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digital photo weirdness
patrickl:
There is an alpha channel in the non-working one. You can remove this with Photoshop (uncheck the alpha channels box when saving).
BTW you should have cleaned the dust and fingerprints off the film before you scanned it.
shmokes:
Thanks. What does that mean, and why does it break the photo?
patrickl:
--- Quote from: RayB on June 17, 2010, 03:01:32 pm ---JPEG is lossy. Just a warning. (Like i said, I recommend PNG or TGA. They will still reduce filesize since TIF is a bloated format to begin with).
--- End quote ---
Yeah JPEG is lossy, but you are really not going to be able to see the difference between a 2MB JPEG and a 20MB TIFF file. Especially not with these unenhanced slide scans. PNG can cut the filesize in half too though.
Also converting to JPEG or PNG also gets rid of the Alpha channel.
Maybe they forgot to get rid of the IR channel that some scanners create for dust removal. Although this Alpha channel seems to be completely black. My slide scanner would to show the dust specks on the IR layer and then the alpha channel culd be use to remove these specks of dust.
patrickl:
--- Quote from: shmokes on June 17, 2010, 04:26:53 pm ---Thanks. What does that mean, and why does it break the photo?
--- End quote ---
Like I said in the previous post. I think it might have been intended as an IR dust removal channel (dust specs show up on film in IR light while the film itself is "black")
Not sure why they left it in. Especially since it doesn;t seem to hold any IR info anyway. It's completely black and thus useless.
So in short, I have no idea why it's there or what it's supposed to do.
I'm guessing there is a bug in the thumbnail software of Windows. Like I said, TIFF is such a free format and not all software fully supports it and all it's features.
:edit: OK it's not a multipage TIFF. It's a 4 layer image. Which explains the odd 32 bit color depth that you mentiond. It's actually a 24 bit RGB image and a fully black 8 bit alpha channel.
Still, I guess it's just a bug where the Microstf TIFF library can't handle the extra layer. Now that I think about it I sometimes had to remove the IR layer too for some software to work with the TIF files.
RayB:
--- Quote from: patrickl on June 17, 2010, 04:27:29 pm ---Yeah JPEG is lossy, but you are really not going to be able to see the difference between a 2MB JPEG and a 20MB TIFF file. Especially not with these unenhanced slide scans. PNG can cut the filesize in half too though.
--- End quote ---
True, but you never know when you may want to retouch a photo, or cut n paste portions of it. When you do that from a JPEG, on saving again, you end up re-compressing an already compromised photo and eventually the image degrades enough to look crappy.
shmokey: Patrick already addressed the issue, but I had a fun refresher on the various formats' file sizes. I did color correction while I was at it: http://www.rayb.com/temp/wed.zip
Let me know when you've downloaded this so I can delete it.
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