Standard for JPG Compression levels?

[FlyingPete]

OK, is there a standard measure of compression in JPG's?

It seems everyone has their own definition, Photoshop uses a scale of 1-12, NeatImage uses a scale of 1-100, my cameras have compressions levels such as 'Fine' and 'Superfine', but no numerical value. What gives?

I would like to be able to maintain the same compression level in my JPG's throughout the post processing environment, it seems that 'Fine' from my 20D is roughly equivalent in quality to 98 in NeatImage and 11 in Photoshop. Recently I have begun just using the highest setting, but this wastes space and I almost might as well be using RAW.

Is there a way of finding out what the compression level in an image is? Photoshop seems to remember for images saved in Photoshop at some point, but doesn't have a clue if it was from another source.

I also know that constantly ‘decompressing’ and ‘recompressing’ images can lead to quality degradation, although tests I have done show this is not really an issue unless you compress at different levels or many times over, hence this question.

[nitsch]

I would like to be able to maintain the same compression level in my JPG's throughout the post processing environment, it seems that 'Fine' from my 20D is roughly equivalent in quality to 98 in NeatImage and 11 in Photoshop. Recently I have begun just using the highest setting, but this wastes space and I almost might as well be using RAW.

Pete, I don't think there is a standard for compression levels as such. I use Macromedia Fireworks for image file size optimization at work and it has a scale of 1-100 which doesn't bear any direct corrolation as far as I can tell to the 1-100 scale within for example Paintshop Pro. My preferred app is Photoshop and of course as you point out it has a completely different scale of 1-12.

Personally I think it is best to save your images in a non compressed format such as TIFF or PSD during the post processing phase. I really wouldn't worry about the extra space taken up by not compressing your files - HD space is so cheap these days.

Only once I am finished editing do I save a copy as a JPG and the compression I choose at this stage will depend on its intended usage. If I were posting it on the web then I'd probably resize and choose an 8 in Photoshop, if I were going to send it to be printed I would save at level 12.

Although I guess I haven't directly answered your question, I hope this helps.

[FlyingPete]

Personally I think it is best to save your images in a non compressed format such as TIFF or PSD during the post processing phase. I really wouldn't worry about the extra space taken up by not compressing your files - HD space is so cheap these days.
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I try to do as much now in Photoshop (plugins etc), I have considered getting NeatImage to output TIF in batch runs though.

Yes standalone disk space is cheap, but for every gigabyte of photos I have, I require three to four times that in actual disk due to the fact I store on a mirroed array, and keep offsites.