Canon EOS 5D Mark III is a significantly improved full frame DSLR over its predecessor except the pixel count, which got just a minor increase. Canon, through some media outlets, claimed two stops improvement in high ISO noise performance. Could it be true?
The JPEG samples posted by DPReview and Image Resources do look impressive but it is difficult to tell the real improvements in sensor high ISO noise performance due to noise reduction applied on the sensor data before JPEG output. In order to answer the question about how significant the improvement is in high ISO noise performance, we need to evaluate RAW image files with noise reduction turned off.
Canon has not released update for its official DPP software that opens CR2 raw image file produced by Canon EOS 5D Mark III. Photoshop users can open the files using Adobe Camera RAW 6.7 RC. Lightroom 4 users are still waiting for a software update. One work-around is to use the Adobe Digital Negative Converter 6.7 to convert the CR2 raw images into DNG format. After the conversion, the files can then be processed in Lightroom.
DPReview user Horshack has done an analysis using RAW image files from Imaging Resources. The analysis was done using Photoshop and Camera RAW 6.7 RC. To make it a valid comparison, the exposure and white balance of the photos were matched. After that, the noise (measured as the standard deviation of each color channel from color checker patches) level of Canon EOS 5D Mark III photo taken at ISO 12800 was compared against photos of Canon EOS 5D Mark II taken at ISO 6400 and ISO 12800.
The data showed that ISO 12800 photo taken with Canon EOS 5D Mark III has slightly higher noise level than the photo taken with Canon EOS 5D Mark II at ISO 6400 but much better than the photo taken with Canon EOS 5D Mark II at ISO 12800. By estimate, the new Canon EOS 5D Mark II offers ~2/3 stops of high ISO noise performance improvement over its predecessor. This evaluation is in agreement with others I have seen on the Internet.
One problem with this analysis, as pointed out by another DPReview user here, is that the numbers are only about quantity of noise but not quality. Eliminating or significantly reducing the banding noise that was well-known for Canon EOS 5D Mark II users should be considered when discussing the high ISO performance improvement.
When Canon EOS 5D Mark III officially ships at the end of March, we will definitely see more analysis and find out what Canon’s claim of “2 stops” improvement actually means. The camera spec sheet does list two extra ISO settings (51200 and 102400) but that is not a proof of “2 stops” improvement.
Keywords: Canon, EOS 5D Mark III, Noise