Computer Graphics with Photoshop - Sharpening changes color

Author

Sharpening changes color - help?

lynn.herrick@lineone.net

2005-06-09, 7:15 pm

Hi, Hope someone can help me with this one, as it's driving me mad. My
images' colour changes when I sharpen in LAB->lightness. I open the
images using the RAW converter in PS CS and then work on them until I
like them, then convert to LAB -> lightness to use unsharp mask. When I
then convert to RGB the images end up with a horrible colour cast. I've
been getting around this by making a duplicate image before I sharpen
and then use color match to try to get the sharpened image back to the
original, but there must be a better way. I'm probably doing something
a bit silly, so any help or advice will really be appreciated! Thanks,
Lynn

Johan W. Elzenga

2005-06-09, 7:15 pm

lynn.herrick@lineone.net <lynn.herrick@lineone.net> wrote:

> Hi, Hope someone can help me with this one, as it's driving me mad. My
> images' colour changes when I sharpen in LAB->lightness. I open the
> images using the RAW converter in PS CS and then work on them until I
> like them, then convert to LAB -> lightness to use unsharp mask. When I
> then convert to RGB the images end up with a horrible colour cast. I've
> been getting around this by making a duplicate image before I sharpen
> and then use color match to try to get the sharpened image back to the
> original, but there must be a better way. I'm probably doing something
> a bit silly, so any help or advice will really be appreciated!

You do not need to convert to LAB. The following method gives you the
same result without converting:

1. Sharpen the image (in RGB)
2. Immediately go to 'Edit - Fade Unsharp Mask'
3. Change the mode from 'Normal' to 'Luminosity'

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl/

Mike Russell

2005-06-09, 11:15 pm

lynn.herrick@lineone.net wrote:
> Hi, Hope someone can help me with this one, as it's driving me mad. My
> images' colour changes when I sharpen in LAB->lightness. I open the
> images using the RAW converter in PS CS and then work on them until I
> like them, then convert to LAB -> lightness to use unsharp mask. When
> I then convert to RGB the images end up with a horrible colour cast.
> I've been getting around this by making a duplicate image before I
> sharpen and then use color match to try to get the sharpened image
> back to the original, but there must be a better way. I'm probably
> doing something a bit silly, so any help or advice will really be
> appreciated! Thanks, Lynn

Normally the conversion to Lab is very reversible. Converting back again
should have no visible effect on your image.

This makes me suspect something is wrong with your working color space
profile.

Are you using an unusual profile - for example a custom profile made for
your camera - as your working space?
--
Mike Russell
www.curvemeister.com

lynn.herrick@lineone.net

2005-06-13, 7:14 am

Thanks for the replies. I shoot in RAW mode and the image is initially
image.nef. Would this make any difference?

Timo Autiokari

2005-06-13, 7:16 pm

"lynn.herrick@lineone.net" <lynn.herrick@lineone.net> wrote:

>I shoot in RAW mode and the image is initially
>image.nef. Would this make any difference?

The file format itself does not affect.

I case your image is in the native color-space of the camera, it can
easily give such color changes. In this case you need to convert the
image to a RGB working-space profile.

In case you convert to a non-linear working-space profile (such as the
adobeRGB or sadRGB) then sharpening will give you the white-haloing
around the edges and it does not sharpen the dark-end of the tonal
range well at all. To avoid this (and many other such errors) the best
solution is to use a linear RGB working-space.

Timo Autiokari http://www.aim-dtp.net

lynn.herrick@lineone.net

2005-06-14, 7:17 pm

Thank you SO much! It works beautifully. I have no idea why, but it
works!!!

Lynn
------
You do not need to convert to LAB. The following method gives you the
same result without converting:

1. Sharpen the image (in RGB)
2. Immediately go to 'Edit - Fade Unsharp Mask'
3. Change the mode from 'Normal' to 'Luminosity'

--
Johan W. Elzenga johan<<at>>johanfoto.nl
Editor / Photographer http://www.johanfoto.nl/