Re: 90 summicron and viso 2.

[Dennis Painter <dwp@deltanet.com>]

Hal Robinson wrote:
> 
> Thanks for helping me with my viso and various lenses a few weeks ago.  I
> have tried different lens and all seem to work fine.  I had excellent
> results with my dr summicron set at 18 inches.  My only question is how many
> stops do you lose when a lens is put on the viso in this way for close
> focusing.  I have found this to be the case with my 90/2 and 502 after this
> role I just got back.  I am guessing it is around 1-2 stops but not sure.  I
> didn't even think about losing stops until after i shot the role, and i use
> a hand held meter with my m4.  Thanks again, Hal
> 

Hal, 

Did you get an answer for this?  

I would need a bit more info to answer your specific setup, but keep in
mind that when you focus to 1:1 your loose 2 f stops.  So a 90mm f/2 at
1:1 would be f/4 wide open.

The formula is T = D squared/F squared

Where T is the increase in exposure, D is distance from lens to film
plan, and F is the focal length inscribed on the lens.

Its really one reason that fully automatic SLRs are good at closeups.

Dennis


- -- 
Experience is a tough teacher. It gives the test before the lesson.
- -unknown