Review Mini review of Tamron 90mm (A7R5 | MFO-1)

[BoltSnap]

I don't get your second question, but the MTF of the lenses drops significantly beyond f/16. There are several physical / engineering factors for this.

I am fasting, so please excuse my slow mental state

In this context, does one have to set the lens's aperture at exactly f/16? They can't set it to f/22 or f/11 (or anything else).

 

[DragonUW]

Ah, OK - BTW, have a rewarding fast.

With high-resolution sensors, it will always be a compromise. A lower aperture, such as f/22, will give you a higher DOF, but the overall resolution (read image quality) will suffer. Apertures between f/11 and f/16 are a sweet spot for modern macro, in my opinion.

 

[Barmaglot]

In this context, does one have to set the lens's aperture at exactly f/16? They can't set it to f/22 or f/11 (or anything else).

You can set it to anything in the range from f/2.8 to f/16. It's not a fixed-aperture lens, but it can't go any narrower than f/16, which is a bit of a weakness. Sony 90mm is already limited to f/22, which is wider than most other macro lenses' f/32. While it is true that very small apertures cause overall image degradation due to diffraction, in many cases it is a worthwhile tradeoff for the increased depth of field. On land, with static subjects and a tripod, it is often possible to focus stack so as to get the required depth of field without diffraction-inducing apertures, but underwater it is a great deal more difficult to pull off.

 

[hedonist222]

While it is true that very small apertures cause overall image degradation due to diffraction, in many cases it is a worthwhile tradeoff for the increased depth of field. On land, with static subjects and a tripod, it is often possible to focus stack so as to get the required depth of field without diffraction-inducing apertures, but underwater it is a great deal more difficult to pull off.

Agree with this.
I took it a step further to decide what works best for me when I had my Canon 5D mkII and Canon 100 f/2 L lens.
I found that I absolutely needed between f18 and f/26.
I then did tests on the same subject from f/18 to f/28 or similar.

I found that remarkable degradation took place beyond f/22 on the Canon lens. No issue because I was okay with f/22.

 

[Interceptor121]

The Tamron 90mm is a sharp lens but all Sony FE AF lenses 90 Sigma 105 are sharp
The difference is the focus speed and the ability to go beyond f/16 which this lens does not have
On land it wont matter much you can focus stack but underwater this is a limitation

I also do not understand how a diopter or any shape or form would improve autofocus
This lens has a focus limiter MOD to 0.7 this is sufficient to avoid the lens scanning the entire focus range
The Sony 90mm also has an even more useful limit to 0.5m the Sigma 105 has the same limit to 0.5m. With the new Sony firmware you can preset focus distance on some cameras with the Sony 90mm so the chances of going hunting are very low and by the way I never got this lens to hunt even in blackwater

If you instead want the lens to focus beyond which in underwater terms means 0.5x1.33=66cm than a diopter helps however am not sure there is any macro subject that requires that we are talking about a frame size of 20cm which would only be useful for larger fish portraits further away

this MFO-1 idea arrives just 10 years too late...