It would probably be helpful to explain ISO in film and that digital cameras attempt to simulate that setting using something that photographers were already familiar with.
Astrophotography taught me this. We use Dark frames to subtract the average thermal noise for a given exposure length and Bias frames to subtract out the average Shot or Read noise from the ADC. I set the sensor gain to the setting that allows it to absorb the most photons without clipping, sometimes refed to as full well depth. Then I dial in the exposure length to the point where the brightest stars just about start clipping. Kinda the same idea, but a little backwards.
Of course, then I take tons of pictures of the same thing and "average" them out to improve the signal/noise ratio.
This is mentioned but not a lot of discussion:
Most cameras can only do 2-3 analog gain levels(so called “Native ISO”). The rest is digital.
This is very subtle, many cameras have dozens of ISO levels but just a few if them are real.
Even more, there are camera can do only one gain(the amp is not configurable) and not rare to find. So check the “Native ISO” before you use it!
Caveat number 5: Some (higher-end) cameras have a "dual native ISO" (which is basically a separate amplifier circuit)... So when you go over a certain ISO, noise plummets again because it swaps over to the secondary amplifier.
This is why, on my Blackmagic camera, ISO3200 often looks less noisy than ISO2800 (as it now uses said second amplifier).
To be fair to the advice to use low ISO, it's often not so much "take a darker photo and then brighten it later", it's more "if you can brighten the image by gathering more light (open the aperture or lengthen the shutter speed) you'll get less noise than by boosting the ISO".
Another quirk is that Sony makes dual gain sensors now so there's a threshold iirc somewhere around ISO640 where the noise goes down slightly when you step the ISO up by one level. I'm not sure if they sell sensors to a lot of other manufacturers or if it's a quirk of Sony hardware only or if it applies to other brands as well
8:05 As a bird photographer, I love these photos! First photo is Hairy Woodpecker with Northern Flicker in the background, second photo is a female Red-winged Blackbird :)
8:30 - so you set your photo in the order the photons move from the object to the final image saved. Light from outside -> lens -> sensor -> ADC -> saved image. Makes sense.
10:03 I just want you all to appreciate that he used a posterized time effect on that digital noise, so that we can see it in spite of YouTube's compression. Just knowing about this requires even deeper fundamental knowledge of the nature of digital noise and video compression that he never mentions directly in the video itself.
Filmmaker and camera operator/gaffer from the German film industry here.
First of all: absolute banger of a video. One of the clearest explanations of ISO I’ve seen.
One small addition that might be interesting is the relationship between ISO, native ISO, and dynamic range. Most cameras have a native (or base) ISO, which is the point where the sensor delivers its maximum dynamic range. Dynamic range refers to the range between the darkest and brightest details a camera can capture at the same time. In other words, how much highlight and shadow information the sensor can record before clipping occurs. This can be checked on Photons to Photos under the Photographic Dynamic Range vs ISO setting. As you increase ISO, the noise floor rises and the total dynamic range typically decreases.
Interestingly, charts like the “Shadow Improvement” graphs from Photons to Photos show that increasing ISO can sometimes make shadows appear cleaner because the signal is amplified relative to read noise. But that improvement comes at the cost of reduced highlight headroom and overall dynamic range and therefor colorinformation.
So the best signal-to-noise ratio in the shadows doesn’t necessarily mea
Man, as an audio guy, if someone had just explained ISO as gain staging it could have made so much more sense so long ago. Thank you for finally putting it in terms I get!
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Of course, then I take tons of pictures of the same thing and "average" them out to improve the signal/noise ratio.
Most cameras can only do 2-3 analog gain levels(so called “Native ISO”). The rest is digital.
This is very subtle, many cameras have dozens of ISO levels but just a few if them are real.
Even more, there are camera can do only one gain(the amp is not configurable) and not rare to find. So check the “Native ISO” before you use it!
This is why, on my Blackmagic camera, ISO3200 often looks less noisy than ISO2800 (as it now uses said second amplifier).
Another quirk is that Sony makes dual gain sensors now so there's a threshold iirc somewhere around ISO640 where the noise goes down slightly when you step the ISO up by one level. I'm not sure if they sell sensors to a lot of other manufacturers or if it's a quirk of Sony hardware only or if it applies to other brands as well
Astrophotography: "Allow me."
First of all: absolute banger of a video. One of the clearest explanations of ISO I’ve seen.
One small addition that might be interesting is the relationship between ISO, native ISO, and dynamic range. Most cameras have a native (or base) ISO, which is the point where the sensor delivers its maximum dynamic range. Dynamic range refers to the range between the darkest and brightest details a camera can capture at the same time. In other words, how much highlight and shadow information the sensor can record before clipping occurs. This can be checked on Photons to Photos under the Photographic Dynamic Range vs ISO setting. As you increase ISO, the noise floor rises and the total dynamic range typically decreases.
Interestingly, charts like the “Shadow Improvement” graphs from Photons to Photos show that increasing ISO can sometimes make shadows appear cleaner because the signal is amplified relative to read noise. But that improvement comes at the cost of reduced highlight headroom and overall dynamic range and therefor colorinformation.
So the best signal-to-noise ratio in the shadows doesn’t necessarily mea
... And then I saw the thumbnail.