Photoshop’s curve fitting in the Curves dialog leaves a lot to be desired

G
Posted By
Greg
Dec 29, 2003
Views
864
Replies
4
Status
Closed
It would be nice if Photoshop could improve the curve fitting in the Curves dialog. I’ve tried two other applications (Picture Window Pro 3.5 and Paintshop Pro 7) and they both do a much better job. The "smooth" command does smooth out the curve, but it’s too extreme, resulting in a shift in the original control points. I realise that backwards compatibility may always need to be retained, but I think Photoshop should provide an option of a more advanced curve fitting algorithm. Note that I have not tried any other Adobe photo editing application yet.

Greg.
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MR
Mike Russell
Dec 29, 2003
Greg wrote:
It would be nice if Photoshop could improve the curve fitting in the Curves dialog. I’ve tried two other applications (Picture Window Pro
3.5 and Paintshop Pro 7) and they both do a much better job. The
"smooth" command does smooth out the curve, but it’s too extreme, resulting in a shift in the original control points. I realise that backwards compatibility may always need to be retained, but I think Photoshop should provide an option of a more advanced curve fitting algorithm. Note that I have not tried any other Adobe photo editing application yet.

I’m interested in how you are getting the original control points. AFAIK Smooth is only available in "pencil mode".
—

Mike Russell
www.curvemeister.com
www.geigy.2y.net
G
Greg
Dec 29, 2003
The original control points have been obtained by measuring the luminance of my Epson 2200 inkjet printer in it’s
raw (non colour adjusted mode)
when printing red, green, and blue wedges – the control points represent a pre-linearisation curve for each channel.

Yes, smooth is only available in "pencil" mode, however, when I initially enter pencil mode, the curve that Photoshop
produced for my control points stays exactly the same. One would think that there’d be an option to retain the control
points, even in pencil mode. Anyway, for the time being, I’m manually smoothing the curves with the pencil. 😉
(I found a clunky bezier curve fit function for Excel but I haven’t used it yet. Unfortunately neither Picture Window Pro
or Paintshop Pro are able to produce AMP files, so despite the fact that they produce better curves, I can’t use them – I need the AMP file so I can insert the curve into ICC profiles)

Greg.

"Mike Russell" wrote in message
Greg wrote:
It would be nice if Photoshop could improve the curve fitting in the Curves dialog. I’ve tried two other applications (Picture Window Pro
3.5 and Paintshop Pro 7) and they both do a much better job. The
"smooth" command does smooth out the curve, but it’s too extreme, resulting in a shift in the original control points. I realise that backwards compatibility may always need to be retained, but I think Photoshop should provide an option of a more advanced curve fitting algorithm. Note that I have not tried any other Adobe photo editing application yet.

I’m interested in how you are getting the original control points. AFAIK Smooth is only available in "pencil mode".
—

Mike Russell
www.curvemeister.com
www.geigy.2y.net

MR
Mike Russell
Dec 29, 2003
Greg wrote:
The original control points have been obtained by measuring the luminance of my Epson 2200 inkjet printer in it’s
raw (non colour adjusted mode)
when printing red, green, and blue wedges – the control points represent a pre-linearisation curve for each channel.

Yes, smooth is only available in "pencil" mode, however, when I initially enter pencil mode, the curve that Photoshop
produced for my control points stays exactly the same. One would think that there’d be an option to retain the control
points, even in pencil mode. Anyway, for the time being, I’m manually smoothing the curves with the pencil. 😉
(I found a clunky bezier curve fit function for Excel but I haven’t used it yet. Unfortunately neither Picture Window Pro
or Paintshop Pro are able to produce AMP files, so despite the fact that they produce better curves, I can’t use them – I need the AMP file so I can insert the curve into ICC profiles)

Here’s an idea. Since an AMP file is just a per channel 256 byte LUT, curve a 256×1 gradient in PSP, save it as a non-interleaved raw file with no header, and rename it with the AMP extension.
—

Mike Russell
www.curvemeister.com
www.geigy.2y.net
G
Greg
Dec 29, 2003
"Mike Russell" wrote in message
Here’s an idea. Since an AMP file is just a per channel 256 byte LUT,
curve
a 256×1 gradient in PSP, save it as a non-interleaved raw file with no header, and rename it with the AMP extension.

Thankyou!! What an excellent idea – that works fine. 🙂

Greg.

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