U of S | Mailing List Archive | alt-photo-process-l | Re: curves and gum and Christopher James book

Re: curves and gum and Christopher James book

Hello Henry,

A correction curve that is meant to be used on a positive image before inverting to a negative should not be confused with a curve that has to be applied to an allready inverted image. There are two 'schools' of curving for digital negatives. It's a bit like driving left or ride side of the road. In both cases you will arrive from A to B but you should never mix the methods.

Anyway, sometimes it comes handy to change a 'before inverting' curve into an 'after inverting' curve. For example when you want to build your curve into a QuadTone Rip profile.

This can be done with the Curve Merging technique described here: http://polychrome.nl/weblog/curve-merging
Actually you will not merge two curves here but you 'wrap' a curve layer with your curve loaded between two invert layers. Then you have to flatten this package and save the .raw file as a .amp curve. When you load that curve you can change it to a regular .acv by clicking on the pencil symbol in the curves palette. When I find some time this week I'll write an article about this on my site.


On 10 mrt 2008, at 20:09, Henry Rattle wrote:

Michael – you are right, of course. But my question was more about – shouldn’t a curve that you apply to a positive, curve in the opposite direction from one you apply to a negative?

David’s curve, like mine, has the shadows in the bottom left corner.


On 10/3/08 18:44, "Michael Koch-Schulte" <michael@mondotrasho.ca> wrote:

Henry, it all depends how the curve data was gathered in the first place. Neither is right or wrong it's more a matter of workflow. I choose to apply my curves to the positive because I'm taking my readings from a developed positive. I also like to work in PS with the curve putting my highlights in the bottom left corner using the graphic scale of 0-100 rather than the binary scale of 0-255. The important thing is that you apply the curve to the image at the correct stage of the procedure. Dan Burkholder started doing it this, I also do it this way. It intuitive for me. Others apply the curve to the negative.

On Mon, Mar 10, 2008 at 6:53 AM, Henry Rattle <henry.rattle@ntlworld.com > wrote:
However one thing puzzles me - there's a note alongside the curve which says
"Note from David: The curve is applied before inversion to a negative and
the image should be RGB."