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> so if you're doing work targeted at a computer screen, it probably doesn't matter anyway Actually, it matters regardless of output device. With higher bit de

> so if you're doing work targeted at a computer screen, it probably doesn't matter anyway Actually, it matters regardless of output device. With higher bit depths, less rounding errors accumulate over time as the image is processed, for example when effects are applied, yielding higher overall output quality. Here is an example, although after many iterations quality loss can be much more dramatic than visible in that picture: http://www.photoshopessentials.com/essentials/16-bit/page-3.php http://www.photoshopessentials.com/essentials/16-bit/page-3....

machrider 16y ago
Yes. It matters a great deal if you're trying to recover information from underexposed or nearly overexposed regions of an image. Adjusting the levels of an image is something photographers do all the time, and having 14bits per channel allows you to do it without producing a grainy-as-hell image. Throwing away almost half of the information on the initial import is unforgivable and relegates GIMP to being merely a toy.
- wazoox 16y ago
  Oh please stop the flame, this is ridiculous. Photoshop didn't support 16 bits before CS, in 2003. Did it prevent people to use it ? Would you say that all magazine covers were "child play" before then?
  - dagw 16y ago
    Not true. Photoshop has had support for 16 bits since at least version 3. What CS brought was full 16 bit support for all layer adjustments and painting features. Before that 16 bit was only supported by a subset of the available editing options.
    - davidw 16y ago
      Still though, the sniffy "merely a toy" is kind of over the top. Are automobiles merely toys because they don't have the range, passenger capacity and speed of a Boeing 747? How about motor scooters? And bicycles? The Gimp is not as good as Photoshop. Is it good enough for many uses? Sure.
      - DrStalker 16y ago
        Having an attitude of "It's good enough" is probably why GIMP has made such a small amount of progress in recent years.
        davidw 16y ago
        That's not the kind of 'good enough' I meant. It's good enough for many things, not "so good that it doesn't need improvement". Anything can be improved, and doubtless the people who work on it know that.
        rbanffy 16y ago
        Indeed. And having progress per se is what proprietary software like Photoshop has to do in order to sell more licenses. Why would you buy the most recent CS version if Photoshop 6 was certainly good enough? The logic is different. GIMP does not have to evolve in order to survive. It's open and if you need it doing something it doesn't, you can hire a developer to do it. The fact nobody does it is because it's good enough for what it's used for.
        davidw 16y ago
        +1, although, to be correct, economically "the fact nobody does it" means the cost is higher than the benefit. You could purchase a copy of photoshop for much cheaper than the cost of hiring a good developer for a week. Open source economics are tricky.
        rbanffy 16y ago
        > You could purchase a copy of photoshop for much cheaper than the cost of hiring a good developer for a week. True. That's why pooling resources is such a good idea. If you need a feature that's missing from Photoshop, you can find other people who need that feature (or would like to have it) and pool resources to hire someone to do it in GIMP. If you have a company with 10 seats using Photoshop, it may start to become cheaper to hire a GIMP developer than providing all employees with a Photoshop license (and Adobe must have corporate licenses exactly to counter that reasoning)
    - wazoox 16y ago
      And the GIMP supports 16 bits for most operations, simply by enabling GEGL in the Color menu, therefore it is quite equivalent to old Photoshop in this regard.
DrStalker 16y ago
> With higher bit depths, less rounding errors accumulate > over time as the image is processed, This could also be solved by another photoshop feature, adjustment layers. Basically instead of applying a filter like levels to an image you make a levels layer that applies the levels affect to everything underneath it. The original data is untouched, and you can tweak the levels at any time. I'm strictly a hobby user for photos I take, but without support either 16 bit colour or adjustment layers GIMP is not good enough for me. My solution is to use an older student version of photoshop I picked up cheaply; I don't need all features in the latest version.
- jerf 16y ago
  No, that doesn't actually do anything to solve the underlying problem. Stacking five adjustment layers has the same accuracy problems as doing the same five operations sequentially. It may let you tweak them without roundtripping through further loss but the loss is already significant by that point.
  - andrewvc 16y ago
    Technically yes, but not at all in practice. Once you run 3 adjustments you generally want to tweak the first. Without adjustment layers you usually just run a fourth transformation.
    - jerf 16y ago
      Ye gods, can't you read until my third sentence between smashing the reply button and "correcting" me?
  - andrewvc 16y ago
    Plus selectively painting the mask of an adjustment layer is useful as well
  - aphyr 16y ago
    Er, theoretically, no. I don't know what Photoshop's implementation is, but computing the cumulative effect of the adjustment layers will result in less error than applying them in sequence. That's part of why GEGL is being written. [Edit] I'm referring to the fact that fixed-precision arithmetic loses (well, stochastically speaking) precision with each operation. You can condense the layer effects and apply the 8-bit operation only once to minimize error. This is especially true if your layer combinator works at a higher level of precision than the layer operation itself. [Edit 2] As an example, consider the layer operations "Multiply each channel by 0.5" and "Multiply each channel by 2." Applying these layers separately to a value loses something like a half bit of precision (more for smaller values, less for larger ones). A layer combinator could multiple 0.5 by 2 and yield ~1.0 (in general, subject to the floating point precision which is generally finer than the image precision). That results in a smaller error.

machrider 16y ago

Yes. It matters a great deal if you're trying to recover information from underexposed or nearly overexposed regions of an image. Adjusting the levels of an image is something photographers do all the time, and having 14bits per channel allows you to do it without producing a grainy-as-hell image. Throwing away almost half of the information on the initial import is unforgivable and relegates GIMP to being merely a toy.

wazoox 16y ago
Oh please stop the flame, this is ridiculous. Photoshop didn't support 16 bits before CS, in 2003. Did it prevent people to use it ? Would you say that all magazine covers were "child play" before then?
- dagw 16y ago
  Not true. Photoshop has had support for 16 bits since at least version 3. What CS brought was full 16 bit support for all layer adjustments and painting features. Before that 16 bit was only supported by a subset of the available editing options.
  - davidw 16y ago
    Still though, the sniffy "merely a toy" is kind of over the top. Are automobiles merely toys because they don't have the range, passenger capacity and speed of a Boeing 747? How about motor scooters? And bicycles? The Gimp is not as good as Photoshop. Is it good enough for many uses? Sure.
    - DrStalker 16y ago
      Having an attitude of "It's good enough" is probably why GIMP has made such a small amount of progress in recent years.
      - davidw 16y ago
        That's not the kind of 'good enough' I meant. It's good enough for many things, not "so good that it doesn't need improvement". Anything can be improved, and doubtless the people who work on it know that.
      - rbanffy 16y ago
        Indeed. And having progress per se is what proprietary software like Photoshop has to do in order to sell more licenses. Why would you buy the most recent CS version if Photoshop 6 was certainly good enough? The logic is different. GIMP does not have to evolve in order to survive. It's open and if you need it doing something it doesn't, you can hire a developer to do it. The fact nobody does it is because it's good enough for what it's used for.
        davidw 16y ago
        +1, although, to be correct, economically "the fact nobody does it" means the cost is higher than the benefit. You could purchase a copy of photoshop for much cheaper than the cost of hiring a good developer for a week. Open source economics are tricky.
        rbanffy 16y ago
        > You could purchase a copy of photoshop for much cheaper than the cost of hiring a good developer for a week. True. That's why pooling resources is such a good idea. If you need a feature that's missing from Photoshop, you can find other people who need that feature (or would like to have it) and pool resources to hire someone to do it in GIMP. If you have a company with 10 seats using Photoshop, it may start to become cheaper to hire a GIMP developer than providing all employees with a Photoshop license (and Adobe must have corporate licenses exactly to counter that reasoning)
  - wazoox 16y ago
    And the GIMP supports 16 bits for most operations, simply by enabling GEGL in the Color menu, therefore it is quite equivalent to old Photoshop in this regard.

DrStalker 16y ago

> With higher bit depths, less rounding errors accumulate > over time as the image is processed, This could also be solved by another photoshop feature, adjustment layers. Basically instead of applying a filter like levels to an image you make a levels layer that applies the levels affect to everything underneath it. The original data is untouched, and you can tweak the levels at any time. I'm strictly a hobby user for photos I take, but without support either 16 bit colour or adjustment layers GIMP is not good enough for me. My solution is to use an older student version of photoshop I picked up cheaply; I don't need all features in the latest version.

jerf 16y ago
No, that doesn't actually do anything to solve the underlying problem. Stacking five adjustment layers has the same accuracy problems as doing the same five operations sequentially. It may let you tweak them without roundtripping through further loss but the loss is already significant by that point.
- andrewvc 16y ago
  Technically yes, but not at all in practice. Once you run 3 adjustments you generally want to tweak the first. Without adjustment layers you usually just run a fourth transformation.
  - jerf 16y ago
    Ye gods, can't you read until my third sentence between smashing the reply button and "correcting" me?
- andrewvc 16y ago
  Plus selectively painting the mask of an adjustment layer is useful as well
- aphyr 16y ago
  Er, theoretically, no. I don't know what Photoshop's implementation is, but computing the cumulative effect of the adjustment layers will result in less error than applying them in sequence. That's part of why GEGL is being written. [Edit] I'm referring to the fact that fixed-precision arithmetic loses (well, stochastically speaking) precision with each operation. You can condense the layer effects and apply the 8-bit operation only once to minimize error. This is especially true if your layer combinator works at a higher level of precision than the layer operation itself. [Edit 2] As an example, consider the layer operations "Multiply each channel by 0.5" and "Multiply each channel by 2." Applying these layers separately to a value loses something like a half bit of precision (more for smaller values, less for larger ones). A layer combinator could multiple 0.5 by 2 and yield ~1.0 (in general, subject to the floating point precision which is generally finer than the image precision). That results in a smaller error.