The synthetic test image is what a “perfect” M8 would show. But “perfect” here means an M8 that matches Leica’s calibration matrixes. However, there is no one single best calibration for a real camera. Pretty much all camera calibration is done via a three by three matrix. Using that, you can dial in any three particular colors exactly. So, for example, you can get the red, blue and green patch on the GretagMacbeth chart down to the last decimal point. If sensors were perfect, that calibration would also mean that every other patch would also be calibrated. However, in a real sensor, there are a whole lot of imperfections – among other things, the filters in the Bayer matrix aren’t ideal, so colors bleed between each other, and the sensitivity of the sensor itself varies with the frequency of the light striking it. So, even if you dial three patches in perfectly, the others will be out. So practically, what camera manufacturers and raw developer software writers have to do is to find a calibration that is a compromise across a whole range of colors. However, because people are more sensitive to certain colors being out (e.g., skin tone, foliage, etc) that compromise is often weighted in favor of the sensitive colors.
The M8 test images can be found here: http://chromasoft.googlepages.com/referenceimages
The charts below show the difference between the theoretical color values that we should see for a selection of six of the more important color patches, and what we actually get. So, for example, if the red bar of the “Cyan patch” shows a value of -5, that means that the actual measured value of the R component of the RGB values as read out by the software in question was 5 units less that the theoretical value as shown in the spreadsheet I discussed in the last post. In all cases, the scale is 0 to 100.
First up is Lightroom. It shows minimal deviations from the theoretical values – all the values are within 3 units. But this shouldn’t come as a surprise – Lightroom internally uses the exact same color model as the DNG file, and we know that Lightroom uses exactly the same color calibration as the Leica DNG’s have embedded into them. The minor deviations that we seeing are really just slight imperfections in the tone curve and in the color temperature interpolation process that Lightroom uses.
Next up is Aperture. There are three Aperture graphs, the first for Aperture V1.5.4. In addition I also have graphs for Aperture 2.0, which came out a few days ago. Aperture 2.0 provides four “Raw Fine Tuning” settings, “1.0”, “1.1”, “2.0” and “2.0 DNG”. I checked, and color rendering from the old 1.5.4 and what you get by setting “1.1” in 2.0 are indeed identical. Firstly, all of the Aperture settings have lot less green in the red patch than Lightroom, and less red in the blue and cyan patches. The 2.0 results are not much different to the 1.5 results; a little bit less red in the blue patch, a bit less green in the red patch, but far less blue in the yellow patch.
The “2.0 DNG” setting is more interesting. There doesn’t seem to be much documentation on what it does – the Apple aperture site itself is silent on the subject, and various third party sites have words to the effect of “changes to the image using the 2.0 DNG converter are made based on the DNG specification of the file”. This implies that rather than using the Aperture color conversion parameters, setting the DNG mode will give you the colors as set by the ColorMatrix values embedded in the DNG. As it turns out however, that’s just not the case – if it were, we’d see values that looked like Lightroom, but what we see are just some subtle changes to the “2.0” profile. Although visible if you change the setting on the fly, the change is actually more subtle than the change between 1.5 and 2.0.
Finally, there is Capture One. During the course of this process, Capture One 4.0.1 came out; the results shown here are for 4.0.1, but they are identical to those for 4.0; as far as I can tell, no changes have been made to color rendering between versions. Capture One provides two profiles, one Generic, and one UVIR, designed to match to the M8’s color rendering when mounted with a UVIR filter. While the differences between these two are there, they are quite subtle. Overall however, there are significant differences to the rendering of either Lightroom or Aperture. Capture One shows less red for most patches, especially the red patch, but more red in the cyan patch. Finally, there is generally somewhat less saturation for most colors. This is broadly consistent with most people’s views on Capture One’s rendering as being “less red” than Lightroom.
Nice review. Keep up the great work, you are providing a great resource on the Internet here!
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Thanks!
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