Astrophotographer 10
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Thanks. Don't they already count electrons? (I mean they measure voltages right? - (not the same thing?))
Greg.
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a7RIV vs a7RIII DR
- Thread starter JimKasson
- Start date
Greg.
PWPhotography
Forum Pro
That further strengthens the point that at similar sensor technology, it's the sensor size determines DR not amount of pixels. 36mp A7r still has the highest total DR at base ISO 100 in A7r series.
Thanks for testing.
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https://www.flickr.com/photos/55485085@N04/albums
Last edited:
MinAZ
Veteran Member
Could the difference in results be due to sample variation between units?
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At the a7RIV announcement, Sony used language that made many think that the camera made impressive strides in dynamic range over its predecessor, the a7RIII. There were discussions in this forum. Now that I have the a7RIV in my hands, I can disabuse you of any such thoughts.
Let’s dissect the above graph. The horizontal axis is the mean signal level in stops from full scale. The rightmost part of the graph is 4 stops down from full scale, so we’re already at middle or dark gray there, and it gets darker as you go to the left. The vertical axis is the signal to noise ratio (SNR) normalized to a 1600-pixel-high print. The black line at 3.3 marks the Claff PDR threshold (log base 2 of 10 is 3.3). The Claff PDR is measured by looking at where each curve crosses the black horizontal line. On the right side of the graph, the most important determinant of the SNR is the full well capacity (FWC) of the camera. On the left, the read noise comes into play. Higher is better.
The a7RIV trails its predecessor by a small amount in the brighter portion of the image, and by a slightly larger amount in the stygian gloom. The GFX 100 does better than both by virtue of its greater sensor area.
Details, other ISO settings, here:
https://blog.kasson.com/a7riv/sony-a7riv-vs-a7riii-shadow-noise/
Jim
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I think not. I suppose it's possible that there's an a7RIV somewhere that's miles ahead of mine, but my numbers aren't all that different from other measurements of the a7RIV.
I meant count the electrons digitally, not just let the photodiode fill up during the whole exposure. There are several ways to do this, but we're a fair piece from commercial implementations in consumer FF cameras.
Entropy512
Veteran Member
Did Bill Claff's samples come from your camera or a different unit?
Given the timing, I'm assuming his came from a different unit and you just received your camera, and your data pretty closely agrees with his.
I've sent Bill samples before, but not for the a7RIV. Not sure about the a7RIII.
Close enough, I think, given different methodologies and samples. When you peel the onion a lot, we are actually measuring slightly different things.
Jim
Entropy512
Veteran Member
If I'm interpreting things correctly, you only tested at base ISO?
The only places in Bill's chart where the R4 outperformed the R3 were in the small range of ISOs between the R4's dualgain cutin and the R3's
I tested for PTCs at all ISO's between 100 and 12800 inclusive.
https://blog.kasson.com/a7riv/sony-a7riv-fwc-pdr-and-input-referred-read-noise/
I have posted shadow noise curves for various ISOs:
https://blog.kasson.com/a7riv/sony-a7riv-vs-a7riii-shadow-noise/
AlephNull
Veteran Member
To be honest, given the increased resolution, and hence the smaller pixels, I'm happy that it manages to get so close to the a7RIII.
Evidentiary
Senior Member
The details of this post are outside my normal technical venue and I found the following tutorial helpful in understanding the basics . I thought some might find it helpful:
https://www.lumenera.com/blog/under...-signal-to-noise-ratio-when-comparing-cameras
https://www.lumenera.com/blog/under...-signal-to-noise-ratio-when-comparing-cameras
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