Posted by
Herbie on
Aug 12, 2020; 7:55am
URL: http://imagej.273.s1.nabble.com/14-bit-NEF-raw-Images-tp5023829p5023841.html
Dear Michael,
although I agree in many points, I disagree regarding two:
1.
Lee will encounter difficulties getting the Lab-Colour space from the
colour stack because ImageJ doesn't provide this conversion feature.
(Doing it with 24bit RGB is not what Lee is heading towards.)
Either he must write a plugin that does the colour space transformation
or he must use another software. (My old Photoshop does 48bit RGB-to-Lab
conversion but there may be other apps that do so for less money.)
2.
I second Gabriel Landini by "doubting" that a correction factor will be
able to correct RGB-information with respect to photometric data. The
reason is that for colours that do not exist there is simply no correction.
Photometric colour information is in principle given by a continuous
(wavelength) dimension, RGB means three points on this dimension only.
Best
Herbie
::::::::::::::::::::::::::::::::::::::::::::
Am 11.08.20 um 19:20 schrieb Michael Schmid:
> Hi Lee,
>
> if you open a raw image you should expect that you get
> (1) no correction for color balance (white balance) and
> (2) a linear response, in contrast to RGB/sRGB formats like jpg etc.,
> where the response is nonlinear.
> (3) There can be some offset, i.e., black won't correspond to pixel
> values of zero.
>
> Thus, your raw image will not look like the corresponding jpg or thumbnail.
>
> For quantitative analysis, subtract a dark frame (raw photo with the
> lens cover closed, but the same ISO value and exposure time). This is
> best done in 32-bit mode. Also take a photo of a white or neutral gray
> object under the same light conditions, than you can calculate
> correction factors for the colors.
>
> For quantitative analysis, don't apply a nonlinear function. For
> viewing, after the above corrections, you may try Process>Math>Gamma
> with a gamma value of about 0.5 to approximate the visual impression of
> a jpg etc. image.
>
> Michael
> _______________________________________________________________________
>
> On 11/08/2020 12:50 am, Lee Berndt wrote:
>> Hi:
>> I'm trying to open 14 bit Nikon NEF images with little success ....
>> using Import/Raw the file opens but is very small (160 x 120 px) ....
>> if I use bio-formats the image opens but is not the correct size or
>> color .... dcraw reader also opens it but the image is still not right
>> .... can someone help me please ? what am I doing wrong? Thank you
>> and have a great evening .... Lee
>>
>> William L. Berndt, Ph.D. 7133 Penner Lane. Apt. #40Fort Myers, FL
>> 33907@Dr_Lee_Berndt239.246.0396
>>
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