A99 vs A900 resolution

Started Jan 19, 2013 | Discussions thread
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Endos Senior Member • Posts: 1,378
Re: Correction

TrojMacReady wrote:

TrojMacReady wrote:

Endos wrote:

TrojMacReady wrote:

Endos wrote:

TrojMacReady wrote:

Endos wrote:

Extinction and average values are two different things. Average values are 2800 for the A99 and 3397 for the A900 (IR). And according to DxO, noise is about the same in both cameras.

You're comparing Imatest results with a subjective visual value given by Dave. Not exactly apples to apples.

As for DXO, you're referring to 18% gray measurements which is only part of the noise story, because it doesn't account for patterns and noise in areas other than midtones. For example at 10% gray, they measured the difference at ISO 6400 to be about a stop.

You can't compare Full SNR charts because they are based in the manufacturer ISO and not in the measured ISO, and the A99 sensor gain for each manufacturer ISO is lower than in the A900.

I corrected 0.4 EV for the measured difference at ISO 3200. Because the difference is about 5.5 to 6 dB, which would be close to 2 stops before correction.

6 dB is around 1 stop, not 2 stops,

It's close to 2 stops in this case. Which is clear from the graphs (the A99 ISO 1600 and ISO 3200 lines have around 3 dB between them). If you go down further in the darker shadows and to the higher ISO's, it indeed gets closer to 6 dB.

In photography 6dB is 1 stop, ND 0.3 = 1 stop, but looking at the graphs as you pointed, seems that you are right. A bit strange.

but I don't know where you has found the 6dB difference. At ISO 3200 and 10% gray the difference is about 2.5 dB before any correction.

I mentioned 1% gray for the ISO 3200 data points. Roughly 10 dB minus 4 dB.

The point stands, noise is a lot more than just a 18% gray SNR graph and it's certainly not the same or similar between both cameras.

I agree.

Especially in shadows the difference can be more than a stop.

Less than 1 stop after correction.

I mistakingly looked at the difference between ISO 3200 and 1600 lines rather than ISO 6400 and 3200 lines. In the latter case it is indeed about 4.5 dB, which would make the quantitative difference after correction around or a hair under 1 stop. Accounting for pattern noise, I still prefer darker areas from a stop higher coming from the A99 though, ceteris paribus.

There is a difference, but is not day and night as some are saying.

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