RT’s camconst.json file has a treatise on specifying and determining a camera’s white level:
https://github.com/Beep6581/RawTherapee/blob/dev/rtengine/camconst.json#L133
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yet another value:
- Sony ARW2: no scaling. Generally black level around 512, and white level 16350 and to be conservative say 16300.
It also looks like the max value is ISO dependent.
Empirically, 15360: if you use 16383 (darktable default) with an image with overexposed areas (sky), you get the effects of clipping (magenta) without the raw clipping indicator showing any over-exposed areas.
Set the raw white point to 15360, and the areas indicated by the clipping indicator correspond to the visually over-exposed areas (more or less).
@priort : the sensor doesn’t fill up to a specific digital value, that’s the job of the amplifier/ADC circuitry. I guess it’s much easier to make sure the valid values are somewhere high enough, and then indicate the maximum reliable value, than to tweak the circuitry to exactly fill up the available range of values…
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What you say makes intuitive sense to me, but there are also lots of entries in cameras.xml where black = zero and white = 2^N exactly.
I am new to dt and trying to make sense of the RAW & EXIF data so am still unclear as what is completely raw or perhaps massaged-raw data to make a product perform/look good.
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I would trust the exif data…. Problem for some cameras is they don’t offer a white value at all…the sony ones have it, its just in the maker notes…
You can of course do the simple thing and try both but I suspect the one in the maker notes lower that the max possible sensor data is correct…
Some of the Canon ones can be even more confusing as they provide no white level or it changes with iso and they give a value around 10000 as max linear ie I assume something like it is linear up to that limit…. But I really don’t know about how this linear value gets used if at all by any raw editors…
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(deleted, wrong thread)
(deleted, wrong thread…)
Well I suspect you could apply offsets or gains or whatever across that 2^14 range and there would be the question of how linear it is across that range…in the end you are going to have in theory 2^14 available for resolution from the sensor but I wonder if most sensors vary enough or batch to batch there is some variability and so this gets pulled back a bit for safety??
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Apparently this varies based on design - MOST cameras have the ADC clip point set before the sensor saturates, but apparently not all. There was a recent post somewhere on DPR regarding this and “extended ISO” from one particular Panasonic camera - for that camera, the “extended ISO” actually exposed a region of sensor performance where the response was nonlinear.
Aha - found it - How to Measure Full Well Capacity (1) « Harvest Imaging Blog was linked to by Iliah Borg of libraw fame from dpreview recently
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Did you want this in the G90 Post??
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No just that you were in the parallel post for the G90 and that was talking black point…this was Sony but you might have been crossing over with your comments… I wasn’t sure…
Oh crap, wrong thread. Too many windows…
Use the command line flag that lists the groups.
You’ll see that there are multiple sources for metadata inside a raw file , and these white level tags are inside different sources of the same file .
In the cheatsheet is an example to ‘list all tags’, because otherwise exiftool will only list one of these kind of duplicate tags.
Anyway, for Sony there is one in the exif data. That’s the 16384 one . And that is somewhat meant to tell the theoretical max white value you could encounter , based on the bitdepth and file format.
The later one is inside ‘maker notes’, a manufacturer set of tags , that differ per camera maker. For instance it can describe settings of your Sony camera at the time of the shot .
The white level there is IN THIS CASE the better one, because it tells the maximum THIS MODEL can do with these settings.
Fuji has a film simulation bracketing setting:
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I believe you can also reprocess raw files on the camera or using Fuji’s software.
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Yeah, you can, but I think it’s model-dependent.
There are actually three ways for doing this:
- directly in-camera pressing Q-menu during playback
- using RAW Convert EX (it’s based on SilkyPix and supports film simulations)
- for models newer than X-T1 you can also use Capture One Express (cameras older than X-T2 / X-H2 are supported, but without film fimulations) or, similarily for newer cameras, connect with USB cable and use "X Raw Studio - you see results on the computer screen, but to process images, camera’s engine is used.
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This is something I wish Sony supported, because then it would be possible to put synthetic controlled inputs into the camera to make it easier to reverse engineer the output.
Yes, you can perform correlations between an arbitrary captured RAW and its output, but it’s a lot easier to put in something synthetic that covers many data points (such as feeding a HALD CLUT to the processing chain to see what comes out, or controlled gradients.)
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I’m not sure you can provide arbitrary input for this feature… Of course I’ve never used it and am not really interested, but it seems unlikely. Maybe someone who does use it can chime in.