Canon EOS-1Ds Mark II

Color Accuracy

The 1Ds Mark II shows generally good hue accuracy, but saturation is a little odd: Reds are a bit hot (as usual with this target), cyans are shifted toward blue (also typical, helps sky colors), but yellows and yellow-greens are undersaturated, pure greens are a bit oversaturated. Overall color accuracy is very good to excellent, but yellows look slightly dull to the eye. Average saturation was 103.6% (oversaturated by 3.6%, mostly in the reds), average "delta-E" color error was 5.86. (Hue error, after correction for saturation.)

Color Analysis

Gray Patch Tone and Noise Analysis

Dynamic Range Analysis

A key parameter in a digital camera is its Dynamic Range, the range of brightness that can be faithfully recorded. At the upper end of the tonal scale, dynamic range is dictated by the point at which the RGB data "saturates" at values of 255, 255, 255. At the lower end of the tonal scale, dynamic range is determined by the point at which there ceases to be any useful difference between adjacent tonal steps. Note the use of the qualifier "useful" in there: While it's tempting to evaluate dynamic range as the maximum number of tonal steps that can be discerned at all, that measure of dynamic range has very little relevance to real-world photography. What we care about as photographers is how much detail we can pull out of the shadows before image noise becomes too objectionable. This, of course, is a very subjective matter, and will vary with the application and even the subject matter in question. (Noise will be much more visible in subjects with large areas of flat tints and subtle shading than it would in subjects with strong, highly contrasting surface texture.)

What makes most sense then, is to specify useful dynamic range in terms of the point at which image noise reaches some agreed-upon threshold. To this end, Imatest computes a number of different dynamic range measurements, based on a variety of image noise thresholds. The noise thresholds are specified in terms of f-stops of equivalent luminance variation in the final image file, and dynamic range is computed for noise thresholds of 1.0 (low image quality), 0.5 (medium image quality), 0.25 (medium-high image quality) and 0.1 (high image quality). For most photographers and most applications, the noise thresholds of 0.5 and 0.25 f-stops are probably the most relevant to the production of acceptable-quality finished images, but many noise-sensitive shooters will insist on the 0.1 f-stop limit for their most critical work.

The image below shows the test results from Imatest for the EOS-1Ds Mark II.

These are good numbers, but as we'll see below, they're actually about in the middle of the range among the d-SLRs I've tested. Let's also look at how the 1Ds Mark II's images behave when processed from the RAW format...

The plots above show the results of the same exposure, only processed from the CR2 RAW file, through Digital Photo Professional 1.5. (This is a case where the 1Ds Mark II's ability to save both a RAW and JPEG file from the same shot comes in handy.) Interestingly, DPP doesn't extract as much dynamic range from the CR2 file as the camera itself manages in the JPEG. The data above was collected from a JPEG image processed with DPP's "as shot" defaults, but I found that no matter how I contorted the tone curve in DPP (cutting contrast, playing with exposure adjustment), I never did any better than the dynamic range levels shown above.

What about Adobe Camera Raw (ACR) though?

Using its automatic settings (which in my experience have generally worked best for dynamic range tests like this), ACR did manage to extract about a half-stop more dynamic range from the CR2 file, but the noise characteristics are quite different: Look at the Noise Spectrum plot in the data above, and notice how the curve is rather lumped up on the left.

Actually, Adobe Camera Raw does even better when dealing with an intentional overexposure. The results above were measured from a density target that was exposed a full f-stop more than the one used in the previous examples. Here, ACR managed to pull back a full stop's worth of overexposed detail in the blown highlights, but lost about a third of a stop on the shadow end in its processing. The net result though, was an increase of two-thirds of a stop over its own performance at the lower exposure level, and more than an f-stop relative to the dynamic range of the camera's JPEGs.

From Camera	From ACR	From DPP
(Same shots as above, but brightened in Photoshop with the Levels tool, setting the highlight slider to 130)

Here's a look at crops from the original camera JPEG, a version processed through ACR, and the one processed through DPP. What's particularly interesting is that ACR does a better job of "flattening" the noise in the individual color channels than either the camera or DPP, but the net result is still a little blotchy-looking. - The magnitude of the noise has been considerably reduced, but the grain pattern is coarser. DPP seems to go the other direction, not flattening the noise as much, but producing a very fine grain pattern.

Bottom line, Adobe Camera Raw does take better advantage of the luminance information available in the 1Ds Mark II's CR2 RAW files, but the character of the noise is changed quite a bit in the process. I do suspect that most photographers would prefer the "look" of the ACR-processed images.

To get some perspective, here's a summary of the1Ds Mark II's dynamic range performance, and how it compares to other digital SLRs that we also have Imatest dynamic range data for. (Results are arranged in order of decreasing dynamic range at the "High" quality level.):

The results shown in the table are interesting. One of the first things that struck me when I initially looked at test data for a wide range of d-SLRs, was that here again, purely analytical measurements don't necessarily correlate all that well with actual photographic experience. There's no question that the Fuji S3 Pro deserves its place atop the list, as its unique "SR" technology does indeed deliver a very obvious improvement in tonal range in the highlight portion of the tonal scale. I was surprised to see the analytical results place the Olympus EVOLT as highly as they did, given that our sense of that camera's images was that they were in fact noisier than those of many other d-SLRs that we looked at. In the other direction, I was quite surprised to see the Nikon D2x place as low on the listings as it did, given that we found that camera's shadow detail to be little short of amazing.

One thing that's going on here though, is that we tested each camera at its lowest ISO setting, which should produce best-case noise levels. This is in fact what many photographers will be most interested in, but it does perhaps place the Nikons at a disadvantage, as their lowest ISO setting is 200, as compared to the ISO 100 settings available on most other models.

Regardless of the positions of the other cameras though, it's clear from its images that the EOS-1Ds Mark II's noise levels are quite low, helped by its relatively large pixels, Canon's advanced CMOS sensor technology, and artful anti-noise processing in its Digic II processor.

As I always say though, at the end of the day, I think you have to take the figures here with a grain of salt, and look at actual images with your own eyes to see what you make of each camera's tonal range and noise levels. We'll continue performing these dynamic range tests on the digital SLRs that we review, but (just as with the laboratory resolution target results), we suggest that you not rely on them exclusively for making your purchase decisions.

Resolution Chart Test Results

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