[filmscanners] Re: [filmscanners_Digest] filmscanners Digest for Fri 27 Feb, 2004

["Bob Frost" <bob@frost.name>]

Tom,

I bow to your obviously superior knowledge on this. I simply remembered my
young days, when learning to get the microscope condenser set up properly
was the most important part of using a microscope.

I do know that when I switch to using the diffuse light option in the
Minolta 5400, the images are 'softer' to me, and I prefer to use it without
that option and clean up the dirt myself. In the light of your comments I
don't understand why.

Bob Frost.


----- Original Message -----
From: "HPA" <tom@historicphotoarchive.com>

Hello Bob, with all respect, I must disagree about condenser light, both
from the standpoint of theory and experience. Sharpness, and diffused vs
collimated light sources have been a raging debate for decades now, in so
far as enlarger light sources are concerned.  The most widely available
discussion is in Ansel Adams' book The Print.  Probably the most scientific
study as it applies to regular photography can be found in Dr. Richard
Henry's Controls in Black & White Photography second edition.  In summary,
equal sharpness is obtainable from either source. There is a substantial
difference in appearance, resulting mostly from the contrast index
(collimated light produces higher contrast, approximately one paper grade)
and the other notable difference is due to the Callier effect, which
accentuates contrast in the denser areas of film (accentuated slope on the
high values of the gamma curve).  Personally I have all types of light
source in my 5 enlargers, condenser and cold light, as well as the semi
diffuse like in the Leitz Focomat.  I have also used Besler point source
heads, which are the most extreme condenser (your lens aperture no longer
works when you use this).

Personally, I think minor differences in production models of scanners make
a big difference.  And I think that the temperature of the scanner light is
sufficient to cause minor softening of the image in any scanner because the
film expands a bit.  I can prove it on my flatbeds, but have not compared
slide scanners.  I measured the temperature of the film plane in a SS4000 at
93 degrees F (and about 72 ambient).  That is more than enough to cause some
unsharpness.  I only scan with glass on top of the film now, so this is not
a problem for me anymore, but it may be with others.

----------------------------------------------------------------------------------------
Unsubscribe by mail to listserver@halftone.co.uk, with 'unsubscribe 
filmscanners'
or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or 
body