In order to support DNG, all four converters first need to support the RAW file format that this DNG came from meaning Adobe/ Apple must have the specific camera or back for testing and creating their "As Shot" settings before they can support it.
Adobe DNG is a standalone format. You can render any DNG without being able or even know about the original raw format. To be true that is the idea behind DNG.
There are Tags which specify the "as shot" values and how to convert the bitmap into XYZ color Space. Which is exactely what an input profile does.
A DNG file is not "valid" without this information.
ACR and Lightroom and Raw Developer support any "valid" DNG you throw at them and render it.
Aperture in contrast only converts DNGs from Cameras, Aperture supports, which makes DNG support, in the sense of support for an universal format, a farce.
I assume Apple is afraid that they could fall short quality wise in comparison to other applications if they do not do some special tweaking.
Or probably Apertures internal processing path will always use the native raw format converter and Aperture does not process the DNG directly , but converts DNG to camera specific raw and converts that.
Whatever the reason is, it's not really DNG dependent, it's an Apple thing.
For programmers DNG is nice. One format to rule them all. No camera specific formats. Input filters once written can be used for any camera model, and all camera models will profit from any improvement.
For those back manufacturers, who supply their own editing software for free (read as part of the bundle) it's different.
The editing software is part of the package and might swing the decision which back to buy into their direction.
If all manufacturers support dng, the best software will be used by all users across all brands, making a waste of the money spend to develop an application as a matter to increase the atractiveness of their digital backs.
So manufacturers will probably incoorperate a protection sheme and support brand specific DNGs only. Or they will ask money for their software.
Or something else, your guess
Regards
Stephan
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