Very cogent description, it's obvious why Mike can make a living with his pen, (ok, word processor).
At 10:05 AM 12/15/2002 -0600, you wrote:
> All you have to do is take a look at the published MTFs for 35 mm lenses and
> compare them with those for Medium Format
Again, Don and Pal are correct here. Look at any measure of resolving power
you please--visual lp/mm, MTF, whatever--the smaller the image circle, the
shorter the focal length for the same angle of view, the brighter the lens,
the higher the potential resolution. There isn't a single medium format lens
that can resolve as much on film as the best 35mm lens.
Where medium format wins is by the measure Greywolf was referencing in his
part of the discussion--final print magnification as opposed to on-film
magnification. With normal-speed pictorial films (i.e., 100-400 ISO), the
limits of enlargement are about 8-12x (depending no so much on the
granularity of the film as upon the quality of the enlarging lens and the
technique of the printer--I'll give you a clue, if you don't know the
optimum magnification and the optimum aperture of your enlarging lens off
the top of your head, you're better off not going to 12x <g>).
An 8x enlargement from 35mm is 12x8 inches. The same 8x enlargement from a
Hasselblad or Rollei negative is eighteen and a half inches square. You can
crop a square medium-format negative and enlarge it to 12x8 inches and
you're still only at about a 5x enlargement. What this means IN REAL-WORLD
TERMS is that a 12x8-inch enlargement from a 2 1/4 negative requires less
skill and less exacting technique from the printer, allows for some
cropping, allows for the use of a faster film, and STILL will give better
resolution in the print. Nothing to be sneezed at.
And if what you want to end up with is an 18x12-inch print, however, that's
a 12x enlargement from a 35mm negative and, in practical terms, you are
working at the limits of 35mm--your equipment, materials, and technique had
all better be top-notch to achieve a better-than-acceptable result. But
you're only at the bottom limit of the enlargability of a 2 1/4 neg.
In fact, subjective evaluation tests show that this is pretty much the story
with competing formats. If both formats are well under the lower
enlargability index of 8x, there isn't a whole lot to choose. By the upper
12x limit of the smaller format, the larger format is beginning to pull away
decisively. At larger sizes, no amount of technique can "rescue" the smaller
format.
The big headache for manufacturers (as I think the "Big Five" found out to
their dismay with APS) is that a format cannot be engineered for the
"average" enlargement--because, in the real world, what people like to do is
to have MOST of their enlargements at a certain size, but then a FEW
SELECTED images they like to be able to enlarge to a significantly greater
size. That is, the APS shooter is happy with 3R prints most of the time, but
occasonally wants an 8x10; The 35mm shooter is happy with 4x6 or 6x9 most of
the time, but SOMETIMES wants an 11x14. So format choice is not only
dependent on the comfort level it allows a fine printer at the average size
of enlargement, but it is also a matter of the LARGEST size he or she is
ever likely to print.
Incidentally, in our subjective evaluation tests, the ideal format turned
out to be 6x7cm. In 11x14 enlargements, photographers could tell, but
visually sensitive laypeople COULD NOT TELL, the difference between 6x7 and
4x5. Yet 6x7 DECISIVELY bettered 35mm at every size above about 6x9,
according to all viewers, and by 16x20 there was not contest at all--100% of
viewers preferred 6x7.
Do note, however, that lens and film resolution, enlargability, print
quality, and all these interlinking qualities are NOT simply a matter of
mathematics and measurements. They are also highly dependent on the skill
and technique of the photographer/printer and the visual acuity and
"sensitivity to photo artifacts" of the viewer. Photographers can more
readily tell the differences between formats because they know the clues to
look for. Ordinary viewers don't see the differences as easily. All these
things have to be taken into account in this argument.
--Mike
"At least they're not talking about my eyes any more. I was starting to get
self-conscious." (Rocky Raccoon)
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