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How often will DNG have to change for new cameras? |
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04-29-2005, 12:20 PM
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How often will DNG have to change for new cameras?
I have a suspicion that, while camera specifications are undoubtedly changing at quite a rate, the proportion of these changes that actually need to change to a RAW format is relatively small. If DNG had existed a few years ago, how often would it have been necessary to issue a new version to date? I can imagine that radical new sensors, (perhaps Fujifilm, Sony, Foveon?), may have required changes. But lots of changes involve things like more pixels, or perhaps more bits per pixel, and such changes don't. And 1/2-offset only had to be done once. (My guess, and I DO mean guess, would be about 1 or 2 per year. A follow-up question is: "how does Adobe handle change requests?") |
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Re: How often will DNG have to change for new cameras? |
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04-29-2005, 02:05 PM
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Re: How often will DNG have to change for new cameras?
Not nearly as often as some people think. The last time a change would have been required (has DNG already existed at the time) would have been when Fujifilm introduced the SR sensor with the Fujifilm F700 about a year and half ago.
The Sony RBGE sensor would not have required an update since four color CFA sensors have been in use for a long time. In fact, most of the first generation digital cameras used four color CFA sensors, and which were already supported by Camera Raw before the Sony camera came out. The particular set of filter colors Sony used was new, but that makes absolutely no difference to DNG since it just means different numbers in the color matrix tags. It takes changes in fundamental technology before changes are required to DNG. Merely refining existing technology (higher pixel counts, lower noise levels, different CFA filter colors, etc), don't require changes to DNG. State of the art cameras such as the Canon 1Ds Mark II and the Nikon D2X are state of the art because they refine existing technology to new levels, not because they introduce fundamentally new technology. They are just very well implemented Bayer array cameras, which have been around for a long time. |
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Re: How often will DNG have to change for new cameras? |
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04-30-2005, 07:07 AM
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Re: How often will DNG have to change for new cameras?
Thanks, Thomas.
One thing I have never seen is the change control process for DNG. One of the primers says: "Ultimately, it may make sense to turn over DNG to an appropriate standards body for further enhancement, so that its evolution can truly be a collaborative effort". But I can't believe that enhancements can't happen under control even without such a hand-over. I speculate: Knock, knock! "I'm from Penolta. I would like to discuss possible enhancements to DNG. Please sign this NDA". Thomas gets out his pen and signs it. "We want DNG to support sensors in the form of concentric pentagons". (Chuckle!) Thomas et al devise an enhancement that will support sensors in the form of any specified regular polygon. Version 2.0.0.0 of the DNG specification is published. Adobe don't publish who requested the change. Some would say that this gives an unfair advantage to Adobe, because Photoshop developers can influence the enhancement to the specification to suit Photoshop. Or because Photoshop gets a development lead. Is there anything like a DNG Developers Forum, where such changes can be discussed with other companies using DNG in a confidential, pre-competitive, environment? Or are there Chinese Walls in Adobe to separate DNG and Photoshop development? I'm just curious. I have no real need to know. But a credible change control process adds quality and gives confidence. |
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Re: How often will DNG have to change for new cameras? |
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05-23-2005, 03:59 PM
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Re: How often will DNG have to change for new cameras?
I think I have a misunderstanding about the DNG format. From the reading I have done in some white papers provided by Adobe, I came to the conclusion that DNG was sort of a "common base" file format that would not be camera specific. However, in reading on some forums that are not associated with Adobe, people are saying that even the DNG format is camera specific, and that they have to create special profiles for the DNG files from different cameras. If this is the case, then the DNG format is not really a common file format. Can someone explain?
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Re: How often will DNG have to change for new cameras? |
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05-23-2005, 04:26 PM
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Re: How often will DNG have to change for new cameras?
however, in reading on some forums that are not associated with Adobe, people are saying that even the DNG format is camera specific, and that they have to create special profiles for the DNG files from different cameras. DNG's have the option of containing camera specific information. DNG's store GLOBAL attributes with options for LOCAL attributes. option aware applications might make use of the LOCAL camera specific attributes--while the universal aspects are PORTABLE amongst all DNG readers. That's my take! :-) |
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Re: How often will DNG have to change for new cameras? |
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05-23-2005, 05:07 PM
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Re: How often will DNG have to change for new cameras?
Thanks.
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Re: How often will DNG have to change for new cameras? |
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05-23-2005, 05:58 PM
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Re: How often will DNG have to change for new cameras?
Jim, I would like to see clarification of this too!
Here is something I know for certain: ACR 2.4 can't handle Raw files from the Canon 350D or the Nikon D2X. But if you take CR2 or NEF files from those cameras, and convert them to DNG, ACR 2.4 will handle those DNG files just as well as it will handle files from cameras that is DOES handle. (I'll ignore D2X "as shot" WB problems). Clearly, this is because the DNG file contains sufficient information about the camera for ACR 2.4 to extract and use instead of having built in information. And it must have been put there by the 3.1 DNG Converter, which must have information built in for those cameras. My assumption: This is the role of the "color calibration tags". One or two of these are needed in the DNG file. With two of them, the ACR white balance handling can interpolate or if necessary extrapolate the colour calibration for the corresponding "color temperature illuminant", or colour temperature. Given a specified colour temperature, and the interpolation or extrapolation, you end up with the required conversion from the sensor data to the required colour channel values. (I think I have have read that ACR uses 2 calibrations for each camera, perhaps one of them for illuminant A, tungsten, about 2856 (?), and perhaps the other for illuminant D55 or D65, about 5500 or 6500. If you know how to interpret the sensor data for both of those, you should be able to make an estimate about the rest. This is stretching my knowledge well beyond its bounds!) Without color calibration tags, sensor data are just numbers. I guess you can't relate a blue sensor value of 22 to a red sensor value of 22. With them, they can be translated into meaningful pixels. And DNG should always have at least one set of them, making it self contained. (Now I'll see what someone who knows what they are talking about makes of that!) But ... I do believe that the DNG-reader doesn't need its own camera-specific information in order to generate a proper 3-colour image. So software that processes DNG doesn't need more than that. (But, again, if it has more than that, as the camera's own software might, it may make the processing easier). |
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