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

19 minutes ago, yiheng said:

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

50mm and slow autofocus seem to go hand in hand... Sony... Canon...

Edited Wednesday at 10:26 AM1 day by CCRphoto