yiheng

I just tested the old Canon EF 50mm f/2.5 Macro in Alor with a 30mm extension ring paired with a 140mm dome port. Overall, this combo produces excellent image quality, with almost no visible edge degradation, and the magnification is satisfying (it allowed a Christmas tree worm to fill the full frame). But I may not use it again — here are the details: Pros: 1. Excellent image quality. I used f/2.5 or f/10 and above; the former gives attractive bokeh in video, while the latter delivers good corner quality. 2. High magnification. It can focus on subjects close to the dome, and image quality remains good at macro distances. 3. Underwater, when facing the sun, there was no visible flare or loss of contrast. Cons: 1. Struggling autofocus. It can focus on stationary subjects or slow-moving fish on coral, but if the water is murky or the subject is not distinct, it struggles a lot; even pressing focus again does nothing, especially in video mode. 2. Huge noise. Almost every video is filled with deafening focusing sound. 3. Not as convenient to use as a zoom lens; it feels like being choked by a sweater. Underwater, prime lenses are always less convenient than zooms. I didn’t do a formal macro test, but I think it can absolutely handle still photography and video. Next time I will test the EF 28-70 with the 140 dome port. Maybe it's a better chouse for video

I have discovered a master who has summarized complex underwater optical problems into easy to understand laws and answered all the questions I mentioned above. I will try according to his method https://www.youtube.com/watch?v=rcRtbHXMQPs

I have 14 35 with 180 dome use for some time，video is good. But not wide enough for some time. So I change to fish eye

Running only FF limited to macro feels like losing a lot of opportunities🤣

This video is really helpful, ultimately I need to test it myself to find the best extension ring。 Thank you

I have a rf 100 macro, basicly efs 60mm in canon r5 apsc = 96mm. That is not I want

Thank you for the reminder. I have checked his post. He used Ivanoff Rebikoff in combination with 24-105, not at dome port I once considered the EF 50 F2.5 macro, based on calculations, it fits perfectly with the 140 dome (telephoto end) without using an extension ring. However, the lens will protrude 22.4mm at macro, which will cause changes in the entrance pupil distance. I don't know if this has a huge impact on the image quality If measured by the entrance pupil distance, the change in entrance pupil distance for rf 24-105 stm will be greater

Marelux and nauticam not recommend use rf 50 1.8，and this lens is external focus design, not like sonny and niko

Hello everyone, I previously used EVA Marine soft waterproof shell with RF24-70 in freshwater underwater photography. Although the edge image quality is poor, it can obtain some behavioral photos of sensitive organisms. Also, my luggage allowance is very tight, and it's a bit difficult to carry the flat mirror port I am looking for a medium focal length lens (50-85mm) that can be used behind a spherical mirror (140mm) on the Canon system with my fisheye lens. Currently, the closest focusing distance of Canon's RF50 1.8 and RF85 f2 exceeds 0.3m, and theoretical calculations show that they are difficult to focus with the 140dome without using an extension ring. If combined with a 30mm extension ring, I can‘’t be sure if better image quality can be achieved because there is no parameter for the entrance pupil distance for rf 50 and 85. Regarding other zoom lenses for RF, it is more difficult to meet the entrance pupil distance as the closest focusing distance is bigger. Do you have any good recommendations or experience sharing？ Thank you

I consulted with the official personnel of Nautiam, and they said that the basis for determining the appropriate length of the extension ring is that the front mirror group and the ball cover surface are parallel. They have given more consideration to the situation of 7mm Based on my measurements, the flange difference between Marelux-rf and Nauticum-rf is 7mm, which means that if Nauticum has a length of 20mm, Marelux needs 27mm

I followed your advice and conducted tests on land using 3D printed extension rings (30mm and 35mm). It can be confirmed that the 35mm extension ring in the 14mm focal length can only see slight dark corners when the camera anti shake group is working, while there are no visible corners in the 30mm range. Checking the image quality, it was found that there was almost no difference between the two under F10 F13. Therefore, 30mm is the optimal extension ring for RF7-14

Thank you Phil. I just got the Marelux 140 dome and tested it with a 40mm extension ring. It has distinct black edges, I guse 35mm will be ok. You mentioned that 20mm is the most suitable, I'd like to know the reason for this setting. Because I obtained that 32-36mm is the best optical distance through the theoretical calculation method in the forum (the entrance pupil distance of rf7-14 comes from the Internet, and other parameters are actually measured by me)

Yes, a smaller aperture definitely helps with the picture quality. I don't have a 20mm extension ring, plan to purchase a 15+20mm extension ring

Thank you for sharing. What brand of diopters do you use?

Yes, there isn't much information. My friend has already used this lens on the Marelux R52, using a 30mm extension ring and obtaining images at aperture F8. I think there is some blurring in the corners, which may not have fully realized the potential of the lens