Can anyone recommend a site or converter program you have used with good success that will convert an RGB-PSD to a CMYK-PSD..   Very large files and the programs I have found on the fly today do not seem to offer a PSD save.. Mostly Jpeg or to small converted sizes back at me....and the printer that will be printing these items for my customer needs RGB-PSD format only..  Anyone please?   The printer did not inform the customer of the CMYK need for some reason till he received my rgb's    and now that I have done all the work I do not want to re-do them all from scratch thus I could use some good advice here.   Yes.. the printer said he could "Tweak" but.. I don't wish to allow that.  Who knows what we would all end up with..  so.. hoping the crew here might know a good resolve..

Lj,
 
We do all of our color conversions in Photoshop, but the price of the application can be prohibitive. On the Macintosh side, you can use an application called Acorn, which is MUCH cheaper and very good. I'm not sure what to do on the Windows side.
 
Jason

hmmm.. .I don't do much CMYK, so I may be doing this incorrectly   but in my Photoshop (CS3)
 
Open your RGB.psd image
Click IMAGE (top tool bar)
Click MODE
Click CMYK color
Save file.
 
Viola!  it is now a CMYK.psd file ...

Thanks Jason.   I have never worked in Photoshop's CMYK mode before and know very little about it.   I am using P.S. CS3 extended and Windows 7.  I am trying to get the colors to be as close as I made them in rgb for this purchase.    I can except some diff in the colors but do not wish to loose the light in them and of course..   The are large vibrant background images and from what I read today..  the RGB format then printed out in CMYK can look really bad in this size-tones.  I don't know really.  Just trying to resolve this problem without remaking everything from scratch..   Took me a week to make them..  Outa time now.  I do appreciate your input very much. Thanks..    Lj

You can check your blacks as well
 
CMYK should be 60, 40, 40, 100 (uk printers require that) if you have black easy to do and doreens suggestion is spot on as well, I had to do the same thing this week, I assumed RGB and dang printer took two months to say that the blacks were saturated as I had not used CMYK very grrr.
 
It will straight convert but blacks can sometimes be rather naughty on a straight CMYK switch not sure why I am CS5

Quote from Lj_135293 on May 13^th, 2011, 12:53pm:

 
No need to move anything
Open in PS. Go to Image>Mode>CMYK.
It may ask you if you want to flatten. ANswer yes or no & poof - done. Some of those parameters suggested by other people can be helpful. ANd yes there is a color shift from RGB to CMYK.  
A rule of thumb I use is that EVERYTHING I do for print gets designed in CMYK (YES even for GCU - I know the uploads are RGB). That way I know that my numbers are true. I can always change to RBG for web. As you pointed out going the other way can result in some surprise color shifts.

Hey Lj,
 
I do the same thing as Susan - create everything in CMYK mode then, if necessary, convert to RGB.  
 
I thought I read somewhere ages ago that it was easier to convert CMYK to RGB then it is to change RGB to CMYK. It looks like lots of people have worked out a way to do it going by all of the reply posts you got so perhaps it's not so hard after all. GCU is the only place that I use that requires images be supplied in RGB, everything else requests images in CMYK which is why I just start off in CMYK.
 
Still, good to know it can be done anyhow  
 
xox

Thanks again everyone..  Great people here to assist me in my time of asap need and hugely helpful indeed..   I got it all worked through pretty much and like I said earlier.. I will use this exp in the future and not let this happen twice..  My Wraps are looking really good and both the buyer and myself are pleased with the results..  A decent commission I received too.  Been better if I only had to do them once but.. hey..  Hahah..