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Interpolate luminance and chrominance before writing to dng

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Offline waterwingz

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Re: Interpolate luminance and chrominance before writing to dng
« Reply #10 on: 28 / November / 2014, 13:32:19 »
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Quote from: dvip on 28 / November / 2014, 12:57:11
One thing I would like to see is a way to add a small memo, notes, copyright, or something like that to the DNG exif. Perhaps it can be read from a text file in the SD card and then inserted in the DNG.
I've wondered about the same thing for the JPG file too.  In particular, a note about any CHDK override settings applied as apparently they are not always recorded by the camera as the exposure used.
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Offline reyalp

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Re: Interpolate luminance and chrominance before writing to dng
« Reply #11 on: 28 / November / 2014, 15:21:59 »
Quote from: waterwingz on 28 / November / 2014, 13:32:19
Quote from: dvip on 28 / November / 2014, 12:57:11
One thing I would like to see is a way to add a small memo, notes, copyright, or something like that to the DNG exif. Perhaps it can be read from a text file in the SD card and then inserted in the DNG.
I've wondered about the same thing for the JPG file too.  In particular, a note about any CHDK override settings applied as apparently they are not always recorded by the camera as the exposure used.
JPEG would be significantly more difficult, since we don't build the exif. You could read/write/modify the file after, but it would be quite slow.

Adding the ability to set DNG comment and similar fields would be a good thing.
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Offline msl

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Re: Interpolate luminance and chrominance before writing to dng
« Reply #12 on: 28 / November / 2014, 15:58:31 »
There is a nice script variant for the user comment in Exif data: http://chdk.setepontos.com/index.php?topic=4533.0 That could help in the moment.

msl
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Offline waterwingz

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Re: Interpolate luminance and chrominance before writing to dng
« Reply #13 on: 28 / November / 2014, 16:12:59 »
Quote from: msl on 28 / November / 2014, 15:58:31
There is a nice script variant for the user comment in Exif data: http://chdk.setepontos.com/index.php?topic=4533.0 That could help in the moment.
I remember that one.  In fact,  I reposted the script there after one of those forum upsets where attachments all were deleted.

As is, the script has a fairly special purpose which does not cover recording shooting information on a per shot basis.  But I agree that the guts of the script ( and the EXIFModule.lua file in particular) would be a great starting point for something more suitable.
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Offline fabri22

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Re: Interpolate luminance and chrominance before writing to dng
« Reply #14 on: 28 / November / 2014, 16:27:39 »
Quote from: waterwingz on 28 / November / 2014, 13:32:19
I've wondered about the same thing for the JPG file too.  In particular, a note about any CHDK override settings applied as apparently they are not always recorded by the camera as the exposure used.

It would be nice to read the right exposure time values in the DNG exif when override applied.
Noticed that values below 1/10000 aren't recognized in my raw editor or exiftool. Av and Sv seem correctly displayed when override applied.
Didn't check long exposure times.
The minimum exp. time never exceeds 1/2000 in Jpg exif from my camera.
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Offline reyalp

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Re: Interpolate luminance and chrominance before writing to dng
« Reply #15 on: 28 / November / 2014, 17:38:30 »
Quote from: fabri22 on 28 / November / 2014, 16:27:39
It would be nice to read the right exposure time values in the DNG exif when override applied.
Noticed that values below 1/10000 aren't recognized in my raw editor or exiftool. Av and Sv seem correctly displayed when override applied.
AFAIK DNG should record the correct times. It's possible that some software isn't able to display such extreme values.

Note there two different shutter values in the exif
1) Exposure Time - the is a "rational" value in seconds, so 1/1000 = 0.001
2) Shutter Speed value - this is a "rational" value in APEX units.

Programs may still display either as a traditional exposure time like 1/1000

If you want to see the raw values in a chdk dng, you can use the following in chdkptp
> dngload file.dng
> dnginfo -ifd=exif -vals

It seems like exiftool should be able to do the same, but I didn't see an obvious way.

The output will be something like
Code: [Select]
ExposureTime                   tag=0x829a type=RATIONAL   count=0000001 offset=0x000004f2
    0:            4079/1000000     0.004079
...
 ShutterSpeedValue              tag=0x9201 type=SRATIONAL  count=0000001 offset=0x00000516
    0:                  762/96     7.937500
The first column after 0: is the raw values in the exif.

If the values in the DNG exif are wrong, please report back here. Otherwise, you can report to the makers of whatever software displays it incorrectly.

jpeg exif is subject the limits of the canon firmware. It is normal that extreme overrides do not get recorded correctly, although in some cases the Canon maker note will give you the correct value.
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Offline fabri22

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Re: Interpolate luminance and chrominance before writing to dng
« Reply #16 on: 28 / November / 2014, 19:12:51 »
Quote from: reyalp on 28 / November / 2014, 17:38:30
...
If the values in the DNG exif are wrong, please report back here. Otherwise, you can report to the makers of whatever software displays it incorrectly.

jpeg exif is subject the limits of the canon firmware. It is normal that extreme overrides do not get recorded correctly, although in some cases the Canon maker note will give you the correct value.
Thanks for explanation reyalp. On left columns exif from pic at 1/10000 (on right at 1/100000 ... just for test)
I was able to read the right Tv in exiftool. The real "Shutter speed" is below "Exposure time" (wrong below 1/10000).
Usually my check stopped at the Exposure time  ::)



Lightroom doesn't show any Tv when below 1/10000



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Offline reyalp

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Re: Interpolate luminance and chrominance before writing to dng
« Reply #17 on: 28 / November / 2014, 21:19:24 »
Quote from: fabri22 on 28 / November / 2014, 19:12:51
I was able to read the right Tv in exiftool. The real "Shutter speed" is below "Exposure time" (wrong below 1/10000).
Some variation between the "shutter speed" and "exposure time" is expected, especially at the extremes. The camera overrides are set in APEX*96 values, so when you enter 1/10000 it gets converted to the nearest integer APEX*96. The "exposure time" then gets converted back from APEX*96 as integer microseconds.  (the camera ultimately also converts APEX*96 to an integer microsecond value for the actual exposure in expdrv, but DNG exif doesn't use the same function. It probably should.)

The errors at this extreme probably aren't very important, it's very unlikely that a 1/100000th override actually works.

I'm not really surprised lightroom fails to display such extreme values. FWIW, raw therapee displays it correctly.
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