How do I specify the jpeg compression ration when setting an attribute

I'm running Win 7 HP 64 bit. I have been storing a value in the file attribute using Windws Explorer. However I notice that when I do this Windows Explorer changes the compression ratio used in my jpeg files. For instance I have been specifying the minimum compression ratio and getting files that are apporx 8 MB in size so that I have plenty of data to loose if I edit these files later (jpeg is a lossey algorithm).

When I set an attribute using Windows Explorer I notice that the file size drops to a value (typically) below 2 MB, so I'm loosing a lot of data. Is there any way I can set the default compression ratio that Windows Explorer will use when it stores an attribute value? I had been under the impression that attribute values were stored separately from the jpeg file, but that seems not to be the case - it seems they are stored as part of the jpeg file.

Actually I did store them as Tiff as well. I know I can always go back to the tiff ones and create new jpegs - that was not the point - I was wondering if anyone knew how to influence the arbitrary decision that Windows Explorer seems to take for me on the compression ratio it uses. Just as a matter of interest tiff does allow one to choose a compression algorithm but it only uses lossless algorithms, so inevitably the files are larger, but as I mentioned earlier that was not really what my question was about.

which file attributes are you changing and how?

i am unable to repeat your problem, and i have no idea why explorer would recompress jpgs by changing attribs.

do you mean the info shown along the bottom of the explorer window?

that information does get stored in the actual image file, and is readable by other software.

i've always found that adding data her in explorer adds about 6 kb to the file size, but i've never noticed any recompression going on.

but then i don't have any 8 meg jpgs - i suppose i'll have to make some and test.

*edit* just tried it with a big jpg - no noticable difference in file size. they certainly haven't be reduced to a quarter.

more testing needs to be done...

OK, let me give you an example - I start off with a tiff file of 17.5 MB and save this as a maximum size jpeg with Adobe Photoshop Elements V9 and I get the size as shown in the first picture (Before Attr Edit) - this shows a size of 7696 KB. I then enter values for the Subject and Title attributes and after clicking on 'Save' I get the size as shown in the second picture (After Attr Edit) which is now 1448 KB, which means I've lost about 80% of my data thanks to Explorer making an arbitrary decision on the compression ratio to use rather than preserving my original ratio. I'd just like to know how to influence this.

By the way if I do subsequent edits I don't believe Explorer throws away any more data, but then its already probably made its maximum impact! Any other application which 'edits' jpeg files gives you the option to specify which compression ratio you want to use - Explorer seems to make the decision for you without giving any warning, and as far as I can see, any way in which you can influence this decision. If you can spot a way of finding out how to influence this while still using Explorer I'd be grateful.

could you please attach the 7.51 meg jpeg to a post, so we can try repeating this?

*edit* i don't think the forum software lets you attach jpgs that big - could you zip it first?

i think there's a 1 meg limit on jpgs but 8 megs on zips.

I don't think I'm convinced about the rougue registry entry - if it were XP I might consider it, but Win 7 seems much better in terms of registry management. I think there is something more subtle going on here. By the way, I checked the Advanced Attributes and mine looks exactly the same as yours - no sign of a tick in the Compress Contents box. I'm going to do a bit more searching around with other image management programs and see if I can understand the characteristics of the output from Adobe Photoshop elements a bit better - if I can find something that gives me more info on the jpeg characteristics of the before and after files I think I may be nearer to understanding what is happening, even if I can't control it.

Also just so that you can see if you get the same results here is a zipped jpeg - the Explorer size on my system is 6480 KB prior to setting the attributes and after setting Explorer shows 1727 KB! Lets see if your mileage varies!

no change here.





sorry, but i don't know how to fix your problem.