JPG vs TIFF Resolution Test

Discussion in 'Digital Photography' started by Jerry McG, Dec 4, 2003.

  1. Jerry McG

    Chris Brown Guest

    It does, it's just not installed by default.
     
    Chris Brown, Dec 5, 2003
    #41
    1. Advertisements

  2. Jerry McG

    Ron Hunter Guest

    No, it's elitist jerks.
     
    Ron Hunter, Dec 5, 2003
    #42
    1. Advertisements

  3. Jerry McG

    andrew29 Guest

    That depends on how you print them.
    Of course, that's true. But the visibility of the artefacts depends
    on how much you enlarge, and how much you adjust the curves. Oh, and
    how much sharpening you do: if you print the image big, and you
    sharpen a lot, you'll see JPEG artefacts. If you're doing something
    less strenuous you won't. It's all about that last 10% of available
    quality.

    Andrew.
     
    andrew29, Dec 5, 2003
    #43
  4. Jerry McG

    Martin Brown Guest

    You are flat out WRONG! Take the difference between the first generation
    image and the original and then rescale the residuals to see why. Even
    if you resave a JPEG with exactly the same settings there are almost
    always some small truncation errors with all standard implementations.

    That affects both IJG and Adobe PhotoShop codecs. The only way the Apple
    product can possibly be generating bit wise *identical* saved files is
    that it has remembered that you haven't done anything to the image and
    then copied the file for you instead of recompressing it.

    And if the files are not bit wise identical then you *have* lost
    something on the deal even if the resulting file is larger than the
    original. The effects gradually accumulate - one or two saves at highest
    quality do very little damage, but that is not lossless by any
    definition.
    Any global change like rescaling the brightness has potentially serious
    effects. Try reading the JPEG FAQ before continuing this discussion.
    Cropping can be done losslessly on block boundaries using a special
    modified transcoder that works in JPEG coefficient space. eg JPEGCROP

    Once you convert a JPEG to and from image space you take truncation hits
    from the DCT transform, YCC to RGB conversion, RGB to YCC, DCT
    transform, and Quantisation. Some blocks can stay identical by sheer
    fluke, but a fair proportion drift gradually away from the master image
    each time you go round the cycle.
    Not a chance. RTFM
    What default mode? Most software I use allows me to set my own default.

    Regards,
     
    Martin Brown, Dec 5, 2003
    #44
  5. Jerry McG

    Eric Witte Guest

    JPEG is too lossy to be useful for pro caliber work, unless shot for low end
    What are the best places to print at? I printed an 8x10 at Walmart.
    The background looked good but the color on the table and people were
    way off. Plus I over did it in Neatimage. A lot of facial detail was
    lost. I redid the background in Neatimage. Then I used PS 8 to place
    more detailed objects on top. I printed this one at Walgreens.
    Walgreens was much better in reguards to color accuracy but the
    background is very dark. On the computer it almost looks like the
    background from Walmart with the foreground from Walgreens. IE it
    looks just right. Also Walgreens did not read 5-6MB jpegs very well.
    All of the 3MB ones were readable. I would eventually like to print
    16-bit tiffs.

    Eric
     
    Eric Witte, Dec 5, 2003
    #45
  6. Jerry McG

    Ray Murphy Guest

    ----------
    RM: Have a look at my previous posts and you will see what results
    were obtained.
    RM: The diference between the original and the first generation JPEG
    have not been a part of the discussion.
    RM: Which is what I got, so did the other poster who tested. In my
    case I could not find one pixel which had a different RGB value when I
    compared the 1st and 12th JPEGS. The figures are in pevious posts.
    RM: There was nothing identical bitwise in either my tests or those of
    the other poster. In my case I was quoting K's a nd not bits.
    RM: No one is claiming the 1st and last generations were absolutely
    identical - but almost identical. The accumualted efects were
    neglibable (if the best quality was used) - which was the whole point
    of raising the issue in the first place; although in my test the PC
    test was not as good as the Mac test, but there may be good reasons
    for that.
    RM: We haven't been talking about rescaling or altering brightness
    etc, or making any claims in relation to any changes.
    The tests have merely been on UNCHANGED JPEGS which are re-saved
    repetitively. We'll get to those things later.
    RM: But nowhere near as much as was popularly believed IF we save at
    the highest quality - which is the main focus here.
    RM: No manual required for this exercise. We are discussing what we
    want to agree upon for our own experiments.
    RM: Photoshop for example has had a default mode for saving JPEGS for
    quite a few years.
    Ray.
     
    Ray Murphy, Dec 5, 2003
    #46
  7. There may be good pro service printers in your local area, but if not the
    popular ones on the web work well, but most are 24-bit and many are limited
    to JPEG which limits you to prosumer quality. For ultimate quality 36-bit
    printing, do a web search for a pro service that uses a Light Jet or Durst
    Lambda, there are quite a few. Cost isn't too bad if you do all the image
    prep yourself and ask them only for print service (no individual attention,
    color correction, etc), $5-8 at 8x10 is typical. The Light Jet can print to
    8' x 4' and the Durst goes up to 4' x 20' or so, I think. Some service will
    take a large 16-bit TIF file online, others will ask for a CD.

    Difference is night and day from Wal-mart. A 16-bit TIF from a RAW file may
    have millions of unique colors present, an 8-bit TIF might reduce that to
    around 700K, most JPEGs shave that to just a few 100K. Plus a 36-bit
    palatte has 68 billion colors vs 17 million for 24-bit images, which makes
    for a beautiful print vs a so so one. Additionally, the Light Jet and
    Lambda produce a true photograph, not a surface print, by exposing silver
    halide paper to light then developing it more or less traditionally. Their
    output is rated at around a 200+ year useful lifetime, depending on who you
    believe, if you care.
     
    George Preddy, Dec 5, 2003
    #47
  8. It really is a lot more than 10%.

    JPEG artifacts might not show in small prints, but the overall color and
    clarity is greatly reduced. The penalty for using JPEG instead of RAW mode
    is, generally, going from a few million unique colors in a 36-bit, 68
    billion color space, down to a few 100K unique colors in a 24-bit, 17
    million color space. A lot of people never see the scope of the difference
    because home printers and monitors are 24-bit eitherway.
     
    George Preddy, Dec 5, 2003
    #48
  9. TIF in camera is always 8-bit, because 16-bit TIFs are enormous and
    therefore are only possible via RAW mode. So the only advantage of TIF over
    JPEG in camera is lossless vs lossy, and this does make a clearly noticable,
    but usually acceptable image quality difference at the 8-bit level. But...
    the much bigger quality difference is yet to come, since you cannot edit a
    JPEG without degrading it even further.
     
    George Preddy, Dec 5, 2003
    #49
  10. Jerry McG

    JPS Guest

    In message <>,
    A better test would be to do an offset (with wrap-around) of 7 pixels in
    each direction, because, theoretically, you should be able to do a
    negative offset of 7*n to get the exact same image back again.
    --
     
    JPS, Dec 6, 2003
    #50
  11. Jerry McG

    JPS Guest

    In message <bqqp9r$e70$>,
    Nonsense. You can convert a JPG to a 16-bit and "save as" TIF as soon
    as you load it into an editor, and there will be no further degradation
    than the original compression (other than the quite finite precision of
    16-bit data).
    --
     
    JPS, Dec 6, 2003
    #51
  12. Jerry McG

    Ray Murphy Guest

    ----------
    RM: Yes, because when a JPEG it is loaded it is virtually a TIFF
    anyway, and there is no need to *ever* lose any more quality.

    Ray
     
    Ray Murphy, Dec 6, 2003
    #52
  13. Small problem -- that's not a JPEG.
     
    George Preddy, Dec 6, 2003
    #53
  14. I think it goes without saying if it's a TIF it's not a JPEG.
     
    George Preddy, Dec 6, 2003
    #54
  15. Same for JPEG.

    Probably because you are viewing/printing both in 24-bit. Try comparing a
    to a RAW produced 68 billion color Light Jet photograph instead.
    Why not batch save all your RAW files as 36-bit TIFs too?
     
    George Preddy, Dec 6, 2003
    #55
  16. Jerry McG

    Ray Murphy Guest

    ----------
    RM: It's neither a TIFF or a JPEG after you open a JPEG image. It
    depends upon how the edited image is saved as to what you end up with.
    If the editing is minimal and the file is saved at the highest quality
    JPEG, then the degradation is minimal. If we don't want degradation -
    don't use JPEGS.

    Ray
     
    Ray Murphy, Dec 6, 2003
    #56
  17. Jerry McG

    JPS Guest

    In message <bqscg9$l0b$>,
    This small problem only exists in your head. Everyone has the ability
    to abandon JPG format after loading the original into a program.
    --
     
    JPS, Dec 6, 2003
    #57
  18. Oh, what a wonderful point: as long as you abandon JPEG, JPEG isn't lossy.
     
    George Preddy, Dec 6, 2003
    #58
  19. Jerry McG

    JPS Guest

    In message <bqt8kb$f74$>,
    We were talking about *FURTHER DETERIORATION* after initial JPG capture.
    Get your head out of your ass, so you can read properly.
    --
     
    JPS, Dec 6, 2003
    #59
  20. Jerry McG

    Eric Witte Guest

    There may be good pro service printers in your local area, but if not the
    The first few I found were like $20. I found a place called
    rivercitysilver for $8 ($6.80 if I had 2). You don't happen to know
    one in houston do you?
    I've not been completely shooting in RAW yet. The one I'm doing is
    jpg. Would it look any better with pro services? I'm redoing it. I
    immediately converted to two 16-bit tiffs. And then upsized slightly.
    From 3072x2048 to 3600x2400 in photoshop using Bicubic. One of them
    I ran through Neatimage to remove noise. Then open up in Photoshop
    CS. Copy the faces and more detailed items back from the 2nd tiff. I
    did the same thing for the Walgreens except I never bothered with TIFF
    or the resample. It looked great but I'm looking for a little closer
    color match.

    Eric
     
    Eric Witte, Dec 7, 2003
    #60
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.