PSCS2: tif to jpeg, color changes


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wind30

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Mar 14, 2004
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Hi People,

I shoot in RAW with my E1, and develop the raw using olympus viewer to 16bit tiff. From the tiff, I use save for the web option to convert to jpeg. I included the ICC profile and used maximum settings but after saving the jpeg, I find that there are color changes. Is it because of the 16bit to 8bit conversion?? I thought the color should be consistent between the tiff anf jpeg..

Do you guys have the same problem? Any solution?
 

wind30

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#3
adobe RGB but I included the color profile in the Jpeg
 

wind30

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using adobe bridge. I think it is ICC aware.
 

#6
I think it's because u used the "save for web" function, which only allows saving in sRGB. Hence, if you save a Adobe RGB image "for web", colours will turn out very flat. Maybe you try converting it to sRGB first before saving?
 

Jan 23, 2005
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+evenstar said:
I think it's because u used the "save for web" function, which only allows saving in sRGB. Hence, if you save a Adobe RGB image "for web", colours will turn out very flat. Maybe you try converting it to sRGB first before saving?
JPEG has defined a whole range of compression/transmission standards. Image file formats that use these standards may differ even more. (A TIFF file may for example use JPEG compression to store image data).

The universally accepted baseline JPEG file format is JFIF. JFIF uses the CCIR 601 YCbCr colour space, not sRGB. In general, no JPEG-DCT compressed image format uses RGB, since one of the major compression principles is based on separating luminance and chrominance (brightness and colour).

There are some file formats losely based on JFIF (e.g. EXIF) that may allow to use other colour spaces and embed colour profiles. Strictly speaking, programs expecting proper JFIF files should reject such files. (If such a file claims it is JFIF, but uses a different colour space, it resp. the program that generated it is broken.) However, in the interest of "user-friendlyness", most JFIF decoders will try to interpret these files as if they were JFIF files, which could result e.g. in colour shifts etc.

Edit: this link is probably the best starting point: http://www.jpeg.org/jpeg/index.html
 

Jan 23, 2005
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wind30 said:
From the tiff, I use save for the web option to convert to jpeg.
Are you by chance using Photoshop CS to do this?

I just looked at two ".jpg" files generated by Photoshop CS. Both are a mish-mash of JFIF and EXIF. The file header claims they are JFIF version 1.02, however there are also EXIF APP1 marker segments, which are not allowed in JFIF files. An EXIF file, in turn, should not have an JFIF 1.02 file header.

In other words, Photshop CS is most likely broken. You could try using standards compliant software and see if that solves your problem.
 

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