Re: Inkjet negatives and Van Dyke Brownprints

Joe,

Looking at the curve values that you came up with here are a couple of
comments.

First of all, I just read Gary Nored's article and notice that he is
exposing his digital negatives using sunlight. If you are using tubes or a NUARC,
there could be a real difference in behavior of inkjet negatives between the
two light sources.

Both your and Gary's curve values indicate a density range in the negative
that is higher than the exposure scale of the Van Dyke process you are using—
he is reducing density range by upping the black point value from 0-24 while
yours is upping the black point value from 0 to 54. As you say, this
compresses the image tones and you end up with fewer printed tones in the VDB
print.

This could be a difference in media settings. It wasn't clear which
media setting you are using. The highest density media setting for the Epson
 2200 with a UV light source is Premium Glossy Photo Paper. The matte paper
settings generally have less density, however the order of the media
settings in the printer driver setup does not necessarily translate to one of
increasing or decreasing density.

On the other end of the Curve Output Values, you show a really strong
increase in density in the (225,133) point on your curve, which may indicate
that your Standard Exposure Value for VDB is too high as this would indicate
trying to compensate for blocked up shadows. It would also lead to
Posterization in the shadows, since the curve is so steep around that point. Also,
when I entered your values, I got a "dip" in the line of the curve,
between this point and the next point, which would also cause an odd
"banding" around those values in the image.

While your overall curve is similar to the shape required for an
adjustment curve, it indicates a number of problems. Adjustment curves should be
very smooth and graceful. The best adjustment curve, is no curve at all,
which is difficult to achieve, but coming as close as you can to that is a
good goal. Even with a good 16 bit workflow, the more exaggerated the
curve, the more problems you have with tonal loss.

Mark Nelson
www.precisiondigitalnegatives.com

In a message dated 11/18/04 10:21:44 PM, jsmigiel@kvcc.edu writes:

> Thanks for the pointer to Gary's site.  I had seen it and read the
> article.  But,  it only adds to my bewilderment about the severity of
> the correction curves.  Look at Gary's curve values compared to mine:
>
> input...Gary's output...My output
> 225...222...133
> 190...190...118
> 156...162...103
> 120...138...93
> 90...121...85
> 44...90...72
> 20...61...64
> 0...24...54
>
> His range of values in the corrected negative is almost 200 levels while
> mine is compressed to around 80 levels.  We are both clipping the high
> and low ends but my clipping is much more severe on both ends and the
> curve much lower in contrast.  I've tried my curve with a couple
> different images and get similar (and nearly acceptable) results from
> the negatives.  I'm perplexed.
>
Received on Thu Nov 18 23:59:39 2004