As I have already compared the Quattro and the Merrill with regard to noise performance and highlight headroom, the only thing left to scrutinize are the shadows, particularly the noise in them. A short comment, before I start explaining my approach and analyzing the results: the comparison of the highlights has shown that the Merrill is more sensitive by 0.66 EVs than the Quattro at equal ISO value. For this reason, I exposed all photos shot with the Merrill shorter by 2/3 of a stop, to get equally bright pictures.
This time, I took 7 photos with both cameras instead of 5: one with correct exposure according DP2Q histogram, four underexposed by 1, 1,33, 1,66 and 2 aperture stops respectively and two overexposed by 1 and 2 aperture stops respectively. I took the overexposed photos because I wanted to verify the result of the highlights comparison. As already mentioned, I adopted the DP2Q’s exposure parameters for the DP2M, but shortened the exposure time by 2/3 of a stop.
This time, all pictures were taken with ISO100, because I wanted to have as little noise in the shadows as possible. Subsequently, I brightened the pictures with positive exposure in SPP 6.0.6 and darkened the four overexposed pictures with negative exposure. For every underexposed or overexposed photo I adjusted the negative/positive exposure by exactly the value the photo was initially under or overexposed. Specifically, this means that for the photo underexposed by 1 stop, a positive exposure of +1 was dialed in. I didn’t adjust the exposure in SPP for the correctly exposed shots.
DP2Q, correct exposure
DP2M +1 EV
Now to the interpretation of the results:
- The Merrill has considerably more highlight headroom, if you adjust the brightness of the photos by means of shorter exposure times. This advantage amounts to one aperture stop, if not more.
- If you take correctly exposed pictures with both cameras, the differences in the shadows are very low. The DP2Q’s luminance noise is a little bit more pronounced, but the DP2M has more visible color blotches.
- The more you underexpose, the bigger the difference between both cameras. Luminance noise gets more visible with the Quattro, but with the Merrill, there are also more color blotches. Whether this is due to the Quattro sensor or the 14-bit RAWs, I don’t know. Anyway, the color blotches are rather weakly pronounced in the DP2Q underexposed pictures by -1,66 or 2 apertures, while these cannot be ignored with the DP2M. You can even see them if you minimize the DP2M pictures to web size.