Curves dialog Box

EGR wrote:

Hi All. I am doing a project in Photoshop 6. and following instructions from a book which makes various adjustments on individual colors in the RGB channel of the Curves Dialog Box. It goes on to say,"Lighten the Overall Exposure using the composite (CMYK) channel" My problem is my curves dialog box doesn’t have a CMYK channel in the dropdown menu. I have searched the PS6 manual for guidance but can see nothing appertaining to this. Have I missed something along the way?Any help would be appreciated. Many thanks. EGR.

For an RGB image the composite "channel" is called RGB.

CMYK is another color space entirely. Although not in keeping with the "conventional wisdom", it is well worth converting your RGB images to CMYK not only to follow the examples in your book, but often for color correction in general, even if your eventual use of the image is in RGB. —

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net

Thanks Mike,
I have seen the light .Thanks again for your help.
EGR

"Mike Russell" wrote in message

EGR wrote:

Hi All. I am doing a project in Photoshop 6. and following instructions from a book which makes various adjustments on individual colors in the RGB channel of the Curves Dialog Box. It goes on to say,"Lighten the Overall Exposure using the composite (CMYK) channel" My problem is my curves dialog box doesn’t have a CMYK channel in the dropdown menu. I have searched the PS6 manual for guidance but can see nothing appertaining to this. Have I missed something along the way?Any help would be appreciated. Many thanks. EGR.

For an RGB image the composite "channel" is called RGB.
CMYK is another color space entirely. Although not in keeping with the "conventional wisdom", it is well worth converting your RGB images to CMYK not only to follow the examples in your book, but often for color

correction

in general, even if your eventual use of the image is in RGB. —

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net

it is well worth converting your RGB images to CMYK
not only to follow the examples in your book, but often for color

correction

in general, even if your eventual use of the image is in RGB.

You have got to be kidding…

Frogiswrong wrote:

it is well worth converting your RGB images to CMYK
not only to follow the examples in your book, but often for color correction in general, even if your eventual use of the image is in RGB.

You have got to be kidding…

Not at all.

Certain images correct more easily, and give a better final result, when corrected in CMYK. The same is true of Lab and RGB.

CMYK is good for controlling shadows, making very fine color adjustments, and for restoring detail to highly colored items, such as flowers. Channel mixing from RGB to CMYK can add punch to certain color ranges. It’s true that some blues get fried when you convert to CMYK, but this may be largely avoided, when it matters, by using the Wide Gamut CMYK profile: http://www.curvemeister.com/tutorials/cmyk/widegamutcmyk/wgc myk.htm

Lab is good for manipulating saturation, correcting very intense color shifts that are not dependent on luminance, such as deteriorated film emulsions, and large changes in brightness without causing color casts.

Lab is also the basis of Photoshop’s selective color adjustment, and using curves in Lab gives you more control over selective color operations. Lab is the best color space for sharpening, and for getting rid of chroma noise.

RGB is good for luminance dependent color casts, such as mixed illumination, and for removing other color casts, provided they are not so extensive that the overall luminance of the image is affected.

More generally, if you are looking for a channel to use as a mask, look outside the RGB cube. You may find just the mask you need in one of the other color spaces, rather than limiting your search to RGB only. The a and b channels of Lab can be a particularly rewarding source of masks.

If you use only one color space you’re limiting your options for certain images.

Take the other color spaces for a spin. You paid for them after all 🙂 —

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net

You sold me. ill give it a burl and see how it goes.
I have some hidieous images i need to correct tomorrow. ill let you know how i go on sunday.

Thanks very much.

"Mike Russell" wrote in message

Frogiswrong wrote:

it is well worth converting your RGB images to CMYK
not only to follow the examples in your book, but often for color correction in general, even if your eventual use of the image is in RGB.

You have got to be kidding…

Not at all.

Certain images correct more easily, and give a better final result, when corrected in CMYK. The same is true of Lab and RGB.

CMYK is good for controlling shadows, making very fine color adjustments, and for restoring detail to highly colored items, such as flowers.

Channel

mixing from RGB to CMYK can add punch to certain color ranges. It’s true that some blues get fried when you convert to CMYK, but this may be

largely

avoided, when it matters, by using the Wide Gamut CMYK profile: http://www.curvemeister.com/tutorials/cmyk/widegamutcmyk/wgc myk.htm
Lab is good for manipulating saturation, correcting very intense color shifts that are not dependent on luminance, such as deteriorated film emulsions, and large changes in brightness without causing color casts.
Lab is also the basis of Photoshop’s selective color adjustment, and using curves in Lab gives you more control over selective color operations. Lab

is

the best color space for sharpening, and for getting rid of chroma noise.
RGB is good for luminance dependent color casts, such as mixed

illumination,

and for removing other color casts, provided they are not so extensive

that

the overall luminance of the image is affected.

More generally, if you are looking for a channel to use as a mask, look outside the RGB cube. You may find just the mask you need in one of the other color spaces, rather than limiting your search to RGB only. The a

and

b channels of Lab can be a particularly rewarding source of masks.
If you use only one color space you’re limiting your options for certain images.

Take the other color spaces for a spin. You paid for them after all 🙂 —

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net

Mike… Not that i think your theories are wrong… BUT the images i happened to be working on responded FAR better to color correction in RGB.

"Frogiswrong" wrote in message

You sold me. ill give it a burl and see how it goes.
I have some hidieous images i need to correct tomorrow. ill let you know

how

i go on sunday.

Thanks very much.

"Mike Russell" wrote in message

Frogiswrong wrote:

it is well worth converting your RGB images to CMYK
not only to follow the examples in your book, but often for color correction in general, even if your eventual use of the image is in RGB.

You have got to be kidding…

Not at all.

Certain images correct more easily, and give a better final result, when corrected in CMYK. The same is true of Lab and RGB.

CMYK is good for controlling shadows, making very fine color

adjustments,

and for restoring detail to highly colored items, such as flowers.

Channel

mixing from RGB to CMYK can add punch to certain color ranges. It’s

true

that some blues get fried when you convert to CMYK, but this may be

largely

avoided, when it matters, by using the Wide Gamut CMYK profile: http://www.curvemeister.com/tutorials/cmyk/widegamutcmyk/wgc myk.htm
Lab is good for manipulating saturation, correcting very intense color shifts that are not dependent on luminance, such as deteriorated film emulsions, and large changes in brightness without causing color casts.
Lab is also the basis of Photoshop’s selective color adjustment, and

using

curves in Lab gives you more control over selective color operations.

Lab

is

the best color space for sharpening, and for getting rid of chroma

noise.

RGB is good for luminance dependent color casts, such as mixed

illumination,

and for removing other color casts, provided they are not so extensive

that

the overall luminance of the image is affected.

More generally, if you are looking for a channel to use as a mask, look outside the RGB cube. You may find just the mask you need in one of the other color spaces, rather than limiting your search to RGB only. The a

and

b channels of Lab can be a particularly rewarding source of masks.
If you use only one color space you’re limiting your options for certain images.

Take the other color spaces for a spin. You paid for them after all 🙂 —

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net

Frogiswrong wrote:

Mike… Not that i think your theories are wrong… BUT the images i happened to be working on responded FAR better to color correction in RGB.

Well, you gave it a shot. Perhaps you will come across an image that would benefit from one of the other color spaces. One very common one is to give colors a boost by steepening the a and b channels in Lab.

—

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net

You should see if "Professional Photoshop" by Dan Margulis is available in your library. It was a real eye-openener for me and I highly recommend it for more understanding of color correction.

On Sun, 2 Nov 2003 11:39:56 +1100, "Frogiswrong" wrote:

Mike… Not that i think your theories are wrong… BUT the images i happened to be working on responded FAR better to color correction in RGB.

"Frogiswrong" wrote in message

You sold me. ill give it a burl and see how it goes.
I have some hidieous images i need to correct tomorrow. ill let you know

how

i go on sunday.

Thanks very much.

"Mike Russell" wrote in message

Frogiswrong wrote:

it is well worth converting your RGB images to CMYK
not only to follow the examples in your book, but often for color correction in general, even if your eventual use of the image is in RGB.

You have got to be kidding…

Not at all.

Certain images correct more easily, and give a better final result, when corrected in CMYK. The same is true of Lab and RGB.

CMYK is good for controlling shadows, making very fine color

adjustments,

and for restoring detail to highly colored items, such as flowers.

Channel

mixing from RGB to CMYK can add punch to certain color ranges. It’s

true

that some blues get fried when you convert to CMYK, but this may be

largely

avoided, when it matters, by using the Wide Gamut CMYK profile: http://www.curvemeister.com/tutorials/cmyk/widegamutcmyk/wgc myk.htm
Lab is good for manipulating saturation, correcting very intense color shifts that are not dependent on luminance, such as deteriorated film emulsions, and large changes in brightness without causing color casts.
Lab is also the basis of Photoshop’s selective color adjustment, and

using

curves in Lab gives you more control over selective color operations.

Lab

is

the best color space for sharpening, and for getting rid of chroma

noise.

RGB is good for luminance dependent color casts, such as mixed

illumination,

and for removing other color casts, provided they are not so extensive

that

the overall luminance of the image is affected.

More generally, if you are looking for a channel to use as a mask, look outside the RGB cube. You may find just the mask you need in one of the other color spaces, rather than limiting your search to RGB only. The a

and

b channels of Lab can be a particularly rewarding source of masks.
If you use only one color space you’re limiting your options for certain images.

Take the other color spaces for a spin. You paid for them after all 🙂 —

Mike Russell
http://www.curvemeister.com
http://www.zocalo.net/~mgr
http://geigy.2y.net

Smeltsmoke