Re: How to apply curves in PS for digital negatives...

George,

You might find the following web pages of interest. They summarize some
tests I ran last year for double-coated Van Dyke Brown printed using a
digital negative generated in Photoshop and output onto Pictorico OHP
using an Epson 2200 printer with Ultrachrome inks and printed onto
Cranes' Kid Finish stationery. Be forewarned of nude content though.

http://my.net-link.net/~jsmigiel/images/technical/vdb_test_11-19-04.jpg

http://my.net-link.net/~jsmigiel/images/technical/VDB_test_prints.jpg

The pages show before and after curve adjustment pics as well as
positive/negative files, a graphical depiction of the curve applied to
the *negative* image file, a table comparing %K values after curving
and resultant transparency density, and a couple of final prints scanned
for comparison of two slightly different curves. There are also digital
density step wedges, both affected and unaffected by the curve
adjustment, as well as Stouffer 21-step wedges printed along with the
files.

Prints were processed in Kalamazoo municipal water using a 2% citric
acid initial wash and gold-toned using Clerc's gold-toner after fixing.

:)

Joe

>>> glsmyth@yahoo.com 11/27/05 3:51 PM >>>
--- Michael Koch-Schulte <mkochsch@shaw.ca> wrote:
> I look at many of the curves in the curves area of
> alternativephotography.com and just roll my eyes. Half of them look
totally
> wrong to begin with and other half give you no details on how there
were
> produced, what printer, what paper, inks, times et al. No one has
mentioned
> so far, although it's been said many times, that applying a generic
curve
> like this will probably only produce mediocre results -- if you're
lucky. To
> truly reap the benefits of the curve function you have to print YOUR
OWN
> step tablets so you can match the tones from your output (i.e. the
final
> VDB) to the tones produced on your digital negative output. For all
you know
> this curve was a VDB produced on a piece of paper towel and developed
in
> creek water. Nothing wrong with that except that maybe it's not your
brand
> of paper towel or you live on a different creek. You need to learn how
to
> produce your own curves. You can buy into someone's system or develop
your
> own as I did. For starters, get a piece of graph paper and map out
where 5,
> 10, 20, 30...80, 90, 95 and 100 per cent black on your negatitve
printed on
> your final output. What you'll find is that the relationship is not
linear.
> Create a table from your results and make a curve based on that. This
is
> where understanding of the process begins.

Michael -

I am sure that you are right and have actually printed several 100 box
step
tablets on different papers. It definitely allows one to see how things
respond.

Cheers -

george

Handmade Photographic Images - http://www.GLSmyth.com
DRiP Investing - http://DRiPInvesting.org

                
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Received on Sun Nov 27 21:20:52 2005