| Canon 500D-T1i | Nikon-D5000 |
| (http://www.dxomark.com/itext/insights_nikon_canon/image018.png) | (http://www.dxomark.com/itext/insights_nikon_canon/image019.png) |
I found especially interesting learning about the conflict between color accuracy and speed in the design of the CFAs.
Cheers
~Chris
I found especially interesting learning about the conflict between color accuracy and speed in the design of the CFAs.
Cheers
~Chris
See the figures below canon has a more permissive "red" channel, so it will permit more light, but needs more math calculate colour.
...As evidenced by the curves above, the human eye does not discriminate very well between red and green. A camera which discriminates better than the human eye will record colour differences that we do not normally see. That will look unnatural.
I have read that because Canon filters are less discriminant between red and green, they give more pleasing results for skin tones under poor light, e.g. fluorescent lights used in sports venues or at home. Conversely, MF cameras are more discriminant and are more sensitive to poor light, but this is not a problem for their intended use. Indeed if one tries to take a portrait under typical home lights, 24*36 cameras will give more pleasing results than a MF, even when one tries to correct white balance (you can try it yourself). On the other hand, MF cameras are better at showing differences between orange and red.
However, the assertion that MF is more discriminant is doubtful.
As evidenced by the curves above, the human eye does not discriminate very well between red and green.
That is an interesting observation regarding channel decompostion of Nikon vs Canon. However, the assertion that MF is more discriminant is doubtful. It would depend on the CFA filters and these could vary among different MF and 24x36 sensors. The DXO data for the Nikon D800e and Phase One IQ180 demonstrate that the D800 is more discriminant than the IQ180. How the new Phase One would compare is not yet available.
Bill
Great article, likely written by two people: the first paragraph (foreword) has a style totally different than the body of the article. Informal vs formal.are you talking about the forward vs the "article". Certainly the article has seen considerable work, and perhaps has been written over a period of time. The forward seems to be added to alert viewers as to what to except in the article. But I don't know they were written by different people, just different objectives for something written probably at different times. I get the sense the forward was added for the purpose of posting to this site, the article itself will probably see a broader distribution.
That said, The article is very informative, who ever wrote it. Kudos to Doug for sharing!
NY
| (http://echophoto.dnsalias.net/ekr/Articles/P45+ColourRendition/WB/WBLeft_vsmall.jpg) | (http://echophoto.dnsalias.net/ekr/Articles/P45+ColourRendition/WB/WBRight_vsmall.jpg) |
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I guess that getting WB right is extremely important for colour rendition.
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I should add that speed isn't the only reason for reduced color accuracy in most DSLRs and consumer cameras, by intentionally manipulating the color response, it's possible to make images look better under poor lighting conditions
The figure below shows colour interpretation as measured by Imatest on the P45+ using Capture 1 (7.1.3). It shows that greens are shifted towards yellows, and this is very visible in landscape shots:
(http://echophoto.dnsalias.net/ekr/Articles/P45+ColourRendition/ColourError/20131224-CF044440_C1_colorerror.jpg)
True, but this is not what we were talking about. This is about a given patch of pigment being rendered of a slightly different colour than the one the human eye would perceive. Metamerism is about two given patches of different pigments which appear of the same colour to the human eye but are rendered of a different colour by the camera.
True, but this is not what we were talking about. This is about a given patch of pigment being rendered of a slightly different colour than the one the human eye would perceive. Metamerism is about two given patches of different pigments which appear of the same colour to the human eye but are rendered of a different colour by the camera.
The effect is common with certain flowers. They appear to be of the same colour to the human eye (e.g. both are red) but are of different colour when photographed (e.g. one is red and one is orange).
Now, imagine a portrait situation. For an healthy model, patches of skin with or without underlying veins appear to be almost of the same colour to the human eye. Our eyes have evolved to perceive skin in that way. Cosmetics appear to our eyes to be of skin colour, because they are designed in that way. However, the spectral content of reflected light may be slightly different for skin, skin with veins and cosmetic pigments. It is just that our eyes are not sensitive to these spectral differences. But if the camera is sensitive to these differences, we will see them on the photographs. In truth, the camera is more sensitive to the differences than the human eye, but the results are still not what we want, for example because veins are more visible.
A high color sensitivity offers opportunities to very precicely tweak certain color differences, either making them more pronounced, or less obvious.
I don't think it is that simple. If the camera sees differences where the human eye does not, removing these differences will be very difficult in post. For example: if a camera exagerates skin defects on a human face (e.g. veins or the blue-green under the eyes), removing these defects will be lots of work.
True, but this is not what we were talking about. This is about a given patch of pigment being rendered of a slightly different colour than the one the human eye would perceive. Metamerism is about two given patches of different pigments which appear of the same colour to the human eye but are rendered of a different colour by the camera.
Eliminating the IR contribution, which registers in all three CFA channels and desaturates and shifts color, is important for accurate skin color
The Color Sensitivity Index and Sensitivity Metamerism Index are metrics for the discrimination sensitivity, not color accuracy. A high color sensitivity offers opportunities to very precicely tweak certain color differences, either making them more pronounced, or less obvious.
Hi,
The description of SMI given by DxO is enclosed.
I should add that speed isn't the only reason for reduced color accuracy in most DSLRs and consumer cameras, by intentionally manipulating the color response, it's possible to make images look better under poor lighting conditions, which tend to have "spikes" in the color spectrum.I propose that there can be a big difference between "objectively accurate color" and "color that works well for the main intended usage". Kodachrome and Velvia were both very popular is some areas of professional and artistic photography, but more for their desirable distortions of color than for superior color accuracy. (AFAIK, Kodachrome has a slight skew to red that was flattering in portraits -- at least of caucasians.)
I propose that there can be a big difference between "objectively accurate color" and "color that works well for the main intended usage". Kodachrome and Velvia were both very popular is some areas of professional and artistic photography, but more for their desirable distortions of color than for superior color accuracy. (AFAIK, Kodachrome has a slight skew to red that was flattering in portraits -- at least of caucasians.)
I propose that there can be a big difference between "objectively accurate color" and "color that works well for the main intended usage". Kodachrome and Velvia were both very popular is some areas of professional and artistic photography, but more for their desirable distortions of color than for superior color accuracy. (AFAIK, Kodachrome has a slight skew to red that was flattering in portraits -- at least of caucasians.)
Every day we tweak individual images to optimize color to produce the final result we desire, not to be "accurate."
I would submit that all the testing really is a means to standardize upon a set of tools that helps us understand what we need to bring any sensor into a range that we can then adjust for our creative purpose and not to somehow attain some Holy Grail of color fidelity.
Hi Erik,
Accurate is mentioned as the possibility to discriminate between metameres. When the sensor cannot discriminate between pure Yellow, and a mix of Red and Green, it cannot be white balanced accurately. It does not mean that very subtle color nuances can be accurately discriminated, that aspect is described in the other metrics mentioned on that DxO page (http://www.dxomark.com/About/In-depth-measurements/Measurements/Color-sensitivity).
Cheers,
Bart
I would submit that the all the testing really is a means to standardize upon a set of tools that helps us understand what we need to bring any sensor into a range that we can then adjust for our creative purpose and not to somehow attain some Holy Grail of color fidelity.
Well put IMO. The Holy Grail of color fidelity is unattainable in any case, short of an accurate emulation of the entire human eye/brain system, color being an interpretive & subjective thing.Something that cannot be fully attained can still be a worthwhile goal.
-Dave-
But under which light?My problem with my Canon camera and default Lightroom profiles is that colors appear to be anything but neutral under any light. They appear to have been made with the goal of "wow". I had to make my own profiles in order to come closer to what appears "neutral" to me.
Niels "The Image (Quality) Professor" Knudsen surely is the most prominent hero in Doug’s text. His color-profiles are highly praised, also those for CMOS cameras that are not PhaseOne-built, i.e. mostly SoCaNikon DSLRs. And as a real hero he’s doing his thing alone, in the basement, with genius-like magic (= no numbers once the basics are set). At least that’s how the story is being told.
My point of view is slightly different. I am really not pleased with CaptureOne’s profiles for the D800E. They have a built-in color-sink towards a brownish red with hardly any discrimination between yellowish-green and reddish-orange. That makes for "healthy", uniform skin tones, but CaptureOne would also be able to perform this stunt on demand with its skin tone color correction tool. With the standard profiles there’s no choice left. So I would like to ask PhaseOne if it would maybe make some sense to double-check their basement-magic with numbers and a second or even third pair of eyes.
Please note: This is no critique towards the person of Niels Knudsen. But maybe towards PhaseOne’s concept of quality control and epic self-praise.
You're welcome to create your own ICC profile using any ICC-compliant software.