On the dynamic range of RAW...

Started Nov 30, 2004 | Discussions thread
Niktron Regular Member • Posts: 156
Re: Anders and Guy...

Hey dude

I think your trouble sparks from different types of compression.

JPG is incorperates lossy compression, i.e. data is thrown away each time a file is saved as a jpg.

TIFF and PNG etc use lossless compression i.e the image is compressed but no data is lost.

When you save a file as a JPG, the program doing so will apply lossy compression to the saved file. Thus if you open a jpg, save it as a jpg, close the file, open it, save it as a jpg, close it open it, save it as jpg, eventually your image will look rubbish.

So if you save your files as a lossless compression such as tiff or png etc there will be no loss on saves, and no matter how many times you save (and therefore apply the compression) the image will always be of the same quality

hope this helps

AJohn wrote:

Thanks, I am starting to understand SOME of it. :] I must admit
though, there is some over load, sparking and sputtering going on
in my brain and I am struggling with some things that may be

I shoot in SHQ Jpeg so my files are already compressed as they come
out of the camera. OK, so if I then convert them to TIFF, what have
I done to that file? I have decompressed it but that doesn't give
me any more info than the file had to begin with, correct?

So, is the purpose of doing this so I won't loose anymore quality
to the file from this point on? In other words, if I open a jpeg
and do the normal adjustments in PSE (color, contrast, etc.) and
then click yes to 'save changes' (not 'save as'), and save at it
the highest quality, the file has degraded some and this would not
have been the case had these adjustments been done in TIFF? MAN, I
hope that made sense. LOL.

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And Trogdor smote The Kerrek, and all was laid to burnination

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