Computers and Software > Raster and Vector Manipulation Programs, and How to Do Stuff in Them.

Converting to bitmap in Photoshop

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Dottonedan:

--- Quote from: kidink on March 18, 2020, 11:12:15 AM ---
Hey Dan, yeah i get that in regards to the input resolution, obviously the higher the ppi the cleaner the edges will be as there are more pixels to work with but i'm thinking about the point at which we convert to bitmap in Photoshop which is essentially mimicking a RIP right?

So if the supplied artwork file is at 300ppi and we convert to bitmap, do i up the resolution to 600dpi or even 1200dpi which is similar to the output resolution of a printer? I'd always do this if I was converting to a greyscale image to halftones but i'm talking about a standard 50% threshold bitmap.

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Yes, to mimicking a RIP.  When they say that a RIP is actually better, it is for a couple reasons.

1, the algorithm or math for doing so is better, more specifically designed for such a purpose...More accurate.

2, There are various other great benefits of using a RIP. But use this method up till you can afford a rip.


If I’m given a 150ppi file, and I need to create halftones for the customer yes, I convert to bitmaps and rip at (the end output devices resolution). Typically 600 or 1200 depending, but 600 at minimum. The reason is more to provide a more detailed and well formed dot shape. 600 is the bare minimum for that. It does not create goods small dots because at that resolution, the small dots in a 55lpi (1-7% range) are more or less a couple square pixels.  But yes, convert any resolution to create ehe halftones at 600 or 1200.  There is some resampling going on, and as a results, (if there are any blurred or fuzzy edges, you will get halftones on those edges but your dots will be well formed.  I sometimes clean up edges (after I convert to bitmap) using the pencil tool and paint in black or white.

Dottonedan:

--- Quote from: Sbrem on March 18, 2020, 11:50:27 AM ---I've left out one of my steps to help smooth the edges; after going up to 600 ppi, I add a little blur with Gaussian Blur, then open either Curves or Levels and move the endpoints inward, which hardens the edge, but with much less discernible pixillation. This while still in grayscale, then I convert to Bitmap after that. The source image is key as Dan says.

Steve

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Yes.  This is similar to deciding if you want anti-aliasing turner don or off before hand. Similar results.  I do a lot of adjusting either way.

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