On Sun, Sep 8, 2013 at 3:27 AM, David Vincent-Jones <[email protected]>wrote:
> I used a fairly normal scene for this test (not sure why but I put it
> totally out of focus). There was a fairly good dynamic range visible.
>
> When the image was imported into dt I only changed the raw basecurve into
> the lineal state everything else was untouched. The jpg file had no
> in-camera tweaks and was left 'as-is'.
>
> This time (with the more 'normal' image the 256 sample values were more
> consistent but there was a definite separation of r,g and b in the toe
> area. Moreover a reversed toe is clearly defined unlike the basecurve in dt
> for my camera.
>
> I then did an grey-scale averaging of the r+g+b values (rounded) and then
> ran a second curve with 256 values . A third graph gives the frequency
> count for grey values.
>
> There are clear problems at the top end of the data with insufficient data
> shown but I think that the curve is generally correct in comparing the raw
> input with the Canon modified data.
>
> I do not know where dt keeps its basecurves and what the format is .... so
> I may 'hand-tool' a test curve as an experiment for my camera although
> frankly I never shoot in jpg format and make my own decisions as to how an
> image will appear in the final form.
>
the logarithmic view in the new basecurve module might help you with this.
or else see tools/basecurve/basecurve.c near the end, it outputs a line of
sql to inject a fitted spline to the database. shouldn't be too hard to
feed it your samples instead (although i think the rest of the binary might
be doing exactly what you're doing).
-jo
>
> David
>
>
>
> On 13-09-07 08:33 AM, Torsten Bronger wrote:
>
>> Hallöchen!
>>
>> David Vincent-Jones writes:
>>
>> [...]
>>>
>>> The image that I used probably had a better grey distribution than
>>> samples previously offered on this subject ... however I will
>>> remake based on a much more normal scene.
>>>
>> I have never smoothed, yet my plots only looked this way for rare
>> grey values.
>>
>> Is is possibly to plot also the frequency of the grey values?
>>>>
>>> Yes, I certainly can do a grey scale plot ... and will do so later
>>> today.
>>>
>> I don't need a look at the original picture, just a semi-logarithmic
>> plot of frequency vs. grey value.
>>
>> Tschö,
>> Torsten.
>>
>>
>
>
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