The Digital Sensor: Part 2

12 Megapixel Cameras

12MP seems to be the resolution of choice for recent high-end or "serious" DSLR cameras. Again, the actual cross-section at 12MP represents a much wider range of models than you might imagine. The Sony CMOS image sensor, used in the top Sony A700 and the "Pro" Nikon D300, basically set 12MP as the next resolution class. However, the 12MP class also includes the mid-entry level Canon XSi and the 2+ year old full-frame Canon 5D.

Now that the Canon 5D is selling for just a little more than the Nikon D300 and Olympus E-3 you have to consider the 5D in a comparison of prosumer cameras. With the $300 Instant Rebates on the 5D that started in the US today the 5D will probably be even less expensive. It is due for replacement this year but it is still very competitive and some would consider it the best available at its current price point.

The four cameras here represent the 12MP models, including two 1.5X, a 1.6X, and one 1X (full-frame) sensors. All sensors in these four cameras are CMOS, which seems to be the trend for new sensors for reasons discussed in Part 1 of The Digital Sensor.

All images were captured using the manufacturers' 50mm f/1.4 normal lens. This represents an equivalent 35mm focal length of 75mm for the Nikon D300 and Sony A700. The Canon XSi equivalent is 80mm. The full-frame Canon 5D equivalent is the specified 50mm. The distance to the subject was reduced when using the Canon 5D so that the captured image was about the same field of view as the crop-sensor cameras. With the 50mm FOV on the 5D much more of the scene is captured at the same shooting distance than with the crop-sensor cameras.

All images were captured at the same f/4.0 aperture using a tripod in the same location except for the full-frame 5D. Focus was manual and the camera program selected the shutter speed. Lighting was a single 100-watt Tungsten bulb high right, and all cameras were set to the Tungsten preset.

12MP Sensor Performance JPEG Comparison over ISO Range
ISO	Canon XSi	Nikon D300	Sony A700	Canon 5D (Full-Frame)
100
200
400
800
1600
3200
6400
Click on any of the above image crops for the full image. Note: Full size images are between 3.9MB and 11.4MB!

12 Megapixel sensors seem to be the hot competition arena in current DSLRs, and it certainly shows in the very different approaches to in-camera processing shown in the JPEGS from these four cameras. You should take a close look at the Sony A700 and Nikon D300 results since they are based on the same sensor. The impact of in-camera processing on the finished JPEG can’t be illustrated more clearly than by comparing the Sony and Nikon images.

You should also pixel peep the images from the full-frame Canon 5D and compare them to the Nikon and Sony. You will probably find a smaller difference in image quality than you expected, which just demonstrates how much progress has been made in sensor technology since the Canon 5D was introduced more than two years ago. The successor to the 5D is expected later this year and it is rumored to feature a 16 megapixel full-frame sensor.