Does LR auto-gamma correct?

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nmasson

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Hello,
I've been combing the literature about gamma curves and correction, and I would like to know where gamma curve changes are applied between the picture-taking and final printing. I would hate to have a correction applied twice etc... and mess up my midtones.

I guess my main question is whether LR applies gamma correction to the photo automatically. I know that JPEG and TIFF images have an implied gamma-- i.e. when you develop from RAW to JPEG or TIFF, some gamma gets applied, but then when you send the pictures to be printed the photo printer knows to undo-the gamma. So effectively the image from RAW to print is linear since the gamma is first applied in TIFF/JPEG and un-done in printing.

What kind of processing happens before the image is sent to post-processing in LR? I shoot with a D7', and i've uploaded a custom tone curve that has gamma compensation (gamma<1). I did this in the hopes of more closely matching the captured data to the way our eyes see it (i.e. changing the linear raw data from the sensor into logarithmic data through the tone curve). I wanted to make sure, however, that LR, or the camera's internal software, doesn't automatically apply a gamma correction curve AGAIN. (i.e. if I shot a picture with a linear tone curve, would the RAW file that I import and work with in LR already have gamma compensation b/c of LR or camera software?).
Anyway, if anybody could clarify this I would be very grateful.
Thanks,
NICK
 
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The custom curve you've installed on your D7' is applied only during JPEG conversion. The raw data is still raw, and is unaffected by that curve.

Did that answer the question?

P.S. Welcome to Lightroom Forums!
 
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LR uses Adobe Camera Raw to create the image from the original RAW data. I'm not sure whether there is an algorithm which is directly specific to gamma adjustment during that processing but there will be a whole lot of processing going on to create the image. I would treat the RAW conversion as the 'negative' because 'gamma adjustment' probably doesn't have any meaning before this stage anyway.
 
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That makes sense, since RAW is in fact what is says, raw data. Gamma correction or not, my main question is whether or not the custom tone curve that I have installed in my D7' will be applied to the image that I import into LR. It doesn't make sense to me that the custom curve would only be applied in the JPEG compression AFTER I do my post-processing in LR. Otherwise a custom curve will just mess up the picture even more... In other words, when I adjust my tone curve in LR to make the image the way I want it, I would like the exported JPEG to reflect the changes I made in LR. If a custom tone curve is applied after I make my LR adjustments, then it defeats the purpose of manually adjusting it in LR (no way to anticipate the outcome if the custom D7' tone curve is applied AFTER my adjustments in LR).

My understanding, rather what would be logical, is that the custom tone curve in the d7' is applied when I import images into LR. That way the a tone curve is ALREADY applied to the image, thus cutting down on work-flow time. If the curve I installed in the D7' is only applied post-LR editing during the development stage, then I might as well get rid of it and keep a linear tone curve to preserve the changes I make in LR...
 
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The custom tone curve in the D7' will be applied to a jpg in the camera.
Will it be applied to the RAW file ? Not sure ? I would create an extreme custom tone (easy to see) and try it. If the tone is applied during the RAW data creation/conversion you will see it in LR. If however it is stored as a an instruction in the RAW file (as I suspect) you won't see it in LR. You will see it in Nikons Capture/View NX software though, as that is capable of reading the instructions about the tone curve and displaying the image appropriately.

If you don't see the tone curve change in LR then you may as well throw it away and create a preset in LR that you can apply as you import.

It *may* also be possible that LR (ACR) does read the tone curve instructions, but I would test it if I were you. In my experience LR (ACR), Aperture etc... don't access the proprietary instructions in the RAW file.
 
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I have tested this on a D3''. LR doesn't 'see' the profile instructions.

I shot 2 images in RAW and imported them. In the camera and during import the images looked different because we are seeing the embedded jpg from the raw file. When LR generated it's 1:1 previews from the raw file data the images were identical.

This is what I expected and I expect the D7' is exactly the same.
 
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Nikons View NX does show the profile, see the shots below. The 2nd image has the saturation & contrast pumped in the camera profile.
 
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Short answer: No. The custom curve is applied by the camera when it converts to JPEG. You don't use the camera's raw converter when you use Lightroom. Lightroom does not see the custom curve.
 
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