What's the point of converting RGB images to CMYK TIF/TIFF before placing them in InDesign?

Question

Currently we receive CMYK TIF/TIFF images of photographs from our design agency (who get them from the photographer). Our in-house designers then place them in InDesign for posters and magazines, or convert them to RGB to be used on the website or in newsletters or presentations.I'm wondering what's the point of taking a photograph, then converting it to a CMYK TIF/TIFF (with HUGE filesize) before placing it in InDesign, and maybe converting it back to RGB for screen-use?I mean, the photograph is RGB anyway, and InDesign can use colour profiles too. So, if InDesign is assigned the correct profile (from the printing press) why convert the images to CMYK beforehand? Wouldn't it be a much wiser choice to save the retouched images as PNG (which is lossless)? The print designer would then place the image in InDesign and then, when the document is done, export to CMYK using the correct profile. Whereas the web designer would take the image, resize it into the correct format and save it as a JPG.Advantages: - Immensely reduced file sizes - One conversion less - On-screen viewing can be done by anyone without them getting off colours because their viewer doesn't support CMYK - 8-bit transparencyAlso, I'm not entirely sure if our design agency actually uses the press profile our printers use because the agency is in a completely different country.Am I missing something crucial here?

Answer 1

RGB is a system based on image emission. Meaning light pours into your eyes. It is an additive processs. So - 255 / 255 / 255 gives you White. CMYK is a Subtractive process. 100 / 100 / 100 with no K gives you dark mud. Now comes the trick. You can see on the screen in RGB. BUT! You will only get the true colors by proofing with a final print proof. Why? The paper is your white level. So the paper already has changed your Whites based on its characteristics. THAT is why you need paper profiles AND printer profiles AND display profiles. But don't these profiles create a corrected image? NOPE! Only if you have a Closed - Loop - Calibration System. IF you were to calibrate EVERY time every unit is involved in the process. Then yes it should match. BUT! If the display - RGB device - is not matched to the clipped subtractive value you printed. Then the images will start to diverge. The Monitor may look good, and the print varies. Or the print looks alright, but the Dispaly looks better. Doing RGB for RGB and CMYK for CMYK guarantess you a better result. How do I know? Only did this for 20-years for The Huntington, Plantary Society, Pasadena Museum of History, and Caltech.