Category Archives: wide angle

Wide Angle Lenses and Adapters for Panasonic LX7

Who has followed my initial LX7 tests is aware of the few issues I have had at wide angle with the LX7.

One was the reflections back on the lens that I have now hopefully resolved using a black marker and changing the camera from white (and silver lens ring) to black and the other was flare.

Flare is an issue at wide angle even on land. What causes flare? Stray light coming from the sides that washes out the picture and eliminates contrast in the process.

Wide angle lens tend to have an ability to catch stray light from the sides and top and this is the reason why wet wide angle lenses have to be really coated well so that this effect is diminished, however it still can happen.

And it did happen to me with the Inon UWL-H100. The general advice to eliminate or reduce flare is to have a lens hood however lens hoods are generally not an option for wet lenses with an M67 thread mount. The only lens that I know that can position the hood on a screw mount is the fix UWL28M52 or UWL04 most of the other lens do not have a hood and have a circular lens unprotected from stray light. And this usually means at some point you will get flare.

So how do you get around it? In the case of the LX7 is pretty much a forced choice as the Inon UWL-H100 is the only lens that does not vignette at 28mm equivalent focal lenght so the possible solution is to put a hood on the lens.

Inon sells a hood for the UWL-H100 but the hood is attached through 6 allen bolts and its position can’t be fine tuned so to use the hood it is a requirement to change mount from M67 to the LD bayonet. You need also to convert the lens itself into an LD bayonet. If you go to your Inon dealer there is a relatively cheap service part that allows you to convert your M67 lens into a bayonet.

LD Bayonet lens holder
LD Bayonet lens holder

The LD bayonet is the latest incarnation of bayonet mount released by Inon. Whilst the old AD mount relied on a mechanical action to secure the lens, the new LD bayonet is much shallower and relies on a pin lock release to stay in place. There are two adapters on the market that are capable of attaching LD bayonet lenses to an M67 thread, one produced by Nauticam themselves and the other by the Japanese Fisheye Fix.

LD Adapters Boxed
LD Adapters Boxed
Nauticam and Fix LD-M67 adapter
Nauticam and Fix LD-M67 adapter

There is a  price difference between the adapters with the Fix being 20% more expensive.

Nauticam LD Adapter
Nauticam LD Adapter

The Nauticam adapter is the largest of the two. It has 6 allen bolts on the front and a thumb screw lock on the back to fix it in position. With LD lenses there is only one position to put the lens hood in the correct place so if for some reason the thread ends in the wrong place with your housing you will need to unscrew the front of the adapter to ensure the release lock is on the upper left of the port this happens the same way on the fix adapter. Make sure the little spring does not jump off in the process…Once the release lock is in the right area the fine tuning of the hood position is done with the thumb screw. A possible weakness is that if your housing port has no room for the thumb screw then this adapter is not good for you.

Whilst the Nauticam is made of plastic and metal the Fix seems to be 100% aluminum, this adapter looks better but does not have a mechanism to fix in place it relies on the strength of the M67 thread, however this locking system is compatible with any 67mm threaded port.

FIX LD Adapter
FIX LD Adapter

The fix allows to perfectly fine tune the hood position and it shows.

Nauticam Hood Alignment
Nauticam Hood Alignment

The alignment mechanism of the Nauticam adapter creates an alignment issue with the hood where the lens is few degrees turned clockwise.

With the fix this does not happen.

Fix Hood Position
Fix Hood Position

The hood can be properly aligned. Note that in both cases this does not mean more vignetting as the corners are not covered by the hood.

The other check I do is the position of the back of the lens, if there is a gap between the thread and the back of the lens this can create vignetting so it has to be as close as possible or even protruding as the Inon UWL-H100 mount type 2 does.

Let’s have a look at the back of those two adapters with teh UWL-H100 28LD attached.

Nauticam Rear Lens
Nauticam Rear Lens

The Nauticam thread is somewhat too long so the lens sits slightly more inside the thread line.

With the fix the situation changes sightly.

Fix Rear Lens
Fix Rear Lens

There seems to be little difference we will now check if there is an impact on the possible vignette in water.

Nauticam 28mm
Nauticam 28mm

As we can see there is a little bit of residual vignette on the bottom right corner when the lens is at 28mm equivalent focal length,

This is the same situation with the Fix

Fix 28mm
Fix 28mm

There is still a dark bottom right corner but it is less.

Inserting a 1.25mm spacer between the inner housing and the left side of the camera improves matters, this is because the lens of the LX7 is somewhat misaligned in the Nauticam housing and this corrects it.

Nauticam 28mm Spacer
Nauticam 28mm Spacer

With the spacer in the housing and the Nauticam adapter there is a tiny little residue of vignette but overall this is ok.

With the fix adapter this is the result.

Fix 28mm Spacer
Fix 28mm Spacer

No dark corners left.

So this is the recap:

  1. You can change the UWL-H100 28M67 into an LD version with a cheap service part
  2. Once the lens has an LD mount it is possible to attach the hood this will reduce flare
  3. Vignetting is slightly increased but can be eliminated with a spacer with the Fix adapter
  4. There is an issue of hood alignment an increased vignetting with the Nauticam LD adapter

A final note: inserting a spacer in the housing is risky, you need to know what you are doing as in theory the chance of flooding could increase so this is not for everyone.

My recommendation to those who want to improve contrast with the UWL-H100 is to convert to LD mount, attach the hood and get a Fisheye Fix LDF-M67 Pro adapter. Changing to bayonet has other advantages making lens swaps in water much faster and easier compared to the thread version especially with a lens as heavy as the UWL-H100.

There are few design issues and manufacturing errors in the Nauticam LD adapter that create issues with the LX7, most likely other cameras that are not so fussy will have no problems but if you have an LX7 avoid the Nauticam adapter entirely until a new production version is defined. I have given Nauticam the feedback and they will probably react.

Grenada Trip First LX7 release

I have just completed the first draft of the clips taken with the LX7 in my trip last week. Links are here:

Youtube may not work in some cases so use vimeo instead

For who wants to know the lens choice for wide angle was as follows

Wet mate: Molinere Sculpture Park, Purple Rain, Veronica L, Shark Reef

Inon UWL-H100: Bianca C (28-40 meters) , Northern Exposures, Southern Comfort, Quarter Wreck, Shake’em (20-32 meters)

You can see in the section of the Veronica L that missing those extra degrees field of view did not allow me to take the full wreck by side even if it was not that big. On couple of reef dives I already had the Inon on the previous wreck dive so I left it you can compare performance of the two lenses in terms of sharpness and flare. Generally I feel the wet mate has less flare and is sharper however it does have an issue of reflections as covered in the previous post.

As always I have used iMovie to edit the AVCHD progressive files that I converted to normal mp4 using the workflow in a previous post. There are no dramatic alterations of colour or exposure and no stabilization has been run in any part of the video (in some parts like the snake eel moving it shows) all was done with custom white balance using the camera functionality, considering how deep were some of the wrecks this is very good I believe.

I would love your comments this was mostly an exploration trip so it is interesting to compare to the RX100 Raja Ampat videos

Panasonic LX7 reference compact for underwater video

So I finally had the opportunity to take the LX7 on a trip after some pool tests.
After my attempts last year with the Sony RX100 I was a bit skeptical that I could actually find something better for video but I think the LX7 beats it.
I put together a sample just to give an idea of equipment used and how it works, please note this is not altered in any way

There is a picture of the rig in this blog on a specific page but let me confirm once again in detail
Panasonic LX7
Nauticam LX7 housing
Ultralight TR-DM tray with extension TR-DUP and two TR-DH handles without ball.
12 segments locline arms on 3/4″ mount base and reducer on the handles
Two sola 1200
Nauticam wet mate
Inon UCL165AD on bespoke M67 adapter
Inon UWL-H100 28M67
Inon M67 double lens holder on custom mount

In a previous post I highlighted that for most the wet mate will be the only lens needed however I had some wreck dives and the 18mm of the Inon wide angle are more appropriate.
I also gave a try to the panasonic intelligent zoom that allows for 2x digital magnification and sharpening that for me works very well and you can see it in the footage. This allows a user with just the wet mate to further zoom without need of a close up lens or a use with a single +6 diopter to achieve super macro.

Pedersen Shrimp with two stacked UCL165AD and intelligent zoom 7.5x The frame height is less than 1cm
Pedersen Shrimp with two stacked UCL165AD and intelligent zoom 7.5x
The frame height is less than 1cm

I found the white balance of the camera excellent on both my hand or sand. I had issues with my padi slate that many times returned a ‘scene too bright’ error. Maybe this is the reason why backscatter failed this camera for video?? Who knows.
You can see that even at 36 meters the colour are as good as they can be.

White Balance on Bianca C 36 meters depth
White Balance on Bianca C 36 meters depth

For macro shots I used the temperature setting at 6500K, I found the white balance tint fine tuning to be excellent to further enhance it.
I shot in shutter priority the whole time with shutter speed of 1/100 or 1/50 depending on conditions and type of shot. The camera autoISO and choice of aperture privilege noise reduction however as the lens of the LX7 is really sharp the relatively wide aperture did not mean soft corners.
I tried the various photo styles and at the end settled for the standard one, I found the natural really to have too little contrast.
I thought of shooting in mp4 for wide and AVCHD progressive for close up but this would have meant two different frame rates to edit, at the end I shot at the highest available setting to avoid confusion.
I had received a new port from nauticam so I had no vignette at 28mm and the full 100 degrees the inon lens can offer.
The ergonomics of the camera that have fixed commands for aperture and shutter proved to be convenient and the built in neutral density filter was very effective at shallow depth or on the surface.
In essence I think that the issues backscatter mention are non existent.
I did have a few problems with the wet lenses though.

Lens Marking reflection on Wet mate dome
Lens Marking reflection on Wet mate dome

The wet mate proved to be a great little tool very sharp and light however none of the sides of the glass have anti reflective coating. In bright scenes or backlit scenes I did not have many issues with flare however I could see the marking on the lens reflected back on the wet mate and in the picture. I suggest putting an inon anti ghost sticker or gaffer tape to hide those shining markers or to colour them with permanent black ink.
Other than this the wet mate performs very well in all reef scenes and close up of critter a few inches big.
The inon diopter did not cause any trouble other than the obvious vignetting until 70mm. One pleasant surprise is the LX7 autofocus. Having struggled with the poor focus of the RX100 at high magnification I was astonished that the LX7 finds focus even with two stacked diopters and keeps it!!! I never had to use manual focus that with the RX100 was the norm at macro range.
I had bought the UCL165 and UCL330 in m67 format but decided to sell them as I will actually switch to bayonet very soon for the wide angle.
The Inon UWL-H100 was probably the most disappointing find of the trip. Image was sharp in normal condition however this lens tends to flare quite a bit and this creates block noise in the water column in video, when I used my hand to shade the lens the flare went away. Inon sells a lens hood for the 28LD version of this lens but not for the M67 as there would be issues to align the hood petals to the frame.

Inon UWL-H100 Flare on top of the frame
Inon UWL-H100 Flare on top of the frame

Considering that the lens is very heavy in water at 350 grams and that screwing and unscrewing was a concern mid water I have decided to convert the lens into an LD bayonet. Inon sells a replacement service part for the 28LD that can be used to replace the M67 thread of the lens. Other than this part the two lenses M67 and 28LD are identical. I will use a nauticam m67 LD adapter I hope this will not increase the vignette. I will connect my AD mount close up with a AD->LD converter when using the wide angle and then use an AD->M67 converter when I use the wetmate. This saves me buying two different diopters and I can stack the two UCL165AD I already have. They do vignette a lot at medium but who cares when you shoot at full zoom.
I look forward to testing the UWL-H100 with the lens hood I am sure results will be better. On the other hand when the sunlight is behind the shots have incredible sharpness with this lens.
So the LX7 gets 5 stars from my side and I leave you with two recommendations:
1. Apply a form of anti ghost sticker to the LX7 lens
2. If you want to get the Inon UWL-H100 go for the LD mount so that you can put the lens hood on

Wet lenses choices for Panasonic LX7

When compact cameras were designed for 35mm it was quite common to shoot just with a camera and strobe; this allowed the average user to take decent close up pictures as long as the camera was capable of focusing within a couple of inches from the subject.

Years later manufacturers started introducing wider lenses first came 28mm equivalent and most recently 24mm, these cameras give an increased field of view on land of 75 and 84 degrees diagonal.

There is a common misconception that as the camera has a wider lens you don’t need to buy a wet lens for underwater activities. This is also reported in otherwise good articles like this one: http://www.scubaboard.com/forums/tips-techniques/46508-getting-started-amateur-underwater-photography-buying-your-first-camera.html

So why is it a bad idea to shoot just with the bare camera and no add-on lenses?

Two key reasons:

  1. Once in water the 84 degrees diagonal of a 24mm equivalent camera reduce to 54 or less because of the water medium
  2. At focal lengths shorter than 35mm pincushion distortion becomes stronger to the point the pictures are awful.
Pincushion Distortion at 24mm with flat port
Pincushion Distortion at 24mm with flat port

So if you plan to use your wider compact camera underwater without lenses make sure you zoom to 35mm to avoid distortion.

This is the same picture at 35mm note how the image is now rectilinear.

Flat Port 35mm
Flat Port 35mm

At 35mm we are back were we were in the mid 2000 and all we can do is close-ups so there is no advantage having a wider lens for underwater use with a compact.

Another common misconception is that a compact camera takes great macro just with the internal flash. Firstly a macro picture has a 24mm height of the capture area, nearly no compacts on the market are capable of this: the Panasonic LX7 and the Canon G15 within the current range are the exceptions. However at 1cm distance the internal flash is completely obscured by the lens, which means there really is no macro without a strobe and a close up lens: all you can shoot are close-ups.

Flat Port Close Up
Flat Port Close Up

This explains the need for wet lenses in water, wide-angle lenses to increase the field of view and allow us to get closer and take advantage of artificial lighting, close up lenses that also allow us to get closer using the full zoom of the camera and shoot at increased magnification without being on top of our subject.

The needs of photography and video differ as lighting tools differ, photos require strobe to freeze motion, video instead uses fixed lights. Photos are also taken at much wider angle than videos and fisheye effect is accepted, an effect that in video is generally not welcome.

With this in mind what are the wet lens options for the Panasonic LX7?

It depends of course on the planned usage of the camera.

Underwater Photographers

The LX7 has extremely good close up capabilities out of the box, however the capture area is around 12×8 cm that is not exactly small. If we want our nudibranch of shrimp to fill more of the frame we need a close up lens.

From my tests the Inon UCL165 brings around 2.5x magnification with the LX7.

Inon UCL165
Inon UCL165

I have tried stacking two UCL165 but the amount of chromatic aberration is too much for my liking, I found that 9 diopters is the max before fringing becomes a real problem and I do not recommend stacking two of those lenses or two equivalent Dyron diopters. I think the most flexible set up is a UCL165 and UCL330, this covers all possible working distances. I do not have a UCL330 yet so I can confirm but I have taken shots with a very similar lens (Olympus PTMC-01) and the results are excellent with a capture area of 48×32 mm that is very close to real macro. The zoom of the LX7 is the real limit here as it maxes out at 90mm versus the 120 of a Canon S110 or 140 of the Canon G15.

For close focus and ambient light wide-angle the bad news is that there is no fisheye lens that works well with the LX7 this is due to the extremely large lens.

I have tested the Inon UWL-H100 and I had to wait for a new port to be delivered from Nauticam as their original one was too long and had vignetting even at 28mm. This lens yields more than 100 degrees diagonal and is my preferred choice for the LX7 for stills. There is however a good amount of blue and yellow fringing if I really have to be picky so the extended field of view comes at some price.

UWL-H100 28mm
UWL-H100 28mm

I use Inon lenses however a possible candidate is the Epoque DCL30, this lens is reported to work with 28mm equivalent cameras however the rear lens is smaller than the Inon so I believe this needs confirmation. There is a $70 difference in US and £70 here in UK between the two lenses and considering that a dome will not worth I encourage testing this lens as the results may be acceptable. I think bluewater photo markets this lens in US under their own brand.

Underwater Videographer

If you plan to use the LX7 for video the situation is different, as the camera close up performance is extremely good and usually macro video is very hard. Most time we shoot with ambient light and if visibility is acceptable getting that close is not so important considering the LX7 ability to manipulate white balance.

The first suggestion is to get a Nauticam Wet Mate, this is a sealed air dome that gives us back the air field of view and works extremely well without any chromatic aberration and extremely sharp corners. This lens keeps the image rectilinear that is also a good thing for video.

LX7 with Nauticam Wet-Mate
LX7 with Nauticam Wet-Mate (do not compare with the Inon Picture this is taken from further away)

For majority of reef dives the wet mate is all is needed as this also allows the full use of the zoom without soft corners that occur if you zoom into a wet wide-angle lens. This lens is the most versatile for general video use and costs $250, great value from Nauticam.

There are however specific situations where the wet mate is not sufficient, as before close up performance with the bare port is good but not great for smaller critter, so a close up lens would be the next addition, again an Inon UCL165 or a Dyron Double Diopter would work just fine and have the same power.

When shooting at closer distance with lights, or when there is large fish or wrecks a wet lens is important as the 84 degrees diagonal of the LX7 are actually only 76 horizontal. Again the Inon UWL-H100 is my choice but would check again for the Epoque DCL-30. One characteristic of the LX7 that is interesting is that the diagonal field of view of the camera remains constant when picture format changes, this means the horizontal field of view is larger at 16:9 movie mode than it is at 3:2 for pictures.

Field of view with the LX7

Those are the maximum angles of coverage horizontal of the LX7 as I measured them at 3:2:

  • Bare Port 24mm: 50°
  • Wet mate 24mm: 71.5°
  • Inon UWL-H100: 88°

At 16:9 there is a wider field of view of:

  • Bare Port 24mm: 54°
  • Wet mate 24mm: 76.2°
  • Inon UWL-H100: 93°

In general terms with the wet mate we can cover 1.56x the horizontal field of view of the flat port and with the wide-angle 2.1x.

The wide-angle offers an additional 35% over the wet mate don’t be mislead by the apparent small difference between 84° and 100° as those are diagonal measures not horizontal and those few degrees more count.

At 1 meter distance the maximum subject size with the wet mate in movie mode is 1.56 meters and with the wide-angle this becomes 2.1, that confirms that the wet-mate is good for general use and the wide-angle is only required for close scenes of larger fish or wrecks.

Those are the three lenses I have used for those tests. A final consideration is about the lens mount. I will use the LX7 for video so my choice has been a 67mm mount, because this is the only format that the wet-mate offers.

If I was using the LX7 only for pictures I would prefer the flexibility of the Inon LD mount even if this costs a bit more as it makes it so much easier to swap lenses in water when you have a bayonet mount.

Underwater Video Tips: Using 24mm Compact Cameras

Some people will recognize the Canon PowerShot A570IS, the Canon S95  and the Panasonic LX7. The first shot VGA video, the second 720p HD and the last AVCHD 50/60p. If you look carefully you can also see how the front aperture of the lens gets progressively bigger and bigger.

Year after year compact cameras are becoming more powerful having electronics that allow higher resolution and image quality, I think the GoPro is a demonstration of what you can do pushing the limits of simple optics using ultra integrated electronics.

Compact cameras like the A570IS used to have lenses that would be equivalent to a full film camera with a 35mm lens, this has been a popular choice for long time. Some years go Olympus and afterwards Canon, Sony and others started offering plastic housing for those cameras to take them underwater this was the start of consumer underwater photography.

There are however a number of challenges using a 35mm camera for underwater photos and the most obvious is the field of view, because of the magnifying effect of water those compact had really narrow coverage that limit them to close up of macro shots. However a little time after wet wide angle lenses come into the market and offered range of coverage up to 100º some manufacturers also produced seme-fisheye lenses with coverage of 165º the most well known being the Inon UFL165AD.

All went well and compact camera photographer could take wet lenses with them and in one dive take pictures of a nudibranch as well as of a wreck thanks to removable lens in water.

Then the consumer market pushed manufacturers to increase field of view so it was the start of 28mm equivalent cameras like the Canon S90, this format is still very popular with the Canon G series and the new Sony RX100, in addition to that there was more and more demand for extended zoom so that the camera could be useful in all situations, today is not uncommon to have compact cameras with 20x zoom.

The introduction of 28mm equivalent cameras meant that the cameras would vignette with a lens designed for 35mm so wet lenses had to be readjusted and re-designed. The extensive zoom by this you mean over 4x meant that the wet lens would be so far from the camera lens that effectively no wet lens would be useful, this has been the curse of the Canon G series a great camera that never had any good wet wide angle solution until very recently with introduction of zoom wide lenses from Inon.

The other bad news is that at 28mm the flat port of the housing introduces already pincushion distortion and fringing as we can see from this photo

Bare Port RX100 wide end

We can see the effect of pincushion distortion in the deformation of the shape of the slate, it is quite apparent when you look at the lines and how skewed they are you can also see a purple tinge to it.

A wet wide angle lens not only expands field of view but also corrects pincushion distortion and chromatic aberration, this is the key reason why some form of wide angle is always required.

In the last two years manufacturers have come up with 24mm equivalent cameras, such as the Canon S100, Olympus XZ-1 and Panasonic LX5, unfortunately those camera have even more pincushion distortion, and for this reason should never be used in water at wide end  to take pictures without post correction that can be quite hard to achieve so as a matter of fact many people live with ugly deformed pictures.

Those cameras make it even more difficult for wet lenses to work and to date there are very few lenses that work without vignetting, those lenses require a wide aperture on the side of the camera also to allow larger and larger image sensors that camera makers use like the LX7 in the feature image.

LX7 Flat port Widend
LX7 Flat port Wide end

To give a demonstration of why is a bad idea to take your 24mm camera in water without any wide angle lens we just have to look at the picture above. Shocking!

So with 24mm cameras we are stuck, the wet lenses with dome that work well with the 28mm cameras end up vignetting so badly that all the advantage is lost when you zoom in. In effect with a 24mm camera all we can aim is 100-110° field of view that for stills is not really that much, there are exceptions like the Canon S100 but in general terms options are limited.

Camcorders on the other hand always had a range between 30mm and 150mm if not more with extensive zoom, you would have needed a dome port atteched to the housing that would allow zoom to give the same functionality in water or diopters to zoom at close range.

A user of a Sony camcorder in a gates housing would be looking at 30mm like a very wide lens!!! Typically you need fathom lenses to reach 90° and lenses with 110° coverage cost $4,000+ so definitely not affordable to the average shooter.

Where does this leave us? Well surprise good news for all 24mm compact users that want to shoot high quality video there are plenty of options that don’t break the bank!!!

When zoom cameras like the Canon G7 come into the market some manufacturers like Fantasea, H2O tools, Ikelite started producing wet domes.

Those domes are made of two lenses with an air space and if set really close to the housing port have the effect of restoring the original field of view of the camera. Now for a 28mm equivalent like the Canon G series this is not that exciting as we are talking about 75º diagonal but for the 24mm camera users we are talking of 84° diagonal coverage, a value that a professional camcorder user would be very happy with. In addition you can also use the zoom which means that if the camera has really close focusing distance a wet dome is all you may need for 85% of shooting circumstances.

So when I got the Panasonic LX7 this is what I was planning and I got a Nauticam Wet-Mate this is the slate from before at the same distance

LX7 with Nauticam Wet-Mate
LX7 with Nauticam Wet-Mate

As you can see the image is not only wider but also rectilinear no barrel distortion as if we were shooting on land.

Personally I do not like barrel distortion for video, and this is the reason I don’t like videos shot with fisheye lenses so this suits me fine. Of course 84° are not really wide for large wrecks, whale sharks or similar for those situations you still need a wet-wide angle lens but the Nauticam Wet-Mate costs $250 plus taxes so you really can’t complain.

At telephoto the flat port does not have pincushion distortion but it could be painful to remove the wet mate in the water the good news is that with the wet-mate you can still make use of the full zoom so if your camera has a really short focusing distance this may be good enough for most situations.

To finish off this is the Nauticam Wet-Mate, there are as I said similar products made by other brands. It is build of Aluminum with two lenses with a sealed airspace, construction seems very similar to some fix products.

Nauticam Wet Mate
Nauticam Wet Mate

So if you have a 24mm compact camera that takes HD video and you are frustrated with still there is a whole world in front of you with those dome adapters you could be well set for underwater video at very little investment.

Those are just some cameras that have high quality HD video the list is of course longer:

  • Canon S100/S110
  • Panasonic LX5/LX7
  • Olympus XZ-1/2

And the good news is that you do not need an aluminum housing just something that takes a wet dome, Ikelite for example has 67MM thread on most housings for those cameras.

Underwater Video Tips: Using filters with your GoPro or Compact Camera

Filters Test

Following a number of posts about filters in various GoPro forums I decided to check in detail the behavior of the UR/PRO filters and see what is that they really do.

I guess the reason is that people do not really know or want to know the physics behind it and prefer to entertain many discussion that involve trial and error.

One of the most interesting one is this clip here that generated some ferocious comments by some users of other products that of course were not pleased having spent money that their choice seemed not to be the best.

To understand a bit more about what filters do we need to look at light temperature graphs like the one below.

techcolour-temp-chart

Light colour is measured in K and high value means cold blue light and low values represent warm red light.

As we know underwater red gets absorbed approximately at a rate of 1 f-stop every 2.5 meters we go deeper compared to blue light with the result that red colour disappears pretty quick followed by green to become completely blue at depth.

Some time ago cameras were shooting film not digital and there was no way to correct colours when the film itself got developed. So to perform some decent underwater photography people used strobes and fisheye lenses to get really near and blast the reef with light in order to restore the real colors.

This worked very well for close shots but was useless for wide angle at distance, so color correcting filters that could go underwater were developed for ambient light photography.

So what is a CC filter? A common misconception is that filters add colours to the picture, whilst this is practically true this is technically incorrect.

So what does a CC filter really do? As the word says it filters light, more specifically filters selected part of the color spectrum. This is done at expense of available light so if we use a filter we will have less total light or for our purposes exposure. This is well explained on the URPRO website where they talk about film sensitivity, if you use a filter you will loose 1 f-stop so use a higher ISO film.

http://www.urprofilters.com/content.do?region=FilterInstructions

The filter can be designed for different purposes and depending on its color and opacity will be more or less aggressive. If you read very carefully the urpro website says that there is a maximum distance that the filter will be effective at.

UNDERWATER FILTER DISTANCE

Photographically and visually reds, oranges and other warm colors become dominated by the natural blue-green (cyan) effects of the water when it is more than 8-10 feet deep.

Because all water is a continuous filter, the deeper a subsea photographer goes beneath the surface, the more colors are naturally “filtered out” of the spectrum.

As a result, the depth of the water must be added to the distance between the camera (or flash) and the subject to give the underwater filter distance. Use the following formula to determine the correct underwater filter distance:

+ Depth of water above the photographer
+ Distance from camera (or flash) to subject


= Underwater filter distance

Scuba divers using a still camera or a movie camera must combine the depth of the water plus the distance of the camera from the subject. This sum should not exceed 80 feet for color negative films and video, and should not exceed 30 feet for color slides. In all cases, the best color is achieved when the camera is close to the subject!

What that means is that the working distance of the distance is not the same as depth so you can push a filter say down to 24 meters but then the distance to subject needs to be zero. So if you are shooting something 3 meters or 10 feet away in 21 meters of 70 feet that as much as you can get.

When it comes to underwater use we are mostly interested in eliminating blue in tropical waters or green in cold algae waters.

In order to eliminate blue that has a high colour temperature we need warm colors typically something around orange. This will some of the blue beams and also part of the green beams and will produce filter light that is of a warmer color and will look ‘more red’.

But how much does for example a URPRO orange filter for blue water really warm up the light?

I have done some empirical tests with my Sony RX100 in a day where the Sony would measure a temperature of 6500K which pretty much correspond to cloudy day indoor.

Filter

The URPRO orange filter which is the same that is on the SRP filter for GOPRO measured 2800K with a tint of 5 Magenta. It also measured an overall absorption of 1 and 1/3 fstop of total light. I measure this filter instead of the one I have (which is not SRP and we can cover why in another place) because I think the SRP is the market lead at this time and it uses UR/PRO filters.

So the URPRO orange filter has approximately a 3700K warming effect with a strong magenta tint. This means that a camera with auto white balance and an average lens like a GoPro can restore some color in the image until the overall color of the light is around 10,000K in water. After that the filter essentially stops working and the light absorption is so much that it just becomes plain noise. I think this website gives a good idea

http://www.seos-project.eu/modules/oceancolour/oceancolour-c01-p07.html

So the reason why the picture stops having any red and starts looking green is that there is no red left in the light!

The breaking point seems to be around 18-21 meters or 60-70 feet and corresponds to our personal experiences I would say.

So what about custom white balance? We are pretty much in the same situation we can re-balance the camera up to 10,000K and add magenta or orange tint to the picture but you reach a point where there is too much red color noise.

The other advantage of custom white balance is that there is no light absorption so the picture ends up being less noisy as at the same aperture a loss of 1 and 1/3 fstop is like saying doubling the ISO from 800 to 1600 to capture the same scene. This is the reason a camera with custom white balance will always outperform the same camera with a filter at depth in terms of picture noise.

And what about Magenta filters? This is an interesting one as magenta filter absorb little light around 1/3 of fstops for URPRO and warm up the colour very little around 700-800K with a magenta tinge more prominent. A magenta filter will therefore absorb less light in total and introduce just a tint to the image.

From my tests a magenta filter is totally worthless on a camera that can white balance and frankly not that good at depth on camera with auto mode only. The reason is that light will get cold very soon at depth and the camera will be outside the AUTO white balance operating range (2700-7000  on average) pretty soon.

So what it means for users of GoPro cameras? The summary is pretty much like this:

  • In blue water filters are worth down to around 18 meters or 60 feet
  • In green water filters are worth even less as the color temperature very soon reaches a temperature where the auto white balance of the gopro is out of range

Although I have not yet measured I would think probably max 10 meters and that is it as I had similar results with my Sanyo that has same sensor size of the gopro and actually a faster lens.

Hope gopro users find this post useful as well as other users of compact camera to shoot video in ambient light.

In the next post I will compare the optical quality of the SRP dome port with the PolarPro snap on filter that generated such a debate on youtube and we will see why this filter could perform better than the SRP dome.

Sony RX100 – Summary of Underwater Video Performance

Few months ago this clip came out

Many people including me got really excited about this camera and had a go at underwater video with it

Now it is time for an end of year review and summary of my experience with the Sony RX100.

Without a doubt the camera is a game changer and there are some feature that are especially suited to underwater video.

Key Strengths

Bright Lens

The RX100 does very well in low light this is a strong selling point for underwater video, even in cloudy days the camera does extremely well

Low Noise

The camera performs very well in video mode up to ISO 800, the level of background noise is really low and the footage clearly benefits from it

Image Quality

The quality of video if we focus on the center, as well at the telephoto end is impressive. Color rendering is very accurate and there is even the option of using Adobe RGB. The dynamic range of the camera is excellent and the image is vibrant.

Video Mode Control

There is full manual control in Video mode and the option for aperture and shutter priority. The program mode does very well. Only an Auto ISO option in manual is missing but this is negligible. Indeed the most interesting mode is aperture priority.

Manual Focus

The peaking function works very well and it is really a strong feature of this camera, it is also very usable underwater

Battery Life

You can easily do 3 dives with the RX100 without having to open the case which is great and actually unusual these days when even a gopro does not last one hour.

Active Steadyshot

I initially slagged the RX100 stabilization system based on performance on land. However at a more in depth analysis it turns out that the RX100 active steadyshot, even if at cost of an image crop is very effective for sudden camera movement and for high magnification macro. The Stabilizer is not as sticky as others so when you eventually vibrate it does not jump. Although the performance for stills is poor to irrelevant and so is the normal mode the active mode is very effective for underwater use.

Tedious Workarounds

Some of the ergonomics of the RX100 are not the best and seriously deduct from an otherwise excellent experience, the most annoying issues:

Lack of focus lock

For some reason Sony decided to skip on this essential feature, the workaround involves switching to manual focus using the function dial however it is then possible to accidentally change focus.

Setting Custom White Balance in Video

Setting custom white balance is only possible in the still modes, while in fact if you shoot RAW don’t actually need white balancing. This is the largest non sense of this camera that requires the user to navigate out into Program to ensure white balance is set correctly and you don’t end up with the Custom WB Error message. Really an awful issue that Sony should try to fix in a firmware update

Lack of 24/25/30 progressive modes at 1080HD

Sony thought that for some reason you either shoot interlaced or you go directly at double frame rate with a 25 or 30 progressive mode only available at reduced bit rate and resolution of 1440×1080 with rectangular pixels. Why did they do that is a total mystery. You are therefore forced to shoot at the highest mode of 1080p50 or 1080p60 that produces large files difficult to digest by many programs. Sony decided to keep a bunch of interlaced modes despite the fact that there are no programs that can edit those without conversion and that CRT Tvs don’t exist since a little while.

AVCHD

Sony embraced AVCHD maybe because their software handles it well but what about the rest of the world? Mp4 is the standard for video clips on the internet and AVCHD adds absolutely no feature to it for simple video recording. Files have to be systematically converted, sometimes with commercial software, to be used with mainstream non linear editors, not only most would not recognize the files at double frame rate.

Key Weaknesses

The RX100 has also some key weaknesses that limit its own performance and can’t be cured by workarounds.

Macro Performance

The camera does an awful job at close range and needs a diopter even to shoot basic macro. To shoot super macro you need +12 diopters and this requires high quality lenses to avoid chromatic aberrations in the image. The focus mechanism with diopter is a bit of a mystery to work out at times. Once you manage to focus the image quality is great. However the need for a +5 diopter as a starter makes this set up expensive and cumbersome to handle in water compared to others.

Stabilizer

Sony has adopted a lens shift approach in this camera instead of the sensor shift of the higher end alpha, maybe due to large size of the sensor compared to the camera body. They have then added some software processing in camera but the results are just average. There are many other cameras that do better than the RX100.

Soft Corners at Wide End

I was going crazy looking at pictures taken with different wet wide-angle lens to check which lens was best, at the end of hours of observation I took some shots on lend at the wide end. The issue is not with the wet lenses is with the camera itself, it has very soft corners until at least f/5.6 and not the sharpest corners anyway afterwards. This cannot be cured and is a key weakness that is not so apparent in stills where you can crop quite a lot 20 megapixels but obvious in video.

No Neutral Density Filter

The RX100 has a bright lens and low noise however in video the ISO starts at 125, in many situation near the surface the camera maxes out at f/11 and then starts increasing shutter speeds to 200 400 800 and so on producing scatty mechanical images. Neutral density filters have been implemented for ages in cheaper camera and take away 2-3 f-stops allowing the camera to operate at wide aperture. For some reason Sony decided not to do anything about this. On land this is an even stronger limitation in bright days.

A final remark that I want to include for all those that use the RX100 for still photography that indeed is the real strength of this camera.

Another key weakness is the strobe recycle time not an issue in video of course but creating several issues of missed shots for photographer

In conclusion the RX100 can produce great footage but has some limitation that need to be taken into account.

If you go muck diving on flat surfaces with a couple of diopters and good video lights it is of course all looking wonderful but the situation changes when you cannot lay down as in my seahorses video

With two Inon UCL165AD stacked it is really hard to get some decent footage and due to the large sensor the depth of field at such level of magnification is pretty much zero.

But the limits show up more in the wide angle where the soft corners come up no matter what you do as very seldom you are able to shoot at f/5.6 or higher at depth below 12 meters or 40 feet

Whoever wants to try the RX100 for video please get in touch if you have more questions and happy 2013!!!

Sony RX100 – Tips for underwater video part 9 Wide Angle Shots and Lenses

During my last trip to Raja Ampat I had finally the opportunity to take the wide angle lenses in a real life situation and test that they were working to satisfaction. As some people know I really like my set of Inon AD lenses and although the RX100 has a 28mm equivalent lens I put together a bespoke adapter to reuse the lenses I already have. At the time of the trip I did not have the final prototype but only a pre-release which meant I could no use the fisheye as I had an alignment issue with the dome so I only used the flat UWL105AD.

There are two videos that are of interest one is the Raja Ampat North sites which is below.

In the north visibility was at best fair and I was struggling with the set up as I had not tested the push up filter. What happened is that the black ring created vignetting so I had to reverse the rubber ring on the lens until I could push the filter deeper. In the video you can see clearly a vignetting issue around 3:50 on the wobbegong approach where I had not yet resolved this problem. The video has no image stabilization nor cropping and it shows! There are also occasional soft corners as due to the low level of visibility and lack of light the camera was working around f1.8 or f2.0 aperture most of the time. This does create soft corners on the RX100 when you have something in close focus because I always shoot at the lowest ISO as I have found that increasing aperture and working with high ISO creates a mayhem of chromatic issues.

Anyway once I got a few dives and the problems were ironed out we also moved down to Misool where conditions where much better. This is the Misool video.

Here because of the increase of light and better conditions the image is sharper due to smaller aperture settings. I did not use the RX100 to take any stills as I wanted to focus entirely on video.

Once I got home I bought a fix M67-28AD adapter PRO, that allows you to adjust the AD lens so that the dome petals are in the right place. I tested it in the bathtub with the UFL165AD and the UWL105AD, in terms of vignetting as we shoot stills at 3:2 the working focal length is 34mm on the zoom or 12.8mm.

This is a shot of the bare lens

Bare Port

You can see the characteristic pincushion distortion that the bare port creates, this is the main reason together to demagnification to have a wet wide angle lens note the purple fringing is evident.

This is a shot at f5.6 with the UFL165AD.

UFL165AD 12.8mm

Despite the zoom the lens performs great and it is very wide. If we look at a 100% zoom of the corner

UFL165AD 100% crop

We can see that at this aperture the corners are sharp and there is a very small amount of red and blue fringing.

Let’s look at the Inon UWL105AD

UWL105AD 12.8mm

If we zoom into the corner this is what we get

UWL105AD 100% crop

Also here there is tiny blue and yellow fringing but the results are comparable to some shots I have been sent taken with the Inon UWLH-100 28LD.

Finally this is the UWL105AD with a 16:9 aspect ratio and 33mm equivalent zoom, this is interesting as it is the way the camera behaves in active steady shot without zoom.

UWL105AD 16-9 100 crop

As you can see even better performance in the corners as the port is closer to the back of the lens with the RX100 because of how zooming is implemented.

For who is interested I sell spacer rings and special screws that you can attach to the fix adapter at $45 get in touch if you have some old AD lenses and you want to reuse them with the RX100. Especially as the UFL165AD has incredible performance with stills and nothing can beat the flexibility of this lens and its very light weight in water let alone the speedy bayonet mount.

A final word about filters, in video filters are essential to restore colour however they also take away 1 1/2 f-stop of light so in low light the footage may get too grainy and it is actually better to work only with white balance.

I have heard many people commenting about the dreaded white balance error 9900K message of the RX100. So why is this happening?

It seems that the RX100 cannot white balance if the exposure is outside the -2 or +2 Ev range. If you do continue and ignore the error message you may end up with strange results.

So how to fix this? Contrary to what I said in my post about white balance I have worked out that it is best to set a custom white balance in P mode and not in M, this is because the camera will adjust exposure and never issue an error message. If you want to keep white balancing in M make sure you are within the allowed range of exposure.