Isaac Szabo

First let me say that I applaud all of your efforts to provide free models and inexpensive parts to the community. In this case my feedback is that I personally wouldn't want to use a cap that leaves open the possibility of objects poking through and scratching the dome or the cap material being bent into the dome (and again potentially scratching it if something like sand is in there).

For me there is a very significant improvement with long macros as well, though different people have different standards for what is/isn't acceptable.

Do you happen to have a link with price? And do you happen to know what the curvature of the dome is?

One interesting thing to note when using domes for macros is that the plane of focus changes from being straight with a flat port to curving a little bit away from the camera with a dome port.

Ah, yeah that site doesn't have most of the lenses I'm working with. It does have the Sony 90mm, but I'm not sure I trust what it says since it differs from what I measured. I also don't think it gives any info on how the entrance pupil changes with focus (unless I'm missing something).

This doesn't necessarily have to be the case. Most dome sections are much larger than they need to be to cover the narrow FOV of macro lenses. For example, today I am testing a small (~50mm) section I cut from a 150mm diameter acrylic dome (shown in red) with the Tamron 90mm. So far, the results are looking very good (on par with the Zen dome shown in black):

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.

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

@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.

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!

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

I recently compared the Tamron 90mm (on full frame) with a flat port, MFO-1, and dome port. I was shooting at a large aperture (f/4), mainly because I was shooting without strobes in my test tank and didn't want to use a high ISO. With the flat port there was good sharpness across the central 50% of the horizontal frame. The MFO-1 improved it to around 80%, and the dome improved it to around 95%. So yes, with this setup at least, the MFO-1 provided a significant improvement in edge sharpness over the flat port, though the dome provided a more significant improvement.

@dentrock The entrance pupil moves a fair amount with focus with all the macro lenses I have tested (from around 15mm to as much as 35mm+). So I measure it at multiple points from 1:1 out to a reasonable underwater shooting distance like 50cm and pick a spot in the middle of the range to center the dome around. It's promising that the EP may not move much with the Sony 100mm and that it seems to be located in an ideal place (not far back like the Sony 90mm and Sigma 105mm). How are you measuring the EP? I should note that I can't speak to the focusing issues you're experiencing. I'm just looking at sharpness in my testing. The Tamron 90mm with Zen WA-100 dome indeed gives me edge to edge sharpness like the Sony 50mm behind the same dome. Did the Sony 100mm behind the 180 port give edge to edge sharpness when you did manage to get shots in focus? I must admit I'm a little confused by you saying "Nauticam 140 / 70mm diameter" and "Nauticam 180 port (110 D)". I'm not very familiar with the Nauticam ports, but do you perhaps mean radius for the second numbers? Or maybe I'm just missing something? Again, I'm not very knowledgeable on Zen ports, but yes, I believe they also make fisheye ports with a smaller diameter dome. It was Matt Sullivan who first had me make him a macro port using the dome from the Zen WA-100 port, and it worked so well that I wanted one for myself as well.

@dentrock I don't have experience with the Sony 100, but I have done a little testing of the Sony 90mm, Tamron 90mm, and Sigma 105mm behind domes. The entrance pupils of the Sony 90mm and Sigma 105mm are very far back (near the rear mount), so I think they will require something like a section of a 300mm diameter dome (or larger) to have a chance of working well (they don't work well with the smaller domes I have on hand). On the other hand, the Tamron 90mm entrance pupil is much closer (near the center of the lens), and it works very well behind dome sections typically used for macro lenses (such as the dome from the Zen WA-100 port, which is a section of a ~170mm diameter dome).

When I first added strobes to my kit around 5 years ago, I started with SB-105s because I could get them for very cheap (like $40-50). I was happy with them except that most of them developed problems or stopped working (I'm guessing just due to their age). I went through 4-5 of them before moving to Inon Z-240s. In my opinion the SB-105s had better quality of light, but the Z-240s were much more reliable, which is ultimately more important.