Converting to CMYK color profile (for print) in raw format

Question

I am looking to self publish a cookbook in lightningsource. They need the photos in cmyk format. When is it best to convert to this color profile from rgb?
I have bridge CS5
What I'm doing currently:
I click on my .arw image file and select "open in camera raw" which brings me to an editing screen. At the very bottom is says rgb, and 240 ppi
I need 300 ppi at least and cmyk color.
Now I know how to change these things in Photoshop, but I was taught that editing it in camera raw in bridge is better to preserve quality for print.
Should I just edit it in raw and then convert to 300 dpi and cmyk color in photoshop? Or is there a way to do this in bridge? Whats the difference? Any advice will help, trying to make my pictures look amazing in print

Answer 1

Correct me if I misunderstood anything!
You are on the right track except for the ppi story. The ppi settings just are a figure expressing the amount of pixels stored in 1 inch, without the width and height figures of the image itself you can't do much with it and just changing this figure is not changing the total amount of available pixels.
For instance create a new document at 300 ppi and use the international paper size A4 (21 x 29,7 cm). The amount of pixels is 2480 x 3508 (roughly the result of an 8 MP dSLR.
Use the image size option in PS and be sure to not resample (meaning creating new pixels or deleting pixels to alter the original file size that is 24,9 MB). Now change the amount of pixels to whatever you like. If you increase the number the width and height decrease, and vice versa. Yet the amount of pixels and file size stay at 2480 x 3508 and 24,9 MB.
But with the specs of wanted width and height for the end result of 300 ppi starts making sense.
For instance you have a image at the size of a post stamp and an image at international paper size (A4) and both are 300 ppi. The small post stamp size would be in cm about 2 x 3,5 while the A4 size has about 21 x 30 cm width and height.
So you can imagine having both needed to be printed at the A4 size in 300 dpi (printers work with dots, hence they use dpi - dots per inch- and while not the same they both often use the 300 figure and stand for pretty high quality result) the A4 sized original will meet the wanted standards without problems   while the post stamp would have to be resampled to the new A4 size and when having still 300 ppi needed there would be a lot of interpolation (creating new pixels to match the new size) and this would often result in pixelated or worse quality print result, because PS has to use guess (albeit quit educated guessing) work to add more pixels that are needed to reach the new dimensions.
ACR has the advantage to set the ppi by default at 300 but as said, as long as you don't alter width and height of the original it is just a figure without any significant importance until you know the complete specs for the output source.