Tag Archives: fisheye lens

Nauticam bayonet mount for wet lenses

Nauticam entered the wet lenses market with their SMC close up wet lens that was optimized for DSLR.

Then it released the CMC compact macro converter for compact cameras and micro four thirds and finally the Wet Wide Angle Lens I that is compatible with compacts, micro four thirds and also full frame cameras with 28mm equivalent lens.

Up to now all lenses were using the traditional M67 mount as most of the lenses, even the close up ones, are pretty heavy this means going for the dive with the same lens. Nauticam has developed the flip diopter adapter for flat ports to overcome this issue.

Flip Diopter on Nauticam RX100 IV
Flip Diopter on Nauticam RX100 IV

The flip diopter is a good solution for micro four thirds and DSLR but looks rather cumbersome on compacts as the image shows.

I asked Nauticam for a bayonet adapter and specifically if they could develop something for the Inon LD bayonet system that so far has been the reference for wet lenses for compacts and micro four thirds cameras.

LD mount converter on RX100 IV
LD mount converter on RX100 IV

Edward told me that due to the fact that the WWL-1 lens rear element is so large the Inon LD system was not an option so they went off and developed their own system.

M67 bayonet mount converter
M67 bayonet mount converter

I would like to thank Nauticam again for making those parts available before general availability.

Looking a bit closer to it you can see that due to the specific construction with two concentric rings you need a special tool to apply the adapter on the port.

M67 bayonet mount converter The large item is to attache the mount to the port
M67 bayonet mount converter
The large item is to attache the mount to the port

Obviously as the Nauticam lenses use an M67 thread new adapter needed to be developed.

Mount converter for CMC/SMC
Mount converter for CMC/SMC

Nauticam does not use ABS plastic and uses aluminum for all their parts.

Now that the items have a bayonet adapter there is a need for a lens holder to put on the arms.

Lens holder looks too big for a 5" arm segment
Lens holder looks too big for a 5″ arm segment

The lens holder is too big for a standard 5″ segment but looks in proportion with a longer segment.

Lens holder on 8" arm segment
Lens holder on 8″ arm segment

The adapter is larger than the LD mount and a bit big for compacts to the point that even with a tray the adapter tips the rig back.

Another challenge is that this system is designed for Nauticam lens that have protruding rear element so when used with standard lenses there is a gap between the port and the wet lens that can be counter productive, not the end of the world and frankly the Inon system has the same problem. This however means that if you wanted to use this system with a different wide angle wet lens this would be suboptimal.

I am waiting for Nauticam to ship me back the WWL-1 so I can show how that lens performs on this system.

Another observation of course is that if you use this system for wide angle the super heavy WWL-1 and the fact that the adapter only works on a normal segment means your rig will be very heavy in water. I am going to discuss with Nauticam the possibility to have the adapter on a float arm however their carbon arms do not have any mounting point to be used.

Stay tuned for a full review of this adapter with the new 29 macro port that looks very promising for video.

Guide to Micro Four Third Lens and Port selection for Underwater Photography

Micro Four Thirds camera have become increasingly popular for underwater photography especially for macro and close up subjects in the last years.

The micro four thirds standard is shared between Olympus and Panasonic however in terms of underwater use Olympus is on the forefront and in fact it produces their own poly-carbonate housings for all new models.

Nauticam has their own N85 port system for micro four third that as of today has 10 different ports, two extension rings and a large number of focus and zoom gear. You can also buy cheaper 3D printed gear to save a few bucks for majority of lenses.

The other interesting characteristic of the micro four third market is that since the introduction of the 16 megapixels sensors, there have not been any substantial improvement in image quality among the various model, we will have to see what the 20 megapixels sensor of the Panasonic GX8 will bring but all in all the camera choice is mostly one of ergonomics and features.

Olympus is quickly clearing stock but you can still found the OM-D E-M10 out there for £478 with kit lens. The might Panasonic GX7 is now £433 with kit lens. In US you can find both the Panasonic GX7 and the Olympus O-MD E-M100 for $599 with kit lens.

The Panasonic LX100 sets you at £589 in UK and $698 in US really if you are into photography and want a micro four third it is a no-brainer you get a previous version GX7 or OMD EM10 (as you can’t find an EM5 new) and happy days.

Now that you have committed to the camera you are into lenses and ports for underwater use. The Olympus housing costs on average 25% less than Nauticam and has less choice of ports for me really is not appealing so let’s assume we are into Nauticam. What lens or port to choose?

Both the Olympus 14-42 EZ and the Panasonic 14-42 II fit in the Nauticam 35 port and require 3D printed gear to operate. The flat port will be OK for fish portrait and if you already have wet lenses it is definitely recommended to buy the 35 macro port first especially if you shoot video.

Nauticam Macro 35 port
Nauticam Macro 35 port
Deepshot zoom gear on the GX7
Deepshot zoom gear on the GX7

Both lenses do need a wet diopter to shoot small subjects in water as the smallest frame is around 7-9 cm width otherwise.

If you come from a compact camera most likely you have wet lenses and therefore you can re-use them for close range work.

Obviously a flat port for a 28mm equivalent lens is not a solution for wide angle.

First of all at the wide end due to water magnification the angle of view is the same of a 37mm lens which gives a field of view of just 60 degrees. The other point is that you really want to shoot at the tele end to avoid cluttering the background too much and typically in water those kit lenses work only at over 25cm from the port which means they are only good for medium size fish portraits.

The sequence of shots shows that even if the size of the cup is pretty much the same it looks much better at long focal length.

Cup at 28mm
Cup at 28mm

At 28mm you can see the glass in the frame on the right side and the window in the background.

Cup at 50mm
Cup at 50mm

At 50mm with similar size of the cup the glass is half gone and the cup looks nicer less of the window is showing.

Cup at 42mm
Cup at 42mm

at 42mm the glass is nearly out of the frames and the windows in the background is gone.

If you did not have any wet diopters the first additional lens and port to get will depend on your subjects, if you shoot macro you need a macro lens, if you shoot close focus wide angle you need a fisheye lens it is as simple as that.

Olympus 60mm and Nauticam 65 Port (35 + 30 mini extension)
Olympus 60mm and Nauticam 65 Port (35 + 30 mini extension)

The Olympus macro 60mm is the preferred lens combined with the Nauticam 65 port (or 35 port plus 30 extension). This lens can focus 10cm from the port and therefore can be used also in low visibility. Really there is no reason to use the more expensive 45mm Leica lens. The 60mm is great also for portrait work of small fish.

Cup at 60mm
Cup at 60mm

The same shot of the cup at 60mm means we now say goodbye to the glass due to the reduced angle of view. The increased working distance also means a more pleasant perspective.

I hope this explains why for underwater macro we want to shoot with long focal length as this helps us to get rid of the background so a longer lens will always be better than a zoom lens with a wet diopter and it will also give more magnification in case you have really small subjects.

If macro is not your priority and you are happy with kit lens and diopter for wide angle the first option is the Panasonic 8mm fisheye, that since the introduction of the Olympus 8mm pro fisheye has also reduced in price.

Panasonic 8mm Fisheye and Nauticam 4.33
Panasonic 8mm Fisheye and Nauticam 4.33″ Dome Port

This lens works best with the Nauticam 4.33″ dome port. If you shoot in 3:2 format you can also try the Nauticam 3.5″ wide angle port that makes the set up even smaller however there are no substantial improvements on how close you can get as the strobes will fail to lit properly anything that is right on the port without risking to see the strobe lights in the frame. The 3.5″ port will vignette in 4:3 image format though some users report success.

EDIT 7 September 2015

The issue of the 3.5″ port has been put forward again with the argument that it allows you to get closer than the 4.33″ dome with the Olympus EM5. I do not have an EM5 but I do have a Panasonic GX7 the end of the dome is 9 cm away from the focus point and this means that the dome allows you to get closer than the minimum focus distance of the lens of 10cm. As the dome is shorter than the minimum focus distance on the GX7 the 3.5″ port does not bring any benefit. Furthermore as trays are in general around 30cm you need to be around 15 cm anyway to be able to illuminate the subject properly with edge lighting, in virtue of this I remain convinced that the 3.5″ port does not bring any real benefit except is a bit cheaper and may vignette.

So your starter kit if you upgrade from compacts of you own a close up lens is Macro 35 port followed by Olympus 60mm and mini extension ring 30 or Panasonic fisheye 8mm with 4.33′ dome for wide angle.

Wide angle zoom lens are less of a priority but the choice is between the Olympus 9-18mm and the Panasonic 7-14mm bearing in mind that if you had a wet wide angle lens you may not even bother getting an intermediate wide angle zoom lens.

That’s all for now hopefully this will cover most of the ground for all new micro four third underwater shooters with kit lenses!

Red Sea Workshop with Alex Mustard – Part III Sunbursts and the Caves

On the early morning of Day 3 we left the Thistlegorm for Ras Mohammed.

Dive number one would have been on Ras Zahatar, this dive site has some great opportunities for sunburst shots in the early morning but generally not a lot of fish as the location is quite sheltered and there is never too much current that I recall.

There are also some very nice gorgonian fans around the 22 meters mark however as soon as we jumped in it was clear it was going to be a competition to have some of it. Besides not having made clear arrangements for modelling with anyone it was going to be a quite technical session.

Since the arrival of digital sunburst shots have proven to be problematic for DSLR and mirrorless users. The issue is with the sunball itself there is an issue of highlights when you try to shoot a coral reef with the sunball in the frame and you are using a shutter speed of 1/250th or 1/320th that are typical DSLR sync speed.

Mirrorless cameras do even worst as usually the base ISO starts at 200 that makes it really difficult to capture this shot.

So the key is to put the sun behind something or have the rays in the frame but not the sunball. Something like this to give an idea

Soft Coral
The sunball just behind the soft coral gives a nice glow so even with a 1/250th shutter and f/8 at ISO 100 is possible to capture a captivating scene.

Few meters away there is a gorgonian with a red soft coral on top that is really exciting to see at naked eye. To me this reminds of a frogfish head profile. It is impossible to capture this scene at 1/250th f/11 ISO 100 it is just too bright you need to reduce at least two stops to get the sun properly however if you did that on a DSLR you would be shooting at f/22 and it is near to impossible to properly illuminate the coral with your strobes at the distance required.

That is where our RX100 compact comes to help as you can sync your strobes at 1/2000th this should give a black background around the coral, the coral properly lit in the foreground as I had the strobes at full power and the sunball in the frame as well without too  many glowing highlights, this is the resulting shot
Sunburst
Note that a model would not be visible in this shot and fish would be colorful only in front of the coral or close by anyway as discussed there was not fish to model for me and this was just technical entertainment. The image is quite strong but the lack of fish makes it less interesting.

I found some cooperating clown fish on this dive however they are those with the dark eyes so despite the eye contact the shot is not as strong as it would be with a better subject
Look Right in
This is taken with a single Inon UCL-165 a luxury of having a compact and being able to wide and macro on the same dive.

Anyway I was happy with the sunburst in the frame so that dive was well worth it.

Dive two was at Jackfish Alley, and proved to be the most entertaining of the day. Who knows this dive sites knows that there are two caves, the first is wide but very dark and at certain times has turtles inside. The second is really narrow but has few cracks the provides a cathedral light effect best experienced in other site of the Southern Red Sea. Anyway we got the briefing and Dr Mustard was going to be marshaling the queue of photographer in cave number 2.

Being familiar with the dive site I knew that cave 2 is quite narrow even for normal diver let alone this big troupe of photographer so I mounted my tripod legs on the tray with a view of working in cave 1 and then move to cave 2 after the chaos was over.

Well it was real chaos as you can see from the feature image divers in the way, bubbles silt, in short it was a mess.

So I spent some time in cave number 1, this cave is really dark and you can’t really shoot handheld. In cave number 2 you can use speeds of 1/25 or 1/30 up your ISO  and put the camera on a rock whilst you take the shot, in cave 1 this results in darkness unless you go to 4 digits ISO.

So my shot on cave 1 is taken at 0.4″ f/4 ISO100.
1st Cave@Jackfish Alley
The shot is taken with the camera on the tripod using self shoot so that there is no shake from the hand pressing the shutter, this means the picture is sharp as it can be and due to low ISO also very noise free. Unfortunately fish did not feature in the shot so this is again a fairly technical shot that is not as strong as it could be.

There were other interesting opportunities in smaller cracks like this one that I like quite a lot though is not a sensational shot.
Window
I like the fact that the two snappers are one silhouette and the other full color.

After the shambles of dive 2 we moved to Shark Reef where the first dive was really more to acclimatise with the site so won’t bore you with the pictures for that dive.

In the evening the sunset dive was at Ras Katy that would have been our regular evening spot from there onwards.

On day one I was playing with dapple light and reflections

Dapple at Ras Katy
Dapple at Ras Katy

 

This is me taking the shot above

Interceptor Shooting Dapple

As you can see I am nearly at the surface thanks to Damo for this picture.

Near surface can also be interesting like in this case

Test Shots dapple Reflections
Test Shots dapple Reflections

Here you can see part of the Snell windows together with the reef and the sunball. This shot can be made much more interesting if you focus on the reflections.

Anyway this was the end of day 3 of diving next post will be about Shark Reef and the schools of fish.

Snell Windows with your compact camera

Snell’s window is a phenomenon by which an underwater viewer sees everything above the surface through a cone of light of width of about 96 degrees [From Martin Edge: Underwater Photography].

During my last Gapapagos Trip there was a bit of an issue in terms of photography subjects, in essence most of them were fairly big like sharks, turtles, eagle rays and of course divers.

After a while shooting or trying to shoot those uncooperative models I had the idea to try and do different things such as silhouettes and Snell windows. You can also combine both as we did in this case.

So what do you need to shoot image of a Snell window:

1. A lens that is wide enough, you need a bit more than 96º field of view to take the whole window

2. Something interesting on the surface (if you have calm water you can see right through)

3. An interesting subject as silhouette to contrast the clear water if there are waves and you can’t easily see through.

A normal flat wet wide angle lens for our compact camera is not sufficient to capture the snell’s windows as in this example

Safety Stop
Divers at Safety Stop – taken with Inon UWL-H100 at wide end

Take into account that even with a fisheye lens on an SLR you can’t capture the Snell’s window on the vertical axis as the field of view will fall short a few degrees.

With a compact camera a semifisheye lens will capture the edges of the window if correctly aimed on the diagonal and horizontal dimensions and will fall short on the vertical.

Snell to boat
Snell window divers exiting the water or ascending – UWL-04 semi fisheye lens Canon S95

I am reporting some of the calculated field of view for the most popular lenses at present for compact at 3:2 image format

Wet Lens Diag FOV Hor Fov Ver FOV Flare/Ghost
UWL-04 151.95 123.22 79.85 Ghost Possible
UWL-100 28AD 149.01 120.97 78.48 No
UWL-28 160.56 129.75 83.81 Both
UWL-H100 157.85 127.71 82.58 No

 

All those lenses will take a good Snell’s window I have not tried the UWL-28 and I have some concerns this lens may flare as it usually does but I do not know for sure.

Both the Inon lenses produce sharp images with no defect.

In general small sensor cameras like the Canon S series will work fine with the fix/idas lenses and should produce good results also of normal shots through the water.

Using the UWL-04 or UWL-28 with large sensor cameras like the RX100 there could be a sharpness issue a larger apertures so make sure you close that at f/8 or smaller instead of using the shutter speed to balance exposure if you want to go through the water.

Snell’s windows are uncommon with compact camera shooters as they are considered an advanced subject but they can be taken. I will be taking more in a next trip to Egypt I hope for calm surface conditions so I can go through the surface with the shots. Failing that this is very easy to practice in a swimming pool.

Have fun shooting snell’s windows!

Tuition Day with Martin Edge

During the London Dive Show I attended a talk from Martin where he covered a number of shooting situations and how to deal with them in terms of composition and settings.

There was a promotion for a two for one tuition day with him that my buddy was keen to take so few months later we made our way to Dorset for a day of underwater photography with Martin.

This will be my first day of shooting with the RX100 Mark II albeit in a pool with my new arms and lenses so I was looking forward to it.

We arrived in Poole the night before and got ready for an 8.30 start with Martin.

We started off with a review of some basic exposure concepts and then looked at competition winning pictures and trying to identify what makes a wow picture. It was extremely useful!

Afterwards we went through our trips pictures so he could see what needed improving. Then look at what was needed for the next trip.

With that in mind we set up to jump in the pool to take some pictures the objective was to improve my buddy close ups and portraits as apparently her wide angle is as good as it gets with the Canon S95 used see featured image on this post.

Pool conditions were low visibility and plenty of suspended particles as the pool is used for kids swimming lessons let me give you an idea!

Pool Conditions
Pool Conditions

The first task was to shoot a frog with a view of eliminating shadows in its mouth. Start with one strobe and finish off with two.

Frog at 28mm
Frog at 28mm

The frog with the bare port gives you an idea of the size and the complexity of the task with one strobe. There are shadows in his mouth.

Frog at 50mm
Frog at 50mm

I then shot a portrait at 50mm, the reason why you see shadows more on the left is because I set the strobe at different powers.

Frog single diopter
Frog single diopter

The magnification of the RX100 is little so I went on with a first Inon UCL-165 and full zoom at 100mm equivalent. Note that everything is pretty much sharp at f/11.

Frog Double Diopter
Frog Double Diopter

With two Inon UCL-165 focusing on the mouth will result in this and the eyes being in focus and the rest blurred because of lack of depth of field.

Octopus fisheye
Octopus fisheye

I then moved to an Octopus rich of textures. I took the first shot with my Inon UWL-100 28AD with dome.

Octopus at 28mm
Octopus at 28mm

The same octo at 28mm fills the frame much more of course.

Octopus at 50mm
Octopus at 50mm

The Octopus at 50mm looks even better. I have topped up the lighting on this one.

Octopus single diopter
Octopus single diopter

I then took this guy with a single UCL-165 note the depth of field insufficient to keep the back of the head in focus, results though are exceptional.

Octopus double diopter
Octopus double diopter

With two close up lenses we go back to the depth of field problem even at f/11.

I thought I had at that point nailed all focus and strobe issues, especially considering I shot with single auto focus, I did not bother using manual focus at all with exception of some double diopter shots.

I then tried a few surface reflections with the fisheye this being the best.

Falcon Fisheye
Falcon Fisheye

You can see the outside of the pool and the windows on the top.

Family Fisheye
Family Fisheye

Afterwards made my own composition of statues for a fisheye shot that I think came out very well. The Z240 performed extremely well in both TTL and external auto as well as manual.

Child with dog
Child with dog

Martin asked me to have a go at the child with the dog as it is extremely difficult to lit up properly.

I went for an alternative strobe placement with light from the bottom as if it was in a gallery. He was impressed with the results.

Lion Mouth Single Diopter
Lion Mouth Single Diopter

To finish off my last task was the tongue and eyes of a lion that I shot with a single UCL-165.

Overall a great day and I definitely recommend you the tuition day with Martin. He is a great person and extremely good at teaching I can see the benefits my buddy had right away.

Lessons learned on the RX100

There were a few things that I learned about my RX100 still rig mode that I want to share with you.

  • The autofocus is incredible. I even used this for macro. If the camera does not focus is because you don’t have enough depth of field and that is it.
  • Best macro performance is with a single diopter and also had a benefit of an increased working distance, this means the shots will need cropping for extremely small critters
  • Two diopters resulted in near bokeh with less than 1mm in focus and difficult to autofocus (though the LCD is great and I could see if things were in focus or not I think this is personal and I would recommend DMF to others)
  • Performance at wide angle with the UWL-100 28AD with dome is stellar
  • Inon float arms (I used two 6″ segments) were perfect with lens holders on it.
  • Inon Z240 twin set with one in TTL and the second in external auto delivered creative lighting without headaches, remember to buy the AUTO diffuser that does not come with the strobe
  • Strobes in manual allowed for even more creativity and the level of precision compared to sea and sea was staggering
  • Despite pool conditions the RX100 focused well in low light and much better than the Canon S95 that was returning focus error on the same exposures. I will not bother having a focus light with this camera and only have a single sola on night dives

That’s all for now any question just drop a comment

 

Which Fisheye Lens for the RX100?

Recently I have started building my RX100 Mark II photo rig and as part of this I had to choose a wet fisheye lens.

For video I do not like the barrel distortion of a fisheye lens, and on top of that you can’t attach a push on filter to a dome so for me those are two big no when it comes to the RX100 and its white balance error woes.

For still instead I shoot only RAW never white balance in the water and a fisheye lens is required so that I can have human size strobe arms when shooting close focus wide angle at distances between 0 and 16”.

I will focus my discussion on the Nauticam housing starting off with a 67mm thread and go from there.

Currently there are 3 options on the market for the RX100 and come from 3 difference manufacturers. I will go through each one briefly and then we will look more in detail at the two I consider best.

The first lens is the FIX UWL-28M52R, this lens is the smallest of all and was originally design to nicely complement the form factor of a Canon S100 in a fix housing, hence the 52mm thread. The lens has a magnification factor of 0.41x and a diameter of 126mm including the hood, the lens is actually much smaller at around 90mm.

Fix has introduced this lens in 2011 as a replacement of the previous UWL-04 model for two reasons, the first is to have a smaller lens as the UWL-04 was a too big in comparison of the housing, second probably cost though this was never declared. However other people tests and plenty of in water images show that this lens is actually worse than its predecessor. It is also smaller making split over-under shots more difficult.

When Fix withdraw the UWL-04 the manufacturer of the lens continued the production and finally put it back on the market under the i-divesite brand. This lens is the same as the Fix except the label.

Both lenses the old and new fix are pretty much a copy of the old Inon UFL-165, both made of 4 glass elements and an acrylic dome with hard anti scratch coating.

Here is a set of shots for the UWL-04 and the various parts in the box.

UWL-04 Box
UWL-04 Box
UWL-04 package contents
UWL-04 package contents
UWL-04 Hood Cover
UWL-04 Hood Cover
UWL-04 with ring
UWL-04 with ring
UWL-04 back lens
UWL-04 back lens

The last lens on the market is the Inon UWL-H100 with dome. This lens is available with an M67 mount and with an LD bayonet mount. Due to the size and weight of those lenses in water (100 to 500 grams weight and diameter between 125 and 152 mm) a bayonet mount is my preferred choice.

The Inon lens is actually made entirely of glass, the dome is the biggest at 115mm for the lens with an overall diameter of 132mm. This lens is the more suitable to split over under shot and promises a better contrast and less flare than the other lenses with plastic domes. Inon had some concerns about plastic domes and flare following the performance issue of their UFL165 so went for 100% glass for all next generation lenses.

Vignetting with RX100

In certain conditions all those lenses actually have some vignette in water. Despite what you read on shop websites if you look at real pictures there is a bit of that.

The Fix and Idas lenses have an issue with the lateral hood, the shots look clear of vignette on land but in water the magnification of the hood petals makes them show in the picture, we are talking a minimum crop required around 1% and usually on one side. The Inon UWL-H100 has a different issue and it gives in specific situations a tiny bit of vignette in the corners, around 2% of the image needs to be cropped. Both lenses will not vignette when image stabilization is deactivated, the image stabilizer tends to aggravate the issue so if you are obsessed switch it off and try to be steady shooting at speeds of 1/125th of a second or faster. For example on the amount of vignette see the following

UWL-04 note the vignette left center
UWL-04 note the vignette upper left center
DSC02620Corrected
UWL-28M52R again vignette on the left upper side
SONY DSC
UWL-H100 vignette in left corners

I would like to thank Alex Tattersall, Tamas Plotek and Troy Williams for those in water pictures.

Inon UWL-100 28AD

Inon has another lens that is suitable for the RX100 and is the UWL-100 28AD a lens originally introduced in 2005. This lens has a smaller rear element than the UWL-H100 and it is not suited to many cameras with a very large lens aperture. The RX100 however works fine with this lens and contrary to the newer UWL-H100 this lens does not vignette in water or on land. The reason is that the de-magnification of this lens is less than the newer lens 0.63x vs 0.6x. This is the lens I have chosen for my RX100 Mark II and I will compare it here with the UWL-04 I have recently bought for my Canon S95. There are no substantial differences between the UWL-100 28AD and the UWL-H100 in terms of optical quality.

Here are few pictures to compare the lenses, take into account that whilst the weight on land is comparable, once in water the Inon lens is heavier at 400 grams versus 160 of the UWL-04.

UWL-04 UWL-100
UWL-04 UWL-100
UWL-04 UWL-100 profile
UWL-04 UWL-100 profile

 

Image Quality

There is no need to take the lenses in water to compare image quality generally things get worse in water not better so it is sufficient to take a shot on land and see how that goes to have a relative comparison between two lenses. In this example the cameras are on a table exactly in the same position when the shots are taken and use the same settings of ISO, aperture and shutter speed.

The first impression is that the UWL-04 is a tad wider but more rectilinear, the Inon lens has definitely more barrel distortion and is more a fisheye than the UWL-04 is. Looking at mid upper frame you can see that at diagonal level the UWL-100 28AD is actually wider than the UWL-04 that remains wider horizontally. This means looking at the specs can be misleading and results depend on the camera lens combination.

So how do these lenses compare when it comes to corner sharpness and flare?

This is a shot with the UWL-100 in very harsh conditions with sun-rays hitting the lens directly on the dome, you can clearly see the ghosting that comes from it.

UWL-100 Sunlight
UWL-100 Sunlight

This is the same shot in the same place taken with the UWL-04 you immediate notice that the ghosting has a green color. This is most likely due to lack of anti-reflection coating inside the dome and to the color of the inner lens mount.

UWL-04 Sunlight
UWL-04 Sunlight

Looking at the image the picture taken with the Inon has a clearer ghosting but then is sharp in the rest of the image, the UWL-04 image has flare around it with comparable less contrast as we move from the center to the corners.

The other two images are a crop in the corner, you can see that despite the high level of distortion you can still distinguish some detail of the small grass bush in the Inon image, the UWL-04 instead is softer and the bush is basically a uniform green shape with no detail at all.

UWL-100  Crop
UWL-100 Crop
UWL-04 Crop
UWL-04 Crop

Update 28 Feb I have taken some shots with the UWL-H100 and the UFL165AD here are the overviews

Inon UWl-H100
Inon UWl-H100

The UWL-H100 is actually wider than the UWL-04 with the Sony RX100 despite the advertised 144.5 degrees versus 165 of the UWL-04. Has the same level of detail of the UWL-100 28AD

Inon UFL-165 AD
Inon UFL-165 AD

The UFL165AD flare issue is obvious in this shot both lower corners are compromised, this confirms why the UWL-04 is the best option for the Canon S series in terms of flare or vignette.

Looking at the UWL-H100 crop you can see the vignette more apparent in the upper corner and the image sharpness, it is possible that with an M67 mount there is no vignette with a Nauticam housing in most conditions, with LD mount you need to turn image stabiliser off or crop. Considering this is the widest lens it is not a big issue. Once cropped the UWL-H100 gives still the widest field of view but someone maybe be annoyed by this. Zooming in results in the same field of view of the UWL-10- 28AD

Ergonomics

The Inon lens presents the benefit of a bayonet mount, although the lens is heavy it can be removed in water quite easily, the UWL-04 has some issues whereby the adapter ring would unscrew instead of the lens, this can be avoided fixing the adapter on the lens but then there is no lens cap that would fit the larger M67 screw in the box so you need to buy one yourself, generally the size of the petals make this lens impossible to handle in water and is more like diving with a dome port. It has to be noted though that you can zoom through with both lenses so still continue and take portrait shots and close ups. Obviously for real close or macro you do need to take the lens off which with the UWL-04 you can basically forget.

Cost

The UWL-04 costs $460 in US as shown here with dome cover and step down ring, and £362 in UK. The Inon UWL-100 28AD with dome costs $907.80 including an M67-ADF adapter in US and £775 in UK. All in all the Inon is around near to double the price of the UWL-04. The UWL-H100 is even more expensive at $970 for the M67 version and $942 for the LD bayonet, you then need to add $160 for an adapter for a total of $1,102 that is a lot of money another reason for the 28AD version.

Conclusion

The Inon is the best lens for the RX100 and there is no doubt, however it costs more than double the UWL-04 not everybody will be able to afford it. The UWL-04 is a somewhat basic lens that lacks sophistication and is essentially not removable in water but comes at a great price. In terms of field of view the lenses are very similar with the Inon lenses having more fisheye distortion and a wider diagonal field of view. The UWL-04 is more rectilinear and as consequence has less field of view diagonally. Only one lens has zero vignette at the wide end and this is the UWL-100 28AD with dome.

In Water Shots

I don’t have shots in water yet pending my next trip but two galleries that give an idea are here:

For the Inon UWL-100 28AD with dome look at my Red Sea Gallery https://www.flickr.com/photos/interceptor121/sets/72157645375379256/

For the UWL-04 instead this is an excellent one

http://www.flickr.com/photos/13930495@N06/sets/72157636133030726/

The second shooter has got rid of the UWL-04 to buy an Inon as not happy with corner sharpness!

My perspective is if I look at the pictures I can barely tell the difference however looking close the Inon lens is sharper at one f/stop less, the UWL-04 requires stopping at f/8 or smaller, you can happily shoot f/5.6 with the Inon which means you need less light and less strobe power.