CMYK .jpg...problem with blacks....

[masofon]

Howdy,

Am helping a friend design a CD sleeve (few different designs) with a lot of black on it... Have been working in CMYK mode and using true black (75/68/67/90) rather than K100...It looks great as a .psd but when saved as a .jpg the background black (and in some cases parts of black from the photography used) are showing up grey when viewed in 'Preview'...Said jpgs look fine in Photoshop and fine in a web browser, but grey in Preview...then also inverted on an iPhone web browser (random) and green in the iPhone picture gallery (also random). .PNGS are fine across the board, .pdfs are acting the same way as .jpgs. I'm very confused about this! Any help would be appreciated. Obviously my main concern is that they will print grey rather than true black.

See pictures! http://img848.imageshack.us/g/screensho ... at094.png/

(I'm a web designer by day, so CMYK mode is a scary place for me!!)

Mx

[Crapaud]

Specifically, I don't know what's causing your prob, but PS does weird stuff when changing coloour modes especially if you don't merge the layers.

I'd be inclined to flatten a copy of the PSD and change the colourspace to sRGB before saving as a JPEG.

Let us know how you get on.

[jerryb]

hi,
i think part of the issue is the fact that jpg is a lossy format...

if the compression is to high you start to get artifacts, lose fine details,
shades can get distorted, etc... so you may not want to use to high of a compression factor...
also doing alittle searching... came across the fact that some programs
can't handle a cmyk jpg image... so it looksl ike be a good idea to change your
cmyk mode to jpg before saving... maybe making a duplicate of the file first and use the 2nd file to do things with... there some tidbits of info in this article..

http://www.cellbio.duke.edu/faculty/kli ... /help.html

myself i very seldom save in jpg , if high quality needed i save mostly in png format.. it larger file size but i don't have to worry about jpeg artifacts or shade distortion etc...

[Medley]

You have a gamma problem that stems, at least partially, from the computer converting colors to other profiles.

The last two images you posted have a file format that does not support embedded color profiles.

Open any of the images where the black is "off", sample the color with the eyedropper tool, then open the color picker. Notice the values in the Hue, Saturation, and Brightness (HSB) section of the color picker. Now change the B (Brightness) value to 0 (or in many cases, 1). Your CYMK values reappear! Hue and Saturation can be any value. If the Brightness value is 0, the color is defined as 'black'.

The gamma setting determines how the computer defines 'neutral gray', and so can have a marked effect on the Brightness value in the HSB dialog box.

- Joe U.