Canon EOS-5D

Color Accuracy

The Canon EOS-5D showed good color accuracy overall, but tended to get pretty carried away with strong reds. This is a fairly common response with this target (the MacBeth ColorChecker), but the 5D falls toward the upper end of the range of oversaturation of reds that we've seen in professional SLRs. Hue accuracy is among the best we've seen though, with only slight shifts in cyans, magentas, and oranges. Average saturation was 108.5% (oversaturated by 8.5%, almost entirely in the reds), average "delta-E" color error was 4.98. (Hue error, after correction for saturation, among the best we've seen.)

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-5D with a nominally-exposed density step target (Stouffer 4110), using the 5D's "Standard" Picture Style.

These are excellent numbers, particularly coming straight from the camera as a JPEG. What I particularly like about the above data though is the very nice "S" shape to the density curve. The Canon 5D's tonal response looks very much like film in this respect, with a nice gentle tail at each end of its tone curve. Let's also look at how the EOS-5D's images behave when processed from the RAW format.

The plots above show the results of a somewhat more overexposed frame, shot to give the RAW processing software more overexposed density steps on the highlight end to play with. These steps show in the JPEG files as completely blown out to white, but cameras often have a little headroom for highlights in their RAW files that some RAW processing software can pull back. In contrast, the camera itself seemed to do about 0.2 stops better when the lightest step was just shy of blowing out.) The results above were obtained after processing a CR2 RAW file through Digital Photo Professional 2.0, and tweaking the controls to produce a final image that just barely revealed all the image data shown in the DPP histogram displays within the available tonal range.

Interestingly, DPP doesn't extract quite as much dynamic range from the CR2 file as the camera itself manages in the JPEG. In particular, no highlight detail appeared that wasn't already present in the original JPEG, no matter how I contorted the tone curve in DPP.

What's interesting about the above data though, is the Noise Spectrum plot in the lower right. Compare it to the same plot in the results for the camera JPEG above. See how relatively high and flat it is on the right-hand side? That's because the image noise in the DPP sample is much finer-grained than that from the camera itself. We'll look into that a bit further down.

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 managed to extract about a third of a stop more dynamic range from the CR2 file at the highest quality level, but did quite well when indistinct steps in the greyscale were considered. In particular, it managed to recover upwards of a full stop more detail in highlights that were totally blown out in the Camera JPEG or DPP-derived image. I played a bit with the controls in Adobe Camera Raw, but no setting did much better than ACR did on its own. (I managed to get a bit smoother tone curve, and a bit more detail revealed in the shadows, but at the cost of a little bit of data in the highlights.) Here again though, the Noise Spectrum plot reveals that the noise from ACR is a bit finer-grained than in JPEGs straight from the camera.

Let's take a look at some crops from the test images, to see what the noise patterns look like from the three sources (camera, ACR, DPP):

From Camera	From ACR	From DPP
(Same shots as above, but brightened in Photoshop with the Levels tool, setting the highlight slider to 100)

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 at its default noise-reduction settings of "flattening" the noise in the individual color channels than either the camera or DPP, but the image is a bit softer with the default sharpness settings. Chroma noise is considerably reduced, and the noise pattern is finer-grained than that produced by the camera, but coarser than that from DPP. DPP's noise is a bit finer-grained than that from the camera's own JPEGs, but there's arguably a bit more chroma noise. Also interesting is that the default settings of both ACR and DPP produced more neutral grey scales than did the camera.

To get some perspective, here's a summary of the EOS-5D'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-5D'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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