JayceeB

2). At home, I use both the 8-15mm fisheye in a 140mm dome and 14-35mm rectilinear in a 230mm dome. I recently traveled to Malapascua for Threshers and wanted more reach than the 8-15mm provided, but did not want to lug along my heavy 230mm dome. Instead, I used the 14-35mm in the 140mm dome with the extension I normally use for my 230mm dome (thanks for the recommendation on this, @Chris Ross ). I am not as conscious of edge sharpness as many folks, so opinions will vary, but I was happy with the results. Here is a sequence with that setup at different focal lengths. (35mm, 27mm, 23mm, 17mm, 14mm) 35mm 27mm 23mm 17mm 14mm (slight interference from dome sun shade required cropping afterwards in post)

I'm not positive on this one. I thought it was due to the risk of corrosion, but @cerich 's response makes sense too. I can say that after the leak and cleaning out the strobe and drying it, that the battery cap was still functional for another 10 days.

Perhaps @MatthewSullivan is onto something. I had an HF-1 flood 2 weeks ago in Anilao. The strobe worked the entire dive and I left the batteries in overnight as I had not taken many shots. I turned the strobe on in the morning with no power. Opened it up and found some salt water and corroded batteries. Rinsed with fresh water, dried, rubbing alcohol, dried. Left it a day to sit. Next day it powered up and continued working for another 10 days, but started to fail after that. It would power up at the surface, but then at depth, it would not power on. I tested again on the surface and it powered on. FYI: I contacted Backscatter, and they will repair the flooded strobe and replace the battery cap for $235. Strobe is now out for repair.

Attached are two images. Not class-leading sharpness, but not horrible. Looks like B+W makes a 43mm +3. null

@Adventurer , I took your advice and purchased an inexpensive diopter lens kit (Vivitar 43mm Close Up Macro Lens Kit - $13). It came with +1, +2, +4 and +10 diopter lenses. I tried the +1, +2 and +4 on the lens within the housing above water. The +1 was the only one that would focus to infinity above water. I naively thought this would be the one to try. I tested it on a dive, and the experience was completely different than above water. Minimum focus distance was 30” with the +1. Much improved compared to no diopter, but still not acceptable. Next, I tried the +2. Minimum focus distance was 18” underwater. This weekend I tried the +4. The lens focuses right up to the dome port glass as well as to infinity. I’m in the early learning stages regarding lens optics, so forgive me for not considering the impact of water in the equation. I can’t believe how spot-on accurate you were in your recommendation, and thank you so much for helping me out on this. My setup is a Canon R5 + RF 50mm f/1.8 + Vivitar 43mm +4 diopter in a Marelux housing with 140mm fisheye dome (no extension). I would highly recommend this setup for anyone interested in this focal length.

I always cover ports in/out of the boat, or to/fro shore entry. Just be careful not to lose the cap...they're $132 to replace...don't ask me how I know that 🙂

Thanks, @Adventurer. Let me ponder on the +4 diopter suggestion. Not sure how far I want to pursue this option as I was looking for a lightweight travel setup for Malapascua Thresher Sharks. I have tested the 140mm dome + RF 14-35mm successfully at the 35mm end. I think that will likely be my choice, as AF is fast and reliable. I'll utilize the 50mm for above water use only.

I tested this setup today with the RF 50mm and 140mm dome port with no extension. It did not go well. The lens would not autofocus on subjects less than 20' away. In most cases, when I pushed the back button autofocus, the focus box (Canon R5) would just turn red, and it wouldn't even attempt to focus hunt. The specs on this lens give a minimum focus distance of 30cm. Could it be that the virtual image of the dome is too close to the lens? I'm wondering if adding some extension would solve this. Test shot of a manta I had to back off by 20' to get focus. (Some color correction, but no sharpening)

I picked up a refurbished RF 50mm f/1.8 from Canon for $160 USD. It is tiny. Image sharpness above water is more than adequate by my standards. Autofocus speed above water is average, but I wasn't expecting class leading performance. This lens isn't listed on the Marelux port chart, but they confirmed that the 140mm dome port should work with no extension. I'll post my experience and samples once I get this combination underwater.

Thank you for posting these. It's nice to see some samples from less common lens/dome/port combinations. Glad it worked out for you.

Thank you for sharing your experience!

Folks, Has anyone tested the Canon RF 50mm f/1.8 or Canon EF 50mm f/2.5 Macro + EF/RF adapter in a Flat Port? Looking for feedback on AF and IQ. Thank you!

I was able to test out the 60mm extension on the 140mm fisheye dome. The sun shade appears at top and bottom slightly at 14mm. At 16mm+, the shade does not show in shots. 14mm 17mm

Awesome information! That makes sense now. My camera is already packed for today with the 30mm extension, but I will try the 60mm tomorrow. If the 60mm causes slight vignetting at 14mm, no problem zooming in a bit. The bulk of my shooting will be at the 35mm end anyways with this setup.

I see what you're saying with the Canon 8-15mm. Both the 140mm and 230mm domes require a 30mm extension. Perhaps a bit different with the 14-35mm? The 180mm dome requires a 50mm extension, but the 230mm dome requires a 60mm extension. The test shots I have been making were using the 140mm + 30mm extension exactly as setup for the 8-15mm. I wonder if it would be worthwhile testing the 14-35 + 140mm + 60mm extension, which I have for my 14-35mm + 230mm dome. I don't have a 50mm extension.