I finally got around to doing some controlled film and lens
testing. I wanted to make sure I knew exactly how Ilford Delta
and DDX chemistry were rendering gradients and tonal scales.
Needless to say, I'm now completely satisfied. Took a new
processing tank to accomplish it, but let's just say that Delta
100 has now found a permanent home in my camera bag.
I used the color/grayscale chart of a Kodak Professional
Photoguide and also made up one a lot more extensive on a
computer output with grayscales and color scales and patches. I
made sure that I didn't overagitate or run over on time. The
steps were quite amazing with excellent seperation between all
levels. Gradients are really nice and each Zone Level is
exactly as expected. I'm going to use one of the frames on this
roll to calibrate my printing now.
Now, to the entertaining part: I made up five resolution charts
and taped them to the wall. (along with the color charts and
post-its describing lens and exposure details). Using a studio
flash to eliminate camera movement, I ran some lens tests on the
24/2.8, 35/2.8, 50/3.5 and 100/2.8. (would have done the 135/3.5
and 200/4 but ran out of floor space and film). I had a couple
flash/sync problems so half of my tests were blank, but I did
get enough right to spot an interesting result.
The 35/2.8 (all silvernose lenses) outperformed the 24/2.8 and
50/3.5. The 24/2.8 also had horrible amounts of barrel
distortion. At F11 the 35/2.8 was steller edge and center.
Essentially, the resolution exceeded my ability to measure it
with the loupe. F11 and F16 resulted in nearly identical imaging
edge-to-edge. No discernable difference between the center
chart and the corner charts.
The 24/2.8 was sharp in the corners at F11, but otherwise was
better in the center. The 50/3.5 is an exceptionally sharp
lens, but compared to the 35/2.8 it was at least one step
fuzzier. It was, however, consistant center to edge at 5.6.
I've talked for years about my 100/2.8 and how sharp I *thought*
it was. Never got around to measuring it. Never wanted to
because I was always afraid of being disappointed in finding out
that it is a C- lens. For my purposes, it always pleased me,
though.
Now that I've done the test, I'm still not sure how sharp it is.
All I am sure of is that I ran out of magnification. I know
there were discernable bars at least two steps smaller than what
were in the 35/2.8 images. Beyond that, I have no clue. F11 and
F16 yielded perfect sharpness AND greater contrast than the
other lenses. I'll have to use the grain magnifier under the
enlarger to figure out where it ends.
F8 experiences minimal resolution fall-off in the corners, but
F4 and 5.6 definitely showed where the sharpness wasn't.
Beautiful. Now I have confirmation on this lens. It really
does rock. It didn't matter that I went all the way down to
F16. It just got contrastier and contrastier and sharper and
sharper--so much for diffraction.
I'm going to take one of the greyscale/color chart pictures and
use it to calibrate my printing. Nice to know what paper grade
to use as the standard launch point.
Under-exposing and Over-exposing definitely skewed the
gradients. One stop either way took out a zone or two on either
end. Test prints will be interesting.
I'm now very, very satisfied that my tonal scale is functioning
properly in Delta/DDX. Oh, and that 100/2.8--to think, it's one
of them garbage silver-nose jobbies.
Ken Norton
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