Canon 600D RAW Tone Curve issue with red image


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lintujuh
Canon 600D RAW Tone Curve issue with red image

Hi,

 

I took today a picture of a bright red flower. When I opened the image in Lightzone, the exposure of the red spectrum sifted significantly to right causing the red to "burn". I located the problem to the RAW Tone Curve, when I unlocked and unselected it, the colors returned to normal.

 

I have uploaded the image in Dropbox (https://www.dropbox.com/sh/4znov9nz42xjf9f/AAB7ApSctCgJe0XToPreATEMa?dl=0). The file image is IMG_7677, I have uploaded the RAW, the _lzn file and the final JPG. I have also uploaded a modified _lzn file (IMG_7677B_lzn.jpg), where the RAW Tone Curve can be turned on or off.

 

-Juha

Jacal
With the same camera model,

I almost always have to desaturate such kind of red colours, most often flowers.

(EDIT: deleted a remark, based on a mistake.)

On the other hand, the red colour in this picture looks heavily "over the edge" in RawTherapee, that uses a modified version of dcraw, and in darktable, that doesn't use dcraw. It looks better in Canon's DPP, but red is still running out of the RGB histogram.

It would be interesting to take this picture with a different camera, if you have one at hands.

 

- Mart

Jacal
Another 600D sample,

a little different, here:

https://filebin.net/yqha1cte2hbwe7wp

With a default lzn file, and one without raw tone curve and some quick fiddling.

But I remember that I took this picture just because I "foresaw" the problem, the "real" flower looked "oversaturated" for my eyes.

 

- Mart

 

EDIT: Added default darktable and RawTherapee renderings to the Filebin collection. Camera's sensor seems to like a lot of red colour.

Photonoxx
I just test the picture. In

I just test the picture. In fact, the embed jpeg (showed in browser mode is not so far from the image opened in the editor. In these case, it coiuld be useful to underexposed a bit.

 

After that, there's strange tihings. Some viewer on linux display an underexposed picture compared to what Lightzone and Digikam display in browser mode and some other display the same burned image. If I oipen it in Digikam editor, I get an underexposed version too (but may be about how digikam work with raw).

 

So I didn't know which version is really the "true" one. After that, there could be some camera settings which modify the final picture that Lightzone can't take into account. 

lintujuh
With another camera

Sorry, it took some time to get the same picture with another camera. We were staying over our friends during the weekend and I took the picture there. I had to ask them to photograph the same flower with their old Nikon D40. I have now uploaded the DSC_8458.NEF and the corresponding _lzn.jpg into Dropbox. The embedded JPG looks oversaturated, but when opening in Lightzone and applying the Raw Tone Curve, the image looks much more natural. Also there is not the same shift of the red channel towards right as the Raw Tone Curve is generating for the Canon image.

 

-Juha