KPV

I hope they will be interested in this topic :)

They said they haven't tested other lesnes. Positions of lenses specified in that chars are as follows: Almost like those RF lenses I mentioned earlier.

Actually RP housing. Sea Frogs don't have separate R8 housing. RP and R8 shares the same body so you can use it for both cameras. Picture from their official site.

TimG, Sea Frogs recommended 6" dome port for EF 16-35 f/4 and f/2.8 lenses. Both lenses have MFD of 28 cm. But they have an 8" dome port and I haven't seen any recommendations if it from Sea Frogs. And I also don't want to buy it for now because it is too bulky.

Thanks for the reply! I don't care much about corner sharpness, but would like to get it within reasonable linits. On this trip I was shooting in natural light during the day and I also have two 5000K video ligths that I used earlier with my action camera. But I don't want to use them for photos because the bright light scares creatures I want to shoot. I also not ready for strobes because they are wery expensive and bulky and I dont want to overcomplicate things from the start. All of the images I attached was taken with shutter speed around 1/160 - 1/250. Anemones and clowns are not in sharp focus because of their movement and mooray eel is very sharp because of good ligthtning conditions and steady shot. I think that the lack of sharpness that I'm refering to is caused by the wrong lens position like described in https://oceanity.com.au/articles/view/understanding-flat-port-and-dome-port-theory. So I wander is that the case, how much does this affects and what is better to have entrance pupil in front or at the back of the dome center? I don't have much opportunity to test all this underwater so I want to find out as much as I can on the shore.

Hi there! Newbie underwater photographer here! Recently got an underwater housing for my Canon R8 and have already tried it on out my dive trip. I used it with the RF 15-30 lens. The photos are great, but I have noticed a slight lack of sharpness. When I first got the housing, I tried it with my RF 24-105 lens and photos were way too blury in comparison to what I shoot on land. After some research how to position the lens in relation to the port I have learned a lot of underwater photography science, so I decided to buy RF 15-30 lens for the start. I'm using Sea Frogs housing with acrylic 6" dome port (it's real outer diameter is actually 160 mm). Not the top choices, but very affordable and good value for money. Some aspects are not fully clear to me and after my dive trip I have some questons. Please, share your knowledge on the topics below: 1. Lens position. I have seen on this forum that right position is when the entrance pupil (I-P according to photonstophotos.net) is exactly in the middle of the dome. So I have chosen spacer of 37 mm to get the minimal misalignment and for RF15-30 its maximum value is 9 mm and the lens always sits in front of the dome center. MFD of RF15-30 lens is big enough, but not a problem at all. I ruined some shots of nudibranches, but all the rest was in good focus. It seems 14-35 is the better lens option for close focusing. There always be misalignment, but what is better: to have lens positioned slightly in front of the dome center or slightly behind? Also I have seen formula: Minimum dome radius = MFD-(I-P), therefore: for RF 15-30 R=280-98=102, so D should be 204 mm for RF 14-35 R=200-112,5=87,5, so D should be 175 mm Is it ok to have 160 mm dome port for both lenses? How does port size affect quality? Are my calculations of lens position correct? 2. Virtual image. How to calculate real MFD underwater for this two lenses? I put MFD plane line on pictures above just for info. I know something about virtual image but don't really understand it. 3. Over/under shots. How to make over/under shots look sharp on the both sides? I saw in some videos that it is possible with wide angle lenses at the f-stops of f/4, f/5.6 on a full-frame cameras, but even at f/16 I had one side blurry and the magnification was different. Is it because of position of the lens inside a dome? 4. Hyperfocal distance underwater. How to calculate it? On some web pages I found formula: 2 dome diameter - 4 thickness of the dome, but no clue from where it should be measured. Does it make any sence? Here are some of my photos that I like to share:

Hello, everyone! I've recently got into underwater photography and want to improve my skills by communicating with you.