16bit vs 8bit for prints

Discussion in 'Digital Photography' started by Terry, Feb 14, 2006.

  1. Terry

    Terry Guest

    A photographer friend of mine processes everything in Photoshop in 16 bit
    RAW. When he wants to have a print made he changes the image to an 8 bit
    tif. He says that the reason for dropping to 8 bit is that most photo labs
    have 8 bit printers.

    It seems to me if you are going to switch to 8 bit for the print, you might
    as well have never started in 16 bit in the first place. Don't you lose the
    extra dynamic range, etc. as soon as you make the change? It doesn't makes
    sense to me. What would happen if you sent a 16 bit file to be printed?
    How much larger would the file size be - twice the size?

    --
    Terry
    Remove the rodent from my email address to reply directly.
    Terry, Feb 14, 2006
    #1
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  2. Terry

    rafe b Guest

    On Mon, 13 Feb 2006 21:52:10 -0500, "Terry"
    <> wrote:

    >A photographer friend of mine processes everything in Photoshop in 16 bit
    >RAW. When he wants to have a print made he changes the image to an 8 bit
    >tif. He says that the reason for dropping to 8 bit is that most photo labs
    >have 8 bit printers.
    >
    >It seems to me if you are going to switch to 8 bit for the print, you might
    >as well have never started in 16 bit in the first place. Don't you lose the
    >extra dynamic range, etc. as soon as you make the change? It doesn't makes
    >sense to me. What would happen if you sent a 16 bit file to be printed?
    >How much larger would the file size be - twice the size?



    I doubt there are any inkjet printers that can use
    16-bits and in any case, the Windows driver interface
    doesn't allow 16-bit print files -- at least that's
    what I've heard.

    A 16 bit workflow is another matter -- easier to
    defend on theoretical grounds if not from actual
    observable benefits.

    The idea behind the 16-bit workflow is that the
    extra bits will minimize the cumulative effects
    of rounding/truncation error in the course of
    several radical color transformations (eg.,
    curves/levels/saturation, etc.)


    rafe b
    www.terrapinphoto.com
    rafe b, Feb 14, 2006
    #2
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  3. Terry

    bmoag Guest

    This is one of those subjects where opinion may matter more than facts.
    Processing color in 16 bit yields a smoother histogram, under some
    circumstances, but whether this will or can possibly improve the 8 bit
    printed result, well, that may be another matter.
    Under some circumstances, maybe.
    The problem has to do with the limits of the ideal 8 bit color gamut, the
    real limits of the printer/paper combo gamut and the limits of human visual
    perception. Alas those slightly smoother 16 bit histograms are showing
    gradations of color that are more subtle than what the eye/brain (not to
    mention any printing process) can actually resolve. You think you are seeing
    this on your monitor but your monitor and your eyeballs are, drum roll
    please, 8 bit (or less) devices in terms of discernible gradations of color,
    It is even worse if you work on an LCD.
    Epson also points out that if you are adjusting a color in 16 bit that is
    just outside or at the extreme edge of the 8 bit printer gamut you may
    actually cause more difficulty accurately printing the color. One would
    assume Epson's engineers know what of they write.
    A similar argument applies to whether recording music with hypersonic
    frequencies, essentially anything higher than 16hz, that cannot be heard by
    anyone except your dog and not reproduced except by specialty speakers,
    really improves the overall quality of recorded sound. Maybe, but we all
    listen to iPods these days.
    If 16 bits seems better to you, and you feel you get better results, then by
    all means work in 16 bits.
    I do it with images that are important to me but when I have experimented by
    making the same adjustments in 8 bits I can't say I see any real differences
    in the printed output.
    My point is that it is naive to assume that 16 bits is a universally better
    mode for working with images that are going to be printed because at some
    point an immutable computer algorithm, totally out of your control, will
    truncate your 16 bit masterpiece to 8 bits (or less) anyway.

    "Terry" <> wrote in message
    news:...
    >A photographer friend of mine processes everything in Photoshop in 16 bit
    >RAW. When he wants to have a print made he changes the image to an 8 bit
    >tif. He says that the reason for dropping to 8 bit is that most photo labs
    >have 8 bit printers.
    >
    > It seems to me if you are going to switch to 8 bit for the print, you
    > might as well have never started in 16 bit in the first place. Don't you
    > lose the extra dynamic range, etc. as soon as you make the change? It
    > doesn't makes sense to me. What would happen if you sent a 16 bit file to
    > be printed? How much larger would the file size be - twice the size?
    >
    > --
    > Terry
    > Remove the rodent from my email address to reply directly.
    >
    bmoag, Feb 14, 2006
    #3
  4. Terry

    HornBlower Guest

    16-bit is great for color and exposure adjustments, but for printing it is
    100% pointless. Print drivers convert to 8-bit when you send a 16-bit image.
    There are currently no 16-bit printers. Now does the printer driver do a
    better job of converting the image data to 8-bit than say Photoshop? Can't
    say. The chances are you will never notice a difference. So why waste time
    converting to 8-bit when you print.

    R


    "Terry" <> wrote in message
    news:...
    >A photographer friend of mine processes everything in Photoshop in 16 bit
    >RAW. When he wants to have a print made he changes the image to an 8 bit
    >tif. He says that the reason for dropping to 8 bit is that most photo labs
    >have 8 bit printers.
    >
    > It seems to me if you are going to switch to 8 bit for the print, you
    > might as well have never started in 16 bit in the first place. Don't you
    > lose the extra dynamic range, etc. as soon as you make the change? It
    > doesn't makes sense to me. What would happen if you sent a 16 bit file to
    > be printed? How much larger would the file size be - twice the size?
    >
    > --
    > Terry
    > Remove the rodent from my email address to reply directly.
    >
    HornBlower, Feb 14, 2006
    #4
  5. In article <>,
    "Terry" <> wrote:

    > A photographer friend of mine processes everything in Photoshop in 16 bit
    > RAW. When he wants to have a print made he changes the image to an 8 bit
    > tif. He says that the reason for dropping to 8 bit is that most photo labs
    > have 8 bit printers.
    >
    > It seems to me if you are going to switch to 8 bit for the print, you might
    > as well have never started in 16 bit in the first place. Don't you lose the
    > extra dynamic range, etc. as soon as you make the change? It doesn't makes
    > sense to me. What would happen if you sent a 16 bit file to be printed?
    > How much larger would the file size be - twice the size?


    It's OK for a perfectly adjusted photo to be 8 bits. The problem is
    that 8 bits isn't always enough for heavy image correction.

    Some print labs use many more than 8 bits for internal processing but
    they still take only 8 bit photos from the customer. Higher bit levels
    are brutal to store and transport.
    Kevin McMurtrie, Feb 14, 2006
    #5
  6. In article <>,
    Terry <> wrote:
    >It seems to me if you are going to switch to 8 bit for the print, you might
    >as well have never started in 16 bit in the first place. Don't you lose the
    >extra dynamic range, etc. as soon as you make the change?


    8-bit/ch files still have a gamma of around 2.2. Paper typically has a
    contrast range about 100:1.

    This basically means that an 8-bit/ch file is precise enough for prints.
    More bits don't really help.

    8-bit/ch is just enough for a print. When an image needs lots of edits,
    you need extra bits to compensate for the loss of accuracy as a result of
    the editing operations. Furthermore, if you need significant changes to the
    contrast of an image, you need extra bits as well, otherwise you will
    get banding.

    If you are essentially printing straight from the camera, you can just as
    well use 8-bit/ch for the entire process.


    --
    That was it. Done. The faulty Monk was turned out into the desert where it
    could believe what it liked, including the idea that it had been hard done
    by. It was allowed to keep its horse, since horses were so cheap to make.
    -- Douglas Adams in Dirk Gently's Holistic Detective Agency
    Philip Homburg, Feb 14, 2006
    #6
  7. Terry

    Andrew Haley Guest

    Terry <> wrote:

    > A photographer friend of mine processes everything in Photoshop in
    > 16 bit RAW. When he wants to have a print made he changes the image
    > to an 8 bit tif. He says that the reason for dropping to 8 bit is
    > that most photo labs have 8 bit printers.


    > It seems to me if you are going to switch to 8 bit for the print,
    > you might as well have never started in 16 bit in the first place.


    This is a very contentious topic, and there is no agreement amongst
    the experts. Lat time I looked, Dan Margulis was arguing one way and
    Andrew Rodney the other, and if they can't come to any agreement after
    years of arguing there's no hope that you'll get any simple answers
    here.

    Andrew.
    Andrew Haley, Feb 14, 2006
    #7
  8. Terry

    carolyn Guest

    the arguement for shooting in raw is to gather as much data as possible
    in camera. processing it in 16-bit means that you will have lots of
    data for maipulations and editing. if you were to color and dinsity
    correct past a certain point in 8-bit, you will end up with combing in
    the histogram which means banding and posterization in your print. i
    have recently brought up the arguement that if you do most of your
    edits in camera raw, why not just process into 8 bit. still, it gives
    you bo wiggle room for edits in photoshop. also, i work for a magazine
    doing their retouching and they have me keep EVERYTHING in 16 bit
    thinking that soon the printers will catch up soon and be able to
    handle 16-bit files. right now they will convert your 16-bit file into
    an 8-bit file before printing. so, in my opinion, at least do your
    major tonal and color correcting in 16 bit and then if you must
    convert, do it now but maybe duplicate and merge visible layers and
    always keep a cpoy of your large file just in case.

    good luck and many good thoughts,
    carolyn

    www.carolyncoffey.com
    carolyn, Feb 14, 2006
    #8
  9. Terry

    carolyn Guest

    the arguement for shooting in raw is to gather as much data as possible
    in camera. processing it in 16-bit means that you will have lots of
    data for maipulations and editing. if you were to color and dinsity
    correct past a certain point in 8-bit, you will end up with combing in
    the histogram which means banding and posterization in your print. i
    have recently brought up the arguement that if you do most of your
    edits in camera raw, why not just process into 8 bit. still, it gives
    you bo wiggle room for edits in photoshop. also, i work for a magazine
    doing their retouching and they have me keep EVERYTHING in 16 bit
    thinking that soon the printers will catch up soon and be able to
    handle 16-bit files. right now they will convert your 16-bit file into
    an 8-bit file before printing. so, in my opinion, at least do your
    major tonal and color correcting in 16 bit and then if you must
    convert, do it now but maybe duplicate and merge visible layers and
    always keep a cpoy of your large file just in case.

    good luck and many good thoughts,
    carolyn

    www.carolyncoffey.com
    carolyn, Feb 14, 2006
    #9
  10. Terry

    Hunt Guest

    In article <>,
    says...
    >
    >A photographer friend of mine processes everything in Photoshop in 16 bit
    >RAW. When he wants to have a print made he changes the image to an 8 bit
    >tif. He says that the reason for dropping to 8 bit is that most photo labs
    >have 8 bit printers.
    >
    >It seems to me if you are going to switch to 8 bit for the print, you might
    >as well have never started in 16 bit in the first place. Don't you lose the
    >extra dynamic range, etc. as soon as you make the change? It doesn't makes
    >sense to me. What would happen if you sent a 16 bit file to be printed?
    >How much larger would the file size be - twice the size?
    >
    >--
    >Terry
    >Remove the rodent from my email address to reply directly.


    If one is not going to post-process the image, especially Levels, Curves, or
    Color correction, then 8-bit is fine. If you are doing work in, say Photoshop,
    then 16-bit to start is the better choice, if you have it. I (almost) always
    shoot RAW, Open as 16-bit and do all corrections, saving as PSD. Convert to 8
    -bit and do any operations that require 8-bit (Filters mostly), then Save as
    xxxxx 8-bit.PSD. Finially, I'll run Neat Image, then Sharpen, saving as xxxx
    8-bit Final.PSD. Flatten and possibly convert to CMYK (depends on where the
    image goes next), saving as TIF.

    Hunt
    Hunt, Feb 14, 2006
    #10
  11. Terry

    Keith Guest

    Terry <> wrote:

    > A photographer friend of mine processes everything in Photoshop in 16 bit
    > RAW. When he wants to have a print made he changes the image to an 8 bit
    > tif. He says that the reason for dropping to 8 bit is that most photo labs
    > have 8 bit printers.
    >
    > It seems to me if you are going to switch to 8 bit for the print, you might
    > as well have never started in 16 bit in the first place. Don't you lose the
    > extra dynamic range, etc. as soon as you make the change? It doesn't makes
    > sense to me. What would happen if you sent a 16 bit file to be printed?
    > How much larger would the file size be - twice the size?


    If you shoot RAW then you can choose to convert to 8 or 16 bit as you
    see fit.

    Thinking about archive and longevity - I prefer to capture at the
    highest possible quality always - ie RAW. Why do anything else with all
    that expensive kit!

    We can't tell what kind of devices we'll be displaying the images we
    capture today on in the distant future.
    Keith, Feb 14, 2006
    #11
  12. In article <>,
    carolyn <> writes

    >thinking that soon the printers will catch up soon and be able to
    >handle 16-bit files.


    Why would printers "catch up"? They perform a different function to the
    image capture - they present the image to the viewer and 8-bits in the
    appropriate gamma encoding is already capable of exceeding what the
    viewer can distinguish.

    >right now they will convert your 16-bit file into
    >an 8-bit file before printing.


    And that is all they ever need to do.

    You capture your image in linear (gamma=1) space. You generally edit
    and print in gamma 1.8-2.5 space. Unless you print in linear space,
    which would mismatch the eye response, then there is no need for more
    than 8-bit output - and you can get bye with even less than that.
    --
    Kennedy
    Yes, Socrates himself is particularly missed;
    A lovely little thinker, but a bugger when he's pissed.
    Python Philosophers (replace 'nospam' with 'kennedym' when replying)
    Kennedy McEwen, Feb 15, 2006
    #12
  13. In article <p8fitakmq0sfubvjamo63hq4e1@inews_id.stereo.hq.phicoh.net>,
    Philip Homburg <> writes
    >In article <>,
    >Terry <> wrote:
    >>It seems to me if you are going to switch to 8 bit for the print, you might
    >>as well have never started in 16 bit in the first place. Don't you lose the
    >>extra dynamic range, etc. as soon as you make the change?

    >
    >8-bit/ch files still have a gamma of around 2.2. Paper typically has a
    >contrast range about 100:1.
    >
    >This basically means that an 8-bit/ch file is precise enough for prints.
    >More bits don't really help.
    >
    >8-bit/ch is just enough for a print. When an image needs lots of edits,
    >you need extra bits to compensate for the loss of accuracy as a result of
    >the editing operations. Furthermore, if you need significant changes to the
    >contrast of an image, you need extra bits as well, otherwise you will
    >get banding.
    >
    >If you are essentially printing straight from the camera, you can just as
    >well use 8-bit/ch for the entire process.
    >

    Philip seems to have been the only responder to raise the significant
    issue of the different gamma between output and input in digital image
    processing. However, at a gamma of 2.2, 8 bits is capable of yielding a
    contrast of (1/256)^2.2, which is a lot more than the paper is capable
    of. It is the minimum perceivable contrast ratio that drives the 8-bit
    criteria, not the total contrast range.

    It is also why those holding out for a 16-bit printer driver will have a
    long wait - there simply is no need for it since 8 bits with the
    appropriate gamma is already well in excess of what you can see in any
    case and certainly well above what even the best papers can reproduce.

    The reason for 16-bit processing is two fold: the actual data
    acquisition from the camera/scanner sensor is in linear space, not gamma
    compensated space, and this requires more bits to address the same
    dynamic range (which I think was what Philip was alluding to in the
    first sentence of his post) and, as others have mentioned, to provide
    additional dynamic range headroom for editing.

    RAW is essentially your digital negative - it *must* capture more
    dynamic range than you can see to be of any value over simpler outputs.
    If you want to do the same processes as darkroom dodging and burning in
    digital then you need more than 8-bits in the original, but you don't
    need that in the output - just as photographic paper doesn't have the
    same SNR or dynamic range as film.

    It will be several million years before humans evolve adequate vision to
    *require* 16-bit print drivers. ;-)
    --
    Kennedy
    Yes, Socrates himself is particularly missed;
    A lovely little thinker, but a bugger when he's pissed.
    Python Philosophers (replace 'nospam' with 'kennedym' when replying)
    Kennedy McEwen, Feb 15, 2006
    #13
  14. Kennedy McEwen <> writes:

    >You capture your image in linear (gamma=1) space. You generally edit
    >and print in gamma 1.8-2.5 space. Unless you print in linear space,
    >which would mismatch the eye response, then there is no need for more
    >than 8-bit output - and you can get bye with even less than that.


    Certainly if the output is to paper, which has perhaps a 100:1 dynamic
    range.

    There is some argument that if your output is transparency film that
    will be projected in a dark room, or a good electronic projector, you
    might want a higher number of bits all the way through the process to
    the output - even with non-linear coding. It's not so much to increase
    the available dynamic range, but to retain small step sizes between
    adjacent pixel code values even in the shadows, to avoid any possibility
    of banding.

    Dave
    Dave Martindale, Feb 17, 2006
    #14
  15. In article <dt5eh3$hn4$>, Dave Martindale
    <> writes
    >Kennedy McEwen <> writes:
    >
    >>You capture your image in linear (gamma=1) space. You generally edit
    >>and print in gamma 1.8-2.5 space. Unless you print in linear space,
    >>which would mismatch the eye response, then there is no need for more
    >>than 8-bit output - and you can get bye with even less than that.

    >
    >Certainly if the output is to paper, which has perhaps a 100:1 dynamic
    >range.
    >
    >There is some argument that if your output is transparency film that
    >will be projected in a dark room, or a good electronic projector, you
    >might want a higher number of bits all the way through the process to
    >the output - even with non-linear coding. It's not so much to increase
    >the available dynamic range, but to retain small step sizes between
    >adjacent pixel code values even in the shadows, to avoid any possibility
    >of banding.


    I am sure there is some argument about it Dave, but it is usually
    between people who have never had the opportunity to create an output
    image with 16-bit coding.

    With a DMD display (the best projection device currently available, by
    quite a margin) controlled directly and linearly, it is fairly trivial
    to demonstrate that even in a darkened room you still won't see
    posterised shadows with even less than 8-bits if it is encoded about
    gamma=2, converted back to a high bit relinearised space.

    However, on commercial DMD projectors you have to live with the driver
    you get, and that may create posterisation in its conversion of the
    gamma input to the linear PWM signal that the DMD is driven by.

    Ignoring contrast limits at the display, an 8-bit gamma 2.2 encoded
    image will require almost 18-bits of data to represent it accurately in
    linear coding. With each pixel being switched on or off on super-frames
    to achieve the PWM, you can see immediately why compromises are required
    in the drivers when you need to retain compatibility with movie inputs,
    as is the case with commercial projectors.
    --
    Kennedy
    Yes, Socrates himself is particularly missed;
    A lovely little thinker, but a bugger when he's pissed.
    Python Philosophers (replace 'nospam' with 'kennedym' when replying)
    Kennedy McEwen, Feb 17, 2006
    #15
  16. Terry

    One4All Guest

    bmoag wrote:
    > This is one of those subjects where opinion may matter more than facts.
    > Processing color in 16 bit yields a smoother histogram, under some
    > circumstances, but whether this will or can possibly improve the 8 bit
    > printed result, well, that may be another matter.


    I'm suspecting that this 8-bit/16-bit controversy is recent, due to the
    predominance of digital image capture, i.e., whether to RAW or not RAW.
    (I don't own a digital camera & maybe don't know what I'm talking
    about, but I'll press on.) A rhetorical question: How has the
    advertising/high-end imaging industry been surviving with "only" 8-bit
    technology all these years? Where did the "need" for 16-bits come from?
    Before long, there'll be a 16-bit/32-bit controversy.

    I agree with your observations, and I think the imaging/printing
    industry has long flourished in "only" an 8-bit environment. It gets
    back to your original statement: It's a matter of opinion, not fact.
    One4All, Feb 18, 2006
    #16
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