Reply To: InDesign/Prepress Myths

I decided to write up my thinking a little more in this blog post: https://creativepro.com/tif…..pdf-vs.php

@Mark: I'm sorry, but I strongly disagree with your idea of “combination tones” requiring 500-900 dpi. If there is vector data in the file, use PDF and you'll get a combination of vector and raster data. If you need it to be all-raster, your higher-res does not (I argue) work. In your example, you're exporting from Photoshop as PDF (which maintains the vectors), then rasterizing in Photoshop! Why on earth would you want to rasterize like this in Photoshop if you wanted sharp edges? 

Please understand that if you have a 500-900 ppi TIFF image, it's going to get downsampled significantly. Either InDesign will do it at print/pdf-export time, or your RIP will do it internally. If you're printing halftones, that typically means it will downsample to 2x the halftone screen frequency (lpi). Downsampling like this is usually done in a non-bicubic manner, which means your final output will be worse than if you downsample the image yourself before printing.

There is little reason to have more than 1.5x lpi in any photographic image, so if you're printing with a 150 lpi, then 225 ppi is all you need in most images. If you do have very sharp edges, then I would suggest 300 ppi.

I'm open to hearing your argument, but I'm not convinced from your samples there. There are too many variables, including your particular rip, your worfklow, etc.