karl shah-jenner <shahjen@xxxxxxxxxxxx> writes: > ----- Original Message ----- > From: "David Dyer-Bennet" > > > > : On the other hand, I *want* the metadata preserved in web images. To > : my mind, stripping metadata is like deliberately erasing what somebody > : earlier wrote on the back of a photo. > > > I agree about exif info, but the 'other stuff' is of concern, stuff that is > not 1k or 2k of text, but neither is it 'image'.. it seems to be something > else - profiles maybe? Monitor/printer information? I don't know.. Hmmm; yes, a profile would add significantly. And I believe it's even documented that images on the web default to sRGB if not profiled. And in fact I don't think I'm leaving profiles in my web images. Exif, yes, and also IPTC (often more text, though all the fields in EXIF may still add up to more bits). > Just did a little test > > I dragged a noisy, busy nocturnal street scene off my memory card, copied > it a number of times and began running it through a few programs to resize > and save it, here's what I found. > > Original Image from the 6 Mp camera pixel dimension 2560x1940 = 1.81Mb > > target size = 800x600 (preserving proportions) > > > > > I then 'stripped' the original image to see what quantity of (arguably ;) > superfluous data was present - 3.6Kb was stripped. > > I then restored this image to it's prestripped state (jstrip backs up if > you ask it to) and proceeded on. > > > I resized using lanczos filter in irfanview and save at 80% quality to get > an file size of 52Kb. > (irfanview has lanczos,hermite,triangle,mitchell,bell and b-spline filters > for resampling by default, others can be added) > > I resized the stripped version also and got an image size of 48.4Kb > > I stripped the unstripped, resized version above and similarly got an image > size of 48.4Kb > > NOTE, Irfanview kept the EXIF information on downsizing and saving (prior > to stripping by jstrip). All that makes sense so far (and Irfanview is a wonderful bit of software, it's the defaulut viewer for nearly all image formats on my system). I don't use it much at all for *processing* files, though, since Thumbs Plus makes it very easy to do batch processing from the thumbnail window. [snip] > Why did PS *not* retain the exif data on resizing and saving? > (Irfanview gives me the option when saving to include or exclude this > information) They've fixed this later, CS doesn't behave that way. And there are options for which bits to save, profile and other stuff separately in the save dialog as I remember it. > What did it put in it's place? > > Why was I stripping a *lot* less data from my images than I've seen in some > other web images I've downloaded and stripped? > > why is Photoshop making such large files - the 60% 'save for web' image > (71.6Kb) was visibly softer and showed more artifacts than Irfanview's 80% > quality 48.4Kb file? > > I know Irfanview outperfoms PS according to many independent tests for > quality, but that's a dramatic fifference.. The quality levels of course don't "really" mean anything, but ignoring them and just taking the file sizes and visual impressions is interesting. > less answers, more questions .. Questions are more fun anyway. -- David Dyer-Bennet, <mailto:dd-b@xxxxxxxx>, <http://www.dd-b.net/dd-b/> RKBA: <http://noguns-nomoney.com/> <http://www.dd-b.net/carry/> Pics: <http://dd-b.lighthunters.net/> <http://www.dd-b.net/dd-b/SnapshotAlbum/> Dragaera/Steven Brust: <http://dragaera.info/>
