Re: Q FOR THE OPTICAL GENIUSES

[sam wang <stwang@bellsouth.net>]

Hello Bob,

One of the resident optical geniuses is off to a photo trip in Spain  
(Sandy), so I'll try to answer instead.

The Dagor is sharp, but its coverage is what gave it special  
reputation. At your bellows draw, you would be using just the center  
of the image circle. So, the APO is probably the one to use.

Have you thought of capturing your subjects with your scanner? Here  
is an article about the folks at the Smithsonian doing just that with  
spectacular results:
http://www.smithsonianmagazine.com/issues/2007/may/creamer.php

You can then make digital negatives of any size, for pt/pd,  
cyanotype, gum, or whatever.

Sam Wang

On Apr 27, 2007, at 9:42 AM, BOB KISS wrote:

> DEAR LIST,
> 	This is for those who REALLY know their optics.
> 	I have a 210 mm Goertz gold dot Dagor and a 210 mm Schneider Apo
> lens.  I want to do some EXTREME close up photos of dried leaves,  
> seeds, et
> alia, on 8X10 to make contact PT/PD (see it IS on topic).  I know  
> that both
> of these lenses will cover the 8X10 format at this bellows  
> extension and I
> am using this focal length to keep from having to stretch my bellow  
> as much
> as I would with a longer focal length lens.
> **********NOW MY QUESTION: Which of these two lenses would give me  
> better
> results in terms of detail and contrast at this magnification  
> (between 5X
> and 10X)?
> 			CHEERS!
> 				BOB
>
>  Please check my website: http://www.bobkiss.com/
>
> "Live as if you are going to die tomorrow.  Learn as if you are  
> going to
> live forever".  Mahatma Gandhi