a camera without stabilisation like the GH5s or the BMPCC 4K all of this is less relevant but still you can have some stabilisation instead of nothing.

I have not shot a comparative Dual IS vs Lens IS vs nothing in the pool but I am planning to do that soon. I can only say once you have dual IS with IS lock you don’t want to go back.

Filters

The final killer feature of the WWL-1 is that it gives you access to the Keldan Spectrum filters review here http://wetpixel.com/articles/review-keldan-spectrum-and-ambient-filters-by-massimo-franzese

Personally I think that any dive down to 18 meters in tropical or subtropical water will benefit from a filter but I also believe that conditions may change and in some cases you want to take the filter off. Now most of the rectilinear lenses for the GH5 do not even take a filter but also consider that once you fit one in dome port you are stuck with it for the dive. With the WWL-1 and the Keldan filter if you feel there is too little light and you want to get rid of the filter you can.

Keldan filter in action

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