Monday, 29 October 2007

Optimising black and white scans

After I posted some of the results from my first foray into B&W film, I decided today to look at options for scanning.

My initial scans had used the negative scanning options of my Epson V750, with the default film curve for Ilford HP5 plus 400 and a gamma of 1.8.

So I tried some things: gamma range 1.0 to 1.8, tweaked film curve, negative-as positive (followed by several inversion options in Photoshop).

Here's what I learned:

  • gamma needs to be high to get a good negative scan. The curve applied for HP5 actual has a quite negative (<1)>
  • Tweaking the applied curve in the scanner (or at least the output range) helped a lot. The default is for the scanner to take the range of tonality found and stretch right out. This buries the shadows and washes out the highlights leaving little room for further processing.
  • Scanning as a positive means a low gamma. 1.0 seems just right to get the full range of info for further processing. I output to 2%/98% range to avoid clipping.
  • Inversion options are varied in PS (I use elements, so there are fewer options). The Invert function is like dragging the thing through mud: it's hopeless. I tried adjusting the curve then inverting: no better.
Then I tried using Levels to invert: set the output range to 250,0 (as opposed to default 0,255) and tweak the gamma: about 1.8 seems good here. quick hiraloam USM (20,50,0) and the final result gives a full range of tonality, amazing shadow detail and a light touch on film grain.

Here's a comparison with one of the shots I showed before. Lower image is with the new negative as positive workflow. Not quite optimised but much, much better.

1 comment:

  1. Thanks for your tip. I've been following the Photostream blog regarding positive scanning and inversion. I didn't know about using levels to Invert, that seems to do a pretty good job with it.


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