Curves question

E
Posted By
embee
May 22, 2006
Views
501
Replies
5
Status
Closed
Hi,

I’m doing more and more of my Photoshop work in CMYK, as most of my pictures are for print rather than screen viewing. When I come to write curves adjustment layers, I like to switch the orientation of the graph to the same as RGB – ie. black on the left.

However, when I click on the little black and white arrows to make the switch, something happens. Instead of my sample point values showing as percentages (as they should in CMYK), they revert to RGB (ie. 50% becomes 128). This only happens after I switch the orientation of the graph – before making the switch I get normal CMYK percentages.

I know I am missing something pretty straightforward, and I know I’m going to feel stupid when I get the answer. But it’s late, I’m tired and I’m willing to feel dumb in order to solve this!!

Thanks in advance.

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MR
Mike Russell
May 22, 2006
"Mike" wrote in message

I’m doing more and more of my Photoshop work in CMYK, as most of my pictures
are for print rather than screen viewing. When I come to write curves adjustment layers, I like to switch the orientation of the graph to the same
as RGB – ie. black on the left.

However, when I click on the little black and white arrows to make the switch, something happens. Instead of my sample point values showing as percentages (as they should in CMYK), they revert to RGB (ie. 50% becomes 128). This only happens after I switch the orientation of the graph – before
making the switch I get normal CMYK percentages.

I know I am missing something pretty straightforward, and I know I’m going to feel stupid when I get the answer. But it’s late, I’m tired and I’m willing to feel dumb in order to solve this!!

This is normal behavior. Photoshop is not reverting to RGB, but it displays color values from 0-255 when you have black on the left, and 0-100 when black is on the right. Black on the right takes some getting used to, but this is the way the really cool people do it, since it indicates the amount of ink.

The Curvemeister plugin allows this to be set independently, so that you can have black on the left and still use ink percentages.

Mike Russell
www.curvemeister.com/forum/
E
embee
May 22, 2006
"Mike Russell" wrote in message
"Mike" wrote in message

This is normal behavior. Photoshop is not reverting to RGB, but it
displays
color values from 0-255 when you have black on the left, and 0-100 when black is on the right. Black on the right takes some getting used to, but this is the way the really cool people do it, since it indicates the
amount
of ink.

Thanks for the reply Mike, good to know I’m not going mad! I now understand that it’s normal behaviour, but I still don’t understand WHY Photoshop does this. If I’m working in CMYK then I want percentages – why can’t I have percentages and use black on the left curves?

I’m working in CMYK after reading Dan Margulis’s book Professional Photoshop and he recommends setting CMYK and RGB curves so black is always on the same side. I don’t recall him mentioning this issue.
The Curvemeister plugin allows this to be set independently, so that you
can
have black on the left and still use ink percentages.

Mike Russell
www.curvemeister.com/forum/

MR
Mike Russell
May 22, 2006
"Mike" wrote in message
….
Thanks for the reply Mike, good to know I’m not going mad! I now understand
that it’s normal behaviour, but I still don’t understand WHY Photoshop does
this. If I’m working in CMYK then I want percentages – why can’t I have percentages and use black on the left curves?

I agree with you, and added this feature to Curvemeister. Photoshop feels differently.

I’m working in CMYK after reading Dan Margulis’s book Professional Photoshop
and he recommends setting CMYK and RGB curves so black is always on the same
side. I don’t recall him mentioning this issue.

Just to keep you on your toes, in some cases Dan will show a composite image with black on the right and the numbers going from 0-255 for RGB. This is impossible to achieve in the real world, using Photoshop. —

Mike Russell
www.mike.russell-home.net
E
embee
May 23, 2006
"Mike Russell" wrote in message
"Mike" wrote in message

Just to keep you on your toes, in some cases Dan will show a composite
image
with black on the right and the numbers going from 0-255 for RGB. This is impossible to achieve in the real world, using Photoshop. —
Thanks for the heads-up about that 🙂 I’ll keep a look out for it as I work my way through the book a second time – my mind is dizzy even thinking of trying to figure out one of those curves!
MR
Mike Russell
May 23, 2006
"Mike" wrote in message
[re Professional Photoshop book]
Thanks for the heads-up about that 🙂 I’ll keep a look out for it as I work
my way through the book a second time – my mind is dizzy even thinking of trying to figure out one of those curves!

I doubt anyone can get it all from reading. One effective way to learn is to load the images from the CD and try the eamples yourself. —
Mike Russell
www.curvemeister.com/forum/

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