Canon 7Dii vs Nikon D750 Dynamic Range Test

[jrista]

Here a image taken from the raw data, at the right the canon 5 dmk3 and left the Nikon 750, stretch with ImagesPlus astronomical software, zero noise reduction. crop and arrows with photoshop.
Red arrows: these are white specks on the card! not noise!
Blue arrow: banding in the Canon image.
Overall: in the Nikon image you see a red hue, but way less noise.
So what you think? especial the red hue, is the card realy red or black?
Garret van der Veen

I am pretty sure the red hue is just due to white balance. I do not believe that is the correct color, but it is easily correctable. The card and wedge should be neutral in color.

It is not as simple as the white balance, if it was all the whites would also be as red, and they are not, don't confuse the magenta fringing as red toned whites. If you look at a channel histogram you can see the red shift in the shadows and a slight lack of red in the highlights.

It is due to changes in the response curve at different tones which could be caused by any number of fundamental things, the only way to sort it out is to apply a channel tone curve, probably several with luminosity masks, to overcome the precise shifts.

The first histogram is the untouched file, the second is the three point three channel corrected file, I have included the tone curve adjustment lines too. Although the resulting lines look linear they are not. And, of course, any adjustments you make to the actual shadows would need a similarly adjusted curves layer.

None of this is that difficult, but the time and skill involved is not as trivial as many would lead you to believe good processing of Exmor files is.

I have not yet opened up the files in a RAW editor. I am still looking at them in PixInsight. As far as I can tell, the white swatches in the NEF are just as redshifted as the black swatches. The overall red hue appears to be consistent to me, at least when the image is rendered in linear space. I can do a non-linear screen stretch, and the red hue disappears and the entire image becomes neutrally balanced.


You can look at the JPEG images I shared in my post a couple of pages back. The Canon image appears to be very slightly blue shifted in the white swatches, while the Nikon image appears to be red shifted in the white swatches. I can share more images...I don't think there is any discrepancy in the red shift between the swatch 1 and swatch 41, or the background for that matter.

 

[privatebydesign]

As far as I can tell, the white swatches in the NEF are just as redshifted as the black swatches. The overall red hue appears to be consistent to me, at least when the image is rendered in linear space. I can do a non-linear screen stretch, and the red hue disappears and the entire image becomes neutrally balanced.

If it was a simple colour shift or WB issue then the three lines in the channel curves adjustment would be straight, but they are not, they are curves. Being curves means the respective colour balance is uneven at different tonalities.

 

[jrista]

As far as I can tell, the white swatches in the NEF are just as redshifted as the black swatches. The overall red hue appears to be consistent to me, at least when the image is rendered in linear space. I can do a non-linear screen stretch, and the red hue disappears and the entire image becomes neutrally balanced.

If it was a simple colour shift or WB issue then the three lines in the channel curves adjustment would be straight, but they are not, they are curves. Being curves means the respective colour balance is uneven at different tonalities.

A assume you are working with images that have passed through one RAW converter or another? I am looking at the RAW linear data...and I am not seeing what you are seeing. Is it possible the RAW converter is complicating things?

 

[privatebydesign]

"Is it possible the RAW converter is complicating things?"

Of course it is, but it could as easily be an intrinsic capture issue, but the point is moot, this isn't an isolated set of images and more than one RAW convertor does the same thing. Besides the output is purely academic until you put it through a RAW convertor, and the number of images most of us shoot means it needs to be one of a small handful of those.

Like I said, it isn't a huge issue for people with above average expectations and post processing skills.