Scan grain aliasing

I just read an article on grain clumping in scans; some other thread here
had a
link that probably led me to that. I forget the details. Anyhoo...

I was just cleaning up some scans made the previous evening, and noticed two
frames shot within minutes of each other, in the same lighting, scanned with
the same settings, came out quite a bit different. One was baby butt smooth;
the other clumpy and wooly. Ah ha! grain aliasing illustrated, I thought.
And then I remembered the details of that second shot. It was overexposed to
the point of clipping on my flatbed; not enough Dmax. Overexposured, and
then developed N+ with halfwit guesstimated temperature conversion. It's
crispy-critter fried. But a pretty severe Photoshop curve made it quite
acceptable and usable. So acceptable and usable, in fact, that I forgot its
crap origins briefly.

Here's my take on grain aliasing. Maybe it happens. I think it just as
likely that other, more easily explainable causes are at work. Whether it's
from hitting the scanner limits, or Photoshop artifacts, or simply the
manipulations accentuating the otherwise hidden noise, it's not always (if
ever) this mysterious aliasing.

So, what does digital noise have to do with MF? Nuthin'. It wasn't even roll
film. I was just too lazy to switch NGs before posting.

In article m,
says...
I just read an article on grain clumping in scans; some other thread here
had a
link that probably led me to that. I forget the details. Anyhoo...

I was just cleaning up some scans made the previous evening, and noticed two
frames shot within minutes of each other, in the same lighting, scanned with
the same settings, came out quite a bit different. One was baby butt smooth;
the other clumpy and wooly. Ah ha! grain aliasing illustrated, I thought.
And then I remembered the details of that second shot. It was overexposed to
the point of clipping on my flatbed; not enough Dmax. Overexposured, and
then developed N+ with halfwit guesstimated temperature conversion. It's
crispy-critter fried. But a pretty severe Photoshop curve made it quite
acceptable and usable. So acceptable and usable, in fact, that I forgot its
crap origins briefly.

Here's my take on grain aliasing. Maybe it happens. I think it just as
likely that other, more easily explainable causes are at work. Whether it's
from hitting the scanner limits, or Photoshop artifacts, or simply the
manipulations accentuating the otherwise hidden noise, it's not always (if
ever) this mysterious aliasing.

So, what does digital noise have to do with MF? Nuthin'. It wasn't even roll
film. I was just too lazy to switch NGs before posting.


Raising the contrast emphasizes the grain. One trick is to select areas
such as the sky and then do a gaussian blur with a radius of 1-2 pixels
to make it less visible in smooth areas. This may also help in deep
shadows with a slightly higher setting. Thus you get the sharpness in
the midtones while minimizing the grain.
Real aliasing seems to occur with scanners having about a 2700 dpi
resolution when used with fast color film. The scanner doesn't resolve
the individual dye clumps and tends to make them look larger than they
actually are.

--
Robert D Feinman

Landscapes, Cityscapes, Panoramas and Photoshop Tips
http://robertdfeinman.com