3 hours ago, Adventurer said:

Yes, overall better! There is nearly no sharpness loss in the edges with that combination.
I am not shooting the Canon RF 24-105mm f/4-7.1 STM IS behind a dome.

But this is can be mainly credited to the lens behaviour on land, were you can see that center and corner sharpness is excellent in the f-stop range we typically use underwater. Also the barrel distortion at 24mm helps when using domes and underwater correction optics. Of course this lens has been roasted as dismal performer in land reviews for that. But for our kind, this is exactly what we need in underwater photography. ( source: review at OpticalLimits.com )

I repeat / clarify, that I am not shooting the Canon RF 24-105mm f/4-7.1 STM IS behind a dome.

I happen to own a unique Rebikov / Ivanoff Style corrector port which allows decent zoom through with that lens. With some tinkering, trial and error I lucked into this lens and specific uw glass combination, and I believe to currently be the only underwater photographer using such a system. There is a complete thread about my lucky find in this forum:

https://waterpixels.net/forums/topic/2637-ivanoff-style-underwater-corrector-port-on-a-canon-marelux-mx-r6ii/

Can you post some examples of what type of images you take with this system you have put together? What kind of FoV are you getting?

@Adventurer could you show us which kind of photos are you getting with your system?

I'm very curious about this Ivanoff system

Hi folks

This lengthy discussion of tradeoffs in imaging system performance piqued my curiosity. It has been very interesting to read and consider. There is a lot there.

I come from the world of the physics of medical imaging systems and in that space I know that imaging system performance is task-dependent. Subjective assessment of image quality ('do I like what I see') is valuable, but it is like art appreciation - I might not see/value what you see/value. Objective assessment and metrology are essential for imaging system performance. Those results are then applied to analysis of specific tasks and required (or desired) performance for particular tasks.

Might I suggest photographing standard test objects in air and underwater with whatever lenses/ports you would like to compare to perform objective assessment and then discuss the tradeoffs on capturing specific scenes? If you don't like some particular degradation in performance with a class of (or specific) lenses/ports/whatever, quantify it under various tasks and consider the implications for those tasks and the associated tradeoffs.

I understand a broad investigation is a big 'ask' for the typical part-time UW photographer like me, but it is an objective approach to describe the underlying issues with specific examples. It might be 'manageable' to do it with two lenses and two ports/WWL on a single camera/sensor just to make a point.

Respectfully,

Tim

I should have provided a specific example that I think is consistent with the discussion here.

Consider the Sony 28-60mm lens in a port with a flat (or spherical) surface versus behind the Nauticam WWL-1. Compare the rectilinear distortion ('barrel distortion'), the point spread function (spatial blurring) across the field, and any potential cropping of the field. Then compare that lens to another under the same conditions.

The same could be said for a different lens on the same camera (sensor - FF) or the same lens on a different camera (sensor - eg, APC).

The objective assessment of performance will provide a basis for analysis suitability for specific tasks.

I hope this makes sense.

Tim