You need to make an export preset for CMYK but you need the correct one the printer wants you to use. EX US SWOP Coated V2 or US SWOP UnCoated V2 or Japan swop or a hundred others. Most large printers have in-house Prepress production departments that should do this for you from your Srgb or Adobe98 files. And do it for no charge if they really want your business. Tell them you only have Adobe98 and need their help … The black and whites should be exported from Ap as B&W but the color space as Adobe98 or SRGB. The printer can convert those to Monochrome as they like. Hope that helps
David

Oh I left off the following. The conversion to CMYK is very specific to the press and inks and thickness of paper, the absorbson of ink, the paper coating, moisture of the air in the location where its being printed etc etc. Most likely a Printer here in the States will say Us Swop V2 (coated? or Uncoated?) will be fine. If printed overseas I have no idea. They should do it for you and guarantee a close match to your RGB files. GoodLuck

No problem. Pre-press for four color output is a subject none of us know very well except for the printers and their prepress dept. Thats why its best for them to convert cuz they have the best possible tools n knowledge to make the best product for you. Cheers

I have been preparing images for CMYK offset color printing since the late 1970’s … long before desktop computers and Photoshop were on the scene … DB is right, Aperture 3 can convert your images to CMYK … though you may be far better off in allowing the printer to handle this task if they are willing. Alas, there are some print houses who still don’t offer this level of service.

While using the proper color profile for your CMYK conversion is extremely important to the process … there is much more to consider when sending press ready files to your printer. Image size, resolution, and sharpening.

Because you are breaking down your image into four separate parts, ensuring your image has enough data to be properly rendered in the final product is important. Conversely, sending too much data for the image can, at times be problematic when it comes to proper output sharpening. Because the two factors are interdependent.

Send in a file that has too much data for the size the image is to be printed, and your sharpening could be rendered moot by the time you reach the final product and the image has been resampled to the proper size.

Ideally, you need to know the physical dimensions the image is to be printed. You need to know the “screen” resolution for the process as well. The term for screen here is how many dots per inch are being used to lay down ink on paper. It gets it’s name from resembling a typical window screen when looking at a separation.

The Rule of Thumb is you need to export the image at a ppi (pixels per inch) at twice the value of your press lpi (lines per inch or “screen” size). This file size will offer the press production equipment enough data to accurately render the image with reasonable detail. For example, if your printer is using a 133 lpi screen, your image will be printed 8 inches on the long dimension, it needs to be exported at 2,128 pixels at 266 ppi. However, say you send a CMYK file at full pixel count of the original capture and 300 ppi, just to be “safe” … and allow the printer layout software to handle the resizing of the image … Sounds good on the surface, though, what happens is when the image is rendered at the smaller size and proper ppi … it has a negative impact on the sharpening you applied to the image and can in some cases be detrimental to fine detail in the finished image.

Sharpening should be applied to the finished dimension and resolution … this would remove Aperture entirely from the task as there is no way to properly define your sharpening needs for CMYK offset printing. This is where you either have to rely on your printer to apply the proper sharpening or take the task to Photoshop (or other capable options) yourself.

The reason sharpening is even more important for CMYK offset printing is that when these four layers are combined, the images shows reasonable fine detail. I have found in many cases, that you need to take the sharpening a bit further further than you would for normal continuous tone (standard photographic prints) or inkjet prints in order to compensate for the loss of detail due to the offset printing process itself, especially in low 85 lpi images for newsprint. Often, when I have sharpened images for CMYK offset printing, they do look over sharpened on the monitor … even a bit ghastly in some cases … though, after working with several presses over the years and analyzing their individual traits, you get a feel for what they can handle in the areas of finding a happy medium for sharpening.

Hope this helps to understand the process and reinforces the concept of CMYK offset printing, and the importance of a good working relationship with your print vendor. If you can get them to handle these details in a trustworthy fashion, so much the better for you.