Gear for wrecks

Hi everyone,

This is my first post and I would like to ask you for advice. I have many years in photography but few as underwater photographer. Underwater, mainly like angular photography. Especially shipwrecks. I usually photograph in Spain at depths of 50-60m with a Lumix GX8 (M4 / 3) + Zuiko 8mm f1.8 + nauticam + Zen 170mm. Sometimes I use a Leica 15mm 1.7 that works perfect with that dome. But basically I use 8mm for wrecks. The advantage of that sensor with that optics is that it allows me to shoot at f2 or even f1.8 at -50m at 250 iso (this is not as bright as the Red Sea) and I get sharpness throughout the frame, including the corners . I'm thinking about acquiring a nauticam for my 5DmkIII and a Sigma 15mm to get a better definition for a project I'm working on. 5D sensor will offer me more quality but I have some doubts. I'm going to lose depth of field, f stop .. I can increase the ISO but I'm not sure if I'll get a significant win by forcing it to shoot at least f8 to not have terrible corners with what it entails to increase the ISO and lower the speed shutter. My idea was to buy the same dome ZEN 170mm. Nauticam recommends the dome 140mm for the sigma 15 but I think I will get better definition in the corners with the ZEN.

Fisheye lenses are not so sensitive to dome size compared to rectilinear wide angle lenses. The issue is the curved virtual image of a dome port. With a rectilinear lens the corners fall outside the depth of field available due the edges being physically closer to the camera because of the curved virtual image located very close to the dome. A fisheye has a 180° field of view at least diagonally this means it is rendering a curved image any way and so it doesn't have issue with DOF when projecting a curved virtual image onto the sensor. what will be important is to use the the correct extension with the dome to place the centre of curvature of the dome at the same location relative to the lens entrance pupil. I don't see an advantage getting the 170mm ZEN dome as it's not big enough for rectilinear wide angle on full frame so would be useful solely for the fisheye lens.

If you were to use the Zen 170mm N120 dome with N85-N120 adapters you could also use it with the GX8 to house lenses like the 7-14mm f2.8 Oly lens so you would get more use out of it that way. I don't believe the images would be any better than those obtained with the 140mm Nauticam dome.

Hi Gonzalo,

I cannot comment on the large sensor, but i am using Canon 8-15mm fisheye (and also Zuiko 8mm 1.8) with EM5-II (MFT sensor), both in Zen DP-170 and Nauticam 140mm domes.

Generally the difference is that the Zen 170 is a wideangle domeport (larger radius (r=110mm) but not full hemisphere (correct positioning of FE lens not possible) => larger virtual image) and the Nauticam 140, a real fisheye domeport (smaller radius(r=7mm) and full hemisphere (correct positioning possible) => smaller virtual image).

At present I could not say which domeport produces better results, both produce very good results, but maybe it is the Zen 170 is slightly better (correct positioning less important than size of virtual image).

At the wide open apertures that you plan to use the incorrect positioning might well have much more effect and ruin the photo - I use the lens mostly @ f8 - f10...

=> I would be interested to see an example image from you, when you use the 8mm fisheye @ f1.8 (I did not even dare to test it out yet )

Wolfgang