Issue with Ikelite Customer Support

[cerich]

That's pretty much par the course for a rectilinear ultrawide behind a fairly small dome at a wide aperture. The shots taken at f/16 look quite reasonable - you can get better with a 230-250mm dome, but corners are never great with this kind of setup. You can make it a little better by using manual focus biased to a closer distance, but it's a big pain in the ass to manage, even if you have the extra focus gear in addition to the zoom one. The wider apertures (not f/4, but something like f/8) are still usable if you're shooting pelagics with just water in all four corners.

Here is a consumer grade rectilinear Oly 9-18 behind a 4" zen dome on a Olympus Em-5 (1st gen 16mp) with a +2 diopter at f8 and 9mm (18mm FF equiv) ,that shows corner distortion well. That is now a 13 year old camera with a consumer lens in a tiny glass port, there is no way that someone that just spent 4k following a manufs recommendations should be getting what the OP is .. sorry.

 

[Barmaglot]

sure, and we could even play with a diopter (if one would even fit) as well to see if can get better. But, regardless, that lens and dome combination are a pretty bad combo and shouldn't be on a recommended list, even if you say use wider apertures.

A diopter won't do anything. Using a +2 or +3 close-up lens used to be necessary with older lenses that had longer minimum focus distances and couldn't focus inside a dome at all, as the virtual image was too close for them - a weak diopter corrected that. Modern lenses typically can focus close enough without assistance, so a close-up lens won't do anything besides some extra vignetting.

This lens and dome combination is not the best, but perfectly usable at smaller apertures - that is just the nature of the beast. At rectilinear 16mm full-frame f/4 no commercially available dome will give you good corners.

Here is a consumer grade rectilinear Oly 9-18 behind a 4" zen dome on a Olympus Em-5 (1st gen 16mp) with a +2 diopter at f8 and 9mm (18mm FF equiv) ,that shows corner distortion well. That is now a 13 year old camera with a consumer lens in a tiny glass port

M43 has a sensor that is literally one quarter the size of full-frame, and you're shooting at f/8. Full-frame cameras are more susceptible to corner issues behind domes than smaller-sensor cameras due to their shallower depth of field; age of the camera doesn't matter.

 

[cerich]

A diopter won't do anything. Using a +2 or +3 close-up lens used to be necessary with older lenses that had longer minimum focus distances and couldn't focus inside a dome at all, as the virtual image was too close for them - a weak diopter corrected that. Modern lenses typically can focus close enough without assistance, so a close-up lens won't do anything besides some extra vignetting.

This lens and dome combination is not the best, but perfectly usable at smaller apertures - that is just the nature of the beast. At rectilinear 16mm full-frame f/4 no commercially available dome will give you good corners.


M43 has a sensor that is literally one quarter the size of full-frame, and you're shooting at f/8. Full-frame cameras are more susceptible to corner issues behind domes than smaller-sensor cameras due to their shallower depth of field; age of the camera doesn't matter.

it's not always necessary with more modern but can improve things, as is the case with the 9-18 in question. Using a diopter will narrow (not necc extra vignetting) the FOV a bit and sometimes help correct annoying corners (so would zooming in fairness, but..)
I hear you regards MFT, but simply saying no dome will give you good corners, as opposed to the results he is getting that is much worse than just corners is apples to oranges.

I suspect with a larger dome, all else being equal, his system should do better than what the EM5 and 9-18 is getting.

honestly, Ikelite is well known for awesome cust service, and I do think they made a mistake having that lens/dome combo listed as compatible, and going by the OP's "tone" in even here to us "english as a first language" folks it may have all gone poorly (and in fairness, I have been on the manuf side and had that happen with me a party as well)

 

[BoltSnap]

I don't use strobes and I am not interested in using strobes

Can you explain why please?

 

[Barmaglot]

I suspect with a larger dome, all else being equal, his system should do better than what the EM5 and 9-18 is getting.

No it won't; not with all else being equal. A larger sensor camera has to do more magnification to achieve identical framing on the same subject, thus getting shallower depth of field. A medium-format camera such as a Fujifilm GFX series would do worse still. The shallow depth of field is a desired trait in some situations, such as portrait photography, but here it is actively working against the user.

Edit: The same, by the way, applies to macro. An A7S III with a Canon EF 100mm lens has the same AoV and pixel count as a TG-6, and while its much larger sensor (30x more area) will resolve a lot more detail, the TG-6 will get a lot more of that same shot in focus - the FF camera will have to do focus stacking to match the TG-6 shot.

 

[cerich]

No it won't; not with all else being equal. A larger sensor camera has to do more magnification to achieve identical framing on the same subject, thus getting shallower depth of field. A medium-format camera such as a Fujifilm GFX series would do worse still. The shallow depth of field is a desired trait in some situations, such as portrait photography, but here it is actively working against the user.

Edit: The same, by the way, applies to macro. An A7S III with a Canon EF 100mm lens has the same AoV and pixel count as a TG-6, and while its much larger sensor (30x more area) will resolve a lot more detail, the TG-6 will get a lot more of that same shot in focus - the FF camera will have to do focus stacking to match the TG-6 shot.

he isn't doing macro from his gallery, and nothing he was taking can't be done FF. His camera with a dome that is appropriate to the lens should do at least as well. By your argument M43 wouldn't be losing ground in UW to FF, yet it certainly has and is.

 

[Barmaglot]

he isn't doing macro from his gallery

I simply brought it up as an example.

and nothing he was taking can't be done FF. His camera with a dome that is appropriate to the lens should do at least as well

And it does - at appropriate settings.

By your argument M43 wouldn't be losing ground in UW to FF, yet it certainly has and is.

Most people spending $10-20k on an underwater FF system also invest the time into learning how to properly use it, and fisheye lenses (8-15mm zoom or 15mm prime; 10-17mm on crop systems) are by far more popular than rectilinear ones for a multitude of good reasons.

 

[cerich]

I simply brought it up as an example.


And it does - at appropriate settings.


Most people spending $10-20k on an underwater FF system also invest the time into learning how to properly use it, and fisheye lenses (8-15mm zoom or 15mm prime; 10-17mm on crop systems) are by far more popular than rectilinear ones for a multitude of good reasons.

everyone starts somewhere, and he did do his research, and followed the lens/port combination that was stated as OK .
It's really not OK at all.

 

[BoltSnap]

and he did do his research

It's a "she"

 

[cerich]

It's a "she"

my apologies to the OP, thanks for the catch