> image "noise" or "grain" that is introduced into a picture as you increase the ISO
Not this absolute shit again. This is not how photography works or how physics actually work. Image noise does NOT come from high ISO, it comes from low exposure (not enough light hitting the sensor). ISO is just a multiplier between a number of photons and the brigthness of a pixel in your photo. The implementation of the multiplier is (usually) half-analog and half-digital, but it's still just a multiplier. If you keep the exposure the same, then changing the ISO on a digital camera will NOT introduce any more noise (except for at the extremes of the range, where, for example, analog readout noise may play a role).
This "simulator" artificially adds noise based on the ISO value, as you can easily discover: Set your shutter to 1/500 and your aperture to F8, then switch between ISO 50 and ISO 1600 and look at the letters on the bulb. ISO 50, dark but perfectly readable. ISO 1600, garbled mess. Since the amount of light hitting the simulated sensor stays the same, you should be seeing slightly LESS noise at ISO 1600 (better signal to noise ratio than at low ISO), not more.
edit: To add something genuinely useful: Use whatever mode suits you (manual, Av, Tv) and just use Auto ISO. Expose for the artistic intent and get as much light in as possible (i.e. use a slower shutter speed unless you need to go faster, use a wider aperture unless you need a narrower one). That’s the light that you have, period. Let the camera choose a multiplier (ISO) that will result in a sane brightness range in your JPEG or RAW (you’ll tweak that anyway in post). If the photo ends up too noisy, sorry but there was not enough light.
ISO is an almost useless concept carried over from film cameras where you had to choose, buy and load your brightness multiplier into the camera. Digital cameras can do that on the fly and there’s usually no reason not to let them. (If you can come up with a reason, you probably don’t need this explanation)
Yes, as the sibling post says, it's effectively the same in most cameras and it's exactly the same in certain cameras (not many). Unless you, of course, actively fuck up by shooting a very low-exposure (dark) shot with low ISO (then you lose precision, because your analog measurements get quantified into small integers, that are also close to the noise floor), or by shooting a very bright shot with high ISO (where your highlights get multiplied right out of the range of your output format). If you don't actively try and fuck up the shot (AND you shoot RAW), you can make pretty wild changes in post and the data will be there.
That's just one more reason not to be afraid of auto ISO. The camera will choose something sane and you'll have ample room on both sides to get the image you wanted.
If you have an ISO-invariant camera, then yes - the final image would look the same whether you shot at low ISO and raised it in post versus shooting at a high ISO and doing no further editing. You can try it yourself. Or you can read the numerous reviewers who have already done that in the past decade, such as DPReview.
> Image noise does NOT come from high ISO, it comes from low exposure [...] changing the ISO on a digital camera will NOT introduce any more noise (except for at the extremes of the range, where, for example, analog readout noise may play a role).
Sounds like you're saying that setting higher ISO does cause noise, but as long as you don't go too high you won't really notice the difference?
No. What they're saying is ISO multiplies brightness, essentially exasperating differences. Roughly, ISO 200 is 2x gain and so on. So if you have one pixel with a brightness value of 1, and the pixel to the left has a brightness of 5, and an ISO of 500, then it becomes brightness 5 and 25 respectively. Oversimplification.
Agreed. In other words, ISO is not exposure. Exposure is purely about how much light arrives on the sensor - which is a combination of scene illumination, object reflectivity, relative aperture, and shutter speed. ISO only plays a part in controlling how bright the output image is.
Not this absolute shit again. This is not how photography works or how physics actually work. Image noise does NOT come from high ISO, it comes from low exposure (not enough light hitting the sensor). ISO is just a multiplier between a number of photons and the brigthness of a pixel in your photo. The implementation of the multiplier is (usually) half-analog and half-digital, but it's still just a multiplier. If you keep the exposure the same, then changing the ISO on a digital camera will NOT introduce any more noise (except for at the extremes of the range, where, for example, analog readout noise may play a role).
This "simulator" artificially adds noise based on the ISO value, as you can easily discover: Set your shutter to 1/500 and your aperture to F8, then switch between ISO 50 and ISO 1600 and look at the letters on the bulb. ISO 50, dark but perfectly readable. ISO 1600, garbled mess. Since the amount of light hitting the simulated sensor stays the same, you should be seeing slightly LESS noise at ISO 1600 (better signal to noise ratio than at low ISO), not more.
edit: To add something genuinely useful: Use whatever mode suits you (manual, Av, Tv) and just use Auto ISO. Expose for the artistic intent and get as much light in as possible (i.e. use a slower shutter speed unless you need to go faster, use a wider aperture unless you need a narrower one). That’s the light that you have, period. Let the camera choose a multiplier (ISO) that will result in a sane brightness range in your JPEG or RAW (you’ll tweak that anyway in post). If the photo ends up too noisy, sorry but there was not enough light.
ISO is an almost useless concept carried over from film cameras where you had to choose, buy and load your brightness multiplier into the camera. Digital cameras can do that on the fly and there’s usually no reason not to let them. (If you can come up with a reason, you probably don’t need this explanation)