Full Frame SLR wide angle corrector port tests

Finally I had the opportunity to test the filter in a pool, in a more controlled situation. I also tried the Canon 16-35mm F4 IS, IMHO a better corner performer than the 17-40mm I was using in my previous tests. I have tried different combinations (230mm glass dome port and Sea&Sea Fisheye "acrylic" port) and I got slightly better results with the 230mm glass dome.

The improvement is near the claimed 2 stops, which is very good news. At F8 the corners are very good and at F11 they are perfect.

The 16-35 IS is known to be a much better corner performer than the 17-40 at the wide end for topside use so not surprising under water. I have now standardized on f/11 for most of my underwater photography with wide angle lenses as I have found this to be best; mostly done with the 8-15mm lens at 15mm. I have shot at larger apertures in 1/3 stop increments - did quite a few at f/9 but lately I prefer f/11. I vary the ISO and flash power to work with f/11. This has meant using fairly high ISO when shooting in Alaska. In 2015, frequently at ISO 12,800.

One thing to consider is that the shape of the virtual image varies with object distance. It is only spherical in shape when the lens is focused under water at apparent infinity. That means our results should vary somewhat unless we all focus at the same distance. I was shooting very close - at around a half meter; the eggs on the bottom may have been slightly closer. The apparent correction provided by the ICL may be different for a distant subject.

I have a attached a shot to better explain how I took the shot I posted above. The housing is on the bottom of the stream. The upper lens shade of the superdome is out of the water. The length of the camera pole is about 1.5m - a now destroyed (for other use) monopod. There are two pairs of salmon on the left side of the pic. One pair with dorsal fins poking out. Another pair can be seen through the branches near the housing. These may have been two of the males fighting over the female that I was attempting to shoot.

Tom

I would be interested to try this Sea & Sea corrector lens. Can someone please tell me if this is a currently available Sea & Sea product and what Sea & Sea's designation for it is? I would want it in the appropriate size for use on Nikon's 16-35mm f4 VR lens. Does anyone know where I can buy one?

Thank you,

Fred Bavendam

I would be interested to try this Sea & Sea corrector lens. Can someone please tell me if this is a currently available Sea & Sea product and what Sea & Sea's designation for it is? I would want it in the appropriate size for use on Nikon's 16-35mm f4 VR lens. Does anyone know where I can buy one?

 

Thank you,

 

Fred Bavendam

Reef Photo and Video has them; that is where I bought mine.

See Sea & Sea's web pages for more info: http://www.seaandsea.jp/products/digital_slr/accessory/lenses/

and http://www.seaandsea.jp/products/system_chart/internalcorrectionlensa.html

For those interested, I have posted different f/stops samples with and without filter in my website:

http://uwaterphoto.com/?p=839

For those interested, I have posted different f/stops samples with and without filter in my website:

http://uwaterphoto.com/?p=839

Nice job! I have been high and dry and not been able to do more testing since we have had either gale or storm force winds with concomitant rain, adding up to about 0.2 meters (half of this yesterday) this week so far with more to come. I am thus keen on your results as well as those of Adam!!

The clouds parted part way today allowing me a chance to do some more testing. I went to a nearby creek. Water was about 1 meter higher than last week where it enters the lake. I found a spot to setup. Housing was on the bottom (what is normally lakeshore - note land plants in the pix) - used a 45 degree finder to shoot. Images needed quite a bit of PP since water was tannin stained. I used ETTL to enable rapid shooting without additional fiddling because the water was quite cold - both my hands got numb in the few seconds it took to place my watch into the scene. Only my right hand fingers were wet to do the actual shots as I found a rock to place my left hand on to prop me up. I used a single Seacam 150D strobe placed about 0.5m above the housing at 12 o'clock - same setup I use use for my salmon photography.

My goal here was to test the Seacam Wideport which I am often obligated to use instead of the Superdome because the water is not deep enough. This first batch is @ 16mm at f/5.6, f/8, and f/9. The strobe output was near 100% at f/9 so I stopped here - the water turbidity being a factor limiting light. Focus is on my watch.

f/9:

f/8:

f/5.6:

I next zoomed the lens keeping the housing at a fixed location (did minimal touching). I used the maximum focal length while keeping the watch within the focus area. Apertures included here are f/5.6, f/8, and f/10. I was able to stop down a tad more since reflected light off the watch affected the ETTL (larger in the picture than at 16mm).

f/10:

f/8:

f/5.6

I shot the final set of shots after tweaking the housing position so my watch would be in the focus area when zoomed to 35mm. I was able to use the same apertures as the previous set.

f/5.6:

f/8:

f/10:

These results of shooting the 16-35 IS with ICL in the Wideport were much better than what I was able to do without it (past experience). f/8 looks reasonable - some softness at the very edge. The tree seeding to the right of my watch was sharper the more the lens was stopped down in the firsts two sets whereas the sharp part of the blade of grass to the right of this seeding (in the third set) was extended towards the edge of the field when stopped down more.

Very interesting discussion!

Once again i am in the shoes of the guy who's wondering how to spend the money he doesn't have on expensive underwater gear...

So my mind wanders around a Nikon DX camera, and i discared FX because of the bulk of large housing + large domes.

Back to Alex's original experimentation on corrector lens, i understand the main targeted benefit is to get better corner sharpness than on a dome port.

Another benefit that i foresee is the more reasonable travel size/weight: i would presume the corrector lens to be much smaller & lighter than the 9" super dome, am i right? I'd be interested in the difference in weight.

I am also wondering whether the concept could apply to DX rectilinear lenses, any reason why not?

cheers

Nicolas

Another benefit that i foresee is the more reasonable travel size/weight: i would presume the corrector lens to be much smaller & lighter than the 9" super dome, am i right? I'd be interested in the difference in weight.

Absolutely. The dome is a bad concept, exchanging a certain set of aberrations to others. The only right way is to use optics, designed for in-water use. These are nikonos lenses and corrective optics for dry lenses.

I am also wondering whether the concept could apply to DX rectilinear lenses, any reason why not?

There is no argument against. The WWL-1 with a 28mm eqivalent DX lens (20mm) and a "tight" flat port should give you better results than most dome configurations.

We need a change of mindset and traditions, domes have their place - for nice over-unders, besides, no reason to carry around the world, exiling those valuable sandwiches and other useful stuff from your hand luggage.

I'd be interested in the difference in weight.

Right now, the wwl option is heavier (WWL1+flat port=2kg, 9" acrylic dome 1.5kg), but probably later iterations of the WWL and maybe competitor products will include more advanced elements (aspheric, SD) thus lower the weight a bit.

 

Absolutely. The dome is a bad concept, exchanging a certain set of aberrations to others. The only right way is to use optics, designed for in-water use. These are nikonos lenses and corrective optics for dry lenses.

 

There is no argument against. The WWL-1 with a 28mm eqivalent DX lens (20mm) and a "tight" flat port should give you better results than most dome configurations.

 

We need a change of mindset and traditions, domes have their place - for nice over-unders, besides, no reason to carry around the world, exiling those valuable sandwiches and other useful stuff from your hand luggage.

 

Right now, the wwl option is heavier (WWL1+flat port=2kg, 9" acrylic dome 1.5kg), but probably later iterations of the WWL and maybe competitor products will include more advanced elements (aspheric, SD) thus lower the weight a bit.

thanks Tamas for the well explained response :-)

Perhaps someone with this corrector lens could measure the curvature of both surfaces, to determine whether one or both are aspheric. The way I would do this is to scribe approx. curvature on a piece of thin card, cut it out, and see if it fits flush to the surface of the lens. Then do another, making adjustments till it's a perfect fit.

In New Zealand 20 years ago I had coated plano-convex dioptres made which were said to flatten the curvature of field, but B&W diopters always seemed to give better results.

Hi Pete,

I had good look at mine and it is a meniscus lens, with the concave side side facing the dome, and the convex side internal. If I was to guess, I would guess it is equi-meniscus.

This explains how it is a corrective, rather than a simple closer focusing, lens.

Sea&Sea designs them specifically for use with their own dome ports, so there is some experimental data needed with other ports. The curve radius of the port is the crucial element and not all of them are the same....

My feeling is that I gain 2-3 stops with the 16-35mm behind a Seacam Superdome.

All the best

Adam

I am amazed! Concave side towards the dome!! I will try to find one at ADEX to look at it! Thanks.

Has anyone tested Sea & sea internal correction lens on a crop sensor camera?

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On 7/9/2015 at 1:12 AM, Alex_Mustard said:

Hi Elmer,

As soon as news is public I will post it here. They are not my secrets to share. Although I have been communicating my test results freely - as this is not a commercial project for me - and I am keen to share what I have been learning.

 

Alex

Hi Alex,

Any updates on this project? I just found this thread and I also have this corrector lens set. 

-Paul