I hesitate to go any further, because I have such respect for your judgment
and the care that you use in your photography.
There is no question that there is variability in the warmth or coolness of
lens rendition. I agree. A lot of it is the taste of the manufacturer and
people used to be advised to buy the camera maker's lenses if you want
uniformity in color rendition if you planned switch lenses in the middle of
ashoot. A good manufacturer who makes their own lenses will attempt to make
the color rendition uniform. It is probably done by absorption of spectral
bands that emphasize opposite parts of the spectra. I remember reading
articles in Leica Fotographie discussing the color effect of the cements
gluing some of the lens elements together. Then different kinds of glass,
number of elements and coatings each have their effects. In those instances
certain portions of the spectrum are being absorbed so that other parts
appear to be enhanced. It seems to me though that no part of the spectral
saturation is increased, just the opposite parts are decreased and our brain
sees the warmth or coolness. If a rose is the equivalent of a photoshop 256
red the lens cannot make it 300 red. The best you can hope for is that your
will transmit close to 256 and that it will do an equally accurate
transmission of the other colors. If it does not, then it could look too red
even even if it only transmits 225 red. It is a question of spectrum balance
in the image made up of less light than that which hit the front surface of
the lens, not that it has somehow increased the saturation of red from the
front to the back of the lens.
I would question whether lens contrast was consciously adjusted down in the
past because of film, that is to match them. I think lenses were made as
well as they could be seen to function considering the level of print
material available. When film materials improved and larger prints became
fashionable so that the lens flaws could be seen, then lens development
proceeded. But I could be wrong and you could be correct. Or we are saying
the same thing in different ways.
Winsor
Long Beach, California, USA
On / March 9, 2008 CE, at 5:51 PM, C.H.Ling wrote:
Many poeple think high contrast is good or as you say a lens close to
perfect design should have high contrast. I have different guess here, in
the film age, lens has to design to match the contrast of film. Or back to
the very old age when multicoating was not very propular, film was
designed with higher contrast and later both have to fix contrast to a
certain range.
Even the very cheap lens can have very high contrast, like the Sigma 70-300
APO UC I once own (Minolta AF mount), the contrast is very high from 70-200,
the images were very un-nautral. The non all MC 35 shift has the natural
color that I like, the 90/2 has higher color saturation and good for
flowers. Too many coating can cause color shift, if you control the coating
better like Zeiss the color will be more natural, if not, like some Pent*a
SMC and Tamron BBAR coating, the color tone could be shifted or at least
different from the others.
At the mean time I think it is well known that even within Zuiko some are
having warmer tone than the other. And in my experience most of the later
Zuiko AF for OM707 have very cool tone.
C.H.Ling
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