Subject:	Great lens, but probably no good under water. (+)
Author:	drdread
Date:	1/14/2002 10:43:52 AM
Message:

I have one of those Tamron lenses, and I love it...on land. Your dive shop was right about the lens not being a great choice for use underwater, although I don't agree with their reasoning. Their point is that the lens is fairly slow, with maximum apertures of f/3.5 - 5.6. For most underwater use this is "ok," as I usually shoot at f/8. Once in a while I'll open up to f/5.6 if the light is poor, but it's rare that I have had to go to f/4....and every time I've had to shoot at f/4, it was wide-angle work, where that lens will reach f/3.5.

The real problem with this lens underwater is the extension range and its close-focus ability. As you probably know, the lens extends to extreme lengths when you want 200mm operation. This means that you will have to find a very long port for the lens in order to use it. That long port, in turn, means that the port will vignette the lens if you shoot it at shorter focal lengths.

The vignetting issue will probably kill you. You'll have to limit the focal length of the lens on one side or the other. That is, you'll only get 28mm to 80mm with a short port, or 80 to 200 with a longer port. I don't think you'll be able to get the whole range of focal lengths unless the port has a very large diameter -- which will make the port itself unbearably buoyant!

Also, I seem to remember the lens having a fairly long minimum focus distance. That's a bad thing underwater. You want all your lenses to focus as close as possible!

All in all, I wouldn't try to use this lens underwater. But if you do, please come back here and tell us how it went!

D

Subject

Author

Date

Lenses for SLR in UW housing (3)

peter van der voort

1/14/2002 5:59:36 AM

Great lens, but probably no good under water. (+) (2)

drdread

1/14/2002 10:43:52 AM

I still think I am going for it (1)

peter van der voort

1/17/2002 5:27:06 AM

Wow. (+) (0)

drdread

1/17/2002 10:45:38 AM

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