Bitmap error

[BenjaminSP]

Hi everyone,

I have a problem with bitmap.

I want to separate a graphic I made into the four CMYK channels for printing.

I start with my design in RGB mode. At first, I reduce the layers to one and change the mode to CMYK.

Then, I separate the channels with the "split channels" function.

Now I have my channels in grayscale and separated.

I go to Mode —> Bitmap —> Input & Output are on 300 Pixels/Inch, Method is Halftone.

Next, I choose the calculated frequency of 30 (120 mesh count, screen printing) and for my first color an angle of 15°. For shape, I choose ellipse.

Then I press Ok.

The result is a completely weird, digital error like picture in halftone, with elements from different layers of the project and sometimes even layers from different projects. It seems like Photoshop somehow empties it's whole media cache into my picture.

Here I have the result before and after bitmap:

I don't really think I'm doing something wrong here, but who knows.

Maybe, it's a common error and I need to install a driver or whatever...

I hope someone can help me with this.

Background information:

I'm working on a MacBook Pro 2014 on OS X 10.10.5

My Photoshop version is CS6, version 13.0

Do you need any further information?

Thank you in advance for your help!

Best regards,

Benjamin

[c.pfaffenbichler]

Does turning off »Use Graphics Processor« in the Performance Preferences (Photoshop > Preferences > Performance > Graphic Processor Settings) and restarting Photoshop have any bearing on the issue?

1-bit bitmaps should usually have 1200ppi by the way.

Why do you do manual separations anyway?

[BenjaminSP]

Hi!

Nope, it kinda stays the same.

I think 1200ppi is too fine for screen printing.

Well, I don't have a program to do it for me and the last time I checked, they were pretty expensive.

The photoshop way is usually pretty simple and works well enough. But not this time.

[c.pfaffenbichler]

The 1200ppi referred to the bitmap file’s resolution, not the Halftone Screen Frequency.

Just to make sure: Did you restart Photoshop after changing the Graphics Processor Setting and is the issue visible at View > 100%?

[BenjaminSP]

I restarted Photoshop and the issue is visible at any view. It does not change when I'm zooming in or out.

These pixels are definitely a part of the composition after converting the image to bitmap, it is not a display error.

I can convert the image to grayscale or whatever and work with these weird structures.

[c.pfaffenbichler]

What have you done for general trouble-shooting so far?

Restoring Preferences after making sure all customized presets like Actions, Patterns, Brushes etc. have been saved might be a good starting point:

https://helpx.adobe.com/photoshop/kb/basic-trouble-shooting-steps.html

[BenjaminSP]

And I just realized, that the problem only occurs when working with .psd or .pdf files. When I export the graphic as .jpg and import it again, separating and converting works without any problem.

Thank you for your help! My problem is solved for now, but I definitely would care about the answer to the problem.

So if you read this, Adobe engineers, maybe you can drop a line. Thanks

[c.pfaffenbichler]

When working with psd did you try flattening the file (Layer > Flatten Image) before converting?

[c.pfaffenbichler · Accepted solution]

Did you flatten the image before converting?

https://feedback.photoshop.com/photoshop_family/topics/split-channels-on-large-cmyk-files-gives-glit...

Photoshop CC 2015: Convert to halftone bitmap wacks the image into unusable tiles | Photoshop Family...

[BenjaminSP]

Hey!

I just flattened it in one step with changing the mode to CMYK.

But you're right, that was the problem. I now flattened it BEFORE converting it to CMYK and the change to bitmap also worked fine.

It also made a transparency layer every time I split channels.

You found the exact same problem I had, thank you!

But funny, the Adobe engineer wrote, he had solved the issue back in CS5...