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361 points Tomte | 4 comments | | HN request time: 0.436s | source
1. schobi ◴[] No.43608456[source]
When building a camera, you decide once and then most parameters stay fixed. It would be trivial to just append 1000 bytes for a mostly fixed DNG header to each image.

But how do you test this? While the DNG specification is open source, the implementation was/is(?) not. Do I really need a copy of Photoshop to test if my files are good? How would I find good headers to put into my files? what values are even used in processing?

Maybe the situation has changed, but in the old days when I was building cameras there was only a closed-source Adobe library for working with DNGs. That scared me off.

replies(3): >>43609220 #>>43609972 #>>43610092 #
2. Cadwhisker ◴[] No.43609220[source]
For testing, there's the Adobe DNG SDK: https://helpx.adobe.com/camera-raw/digital-negative.html

You'll find the whole spec there, too. I think the source is also available somewhere.

3. goeiedaggoeie ◴[] No.43609972[source]
Things like camera intrinsics and extrinsics are not fixed. 1000 bytes seems small to me given the amount of processing in modern cameras to create a raw image. I could easily imagine storing more information like focus point, other potential focus points with weights as part of the image for easier user on device editing.
4. seba_dos1 ◴[] No.43610092[source]
The camera app on my GNU/Linux phone stores DNGs with no troubles using FLOSS only.