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Question

Find bitmap settings on existing file

Forum|Forum|3 years ago
August 25, 2022
5 replies
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How can I find out what settings I used on a bitmap file? I open it, it's clearly bitmap, but when I go to Mode it shows it as grayscale. I need to experiment with different angles on my file because we are getting some moire in the less contrasty parts of the image. I want to see what the file information is, and I don't know where to find that or even if it's stored anywhere. It's not on file info. Can anyone tell me how to store this in a file for future reference and how to find it on existing files, if that's possible? And why does the file mode show grayscale instead of bitmap? Thanks in advance. I'm doing a lot of silkscreens from photos. I'm using 30 ppi at 22.5 angle. 45 angle is too grid-like.

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L

Lumigraphics

Brainiac

You can turn on the History log in Preferences if you need a record of what editing steps you take with a file.

Brad @ Roaring Mouse

Community Expert

How have you been achieving your halftone effect. There are two ways.

One is Converting to Bitmap using Image > Mode > Bitmap. This is a destructive process so there's no "record" of what you did before. What you want to do to improve the look of these is to UP your resolution to 1200 or even 2400. A true Bitmap file takes very little space so the more pixels you have to create a halftone dot, the better they will look.

The other is using the Color Haftone Filter on a Greyscale image... It's not as logical to use, it stays a a grey-scale image (you can confirm this by zooming in: you will see nice anti-aliased dots) but what it CAN do is be used as filter on a Smart Object (i.e. convert your image to a Smart Object in Layers) so it can be modified at will without baking it in.

If you truly require a bitmap image from this (I don't think you do if you're just using this effect in a larger composition), save a copy of this layered file, Convert to Bitmap ( Image > Mode > Bitmap... selecting a resolution (again, higher is better) that leaves you with attractive dots)

Stephen Marsh

Community Expert

~~An alternative option for you, presuming a grayscale mode file:~~

~~1) Convert the layer to a smart object~~

~~2) Run the Filter > Pixelate > Color Halftone~~

~~The result will be a smart filter, which allows one to recall and adjust the settings.~~

EDIT: I didn't read the OP, bitmap mode would be best for actual halftone output for screenprint... However, I'd imagine that you would need 600 – 2400ppi for well formed dots.

You can record the conversion into an Action so that it can be repeated multiple times, same for entering the info into the File Info metadata.

D

dbr 200Author

Known Participant

This is one of the finished ones, they're printed on bark paper

D Fosse

Community Expert

You seem to misunderstand the terms.

Bitmap is just another word for raster, in other words a file made up of pixels (discrete data points).

It's grayscale because it only has one channel of information. So it's a monochrome image, not a color image.

If your image is made as a halftone screen, that's baked into the pixel data. You can't "extract" that from the file any more than you can extract the yeast from a loaf of bread. It's integrated into the pixel structure of the image.

There is no "hidden" information in an image file, aside from what can be saved with the file as metadata. What you see is what is there.

D

dbr 200Author

Known Participant

Thanks. Very possible that I don't understand the terms completely. I'm an artist and I use PS for specific things. Actually I posted incorrectly: the resolution is 200, the *frequency* of the dots is 30 because I want the printed image to look almost like a newspaper photo. It's an aesthetic and conceptual decision.

But when I convert the grayscale to bitmap I have to make choices and I thought I could go back to the file and see what those choices are. At that point, the mode is bitmap and that's what I saved. So why does that not show up? In future I'll save the settings in the File Info tab. But for now, there's no way to see what I did before, is that correct? The only way I can see it is to once again start to convert to bitmap and see the last settings used, but if I start fiddling with that it won't help in the future.

Is it the case that "bitmap" is not a mode, per se? It's just a way of organizing a grayscale image?

Semaphoric

Community Expert

A Bitmap in Photoshop is a single channel, one-bit image (black/white, with no grays). One thing you could do is to copy the various fields into Photoshop's Notes tool, and then save.

c.pfaffenbichler

Community Expert

I don’t think the information you expect is stored at all and you may have to manually measure the angle and frequency.

Could you please post a screenshot taken at View > 100% with the pertinent Panels (Toolbar, Layers, Channels, Options Bar, …) visible?

As for grayscale: To me a user error seems more likely than Photoshop suddenly converting the image from bitmap all by itself.

30ppi? That seems terribly low.

What it your actual output device? What is its resoution?

Regular film printers might well offer about 2540dpi resolution.

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