p.1 #1 · A7R2 dual gain sensor, should I go straight from ISO 200 to 640?
Hi guys I have an A7R2 - from this chart (below), it looks like if I need approx ISO 250-500, I should skip right up to ISO 640 for best noise performance, correct?
p.1 #3 · A7R2 dual gain sensor, should I go straight from ISO 200 to 640?
There are other charts there where can see that ISO 640 has slightly less dynamic range than ISO 400. Basically if you are shooting raw you can choose between ISO 100 and ISO640 to maximize dynamic range/noise. Other ISO settings for raw mostly just lose dynamic range without a real benefit.
p.1 #4 · A7R2 dual gain sensor, should I go straight from ISO 200 to 640?
Agree with QuietOC. For subjects with a large range of light values, I would shoot at ISO 100 and push in post as far as 640 equivalent. This method loses virtually no image quality compared to shooting at intermediate ISOs, and maximizes dynamic range. The only downside is a darker finder, depending on the way your camera is set up. I'd do the same thing with ISO 640, using it instead of intermediate ISO values up to 3200.
I do something similar with my A7RIV, which has dual gain at 320 instead of 640. I use this method because many of my subjects benefit from max dynamic range. For some other kinds of shooting, I wouldn't bother.
p.1 #5 · A7R2 dual gain sensor, should I go straight from ISO 200 to 640?
For stills, yes, but with mechanical shutter only. Dual gain seems to be ISO100 & then 640.
With E shutter ISO640 isn't as clean and with less DR than any sensitivity setting below it, so of you're shooting silently use the sensitivity you need to ETTR.
With mechanical or silent shutter set zebras to 100+ and shoot 1EV over then reduce your exposure in post for cleaner shadows. I'm not sure why but there is a stop of headroom other sensors don't have.
If you're using the SR app, the headroom isn't there, use zebras to protect highlights.
In video shoot correct exposure except LOG, SLOG2 (at ISO800+) likes to be shot 1EV over and correct exposure brought back in post.
None of the above has any data to support it, but I've shot hundreds of thousands of still images and hundreds of video productions with the 7R2 and tested my advice above dozens of times.
Hope that helps. The 7R2 has still the best bang for buck sensor Sony offer, very underrated device.
I used one body until it gave up and bought a second new for peanuts because the device is so good.
p.1 #6 · A7R2 dual gain sensor, should I go straight from ISO 200 to 640?
Bob_S wrote:
For stills, yes, but with mechanical shutter only. Dual gain seems to be ISO100 & then 640.
With E shutter ISO640 isn't as clean and with less DR than any sensitivity setting below it, so of you're shooting silently use the sensitivity you need to ETTR.
With mechanical or silent shutter set zebras to 100+ and shoot 1EV over then reduce your exposure in post for cleaner shadows. I'm not sure why but there is a stop of headroom other sensors don't have.
If you're using the SR app, the headroom isn't there, use zebras to protect highlights.
In video shoot correct exposure except LOG, SLOG2 (at ISO800+) likes to be shot 1EV over and correct exposure brought back in post.
None of the above has any data to support it, but I've shot hundreds of thousands of still images and hundreds of video productions with the 7R2 and tested my advice above dozens of times.
Hope that helps. The 7R2 has still the best bang for buck sensor Sony offer, very underrated device.
I used one body until it gave up and bought a second new for peanuts because the device is so good....Show more →
Thanks Bob...that's all great advice.
I feel the same way about the A7R2 sensor...it was released 6 years ago in 2015 and is STILL rated 7th best full-frame sensor EVER.
Another under-rated sensor (for the money) is the Nikon D600/610, but for stills only of course (even though it does shoot 1080/30 video)...the sensor performance to price ratio is quite high.
p.1 #8 · A7R2 dual gain sensor, should I go straight from ISO 200 to 640?
wsalopek wrote:
Hi guys I have an A7R2 - from this chart (below), it looks like if I need approx ISO 250-500, I should skip right up to ISO 640 for best noise performance, correct?
The data you cite is the least valuable of the A7R4 data on the PhotostoPhotos site.
First look at the PDR curve. On these curves the ISO setting reflects lower exposure, which means fewer photo-electrons (i.e. lower signal). You see that as you get fewer photo-electrons the PDR goes down. You know that without looking at the data.
You see that at ISO 400 the PDR is essentially identical to ISO 640. If you move to ISO 640 need to use a lower exposure so you get fewer photo-electrons, but less read noise, so the PDR is the same. Depending on what you are shooting, you are probably better off at 640 so you can get faster shutter or more DOF. ISO 500 is not a good choice.
Now the question is should you move from ISO 100 to 400 as the exposure is reduced or just boost the tone curve in post. The same question arises above ISO 640. In order to answer that question you need to look at the input referred read noise chart. If that chart is horizontal, there is no PDR penalty if you push the tone curve in post, if it slopes downward, you get less read noise, consequently better SNR and PDR, by increasing the ISO. For the A7R2 it slopes downward so it is better to increase the ISO.
This assumes you are always setting the camera for maximum exposure to get the maximum number of photo-electrons, as limited by the subject you are trying to photograph. That is you are implementing the ETTR method, which really means get as many photo-electrons as you can.
The noise performance of the A7R2 is such that you benefit from setting the ISO as high as possible after you set the exposure. The dual gain helps a lot above ISO 640. ISO 500 should be skipped.
p.1 #9 · A7R2 dual gain sensor, should I go straight from ISO 200 to 640?
Bob_S wrote:
For stills, yes, but with mechanical shutter only. Dual gain seems to be ISO100 & then 640.
With E shutter ISO640 isn't as clean and with less DR than any sensitivity setting below it, so of you're shooting silently use the sensitivity you need to ETTR.
With mechanical or silent shutter set zebras to 100+ and shoot 1EV over then reduce your exposure in post for cleaner shadows. I'm not sure why but there is a stop of headroom other sensors don't have.
If you're using the SR app, the headroom isn't there, use zebras to protect highlights.
In video shoot correct exposure except LOG, SLOG2 (at ISO800+) likes to be shot 1EV over and correct exposure brought back in post.
None of the above has any data to support it, but I've shot hundreds of thousands of still images and hundreds of video productions with the 7R2 and tested my advice above dozens of times.
Hope that helps. The 7R2 has still the best bang for buck sensor Sony offer, very underrated device.
I used one body until it gave up and bought a second new for peanuts because the device is so good....Show more →
Now we are in fantasy land - camera esoterics unleashed.
Of course the quality of the resulting file (in respect to DR and noise) is NOT dependent on whether one uses mechanical or electronic shutter. That's utter BS, as there is - as you rightly wrote - no data to back that claim up.
If you now feel insulted, you could send your claim to Tony Northrup. Perhaps he then does a debunking video about it 😂
p.1 #10 · A7R2 dual gain sensor, should I go straight from ISO 200 to 640?
I'm not insulted, but I also don't care, I know full well the 7R2 performs worse in terms of IQ at ISO640 in silent mode versus mechanical shutter, which is why I choose to wear my shutter out for scenes that could've used e-shutter.
I'm unfortunately too old and time limited to bother to argue, but I offer the advice for those willing to at least trial it themselves.
I'm not technically great, but that doesn't matter, I know what I see on my screen and after hundreds of thousands of exposures with my favourite camera from the last decade, I know that when I push and pull my e-shutter ISO640 image, it breaks earlier and in a significantly fuglier way than my ISO640 mechanical shutter image.
I use the same dual gain method for video, I use either ISO100 or ISO640 and adjust lighting and/or iris and/or ND for desired exposure (which is rarely correct exposure) unless I need SLOG which is only available at ISO800+.
Since I've used the 7R2 as a B or C cam to match other much 'better' cameras, I'm keen to eek our every millimetre of performance from it.
I usually match the other cameras to the 7R2 resulting image.
p.1 #11 · A7R2 dual gain sensor, should I go straight from ISO 200 to 640?
hasenbein wrote:
Now we are in fantasy land - camera esoterics unleashed.
Of course the quality of the resulting file (in respect to DR and noise) is NOT dependent on whether one uses mechanical or electronic shutter. That's utter BS, as there is - as you rightly wrote - no data to back that claim up.
If you now feel insulted, you could send your claim to Tony Northrup. Perhaps he then does a debunking video about it 😂
p.1 #15 · A7R2 dual gain sensor, should I go straight from ISO 200 to 640?
robfilms wrote:
So I will ask again, is this conversation solely about the A7R2 or does the 100 - 640 ISO insight relevant to those of use with the (new to me) A7R3?
Stay well.
Rob
The "100-640 insight" is not an insight, it's an error.
If you reduce the exposure the PDR is reduced whether you change the ISO or not. There are two reasons the PDR is reduced. The main reason is the reduced number of photo-electrons which results in lower SNR. That reduction in SNR will happen whether you change ISO setting or not. The second is the read noise. If the read noise is reduced by increasing the ISO you get more noise (and consequently lower SNR) at ISO 100 than you get if the ISO is increased to 400. The idea that by leaving the ISO at 100 you continue to get the same PDR as you reduce the exposure is wrong. If you reduce the exposure by a factor of 4 and don't move from ISO 100 to ISO 400 all you get is more read noise than you would have gotten if you had moved to ISO 400. That is why you need to look at both the PDR curve and the read noise curve. If the read noise curve is flat, then moving the ISO is not necessary to avoid the read noise penalty. If the read noise curve is not flat, there is a penalty if the ISO is not changed. For both the A7R2 and A7R3 there is a read noise penalty if you do not change the ISO. The read noise penalty is somewhat smaller in the A7R3.
There is actually another benefit in better sampling of the noise in the shadow regions of the image, but that is more complex.
Newer sensors have much flatter read noise charts (e.g. A1), and the ADC's are 14 bits, so the benefit of increasing the ISO as the exposure is reduced is minimal. Not so true for some of the older sensors.
If you are not trying to capture image detail in the shadows you may not see the difference.
p.1 #16 · A7R2 dual gain sensor, should I go straight from ISO 200 to 640?
Dave, for the scientifically challenged - like me - could you explain this in common English? I'm very interested in this but I need the "Dummy's" version. Thanks.
Hi guys I have an A7R2 - from this chart (below), it looks like if I need approx ISO 250-500, I should skip right up to ISO 640 for best noise performance, correct? What about dynamic range and color depth? Thanks... https://www.photonstophotos.net/Charts/RN_ADU.htm#Sony%20ILCE-7RM2_14
Oct 06, 2021 at 03:21 PM
AmbientMike Offline • • • • • • [X]
p.1 #18 · A7R2 dual gain sensor, should I go straight from ISO 200 to 640?
I doubt it's going to hurt much to pick up a ff file 2 stops from ISO 100. I doubt any camera is truly ISO-less, though, so you're probably better off getting the exposure right on a good ISO.
Which isn't such a revolutionary idea if you think about it.
p.1 #19 · A7R2 dual gain sensor, should I go straight from ISO 200 to 640?
andyptak wrote:
Dave, for the scientifically challenged - like me - could you explain this in common English? I'm very interested in this but I need the "Dummy's" version. Thanks.
What he means is if you are considering just shooting at base ISO 100 and then pushing the exposure in post you cannot just base the decision on the PDR. Say you actually need a correct exposure at ISO 800 but decide to shoot at ISO 100 so that's 3 stops you have to underexpose. But if you shoot ISO 100 3 stops underexposed that PDR shown in the chart is not relevant as that's based on full well capacity relative to the read noise. You will now have a much lower well capacity 3 stops underexposed, so PDR would drop a lot. What you need to check then is the read noise at ISO 800 much lower than at ISO 100. If the read noise curve was flat at all ISOs then it wouldn't matter, but the read noise is what reduces greatly at ISO640 and above. It's due to this large drop in read noise it's better to push process using ISO's of 640+ than lower ISO's. But for normally exposed ISO 100 shots the full well capacity is so much larger than at ISO640 it still has higher PDR despite much higher read noise.
So if I'm shooting a landscape with large dynamic range I'll try to stick to ISO 100 or 200, or 50 for slower shutter speeds - avoid 64 and 80 though. But if say you wanted to shoot in low light and as long as fast shutter speeds aren't needed, since read noise is flat from ISO 640 to ISO 25600 you might as well just use underexposed ISO 640 and push it in processing as ISO640 has much better PDR than say ISO6400 9.6 vs 6.3.
