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Halftone banding in PS when using bitmap to create halftones?

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mimosatexas:
I started noticing this on certain images and I am honestly clueless as to why it is happening.  Google is failing me completely...

I have tried TONS of different resolutions, LPI's, angles, shapes, etc and it is pretty much always happening with this image.  I can create a simple gradient and it just isn't happening.  When you zoom in super close it looks like the issue is the actual pixel shape of the dots is inconsistent, even at something like 5000ppi, which I understand is due to the size changing based on the % of the gradient at that point, but why is it banding in this way and so noticeably, even at super high resolutions?  Changing the angle/lpi/shape will change the angle and size of the banding, but it is always there.  It's super obvious on the film and in the print as well.

The attached images are the photoshop file zoomed out to a point exaggerate the effect a little, but the second one if pretty close to what it looks like.

Colin:
Was this image a scan from pre printed materials like a magazine?

If so, it will pick up the artifacts from the rosettes used to print that image....

Sbrem:
Here's what I do with those, it's worked so far. A raster image is made up of consistent pixels when created, you set the resolution and go. If creating art, a good rule of thumb is 300 ppi minimum at the final size. But this isn't that particular situation, we have to deal with it as is. So, I'll take a crappy jpeg someone gives me, convert to grayscale using the Black and White adjustment to control the shades. From here, I go to Bitmap mode, input resolution is a crappy 72 ppi of course, but set the output resolution to 1200; set the halftone to the desired line count, angle and shape. The high output resolution will make the resulting dots exceptionally clean. Trying to change the resolution of a raster image is rather fruitless, at least for me. I'd love to hear something to the contrary if there is a tip or two floating around out there...

Steve

Edit, just saw the above post, and yes, if you took that from a printed piece, there is not a lot you can do. The descreening filter found on a good scanner software may help, and you may have to blue more in Photoshop to make a new starting point.

lrsbranding:
Would cleaning up the image with this software-  http://www.benvista.com/  before going to PS help with the problem?

mimosatexas:
The art is not scanned from print and the original image resolution is 300ppi.  I was wrong in my original post as well, it is happening no matter what, even on a simple gradient in photoshop.

Attached is an image of a test.  I made a 1200ppi image, added a 0-100% white to black gradient, then bitmapped into halftones, also at 1200ppi.  Again, regardless of angle, shape, lpi it is causing the banding.  what gives?!  It definitely did not always do this...and I haven't changed anything that I know of...

It must have to do with some math related to the way PS is creating the halftones.  the first image below is standard 22.5degrees 55lpi 1200ppi ellipse.  The second is 25degrees 50lpi 1200ppi round.  third image is zooming in on the halftones around the 10% range.

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