“Better”? Define better. I’d suggest if you’re happy with the image quality of what you’re now doing , why chase nirvana? That can prove frustrating, expensive and often of nugatory gain.

23 hours ago, Isaac Szabo said:

I made a custom port using the glass dome from the Zen WA-100 port.

I think I am going to try this as a fun and challenging project. I just bought one of these Zen ports on Ebay for about $250 shipped. It's not pristine but doesn't look too bad. I have some old ikelite ports I can experiment on before moving to the "good" glass dome from the Zen 100.

41 minutes ago, Dave_Hicks said:

I think I am going to try this as a fun and challenging project. I just bought one of these Zen ports on Ebay for about $250 shipped. It's not pristine but doesn't look too bad. I have some old ikelite ports I can experiment on before moving to the "good" glass dome from the Zen 100.

Oh nice find! Looks like you shoot Nikon. It should work well for the 60mm. Not sure about their longer lenses (depends on the entrance pupil location). Good luck with the project!

16 minutes ago, Isaac Szabo said:

Oh nice find! Looks like you shoot Nikon. It should work well for the 60mm. Not sure about their longer lenses (depends on the entrance pupil location). Good luck with the project!

The Nikon Af-S 60 entrance pupil is apparently 48-50mm behind the front element at Infinity focus and 20mm at 1:1.

The Nikon Z 105mm (which i am more interested in making the port for) is approximately 42.2mm behind the front element when focused at infinity and 18.5 at 1:1.

The Sony Tamron 90mm looks like it is 46.5mm at Infinity and 22mm at 1:1.

Is shorter better in this application?

@Dave_Hicks Yes, shorter is generally better in this case. If the entrance pupil is too far back, the dome's center of curvature cannot be positioned there because the dome will hit the front of the lens first. Hopefully this illustration helps. With the Tamron 90mm, the dome's center of curvature can be positioned over the entrance pupil. However, with the Sony 90mm, the entrance pupil is located way too far back. The dome hits the front of the lens well before the center of curvature can reach the entrance pupil. This lens would require a dome with a much larger curvature.

Edited 1 hour ago1 hr by Isaac Szabo

@Dave_Hicks May I ask how you are getting the entrance pupil locations? Your numbers for the Tamron 90mm differ substantially from my measurements.

3 minutes ago, Isaac Szabo said:

@Dave_Hicks Yes, shorter is generally better in this case. If the entrance pupil is too far back, the dome's center of curvature cannot be positioned there because the dome will hit the front of the lens first. Hopefully this illustration helps. With the Tamron 90mm, the dome's center of curvature can be positioned over the entrance pupil. However, with the Sony 90mm, the entrance pupil is located way too far back. The dome hits the front of the lens well before the center of curvature can reach the entrance pupil. This lens would require a dome with a much larger curvature.

Thanks for the explanation! That would

Just now, Isaac Szabo said:

@Dave_Hicks May I ask how you are getting the entrance pupil locations? Your numbers for the Tamron 90mm differ substantially from my measurements.

Internets. There are some tests and a database that puports to list this for various lenses. I will double check in a little while.

6 hours ago, Mike Saunders said:

the video is absolutely great- well laid out, very clear and objective

I have been using a sony 90mm macro lens a long flat port. Am I to understand that it would be better with a dome - in which case I presume you would have to use a dome with some long extension rings to accommodate the bulk of the lens?

I'm shooting in APSC so I have thought it wouldn't really make any difference but the video seems to suggest otherwise

In general, no, flat ports are used with macro lenses for a reason. Yes the corners will be slightly better, but you can't add on a diopter if you wanted to and the large size of the dome makes it more difficult to work in close. For some specialised uses a dome has some advantages, but it seems not all macros lenses work well in domes due to the location of the entrance pupil either moving or being right at the back end of the lens.

48 minutes ago, Dave_Hicks said:

Internets. There are some tests and a database that puports to list this for various lenses. I will double check in a little while.

This is the technique I've always used:

"Parallax/Alignment Test: Place two objects (e.g., sticks) at different distances, aligned in the viewfinder. Pivot the camera on a tripod. If the objects shift, the camera is rotating in front of or behind the entrance pupil. Move the camera forward/backward until the objects stay perfectly aligned during rotation."

It's pretty easy if you happen to have a focusing rail.

18 minutes ago, Isaac Szabo said:

This is the technique I've always used:

"Parallax/Alignment Test: Place two objects (e.g., sticks) at different distances, aligned in the viewfinder. Pivot the camera on a tripod. If the objects shift, the camera is rotating in front of or behind the entrance pupil. Move the camera forward/backward until the objects stay perfectly aligned during rotation."

It's pretty easy if you happen to have a focusing rail.

That Tamron number looks to be for an earlier incarnation of the 90mm lens, from 2013. The F017.

There is a bunch of lenses with this data collected here:

Optical Bench Hub https://www.photonstophotos.net/GeneralTopics/Lenses/OpticalBench/OpticalBenchHub.htm