jpg bit depth

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MikeFromMesa
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jpg bit depth

Beitrag von MikeFromMesa »

I have always believed jpg images to be 8 bits, and so used other formats, usually tiff, if I wanted more bit depth. However when I loaded a jpg into PhotoLine recently I noticed that although the Layer information showed the image to be 8 bits it could be set to 16 bits and, if it was and the file was saved, when it was reloaded the image display showed the image as 16 bits. That is, both the Layer information showed 16 bits and the image name showed 16 bits.

Is it possible to save a jpg as 16 bits? Or is this just some 16 bit envelope around an 8 bit image?
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Hoogo
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Re: jpg bit depth

Beitrag von Hoogo »

Afaik Jpg is still 8Bit.
Maybe you have the .PLD sidecar enabled? Any file you save is also saved as an additional .pld to store everything without losses.
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cathodeRay
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Re: jpg bit depth

Beitrag von cathodeRay »

I stand to be corrected by those more knowledgeable than me, but my understanding is a real jpeg can only ever be 8 bit. I say 'real' because once loaded into PL the jpeg enters a brave new world where it can have all sorts on non-jpeg things, like layers, for starters, and I think this may be why PL treats the jpeg as 16 bit once it has loaded the image, having previously had it set to 16 bit. In fact, I think I'm right in saying PL actually does the maths at 32 bits.

I wonder what you would see (as bit depth) if you opened the jpeg in another image editor/inspector?

cathodeRay

PS I see Hoogo posted while I was writing my comment!
MikeFromMesa
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Re: jpg bit depth

Beitrag von MikeFromMesa »

Hoogo hat geschrieben: Di 31 Okt 2017 19:56 Afaik Jpg is still 8Bit.
Maybe you have the .PLD sidecar enabled? Any file you save is also saved as an additional .pld to store everything without losses.
How would I know? Where is that setting? I looked in Preferences but did not see anything that I could set to ON or OFF that seemed related.

I can see no .pld file in my folder, but perhaps it is being created and is a hidden file.
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Hoogo
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Re: jpg bit depth

Beitrag von Hoogo »

MikeFromMesa hat geschrieben: Di 31 Okt 2017 20:08 How would I know? Where is that setting? I looked in Preferences but did not see anything that I could set to ON or OFF that seemed related.
I can see no .pld file in my folder, but perhaps it is being created and is a hidden file.
"Edit > Options > File > Save options", "Save additional .pld file"
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bkh
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Re: jpg bit depth

Beitrag von bkh »

MikeFromMesa hat geschrieben: Di 31 Okt 2017 20:08 I can see no .pld file in my folder, but perhaps it is being created and is a hidden file.
Normally, the pld sidecar file isn't hidden. However, to be sure, move the jpeg file into a different folder and open it from there. (Or attach a small sample jpeg to a forum message so others can check its bit depth.)

There is a 12 bit variant of jpeg, but PL can't save 12 bit jpegs. (In fact, there are only a few programs out there which can open 12 bit jpegs.)

Cheers

Burkhard.
MikeFromMesa
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Re: jpg bit depth

Beitrag von MikeFromMesa »

Hoogo hat geschrieben: Di 31 Okt 2017 21:21 "Edit > Options > File > Save options", "Save additional .pld file"
OK. I found it and it was checked. I have turned it off and will see if that changes the behavior.

Thank you for the location.
MikeFromMesa
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Re: jpg bit depth

Beitrag von MikeFromMesa »

I turned off the auto pld file save and then I went through the process of testing saving a 16 bit file as a (supposed) 16 bit jpg. That is, I did the following:

1) Loaded a raw image into PL,
2) Adjusted it,
3) Explicitly flattened the image,
4) Make sure the Layer information listed it as a 16 bit layer,
5) Saved it as a jpg,
6) Closed the current image,
7) Opened the saved jpg.

What I found is that the layer was now marked as 8 bits, and nothing in the title lists it as 16 bits. So, perhaps it was the auto saved PLD file that was causing the jpg to show as a 16 bit image.

Thanks for the information about removing that auto file save.
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