Tips and Techniques

[Padipro]

Blacknet,

Is there a proper distance that the front of a lens is supposed to be behind a dome port? This might be a little off topic as it concerns video instead of still photography but I recently installed a 4 inch dome port on a custom made housing and could not find any information on this subject prior to instalation.

With the old flat port I had trouble with the auto focus trying to focus on the suspended particals in the water so I always set the focal length to infinity and changed the camera to manual focus. This worked good as I don't have zoom control on the housing. I had heard that a dome port would give me better field of view so I purchased and installed the port. Not being able to find any information on my question to you I just installed the port hoping for the best. The first time I used the camera after installing the port I again set the camera to manual focus and the results were horrable. Nothing was in focus. The last time to tried it I left the camera in auto focus and everything seemed to work great. The image was sharp, the field of view seemed to be greater and the color was better then ever so it seems that everything has worked but I still wonder if this was just luck.

Thank you,

Scott

Video housing before and after port installation

 

[blacknet]

Hello,

The only consideration you need is the min focus distance. I have a port that is to large for my macro lens and light will shine thru the port from the side and you can clearly see the virtual image of the port. Also keep in mind you may get glare from other light sources.

Remember that infinity is now 3 * radius of the dome port. So set your end distance scale to that number and it should work. In low light conditions or bad conditions autofocus does tend to fail.

Ed