How would an 8 inch dome perform with an 16mm FF equivalent fast lens?

Hi there,

I am planning to use the Zen 8 inch dome and I am worried about corner sharpness at the widest aperture of the lens. My setup will be consisting of a FF Canon 16-35mm 2.8 LII lens with an ultra speedbooster for Sony super 35mm sensor. The lens will be equivalent to 11.36mm FF with f2 aperture.

I will be shooting in ambient light (no video lights) and at the widest & fastest f2 aperture most of the time.

The closest I found was a good review by Ryan Canon for Zeiss Touit 12mm 2.8 behind a 7 inch dome. But that was still photography and I "think" is taking with flash at medium f-stops.

http://www.reefphoto.com/kb.php?id=63

I would appreciate any help.

Salam Thani, with the speed booster, it's actually just a bit over 16mm FF equivalent. Remember the S35 sensor is approximately 1.5x crop. At 16mm at f2 on FF, you will have soft corners from the adapter+lens anyhow, and behind the dome it will be even softer I'm afraid. No such thing as a free lunch. I would keep it at f11 and above, especially if you want to pull still frames out of the 4k.

The 8" dome will work albeit with a negligible soft corner that disappears with motion. The distortion can be distracting though so I'd be more worried about that when shooting seascapes.

Hi Drew, Thanks for correcting me. The crop factor is actually 1.39 and I totally forgot to multiply by it. So here what I think the equation off Speed Booster For Canon EF (full frame lenses) which has a magnification of 0.71 and sony Super35 mm which has a crop factor of 1.39:

FF lens focal length x Speed Booster magnification x Crop factor = Full Frame equivalent Focal Length

In my case at the widest 16mm:

16 x 0.71 x 1.39 = 15.79 almost 16mm FF

At the full Zoom 35mm:

35 x 0.71 x 1.39 = 34.54 almost 36mm FF

Therefore, the speed booster from Metabones gives me the advantage of a FF lens on a Super35

It also makes the lens faster by one f-stop. My 2.8 becomes a 2.0

I have asked on the Sony community about the corner sharpness when using the speed booster and got a confirmation that it is good. And as you've said for motion/video it will not be noticeable.

With this setup, in air, the lens doesn't show distortion at the widest and it produces a little wider feild of view than the 12mm Zeiss.

Do you mean the distortion will be more obvious behind the dome in water?

Kevin Palmer, who is a very supportive customer oriented person, from Reefphoto has replied to an email I sent to him yesterday clarifying that he took those stills with the Zeiss 12 mm behind a 7 inch dome at 5.6-8f. Now the 12mm on 1.5 crop factor is equal 18mm FF. The images that he produced were amazingly sharp and distortion free.

Please remember I am not using video lights and that I'd like to take advantage of the fast lens I am using. I know it's quite a challenge.

Drew, is it possible to correct the 11mm to 16mm in the post title?

Thani, S35 film is 1.39x crop. The Sony S35 sensor is 1.5x AFAIK.

As for corners, I can only go with my own experience and dome physics. Extreme corner softness is a reality especially with fast apertures. I've not seen Kevin's pics, but the physics is sound. However, it's not that big a deal so if you can't notice it, then it's not there!