TIFF vs JEPG
in [Scanners]
|
Prev: canon F914900
Next: Canon FB 630 U - Driver
From: Scott W on 19 Apr 2006 12:52 Bruce wrote: > Don, > > Yes, everyone agrees that with high compression JPG artifacts can be > objectionable. But the point is that at low compression the quality can > be so good that any data loss is imperceptible even after zooming in. > Your answer when shown examples of this is to repeatedly accuse them of > lying (you question the "veracity" of the examples) and then to attack > them for taking offense to your accusations. > > The fact is that if you need to save a photographic image to a limited > file size you will always get a better quality image from a JPG than a > TIF. For example, to fit 100 large images on a CD, with quality JPGs > you could use higher DPI (a very perceptible difference) than you could > with TIFs. > > And Don, anyone watching sees the pattern where you provoke attacks and > then feign innocence. In this case, if you don't like the data they > show, maybe you should try and reproduce their results before publicly > announcing (on theoretical grounds) not only that they are wrong, but > that they also must be purposely lying. > The other myth out there is that a jpeg image might look ok for a photograph it can not show clear high contrast text. With 5 minutes of work anyone can tell this is simply not true, as this image shows. http://www.sewcon.com/tiff_vs_jpeg/text.jpg For those who believe they see jpeg artifact here is the tiff that the jpeg was made from. http://www.sewcon.com/tiff_vs_jpeg/text.tif And for those super paranoid here is the psd file, with the text layers intact. http://www.sewcon.com/tiff_vs_jpeg/text.psd Now other file formats do better at this kind of image (make smaller files) but that fact remains that there is no visible degradation from the jpeg compression. Scott
From: Raphael Bustin on 19 Apr 2006 20:04 On Wed, 19 Apr 2006 16:38:18 +0200, Don <phoney.email(a)yahoo.com> wrote: >I only talk about objective facts and, as you >yourself confirm, clearly visible JPG artifacts at 100% are a >self-evident, axiomatic fact. Try this for yourself. Or don't. 1. Pick a really crisp, sharp, hi-res film scan. Give it your very best. The more pixels, the merrier. 2. Downsample heavily, say 8x. Now you've got an image that's razor sharp and chock-full of detail. You'll have single-pixel transitions. 3. Now try to mess up this image using best-quality JPG-save settings. Use Quality=Max, regardless of how the application presents or labels it. I can observe no JPG-related image degradation with such settings. Not by eye. Not at any degree of resizing or resampling. Not at any screen magnification. Not with any image. Not with any app that matters. rafe b www.terrapinphoto.com
From: Colin D on 20 Apr 2006 08:44 rafe b wrote: > > "Don" <phoney.email(a)yahoo.com> wrote in message <snip arguments> OK guys, there's an easy way for Don, Noons, and others to check Rafe's contention that there is no observable difference between a tif and a 12-level jpg. I loaded both of Rafe's images, the tif and the jpg into Photoshop, They are both exactly 1001 pixels square, so if scanned at 4000 ppi the crops represent a 0.25-inch square piece of the negative or slide, and when viewed at 100% on my monitor at 72ppi, the magnification is 4000/72, or 55x. Then I made a duplicate image in PS of the tif file, and saved it as a level 12 jpg, wrote it to disk and then reloaded it into PS. OK. Results: at 400% on the screen, each pixel was visible, and at that level there was no discernible difference among the three images side by side, notwithstanding that Rafe's jpg was 980-odd KB and mine was 1200-odd. Maybe his was a level 10 compression. Under blind test conditions I don't think anyone could nominate which was which. An interesting point, though. I understood that for the best jpg results the pixel dimensions should be divisible by 8, which 1001 certainly isn't. Since the jpg's remained at 1001 pixels, the jpg process didn't crop the image, so maybe it ignores the extra pixel, and just operates on the 1000 x 1000 area. Anybody know? Colin D.
From: Noons on 20 Apr 2006 11:16 Don wrote: > That's one example. Another one is areas with lots of high contrast > detail where the 8x8 pixel JPG squares are as plain as can be. Bingo! And why I make a point of NEVER commenting on a "crop" of an image without having the original ENTIRE file to compare against: it's only too easy to - intentionaly or not - make a crop at anything other than 100% where artifacts don't show as well or get masked by other noise effects. With the original file that is a lot harder to do and it becomes clear which is jpg or tiff. > Both of those are statements of subjective opinion (i.e. a reflection > of how much one values image content). I never talk about that because > that not only depends on the context but each person has their own > individual requirements. I only talk about objective facts and, as you > yourself confirm, clearly visible JPG artifacts at 100% are a > self-evident, axiomatic fact. Couldn't agree more.
From: Scott W on 20 Apr 2006 11:50
Noons wrote: > Don wrote: > > > That's one example. Another one is areas with lots of high contrast > > detail where the 8x8 pixel JPG squares are as plain as can be. > > Bingo! And why I make a point of NEVER commenting > on a "crop" of an image without having the original > ENTIRE file to compare against: it's only too easy to - intentionaly > or not - make a crop at anything other than 100% where artifacts > don't show as well or get masked by other noise effects. > With the original file that is a lot harder to do and it becomes > clear which is jpg or tiff. Well I did give you the entire file to compare too in my sample. But please if you don't like my image how about one of yours, just a small crop will do. In case you missed mine here it is again I did the test, here is my crop, one side was save as a jpeg the other is the original tiff. http://www.sewcon.com/tiff_vs_jpeg/compare.tif 2.8 MB Note not all browsers will view a 16 bit tiff and so this might have to be downloaded and viewed in something like Photoshop. This is an overview of the full image http://www.sewcon.com/tiff_vs_jpeg/overview.jpg And for those just for grins this is the full image as a fairly highly compressed jpeg http://www.sewcon.com/tiff_vs_jpeg/overview.jpg 13.5 MB Scott |