TIFF vs JEPG
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From: Noons on 12 Apr 2006 23:12 Alan Meyer wrote: > I believe that the TIFF vs JPEG issue is a red herring. I defy > you to look at an image on screen or on paper from a TIFF > vs. one from a JPEG compressed to 1/10 original size, and > tell which is which. Now, crop the JPEG and increase its size. What a bloody mess, eh? ;-) What, you never cropped an image? Tsk,tsk... > different in the two images. But even then, unless you know > in advance, you won't be able to tell which was the original, but I'll darn be able to tell which one is the JPEG! > So I store my scanned family archive as JPEGs only. Let's hope no one ever wants to see what aunt Emilie's face really looked like in that only group photo of her marriage. Ah yes: you destroyed the original photo and film... > The one thing that I strongly suggest that you can do for your > descendants is to write text to accompany the pictures. Write > down who the people are, what their relationships are to each > other, what they did in their lives, what they were like as people, > what those buildings and settings and scenes are in the images. > Then store those notes on the same DVDs as the images. A very good point. Duly noted. > And don't use Microsoft Word to write the notes (or at least > don't store them as Word files). Who knows if Word will > exist 100 years from now, or if Microsoft will exist. Store them > as plain old text files that any application whatsoever can read. Another very good point.
From: Raphael Bustin on 13 Apr 2006 00:09 On 12 Apr 2006 20:12:04 -0700, "Noons" <wizofoz2k(a)yahoo.com.au> wrote: >but I'll darn be able to tell which one is the JPEG! I doubt that, if it's a first-generation conversion from TIF, and if it's high-quality (low-compression) JPG. Obviously, JPG is inappropriate for works-in-progress. But it can be perfectly appropriate as an archival format, even for critical work. The rule is: never more than one conversion to JPG. Here's a 4000 dpi film scan snippet as JPG: <http://www.terrapinphoto.com/jmdavis/chrome_41_jpg.jpg> and here's the same as a TIF: <http://www.terrapinphoto.com/jmdavis/chrome_41_tif.tif> rafe b www.terrapinphoto.com
From: Noons on 13 Apr 2006 01:15 Raphael Bustin wrote: > >but I'll darn be able to tell which one is the JPEG! > I doubt that, if it's a first-generation conversion from TIF, > and if it's high-quality (low-compression) JPG. At high magnification? It's very clear which ones are JPEGs. At least the ones I take... Note: I said "at high magnification"! That's what the original post implied. At normal viewing in a monitor or print, it's impossible to separate them on first copies. > The rule is: never more than one conversion to JPG. I'd go along with that one. My finding as well. The concern for me would be: IF I need to do some detail image cropping and/or processing later on, it'll be nearly impossible if I archived in JPEG. While with TIFF it's all there without any loss. So I archive in compressed TIFF. Uses more cds, but that's cheap. For snapshot quality anything will do, 100%agreed. > Here's a 4000 dpi film scan snippet as JPG: sorry, without knowing how magnified the images are it's impossible to do a comparison. Still, the jpeg one appears to be slightly more "muddy" in the shadows under the roof eaves. That's consistent with what I've seen it do in similar cases.
From: Don on 13 Apr 2006 08:33 On Wed, 12 Apr 2006 13:50:35 -0400, "Alan Meyer" <ameyer2(a)yahoo.com> wrote: >I believe that the TIFF vs JPEG issue is a red herring. I defy >you to look at an image on screen or on paper from a TIFF >vs. one from a JPEG compressed to 1/10 original size, and >tell which is which. > >If you blow up the images to the point where you can see >individual pixels, you will see that some of the pixels are >different in the two images. But even then, unless you know >in advance, you won't be able to tell which was the original, That's just patently false! At 100% magnification (i.e. 1:1) even a JPG image at lowest compression (i.e. highest quality) stands out like a sore thumb when compared to the original. If you find it hard to see simply overlay the images and flip between them. The JPG one will have quite easily identifiable 8x8 pixel blocks which is how JPG compression works. >Furthermore, if any of your descendants view these images, >(and I hope they will - I also scan old family images for the >same reason) the tiny differences in pixel values wouldn't >mean anything to them even if they could see them. *Objectively* speaking that's wrong too. JPG uses 8-bit precision simply because that's all today's monitors can display. However, in not too distant future monitors will expand this dynamic range and then a 16-bit (or higher) dynamic range will become essential. An analogy is if you view a standard TV image side by side with HDTV. Murky shadows on a standard TV reveal tons of detail on HDTV. However, HDTV will not reveal new detail in old (i.e. standard TV) video tapes. What you are advising is to use standard video tapes for archiving (without significant loss of data) and that doesn't make any sense. >You'll get much more mileage out of careful scanning with >good color restoration, dust removal, etc., than out of using >TIFF. No, you certainly will not! All that "careful scanning" and processing will go to waste if you keep the images as JPGs in your workflow. >So I store my scanned family archive as JPEGs only. That's a subjective preference and everyone is, of course, entitled to do that. But they should be aware of the conseqences. If they are, then, more power to them! Enjoy! However, projecting this *personal* preference and drawing false conclusions is just factually incorrect! By all means, archive your images as JPGs but don't mislead others into thinking they are not losing massive amounts of data if they do so. They may still decide to use JPGs, and that's fine too, because in that case they made an educated choice and did not base their decision on factually wrong (mis)information. Don.
From: Alan Meyer on 13 Apr 2006 12:13
Don wrote: > On Wed, 12 Apr 2006 13:50:35 -0400, "Alan Meyer" <ameyer2(a)yahoo.com> > wrote: > >If you blow up the images to the point where you can see > >individual pixels, you will see that some of the pixels are > >different in the two images. But even then, unless you know > >in advance, you won't be able to tell which was the original, > > That's just patently false! > > At 100% magnification (i.e. 1:1) even a JPG image at lowest > compression (i.e. highest quality) stands out like a sore thumb when > compared to the original. I downloaded the two images that Raphael referenced in his reply then magnified them 16 times (i.e., 4004 pixels per dimension instead of the 1001 pixels of the original image.) I'm not sure I can tell them apart. Then I magnified them almost 100 times i.e., almost 10 times as many pixels per dimension. Now, if I looked closely, I could see that some individual pixels had different colors. But I still couldn't see JPEG artifact squares, and still wasn't sure which image was which without looking at the file names. > If you find it hard to see simply overlay the images and flip between > them. The JPG one will have quite easily identifiable 8x8 pixel blocks > which is how JPG compression works. Try it with the two images Raphael provided. > JPG uses 8-bit precision simply because that's all today's monitors > can display. However, in not too distant future monitors will expand > this dynamic range and then a 16-bit (or higher) dynamic range will > become essential. Leaving aside the monitors, how much precision can the human eye distinguish? I suspect the best eyes can only do around 10 bits, though I'm not at all sure about that. Furthermore, human perception is non-linear. There are some ranges in which we are more sensitive than others. I believe that some JPEG compression algorithms know that and take advantage of it to produce images that are really very close to the maximum human perception. However I'm not an expert on this. Someone who is should post the facts. > That's a subjective preference and everyone is, of course, entitled to > do that. But they should be aware of the conseqences. If they are, > then, more power to them! Enjoy! > > However, projecting this *personal* preference and drawing false > conclusions is just factually incorrect! Your observation about personal preference is perfectly valid. There may indeed be some people for whom the subtle differences between TIFF and good JPEG is detectable and objectionable. > By all means, archive your images as JPGs but don't mislead others > into thinking they are not losing massive amounts of data if they do > so. They may still decide to use JPGs, and that's fine too, because in > that case they made an educated choice and did not base their decision > on factually wrong (mis)information. I agree with part of that too. And I agree that people should do their own tests and draw their own conclusions. I'll go further and say that whether you are losing "massive" amounts of data is also a subjective conclusion. There's no doubt that a computer will find a signficant difference between TIFF and good JPEG. But whether that's "massive" from a human point of view is not obvious to me. Finally, I want to defend my point that good scanning is more important than saving TIFFs. The quality of the scanner, the decisions made by the scanning software, the adjustments for color and contrast, the cleaning of the image and the glass plate - all have a bigger effect on final results than TIFF vs. good JPEG. But, as you say, people need to do their own tests to confirm or disconfirm this for themselves. Alan |