Rebreather World - View Single Post

PeteS · 23rd December 2006, 10:36

Quote: (Originally Posted by Sutty)

Johnny is right in thinking that I have a "compact" camera (Canon G2).
The optics of a dome port mean that once immersed in water it produces a virtual image at a very short distance from the lens (I think its usually a only a few inches, but don't rely on this). It is this virtual image that the camera has to focus on. With my camera in order to focus so close you have to change to "macro" mode. If your camera cannot focus close enough you will have problems focusing.
One way around the problem (I haven't tried this) is supposed to be to add a close-up lens (dioptre) on the front of your lens (or on top of a wide-angle lens if this is what is fitted to match the port - this then enables your camera to focus close enough.

Ahhh, it's a compact..... The reason for my confusion was that my Nikon 10.5mm focuses at the correct distance from (140mm to inf) under a 10" dome - for wide angle. I assumed that most other cameras did the same. Ho hum.

23rd December 2006, 10:36	#13 (permalink)
PeteS Consent Issued! Current Rebreather/s: Inspiration Classic Inspiration Vision Other Rebreather/s: Join Date: Jun 2005 Location: New Zealand Posts: 539	Re: Auto Focus or manual? Quote: (Originally Posted by Sutty) Johnny is right in thinking that I have a "compact" camera (Canon G2). The optics of a dome port mean that once immersed in water it produces a virtual image at a very short distance from the lens (I think its usually a only a few inches, but don't rely on this). It is this virtual image that the camera has to focus on. With my camera in order to focus so close you have to change to "macro" mode. If your camera cannot focus close enough you will have problems focusing. One way around the problem (I haven't tried this) is supposed to be to add a close-up lens (dioptre) on the front of your lens (or on top of a wide-angle lens if this is what is fitted to match the port - this then enables your camera to focus close enough. Ahhh, it's a compact..... The reason for my confusion was that my Nikon 10.5mm focuses at the correct distance from (140mm to inf) under a 10" dome - for wide angle. I assumed that most other cameras did the same. Ho hum. __________________ Pete S. http://www.steggle.co.nz Every silver lining has a cloud
(Online)