CHDK DNGs "cooked" or not? (SD4000) - RAW Shooting and Processing - CHDK Forum
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CHDK DNGs "cooked" or not? (SD4000)

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Offline Robert1975

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CHDK DNGs "cooked" or not? (SD4000)
« on: 02 / July / 2017, 06:49:04 »
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Meanwhile, I moved on to colors etc. Everything sorted out!

But, I have one simple question: are CHDK DNGs pre-processed before saving? I did notice earlier that highlights are less blown in DNG than JPG and that was useful in almost all situations. But this confuses me, because with my Nikon DSLR it's usually RAW file which is blown and JPG has D-Lighting applied. On SD4000 it's vice versa. JPG is blown but DNG has better highlights. So I stumbled upon a sunset shot in which I actually WANTED blown highlights. But no matter which processing I applied to DNG in LR, I couldn't get the highlights to look like JPG, the color, the lightness. Not even using curves, nor brushing helped. Perhaps adjusting the yellow hue luminance helped a bit, but it's not the look I wanted.

Also, I've noticed that DNG has less aberrations, less fringing, and I believe in this case it's easily noticeable. That is also a bit counter-intuitive for me, since I'm used to fixing this stuff in DSLR RAWs. I attach two samples: IMG_0798-2 is OOC JPG crop, and IMG_0798-2-2 is the untouched DNG crop. In DNG, highlights appear dull and lifeless - in this particular scene I wouldn't want any DR correction, but I seem to be unable to turn it off...

SD4000 is 12bit so I'm sure there are no curves applied by CHDK. Also, i-Contrast is off and I bumped saturation and sharpness only in JPG. It doesn't affect highlights.

Is this normal behavior, or should I adjust something?
« Last Edit: 02 / July / 2017, 06:52:57 by Robert1975 »
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Offline reyalp

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Re: CHDK DNGs "cooked" or not? (SD4000)
« Reply #1 on: 02 / July / 2017, 15:28:27 »
Quote from: Robert1975 on 02 / July / 2017, 06:49:04
But, I have one simple question: are CHDK DNGs pre-processed before saving? I did notice earlier that highlights are less blown in DNG than JPG and that was useful in almost all situations.
No. What CHDK saves is exactly what the Canon firmware produced*. The Canon jpeg is produced from the same raw data, so in principle, you should always be able to produce the same result. In practice, Canon puts a lot of engineering into producing nice jpegs and matching it in a given raw program can be quite difficult.

* Two minor caveats for completeness
1) There are some details involving bad pixels
2) The raw data produced by the Canon firmware is may be processed in some way compared to what was read out from the sensor. The only instance of this we really know of is that some level of vignette correction may be applied in some cases.
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Also, I've noticed that DNG has less aberrations, less fringing, and I believe in this case it's easily noticeable.
This is all dependent on your raw processing software.


edit:
I too have had a hard time getting punchy sunsets like the Canon jpegs.
« Last Edit: 02 / July / 2017, 15:30:12 by reyalp »
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Offline Robert1975

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Re: CHDK DNGs "cooked" or not? (SD4000)
« Reply #2 on: 02 / July / 2017, 16:28:44 »
Yes, I thought so... But I had to verify.

Canon firmware definitely does "something" to RAW data, it's subtle, but it's there. Sometimes when I get highlights warning on LCD, everything is fine when I open DNG in LR. This is actually very practical, I'm just used to pulling down highlights slider with DSRL RAWs.

I came close to OOC JPEGs particularly in daylight WB. I downloaded a color profile for similar sensor and re-saved it with Adobe Profile Editor as IXUS 300 HS. It's not perfect but it works, together with a similar lens profile. However, between 2000-3000K things are usually getting complicated - playing with Curves & HSL sliders might produce decent results.

On the other hand, on most occasions it's not even desirable to re-do JPEG look...
« Last Edit: 02 / July / 2017, 16:33:39 by Robert1975 »
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