RE: [APML] Medium format cameras and films, along with Tak scopes

["Jon Kolb" <jkolb@datawest.net>]

Hi Alan,

> If I understand (debatable) what I have read, the following 
> applies to my situation: Given that I currently have a Tak 
> FS-102, anything larger than a 645 size will be useless for 
> prime focus with a 2.7" focuser. Correct?

In my view, yes. 
 
> 1. Film size: is it true that 120 and 220 are the same film 
> except that 220 is longer? 120 has paper backing, why? Are 
> those the only differences between the 2?

Yes. The paper backing keeps the film the same size on the spool, and
probably there are other reasons as well. Yes.
 
> 2. Are there any decent film choices at this size (thanks 
> Stuart) other than E200 or TP?

Provia 400F, Provia 100F (need fast optics, but it's a great all-around
film).
 
> 3. Say I locate a decent Pentax body, what would be a good 
> first lens to use as a piggyback lens? What else should I 
> look for in a body? Mirror lock up, anything else?

The 200mm f/4 is very sharp.  MLU is a definite need.  You'll want the
Pentax 67 battery eliminator from Hutech also, to avoid the expense and
hassle of batteries.
 
> 4. Of the FS-128 & FSQ-106, which is the superior imaging 
> platform for prime focus? I don't think all 128s have 4" 
> focusers, but I intend to get one that does. I suspect the 
> answer is the 106, but does the extra aperture of the 128 
> carry weight here?

Can't answer that one.
 
> 5. Given a 4" focuser, is the Pentax 67 a good choice?

Yes!
 
> I have had a hard time sometimes distinquishing between what 
> is medium and what is large format. I took a pen and paper 
> and drew out the following sized rectangles: 24X36mm, 
> 6X4.5cm, 6X7cm, 6X9cm and 4X5 INCHES. Could be that is the 
> problem; someone decided to use different formats to measure 
> film sizes. How confusing. 

Large format is generally considered to be anything from 4x5 on up (5x7,
8x10, and even larger cameras exist).
 
> Anyway, I now believe that all the sizes that are measured in 
> centimeters are medium format sizes. 4X5 inches is large 
> format, correct?  

Yes.
 
> I can't believe how puny 35mm looks on the same page with the 
> larger sizes. I didn't believe it until I pulled a negative 
> out and determined that I had drawn the right size box. I've 
> heard it, but now that I can see it, I believe it.

Wait until you get your first 6x7 slide back from the lab!  If that
won't hook you on medium format, nothing will.

Sincerely,
Jon Kolb
Adventures in Astrophotography
http://home.datawest.net/jkolb/
Life Member, International Dark-Sky Association
jkolb@datawest.net



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