The main (theoretical) differences between APS-C and Full-Frame?
tschopp wrote:
The discussion of amplification, iso, and dynamic range is well understood for the Sony sensors. The Sony sensors have a dual gain stage. For the a7Riv that I have the second gain stage comes on at 320 iso. Other cameras this happens at higher iso. This is an electronics gain applied between the photo site and the analog to digital converter. This amplification does introduce noise, but the noise it introduces is less than the dynamic range improvement. So in graphs of dynamic range we see a bump up at this iso.
For the rest of the range the dynamic range drops for each increase in iso. In Sony the drop is linear and the sensors are known to be iso invariant. That means the information in the raw data does not change as a function of iso ( except at the change in the dual gain stages). The affect of increased iso is done after the analog to digital conversion and is a digital multiplication of each value by 2 for each stop in iso increase. This does not add any noise, but dynamic range must decrease by 1 bit for each stop of iso. The danger is in setting too high an iso and clipping the highlights. As far as I can tell the main reason to increase iso is to produce a properly exposed jpg. For a raw, I don’t see any point to increasing iso once you have entered the second gain range besides easier viewing of your raw file.
Thinking about some of the differences between aps-c and FF. They generally assume you are exposing to the right and trying to fully utilize the dynamic range available. If you under expose by a stop or two, but expose the smaller sensor fully, then the benefit of FF vs aps-c or mft largely goes away. I tend to think computational photography will be a great equalizer. Stacking of small sensor photos will negate the noise and dynamic range benefit of large sensors. Focus stacking of FF could eliminate the depth of field advantage of smaller sensors.
[EDIT: This is wrong!] If I understand (which is questionable) the dual-gain function of a sensor, what it does is to treat the readout from the sensor twice, in two different ways with different amounts of gain, one for the highlights with less amplification and the second for the shadows with more amplification. It then combines them. But I think that the amount of amplification still does vary proportionally with the amount of noise in each of the two parts of the dual-gain. It is just that the dual-gain combines a less amplified signal with a more amplified signal, one with less noise and the other with more.
The main (theoretical) differences between APS-C and Full-Frame?
tschopp wrote:
The discussion of amplification, iso, and dynamic range is well understood for the Sony sensors. The Sony sensors have a dual gain stage. For the a7Riv that I have the second gain stage comes on at 320 iso. Other cameras this happens at higher iso. This is an electronics gain applied between the photo site and the analog to digital converter. This amplification does introduce noise, but the noise it introduces is less than the dynamic range improvement. So in graphs of dynamic range we see a bump up at this iso.
For the rest of the range the dynamic range drops for each increase in iso. In Sony the drop is linear and the sensors are known to be iso invariant. That means the information in the raw data does not change as a function of iso ( except at the change in the dual gain stages). The affect of increased iso is done after the analog to digital conversion and is a digital multiplication of each value by 2 for each stop in iso increase. This does not add any noise, but dynamic range must decrease by 1 bit for each stop of iso. The danger is in setting too high an iso and clipping the highlights. As far as I can tell the main reason to increase iso is to produce a properly exposed jpg. For a raw, I don’t see any point to increasing iso once you have entered the second gain range besides easier viewing of your raw file.
Thinking about some of the differences between aps-c and FF. They generally assume you are exposing to the right and trying to fully utilize the dynamic range available. If you under expose by a stop or two, but expose the smaller sensor fully, then the benefit of FF vs aps-c or mft largely goes away. I tend to think computational photography will be a great equalizer. Stacking of small sensor photos will negate the noise and dynamic range benefit of large sensors. Focus stacking of FF could eliminate the depth of field advantage of smaller sensors.
If I understand (which is questionable) the dual-gain function of a sensor, what it does is to treat the readout from the sensor twice, in two different ways with different amounts of gain, one for the highlights with less amplification and the second for the shadows with more amplification. It then combines them. But I think that the amount of amplification still does vary proportionally with the amount of noise in each of the two parts of the dual-gain. It is just that the dual-gain combines a less amplified signal with a more amplified signal, one with less noise and the other with more.
Or, no?
Jul 03, 2023 at 09:43 PM
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