Re: 6x6 and lenses shorter than 80 mms

[P3D John Bercovitz <bercov@xxxxxxxxxxx>]

Dale Walsh wrote:

>> If you use a lens shorter than 80 mm in
>> the 6x6 format, you'll have no end of trouble finding something with
>> which to view a transparency.  Either the coverage will be inadequate
>> or the aberrations will be insufferable or the price will be out of
>> anyone's range because you'll need custom designed and built optics. 

> 	What exactly do you mean by this?  Why would prints be easier to
> view that transparencies?  I have a 65 mm lens for a Mamiya C330 so I
> am interested in knowing why a regular 6x6 transparency viewer
> would not work.

Sorry to be so slow answering; some of our machines were down over the
weekend and I couldn't read mail.  8-(  Also sorry to have apparently
left out an essential piece of information in my previous posting.  
The essential piece of information is that viewing lenses match taking
lenses to the first order else there is an intolerable distortion (stretch
or squash) of one of the three dimensions, namely depth.  If you use a
65 mm Mamiya lens (I have one of those too.  You think it's a little soft?),
you need a 65 mm viewing lens and it's going to be hard to find one that
will cover the whole 6x6.  65 mm is (250/65 + 1) 5X in the usual sales
method of calculating power and so the problem is to find a 5X with that
amount of coverage and not a lot of noticeable aberrations.

John B



------------------------------