On 5/16/2012 6:03 AM, Noons wrote:
David Dyer-Bennet wrote,on my timestamp of 16/05/2012 11:06 AM:

You can see grain quite clearly with moderate optical magnification; a
few tens.

No you CANNOT. Not with Tech Pan. THAT is the point. Stop changing the subject to match your
"theories": it won't work.



I have lots of Tech Pan negatives, so I was going to
look at them with my excellent microscope.

But what I found first was Tri-X.

At 100x all I could actually resolve was grain clumps. At 400x
(N.A. 0.75) I could see individual grains, and resolve some
but not all. At 1000x (N.A. 1.30) I could resolve all the grains.
There is a huge variation in grain size, and in clumpiness.

Then I looked at Tech Pan. There are no clumps. And the grain
size is far more uniform. I actually need 1000x to truly resolve the grains.
It really can't be done at 400x, though that is perfectly adequate
to see the individual grains. Resolution is clearly limited
not by grain size but by emulsion thickness.

But can you see the grain "structure" at 50x in Tech Pan?
Yes, you can ... the fluctuation in density is easily seen.
In fact, at background density you can see individual grains
at 50x, but they are far from resolved. At ordinary density
you see only fluctuations and the image itself. The bottom
line is that at background density you should indeed be able,
with a good enlarger lens ( at f/4) and a grain focuser,
to actually focus on the grains themselves ... but they
won't be resolved at all. You will be seeing little gray spots,
not black.

Doug McDonald