Lens vs Camera: The FF APS-C Dilemma

Started Aug 3, 2014 | Discussions thread
Erik Magnuson Forum Pro • Posts: 12,247
Re: Say what?

ProfHankD wrote:

Erik Magnuson wrote:

This doesn't make any sense - lower base DR does not mean higher contrast since it's noise level derived.

Coarser sampling (which lower DR implies) slightly increases intermediate contrast

Woah! Stop and think about what you are saying. Lower DR (as expressed by DxO measurements) does NOT imply anything about sampling depth -- it's strictly about the ratio of noise to saturation. The DR of the NEX-7 is lower at ISO 200 than ISO 100 - did the bit depth of the ADC change? Of course not.

it's sort of like applying autolevels to stretch-out a histogram, but this happens even in the analog domain going to the ADC before the raw is encoded (along with non-linear stuff we'll ignore for now). It's a small effect, but I suggested it could be enough to explain the NEX-7 vs. A3000 difference.

That's quite a complex mechanism when there is a much simpler explanation: the A3000 sensor is slightly noisier at base ISO.

There is a lot of analog and digital processing that can affect MTF measurements on so-called "raw" files.

For example, sony processing lowers the effective bit depth when shooting in continuous mode (http://blog.kasson.com/?p=4919). This would not change the P-Mpix though because the contrast levels used are far above the noise floor.

Whatever the cause may be for the A3000 vs. NEX-7 P-MPix values, there's very little to it. Overall, both cameras perform very similarly and very well, but a full set of metrics puts the NEX-7 ahead.

So you think the 1 or 2 P-MPix values are not significant, but the DR difference at base ISO is? Your full set of metrics also curiously stops at at ISO 200 (the A3000 numbers are equal or better for ISO 400-3200).

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