Re: Leica-Users List Digest V1 #34

[Gary J Toop <gtoop@uoguelph.ca>]

On Thu, 18 Apr 1996, TK Chan wrote:

> I am no technical man on this subject but from actual experience in the use
> of the 120 and 135 films, I have the following observations:
> 
> (a) I've use the Kodak Gold 120 and 135 for experiment, when the 120 and 135
> images are enlarged to the same ratio (not print size), the print made from
> the 135 image produces far better quality in terms of definition and
> sharpness. I know that this depended on many variables, the lens quality
> being a vital factor. But my ignorant guess is that the 135 emulsion is of
> better quality than that of the 120. This wild guess is based on the fact
> that 135 film is more and more accepted for commercial use and very
> enlargement is required so the film manufacturer will need to ensure that a
> good quality enlargment size is possible. On the other hand, the 120 is
> already 3 times the size of the 135, so given the enlargement is to the same
> print size, the quality is made up by the advantage of the larger film area.
> Therefore, the quality of the emulsion can be compromised.  I know this is
> very non-sense guess but very actual in experience.

SNIP

	This is a very interesting result and differences in the emulsion 
could be a factor, alright.  However, it is probably worth keeping in 
mind that Kodak Gold 25 has sufficiently high resolving power to extend 
past the range of the lenses of at least most MF cameras.  Even 
Hassleblads are reputed to resolve no better than 80 lpmm at the centre, 
stopped down.  Most good 35mm lenses can do a good deal better than 
that.  Given that Gold 25 can probably resolve something like 125 lpmm 
in camera (200 lpmm in test if you believe Kodak), you could well be 
looking at a difference in lenses.

	There was an article in Popular Photograph a few months ago which 
reported some test results that support this, although I think 
that they claimed that the 80 Planar lens on their Hasselblad could do no 
better than 40 lpmm in the centre at f8!  (I tend to take PP's results 
with a large grain of salt.)

Hope this helps
Gary Toop