Does changing shutter speed and aperture create equalized exposure?

[Ysarex]

The only reason to raise the ISO is because you either want to increase DOF requiring a smaller aperture, or you want to increase the shutter speed to prevent subject movement blur. In both cases, you reduce the amount of light to the sensor when you concurrently increase the ISO.

In at least Canon, Pentax, Fuji and Olympus cameras a reason to raise the ISO is to extend the DR of the camera's output image and not just because you need a smaller aperture or faster shutter speed.

In both cases you reduce the amount of light to the sensor if you don't concurrently increase the ISO. Concurrently raising the ISO has no effect on how much light reaches the sensor. Some photographers who have been misled into thinking ISO causes noise will NOT concurrently increase the ISO in an attempt to avoid causing noise.

So, the affect, whether called shot noise or something else, is to get a noisier pictures.

And if you use a smaller aperture or faster shutter speed (reduce exposure) and do NOT increase the ISO then with some cameras you get the same noisier photo you would get if you raised the ISO, BUT with other cameras you would get an even noisier photo because one of the benefits of raising ISO is that signal amplification can suppress certain types of noise. Some photographers who have been misled into thinking ISO causes noise may fail to take advantage of the fact that raising ISO can make your photo less noisy than it would be otherwise.

Everything else is just conversation and confusing to the photographer.

The photographers who get confused are the ones who have been previously misled. Mixing up cause and correlation or insisting the distinction doesn't matter is confusing.

 

[ACS64]

I’ve been wanting to for quite a while. They’re so expensive though
It is on my next-to-buy list though

Yes they are but you might try looking at the used market. If the used one you like is battery powered make sure you can still get the battery. My meter from the film days are either broken or the batteries are no longer available. I wanted an incident Iight found a functioning Sekonic Studio Deluxe selenium incident/reflected light meter with case, original box and manual for well under $100. If what you find doesn't come with the manual no big deal as you generally download one from the web. Caution, selenium slowly loses sensitivity so you will need to calibrate against your camera or a known accurate meter.

 

[cgw]

Yes they are but you might try looking at the used market. If the used one you like is battery powered make sure you can still get the battery. My meter from the film days are either broken or the batteries are no longer available. I wanted an incident Iight found a functioning Sekonic Studio Deluxe selenium incident/reflected light meter with case, original box and manual for well under $100. If what you find doesn't come with the manual no big deal as you generally download one from the web. Caution, selenium slowly loses sensitivity so you will need to calibrate against your camera or a known accurate meter.

Best to get the newest Sekonic L398 you can find. Absolutely crucial that any 398 includes the high slide that tucks into the backside of the meter--without it, they're useless in sunlight or brighter settings. Working properly they're deadly accurate for incident measurement. Be aware they're not great for accurate low-light readings--a baked-in problem.

 

[AlanKlein]

In at least Canon, Pentax, Fuji and Olympus cameras a reason to raise the ISO is to extend the DR of the camera's output image and not just because you need a smaller aperture or faster shutter speed.

In both cases you reduce the amount of light to the sensor if you don't concurrently increase the ISO. Concurrently raising the ISO has no effect on how much light reaches the sensor. Some photographers who have been misled into thinking ISO causes noise will NOT concurrently increase the ISO in an attempt to avoid causing noise.

And if you use a smaller aperture or faster shutter speed (reduce exposure) and do NOT increase the ISO then with some cameras you get the same noisier photo you would get if you raised the ISO, BUT with other cameras you would get an even noisier photo because one of the benefits of raising ISO is that signal amplification can suppress certain types of noise. Some photographers who have been misled into thinking ISO causes noise may fail to take advantage of the fact that raising ISO can make your photo less noisy than it would be otherwise.

The photographers who get confused are the ones who have been previously misled. Mixing up cause and correlation or insisting the distinction doesn't matter is confusing.

Sometimes yes sometime no. What you suggest is very confusing. There's no standard.

So let;s say you increase ISO to increase the DR as you suggested in BOLD above. Well, then you have to change the shutter or aperture lowering the amount of light and causing more noise. So you still increase noise even though it;s no the ISO that does it but rather the amount of light. You also said that increasing ISO will increase noise depending. You're all over the place and not consistent or clear. Maybe I just don't understand. In any case, I'm moving on.

 

[Ysarex]

Sometimes yes sometime no. What you suggest is very confusing. There's no standard.

Back on page three I said: "There are two common types of noise that concern us in our photos: shot noise and read noise. Shot noise is by far and away dominant and typically what we see when we see a noisy photo. Read noise, from the camera's electronics, is less a problem and getting less all the time as the hardware improves. Shot noise is entirely a function of exposure -- SNR (signal to noise ratio) get's better with more exposure and worse with less exposure. What ISO is doing in the camera doesn't directly alter exposure and so doesn't cause shot noise. ISO implementation in the camera via amplification of the analog sensor signal suppresses read noise."

So let;s say you increase ISO to increase the DR as you suggested in BOLD above.

I noted that because you said, "The only reason to raise the ISO is because you either want to increase DOF requiring a smaller aperture, or you want to increase the shutter speed to prevent subject movement blur." Those camera's have DR expansion functions for the camera output image that require raising the ISO above base -- a reason to raise the ISO other than your "only" reason.

Well, then you have to change the shutter or aperture lowering the amount of light and causing more noise. So you still increase noise even though it;s no the ISO that does it but rather the amount of light. You also said that increasing ISO will increase noise depending.

No I did not. I said brightening the image by raising ISO reveals the noise that's already there. That's not the same thing as increasing noise.

You're all over the place and not consistent or clear. Maybe I just don't understand. In any case, I'm moving on.

 

[RAZKY]

Now I'm wondering if noise would increase if I took a series of exposures increasing the light each time, compensating by reducing exposure but keeping ISO the same. And what about High ISO Noise Reduction?

 

[Ysarex]

Now I'm wondering if noise would increase if I took a series of exposures increasing the light each time, compensating by reducing exposure but keeping ISO the same.

Same amount of light reaches the sensor = same amount of shot noise. When we look at our photos today and see noise we are overwhelming looking at shot noise. Shot noise is in the signal itself (light) so there's nothing we can do about it. We talk about SNR (signal to noise ratio); with a stronger signal (more exposure) the ratio of noise to signal goes down and we see less noise, and of course vice versa. If we're seeing shot noise in our photos we caused it by not exposing enough. If circumstances force that on us we can then look to post processing to gain improvement.

Today in 2023 we can pretty much stop there. In the past decade and a half the engineers building our cameras have managed to reduce read noise (caused by the electronics in the camera) to the point of insignificance. In that same time you start hearing talk of cameras that are ISO invariant. ISO invariance occurs for our cameras when the engineers have beaten the read noise out of the hardware. Apart from brightening the camera's output image ISO has had the added benefit of suppressing some types of read noise. Well if the engineers have removed that noise source from the hardware then that benefit becomes moot = ISO invariance: ISO Invariance Explained. So if we've got the read noise pretty much beat all we have to worry about is shot noise and the only control we have over shot noise is exposure.

And what about High ISO Noise Reduction?

Circumstance can force us to reduce exposure if we want the photo. Getting the photo is better than not getting the photo even if to get the photo we have to accept some compromise. So if we're forced to reduce exposure to the point where shot noise in the photo is becoming a problem -- we have post process remediation available. In recent years that option has also improved dramatically, even Adobe is catching up.

 

[smoke665]

what about High ISO Noise Reduction?

Speaking only for Pentax but I believe it applies to other brands as well. High ISO noise reduction does not apply if you save as a RAW file.

 

[AlanKlein]

Back on page three I said: "There are two common types of noise that concern us in our photos: shot noise and read noise. Shot noise is by far and away dominant and typically what we see when we see a noisy photo. Read noise, from the camera's electronics, is less a problem and getting less all the time as the hardware improves. Shot noise is entirely a function of exposure -- SNR (signal to noise ratio) get's better with more exposure and worse with less exposure. What ISO is doing in the camera doesn't directly alter exposure and so doesn't cause shot noise. ISO implementation in the camera via amplification of the analog sensor signal suppresses read noise."

I noted that because you said, "The only reason to raise the ISO is because you either want to increase DOF requiring a smaller aperture, or you want to increase the shutter speed to prevent subject movement blur." Those camera's have DR expansion functions for the camera output image that require raising the ISO above base -- a reason to raise the ISO other than your "only" reason.

No I did not. I said brightening the image by raising ISO reveals the noise that's already there. That's not the same thing as increasing noise.

A distinction without a difference.

 

[Ysarex]

A distinction without a difference.

Nonsense. Reveal shows you what's already there while increase changes what's already there. If what's already there is bad then increase makes it worse, but reveal does not. Making something worse or not is a difference.

 

[AlanKlein]

Nonsense. Reveal shows you what's already there while increase changes what's already there. If what's already there is bad then increase makes it worse, but reveal does not. Making something worse or not is a difference.

View attachment 269343

You're playing word games. Have a nice day.

 

[RAZKY]

Same amount of light reaches the sensor = same amount of shot noise. When we look at our photos today and see noise we are overwhelming looking at shot noise. Shot noise is in the signal itself (light) so there's nothing we can do about it. We talk about SNR (signal to noise ratio); with a stronger signal (more exposure) the ratio of noise to signal goes down and we see less noise, and of course vice versa. If we're seeing shot noise in our photos we caused it by not exposing enough. If circumstances force that on us we can then look to post processing to gain improvement.

Today in 2023 we can pretty much stop there. In the past decade and a half the engineers building our cameras have managed to reduce read noise (caused by the electronics in the camera) to the point of insignificance. In that same time you start hearing talk of cameras that are ISO invariant. ISO invariance occurs for our cameras when the engineers have beaten the read noise out of the hardware. Apart from brightening the camera's output image ISO has had the added benefit of suppressing some types of read noise. Well if the engineers have removed that noise source from the hardware then that benefit becomes moot = ISO invariance: ISO Invariance Explained. So if we've got the read noise pretty much beat all we have to worry about is shot noise and the only control we have over shot noise is exposure.

Circumstance can force us to reduce exposure if we want the photo. Getting the photo is better than not getting the photo even if to get the photo we have to accept some compromise. So if we're forced to reduce exposure to the point where shot noise in the photo is becoming a problem -- we have post process remediation available. In recent years that option has also improved dramatically, even Adobe is catching up.

Due to my preferred subject matter and methods my exposures are rather long, ISO low, and noise is seldom an issue. With a microscope or extreme close-up work I often apply in-camera long exposure noise reduction to advantage.
Edit: Looks like I inadvertently scrambled your reply, and I'm not sure how to correct it now. My apologies.

 

[RAZKY]

Speaking only for Pentax but I believe it applies to other brands as well. High ISO house reduction does not apply if you save as a RAW file.

Same with my Nikon Df. I shoot RAW, save as 16-bit Tiff.

 

[smoke665]

Same with my Nikon Df. I shoot RAW, save as 16-bit Tiff.

The other problem with raising ISO is some cameras have maximum native ISO and some have Enhanced. With enhanced the camera sensor will purposefully underexpose the image at the highest base ISO setting, and then through processing, bump up the exposure to simulate what it would look like at your chosen extended ISO. The result is more shot noise as Joe explained above.

 

[Ysarex]

Today in 2023 we can pretty much stop there. In the past decade and a half the engineers building our cameras have managed to reduce read noise (caused by the electronics in the camera) to the point of insignificance. In that same time you start hearing talk of cameras that are ISO invariant. ISO invariance occurs for our cameras when the engineers have beaten the read noise out of the hardware. Apart from brightening the camera's output image ISO has had the added benefit of suppressing some types of read noise. Well if the engineers have removed that noise source from the hardware then that benefit becomes moot = ISO invariance: ISO Invariance Explained. So if we've got the read noise pretty much beat all we have to worry about is shot noise and the only control we have over shot noise is exposure.

Due to my preferred subject matter and methods my exposures are rather long, ISO low, and noise is seldom an issue. With a microscope or extreme close-up work I often apply in-camera long exposure noise reduction to advantage.

You're a special and fairly rare case; very long exposures allow heat build up in the system and that's an uncommon source of read noise. Most of us don't have that problem as the heat never get's to build with our usual fraction-of-a-second exposures.

Edit: Looks like I inadvertently scrambled your reply, and I'm not sure how to correct it now. My apologies.