Tiff Thumbnails have strange grid pattern and come out grey when saved

[KillerRabbit]

Hello,

This has been happening for years to Tiff Files and realized it has something to do with Alpha Channels. When I delete all the alpha channels the thumbnail is normal. When there are any alpha channels it gives you this strange thumbnail. It's more annoying than anything since it isn't giving you the information you need to be able to pick the file and if most of the files are affected this way it starts to become cumbersome to find what you are looking for. If anything just distracting.

So this might not be a question since I have the solution, but I don't know why I can't have alpha channels in these files. If they are PSDs files they come out fine or cut off sometimes when you open up a preview since alpha channels are masks. I don't know if this is a Photoshop issue or a Mac issue. I think I may have experienced this on other macOS systems prior to Monterey. I don't think this has anything to do with upgrading or anything though maybe a newer imac might solve this issue (newer than a 2015 imac).

I just wanted to see if anyone has had these issues before and maybe there is some kind of saving thing I'm not doing right. I typically don't compress TIFFs. I treat them like high quality final versions usually flattened. PSD files I save them with layers as Final.

[Jeff Arola]

What version of macOS and Photoshop are you using?

What model and year Mac do you have?

You flatten the tiffs, but keep the Alpha Channels and then save?

[KillerRabbit]

macOS Monterey iMac 2015.
This has always happened. I'm talking about over a decade or more. It happens to TIFF files only. If you take out the alphas the thumbnails are fine. If they have alphas it behaves this way. 

[KillerRabbit]

TIFFs might be flattened, but I don't recall that having any bearings on the weird thumbs. All I know of if I delete the alphas the file behaves fine. If it has any alphas regardless of it's a solid white or black or a shape the finder will make those TIFF files have that strange effect. 

[D Fosse]

Not a Mac user, but Windows too interprets any alpha channels as transparency in TIFF.

IOW not Photoshop, but the operating system.

[Jeff Arola]

Does it make any difference if you change the Icon size in the Finder window using the slider in the bottom right corner of the Finder window?

[KillerRabbit]

Wow! It definitely does. When it's at a very small scale it goes back to the correct image preview and when enlarged it gets the weird effect. Is this something that may have been solved in later macOS versions. I think I mentioned it, but I was aware of this strange thing for a long time and partly the reason I stopped saving documents as TIFFs.