RAW and changes
Jun 10, 2019 11:41:56 #
Ysarex
Loc: St. Louis
bleirer wrote:
So when tiff and some others are said to be lossless, what is the meaning of that in this context? One can still change the color temperature for example, up or down on a 0 to 100 scale when editing a tiff file. Is something lost in IQ when you do this vs. reopening a raw file, or is it just another way to do the same thing?
TIFF is lossless and editable but it is structurally different than a raw file and so the edit procedures used to effect a change in either are different and can have different outcomes. So we're not doing the same thing and as such the difference matters in the result.
In a TIFF file each pixel in the image contains full color information. A pixel in a TIFF file can be orange or pink or maroon or robin egg blue and to do that each pixel contains three values. There are three channels per pixel in the structure. A pixel in a raw file is either red, green or blue and contains only one value. There is only one channel per pixel in a raw file. So the underlying software procedures for effecting changes will vary with the structural differences. Unfortunately the software vendors don't always make this clear.
It's appropriate to be able to edit a TIFF file and it's OK to do that but it will not produce the same result as editing a raw file. Try it:
https://www.dropbox.com/s/p4mtk2pk8lcu6e0/IMG_0146.CR2?dl=0
Open that Canon raw file in ACR and set the WB by clicking with the WB dropper on a sample point in the image -- the white card sticking out of the black case is good. Save that version of the image as a TIFF or JPEG. Then go back to the raw file and reset the WB to as shot. Open the photo as is in PS and then try and set the WB using Camera Raw Filter with the previous saved image loaded for comparison. You will not be able to match them.
Joe
Jun 10, 2019 11:49:30 #
Ysarex
Loc: St. Louis
gvarner wrote:
When JPEG file’s are opened, then edited, then saved again, the process compresses the original data to make the file smaller, it throws some of the data away. TIFF and other types of files are not compressed on saving, thus they are called lossless. I don’t know why the creators of the JPEG process decided it was a good idea to throw data away. Maybe they thought they were doing everybody a favor because disk storage was so limited way back in the Dark Ages.
The JPEG algorithm is brilliant and does it's job superbly. The only time it causes problems is when it's abused out of ignorance. If all the JPEGs moving around the Internet right now were suddenly uncompressed to their original size the Internet would choke and die instantly. JPEG is fantastic.
Joe
Jun 10, 2019 13:49:14 #
gvarner wrote:
... I don’t know why the creators of the JPEG process decided it was a good idea to throw data away...
Consider this, my camera takes photos with ~24 million pixels. My monitor can only show ~1 million pixels at a time. If I threw away all but every 5th pixel in both height and width the result would look the same as the original on my monitor when viewing the full image.
Jun 10, 2019 14:35:23 #
gvarner wrote:
When JPEG file’s are opened, then edited, then saved again, the process compresses the original data to make the file smaller, it throws some of the data away. TIFF and other types of files are not compressed on saving, thus they are called lossless. I don’t know why the creators of the JPEG process decided it was a good idea to throw data away. Maybe they thought they were doing everybody a favor because disk storage was so limited way back in the Dark Ages.
Now that is funny.
Do you ever crop or resize any of your images? Do you ever post or view images online?
Mike
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