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Paul Kay

Testing lenses underwater.

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Since art directors love to 'discover' pictures within pictures, thereby awarding themselves the credit for making a picture out of nothing, they love to crop off-centre. To this end I have now equipped myself with a D800 and 15mm so that I can shoot lots of extra space all round my subject. Of course, the dome port needs to give a sharp image across the frame which mine do with fish-eye lenses. However, if you are the one that needs pleasing, make your own mind up if it's sharp enough.

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post-23126-0-61715300-1344228192_thumb.jpg

 

Here's the latest iteration of my plastic garden mesh test chart, 1m x 1.5m, attached to the bottom of the pool with bathroom sucker hooks. This is the Sigma 8-16 at f16 behind a custom 8" hemispherical dome, If it doesn't fill the angle of view, I simply place it in the corner of the picture. I hook my feet over the edge of the pool to get more stability floating on the surface. Attached to the side of the pool might be better for camera shake.

When I built housings, I was always careful to build the domes so the centre of curvature coincided with the apparent front entrance pupil of each lens. I liked the 18mm f2.8 a lot. The corner looked good to me, but I was looking at a slide with an 8x loupe. With the advent of digital and zoom rectilinear lenses like the 12-24 and 8-16,the corners seemd bad, but then I was looking at them at 100% on a good monitor. I tried the 18mm the other day on the D7000 with the 9" Nauticam dome and the corners were far better than I can get at an equivalent aperture with the 12-24. But on a crop sensor the 18 is not usefully wide. I will be interested t try it on a full-frame camera sometime.

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I have been using this software and charts with another guy in Sydney to test still and cine lenses

http://www.imatest.com/

 

I produces some really interesting results, and really shows where lenses fail on the corners. The guy the owns it (Pawel Achtel) has created a rig that locks the camera in place too so that the results are repeatable. He used it when testing the resolution of Nikonos lenses for his Deep X rig. We will be also testing my Gates Deep Epic with the Tokina 10-17, 11-16, Canon 16-35L, plus we have some other results with Zeiss MkII behind Aquatica domes.

 

I'm sure if anyone is based in Sydney and had any more lenses and port options we could organise something.

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A very inexpensive test chart to do, at whatever size you want will be a simple white 3mm thickness PVC board (I use one with around 1 m wide). Then one simply mark (at the edges) 5 or 10 cm spaces all around. To make the grid (to focus or to evaluate edge sharpness or lens distortion - optical or chromatic) just use black electrical tape. It's quite easy and quick to make lots of horizontal and vertical lines (the grid) and two at the diagonals.

 

Then you can put in in the pool floor or (better) at a pool wall (just make tho small holes at the corners and suspend it with some line and weights (out of the water) at the pool side. You can even use a tripod with a quick release plate so you can repeat results at exact the same distance while you change lens/port/extensions.

 

Cheers,

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This is a great idea. Along with standards for target and shooting distance how about the same for target illumination?

 

I happen to write procedures for work and would be happy to contribute to a writen testing procedure.

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I am new to this forum. I go underwater for more than 41 years and underwater photographer for 20 years. I have a Nikon D300 in Sealux CD300 UW housing. Objectives: Nikkor 10.5 DX and sigma 17-70 macro. I want to buy a wide angle zoom and are very torn between this two: Nikkor 12-24 f4 or Nikkor 10-24 f3 ,5-4, 5. Some of you advise me on the right choice? thanks

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The inclusion of illumination tests will be welcome and useful for someone who is not sure about what to buy or just wants to knows exactly the light quality and intensity of one's strobes/video light.

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Did this thread ever get anywhere.. it seems to have died a death?

 

I am having some dome port dilemmas which a Sea & Sea MDX 5II and a 16~35mm USM L lens and I was hoping to find a conclusion here.

 

There are lots of good ideas here, Is anyone interested in trying to resurrect this?

 

I can knock up a test chart and share it, if we can agree on some content... I propose a combination of the mesh idea of Pete Atkinson and smaller charts positioned at key places.

 

 

 

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The problem of too many lens/domes/strobes on the market will be a challenge to test everything. I've done my tests with my Subal gear and my lens in order to exclude /include some bad/good combinations and to have a good feel of distances/magnifications that each combo can deliver. I've used the test chart I've mentioned above.

 

I don't mind to where some thoughts and some personal conclusions if there are some more people that have done the same thing, so we can start some sort of database.

But of coarse that it will be just a starting point, because I believe that each photographer should do his own test with is own gear.

Edited by Rui_Guerra
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Has anyone tried a 35/1.8 or 50/1.8 in a small dome (like the zen dp-100)? Just wondering...I have a 10-17 but just thinking about how some of my other lenses might do.

 

Yes, I am kinda bored, thinking about upcoming trip, etc :)

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