What is the best exposure for your Olympus? (ETTR and other techniques)

Mack

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......

@Mack, I would love to see the differences in Sekonic's S curve for high key, normal and low key settings of gradation.
hmmm...makes me wonder if that was went wrong above. :confused-53:

Here is the combined gradations in AUTO, NORMAL, HIGH, and LOW. (Ignore the Z prefix as its just a placeholder for the file.).

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ll shot the same and verified the shutter speeds, f/stop, ISO never changed. I used the HDR 3-shot & 3EV change which Sekonic likes.

The AUTO is a mess if you look at the dark line. This is being done in camera too with no change to speed, f/stops, ISO, etc. Likely why my first attempts above were a broken and shifted S-curve by about a stop off in the lower shades. I had difficulty just trying to get a gray card (sRGB=118) within the 1/3 stop exposure range as that line is really busted up in the mid-tone 118 area. A little change in exposure threw it way off, and I began to doubt the shutter or diaphragm being consistent - but they are okay and just Olympus's funky AUTO gradation playing with the curves. AUTO does appear to hold onto highlights the best, but mids are questionable, as are the lower values that moved to the right. Very unpredictable gradation, imho.

Safest seem NORMAL, HIGH, and LOW.

As expected, the Yellow HIGH is steepest. The Cyan LOW has more highlight detail. The NORMAL has even more highlight detail but also a longer Shadow as well.

Well, at least I may now know why I fought with the E-M1 Mark II as it must have been set to AUTO Gradation and the E-M1X is NORMAL. :thumbup:
 

mfturner

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Thanks for running the test. I wonder if this is how the blue auto "works", the split base curve makes an hdr-like tone map?

Magenta, yellow and cyan do what I hoped to see, subtle yet obvious shifting of the base curve, giving the different effects.
 

Mack

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For sadistic fun, I also took the Olympus RAW AUTO Gradation files and made them into a JPG for the Sekonic software to read using Workspace 3 and DxO Photolab 3.

Olympus Workspace produced about the same broken line as did the JPG straight from the camera doing the RAW-to-JPG. But DxO Photolab 3 tried to make the over and under RAW files normal (I didn't apply any presets or editing, just exported the RAWs to JPGs.) and it really busted apart the curve. Guess it cannot read all of what Olympus hides in their RAW data.

Test-4.jpg
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Fwiw, when I accidentally had the AUTO gradation set, which produces the broken and shifted curve, just a third f/stop could cause a massive mid-tone change. If the gray card was reading sRGB=135 in Workspace (i.e. Too light.), a third stop less might drop it to sRGb=90 or 95 and too dark. Trying to hit sRGB= near 118 was impossible! It was either too light or too dark.
 
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PakkyT

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Emil Martinec has good article about sources of noise here.
Great article. Thanks for posting that.


am very skeptical about the real impact of photon shot noise in relation to all the other factors that all contribute to the noise we see in our images. In other words if we had to list a few components in the image signal path that add SNR noise to the image and we weigh them, how will they compare to each other?
{snip}
This is exactly what I explain in my article - shift the focus away from the photon theory and put your effort on the sensor.....
Your contention is that the vast majority of the noise is due to the sensor and we can ignore the photon shot noise. No opinion on that one myself, but let's go with that. Then anytime you raise the ISO you are going to raise the sensor noise levels, so don't you always want to be at the base ISO for minimum noise?

It seems to me you are adjusting the histogram to the right using ISO just like all those people whose videos and blogs you are claiming are doing it wrong as @pdk42 was trying to point out. As an example, let's say we are using an f2.8 lens and our shutter is 1/125 because of subject motion we can't get any slower.

With your method you start at ISO 1600, f4, and your histogram is mostly on the left half. You then change your aperture to f2.8 to fill the right side of the histogram, bumping the exposure +1EV. Then on your computer readjusting the exposure back -1EV, right? You shot your picture at ISO 1600, 1/125, f2.8.

The YouTube guy in his demo shooting the same thing starts at ISO 800, f2.8 and because the histogram is mostly on the left half, he now does his "ETTR" adjusting the ISO +1EV by changing ISO 800 to 1600 (because he already maxed out aperture). Then when he gets home he makes the same -1EV compensation on the computer. He shot his picture at ISO 1600, 1/125, f2.8.

In your mind he did it wrong because he adjusted ISO last where as you think you adjusted exposure last and therefore did the real ETTR. In both cases you both used the exact same setting for the shot. And both of you could have simply started with ISO 800, 1/125, f2.8 for the least amount of noise and not had to adjust down the exposure on the computer.

Am I missing something?
 

mfturner

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So Auto==Trickery :)

I guess that shouldn't surprise me, but I'm happy with the other three curves, I think I can find use in low and high key, while using normal 99% of the time. I bet Auto is the default when you reset a camera though.
 
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Great article. Thanks for posting that.




Your contention is that the vast majority of the noise is due to the sensor and we can ignore the photon shot noise. No opinion on that one myself, but let's go with that. Then anytime you raise the ISO you are going to raise the sensor noise levels, so don't you always want to be at the base ISO for minimum noise?

It seems to me you are adjusting the histogram to the right using ISO just like all those people whose videos and blogs you are claiming are doing it wrong as @pdk42 was trying to point out. As an example, let's say we are using an f2.8 lens and our shutter is 1/125 because of subject motion we can't get any slower.

With your method you start at ISO 1600, f4, and your histogram is mostly on the left half. You then change your aperture to f2.8 to fill the right side of the histogram, bumping the exposure +1EV. Then on your computer readjusting the exposure back -1EV, right? You shot your picture at ISO 1600, 1/125, f2.8.

The YouTube guy in his demo shooting the same thing starts at ISO 800, f2.8 and because the histogram is mostly on the left half, he now does his "ETTR" adjusting the ISO +1EV by changing ISO 800 to 1600 (because he already maxed out aperture). Then when he gets home he makes the same -1EV compensation on the computer. He shot his picture at ISO 1600, 1/125, f2.8.

In your mind he did it wrong because he adjusted ISO last where as you think you adjusted exposure last and therefore did the real ETTR. In both cases you both used the exact same setting for the shot. And both of you could have simply started with ISO 800, 1/125, f2.8 for the least amount of noise and not had to adjust down the exposure on the computer.

Am I missing something?
"It seems to me you are adjusting the histogram to the right using ISO just like all those people whose videos and blogs you are claiming are doing it wrong."

If you happy with that line....myself, I was 100% lost with that logic..... but I am cool with whatever you feel is in my mind....have fun :)

If you in-fact serious.....I think you missed what I wanted to achieve 110%

Best
 
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@BushmanOrig
I finally got around to reading your excellent article. I think your suggested settings make sense given the comments you added. However, I do have a question. Why add 1/2 stop to exposure shift? Is that just an arbitrary push to ETTR?
 
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@PakkyT

Let me see if I can explain what you are missing.

Both cameras are receiving the same amount of light shooting the same scene.

camera 1 starts at (1600 iso, f/4, 1/125) then adjusting aperture to 2.8
camera 2 starts at (800 iso, f/2.8, 1/125) then adjusting iso to 1600

So your point is that since both photographers achieved the same exposure settings, that neither approach is wrong when trying ETTR.
@BushmanOrig point is that raising iso first is the wrong approach.

However, camera 2 started with less noise and then bumped iso introducing more noise.
Camera 1 did not introduce more noise since it was already at iso 1600.

A clearer example would be:
camera 1 starts at (1600 iso, f/4, 1/125) then adjusting aperture to f/2.8
camera 2 starts at (3200 iso, f/5.6, 1/125) then adjust iso to 6400.

If rasing iso first, camera 2 will introduce more noise.

In both cases, ETTR was achieved, but the idea is always to adjust aperture and/or shutter speed before iso to let in the most light.

Hope the helps.
 

Machi

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I am very skeptical about the real impact of photon shot noise in relation to all the other factors that all contribute to the noise we see in our images. In other words if we had to list a few components in the image signal path that add SNR noise to the image and we weigh them, how will they compare to each other?

Could it be something like this:-

ComponentDescription%SNR
The ADCThe ADC = fixed SNR, we cannot change that1%
Analog Gain AmplifierFixed SNR or variable SNR?2%
The sensorOne should break it down in components but lets view as is8%
Photon theoryTry the same 35mm f2.8 on A7 II and A7III0,0001%

I do believe photons and lost or deflected photons does contribute to noise (signal integrity breakdown) but its total impact on noise is irrelevant when compared to the losses we could see in only the sensor.

Like all things, it all depends on what we focus on. The photon theory is not incorrect its just not that important. Why the photon theory? It was promoted at the time Canon pushed DSLR full frame cameras as answer to the fast growing mirrorless sector.

I think the one biggest event that started shifting the photon theory was when Sony launched the A7II follow up, the A7 III - two 24MP full frame cameras with radically different noise characteristics - same photons, same lens, same sensor size but hugely different noise results..... If you doubt...take an image with your camera, change the lens and take another and spot the differences in photon behavior...

When you step away from the photon theory and reduce it to its correct weight in the chain and you put your focus on the sensor and search for answers. This journey is way more interesting than the photon journey that never really came up with any other solution than buy a full frame camera....

When you focus on the sensor it will result in interesting answers and solutions like ETTR or just mastering your exposure techniques. The next solution is understanding the roles of exposure (shutter & aperture) and then separately ISO. Only this one paragraph and what we learn can complete change any photographers experience with his or hers camera........something the photon theory never managed....

This is exactly what I explain in my article - shift the focus away from the photon theory and put your effort on the sensor.....

So one can say but Siegfried what's new? I think its BIG.....and one see why, just from the replies to this discussion....

See this paper

Best

Siegfried
Unfortunately I haven't much time now so just quickly. There isn't SNR noise, that's like saying signal-to-noise ratio noise. It's just SNR and it's exactly what it's saying it is - ratio of signal to the noise.
Noise has in photography many components but generally main of them are just two. Those caused by photon nature of the light (shot noise) and those caused by camera (read-out noise) which has many subcomponents (read noise, dark/thermal noise, pattern noise, etc, look at the Martinec' article).

Camera's noise is for the majority of practical application constant at given ISO (only for long exposures it will be larger by growing contribution of dark noise).
For modern cameras it's 1-10 electrons rms (~equal or less than 1 DN at base ISO).
DN means digital number and gives amount of output in the RAW file if opened linearly (without gamma correction). Exact number is dependent on ISO.
One can measure this in appropriate software (ImageJ, RAW digger?) for totally black image as standard deviation.

Photon shot noise is dependent on the amount of detected photons and it's equal to square root of number of detected photons. For 10 000 photons it's equal to 100, for 16 photons it's 4.
As photons are detected as electrons in the camera, it's easy to compare contributions.
For modern camera with standard deviation of read-out noise 5 electrons, photon shot noise has the same contribution to the overall noise at just 25 photons/electrons (square root of 25 is 5).

So read-out noise (noise inherent to the camera) will be visible only in cases of very low signal (in shadows).
In majority of cases, shot noise will be much larger.
Now magnitude of photon shot noise can be demonstrated also in the appropriate image of luminated homogenous target, for example white paper.

noise.jpg
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Here is quick demonstration for totally black frame and for white paper shot.
In the histogram look at standard deviation (STD) which measure variations (=noise) for given area.
As you can see, luminated target has much more noise (STD equal 10 vs 1 for black frame).
More noise in the shot of white paper is not so important because signal is much higher which means better SNR.
Better SNR means image which looks less noisy.

If one improves signal further by using ETTR technique it surprisingly leads to more noise in the image!
So why images taken by ETTR looks better?
Trick is in the fact that noise is growing by square root of increment and signal is growing linearly so SNR is growing too. For 2× times higher signal, noise will grow as square root of 2 which is equal to 1.41 and SNR will be better by factor 2/1.41 which is equal to 1.41 (square root of 2 again).
In fact for every increment of signal, SNR will be better by square root of it.
And that's why ETTR works, it improves SNR.

EDIT: I've deleted last part, where I wrongly stated that ETTR lowers noise. and I've also improved readability of text (hopefully).
 
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T N Args

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@PakkyT

Let me see if I can explain what you are missing.

Both cameras are receiving the same amount of light shooting the same scene.

camera 1 starts at (1600 iso, f/4, 1/125) then adjusting aperture to 2.8
camera 2 starts at (800 iso, f/2.8, 1/125) then adjusting iso to 1600

So your point is that since both photographers achieved the same exposure settings, that neither approach is wrong when trying ETTR.
@BushmanOrig point is that raising iso first is the wrong approach.

However, camera 2 started with less noise and then bumped iso introducing more noise.
Camera 1 did not introduce more noise since it was already at iso 1600.

A clearer example would be:
camera 1 starts at (1600 iso, f/4, 1/125) then adjusting aperture to f/2.8
camera 2 starts at (3200 iso, f/5.6, 1/125) then adjust iso to 6400.

If rasing iso first, camera 2 will introduce more noise.

In both cases, ETTR was achieved, but the idea is always to adjust aperture and/or shutter speed before iso to let in the most light.

Hope the helps.
So there is nothing more to it than try and adjust aperture and shutter speed instead of, last resort, raising ISO? Pretty simple, and well known.

I say "well known" because almost everyone knows that raising ISO leads to more noise, so don't do it unless you have to. This is so widely known that I don't think it needs to be said as a whole new thread with 'revelations'.

ETTR is a bit more esoteric, or misunderstood, and misused, but seems to be a side-issue to this thread and could be dealt with better in a separate thread -- and already has, IIRC.

Still not sure what the Olympus-specific advice is, but maybe it's still coming.

cheers
 
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View attachment 800514

How do you move the histogram to the right? (ETTR)
  • Increase the exposure (Shutter speed or Aperture)
  • Or dial in a permanent "Exposure Shift" (Menu K in the Pen F - P45, 114)
  • Do not increase the ISO - that will be wrong because the ISO increase image brightness NOT exposure
Does not matter at which ISO you are - the moment you increase the exposure (aperture & shutter speed) you give more light to the sensor and the sensor performs at its best when it has enough light (sweet spot).
I'm not sure about that.
Let's take an example and say that you're histogram above is : 1/100 s - f/4 - ISO 200.
If we use the first method, you could achieve ETTR by choosing, let's say : 1/50 s - f/4 - ISO 200.
(that means that with 1/40 s, your sensor is overexposed).

Increasing the ISO only (1/100 - f/4 - ISO 400) is useless for ETTR.
However, what happens if you choose (1/50 - f/4 - ISO 400) or even (1/50 - f/4 - ISO 800).
You will have, on the JPEG, overexposed photos (+1 and +2IL) with clipped highlights.
But what about the RAWs? Will highlights be clipped?
When choosing respectively -1IL or -2IL exposure on you RAW software, will you recover the highlights?

Always check that you do not over expose the sensor - that is also not good....
It's difficult because you cannot see on your camera if you are really clipping highlights.
Sometimes it's even hard to see on my RAW software... when I use bracketting, I sometimes have to try the exposure correction on my software to know if I clipped or not one of the channels...
 

PakkyT

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However, camera 2 started with less noise and then bumped iso introducing more noise.
Camera 1 did not introduce more noise since it was already at iso 1600.
But you are saying those two lines as if they are two different results. In the end, both photographers used identical settings so both photographers ended up at the exact same noise levels. One method did not result in lower noise than the other, right?


A clearer example would be:
camera 1 starts at (1600 iso, f/4, 1/125) then adjusting aperture to f/2.8
camera 2 starts at (3200 iso, f/5.6, 1/125) then adjust iso to 6400.

If rasing iso first, camera 2 will introduce more noise.

In both cases, ETTR was achieved, but the idea is always to adjust aperture and/or shutter speed before iso to let in the most light.
Your camera 2 example violates your last line of adjusting aperture and shutter before bumping ISO. If Camera 1 can shoot at 1600, f2.8 why is camera 2's example artificially crippled to 6400, f5.6? Seems like you are purposely forcing camera 2 to a smaller aperture for no other reason than the force the higher ISO and claim, "see, camera 2 has to use a noisier ISO level" when the obvious solution is for camera 2 to also dial open to f2.8 and that two-stop aperture gain now allows you to drop your ISO back to 1600 just like camera 1.

I am still not buying the original articles premise that if you are using an ISO above the base ISO and you can still adjust the aperture and shutter for more exposure that you are somehow not using ISO to ETTR. In the article example of the room, he is allowing auto-iso to first put the exposure in the right ballpark (so he has already "ETTR" using purely ISO), then final adjusting to get as much aperture and as low a shutter speed as possible for "(DOF & movement)". What if he started first with those two settings, aperture & shutter set to where he wants them at the base ISO which of course would be wayyyy to dark? So his final adjustment is bumping the ISO to bring the image brightness to the histograms he shows. But he says that is wrong. Just because you let Auto-ISO make that exposure compensation for you, doesn't mean it didn't happen. Again, I could be completely mixing something up here and am confused.
 

PakkyT

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If you happy with that line....myself, I was 100% lost with that logic..... but I am cool with whatever you feel is in my mind....have fun :)

If you in-fact serious.....I think you missed what I wanted to achieve 110%
So you don't see a error in your logic when in your article you write:

Our aim should always be to operate the sensor inside its sweet-spot. How does one achieve that? The answer is as simple as exposing the sensor correctly. This is the reason why it is so important to master exposure skills. When talking about ETTR we only refer to Shutter Speed and Aperture. These two variables determines how much light will reach the sensor. This is so important.
Then immediate on the next line start with "Let's discuss ETTR and the three images below." and all three images are already at an ISO of 1250 or higher? You just violated your rule that with ETTR we only "only" refer to Shutter Speed and Aperture but have biased your images' exposures to the right using high ISO. Just because you let the camera auto-adjust the ISO for you, you can not somehow pretend it isn't now part of your ETTR effort you are showing.
 

relic

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Please forgive me for butting-in when I know that I don't know what I am talking about. I tried hard to follow the arguments above but I'm confused. And I don't know if what I say below is repeating what was said above or whether it is heresy. But if I set the shutter speed at the slowest that the conditions allow. And I set the aperture to give me sufficient depth of field (this could be the maximum aperture of the lens), so both shutter speed and aperture are predetermined for the shooting conditions, then the "correct" exposore must be set by choosing ISO. If I am now to bump the exposure in order to achieve ETTR, the only way to do that would be to increase ISO (as my shutter speed and aperture are predetermined as I described above). But increasing ISO would increase noise, but then what I understand (or don't understand) from the reasoning above is that this would result in lower noise in the shadows once the exposure is brought down in post processing even though I used a higher ISO in shooting to obtain ETTR?
Also I don't see how one can increase exposure without increasing ISO if one started from the assumption that one is already using the largest appropriate aperture (given need for depth of field) and the slowest shutter speed (consistent with getting a sharp image) in order to be able to use the lowest ISO for the shooting conditions (light, movement). Again, sorry if I am being too naive.
[I did post a similar argument in another thread, but I don't think I made my argument sufficiently clear]. [I tried to follow the very comprehensive and detailed article, but it is too learned for my brain and is way over my head].
 
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pdk42

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So there is nothing more to it than try and adjust aperture and shutter speed instead of, last resort, raising ISO? Pretty simple, and well known.

I say "well known" because almost everyone knows that raising ISO leads to more noise, so don't do it unless you have to. This is so widely known that I don't think it needs to be said as a whole new thread with 'revelations'.

ETTR is a bit more esoteric, or misunderstood, and misused, but seems to be a side-issue to this thread and could be dealt with better in a separate thread -- and already has, IIRC.

Still not sure what the Olympus-specific advice is, but maybe it's still coming.

cheers
Precisely. I think Siegfried has really over-complicated it. The rules really are very simple:

- Use the lowest ISO possible.
- Give the sensor as much light as possible, whatever the ISO. Use the histogram or blinkies to help
- If at base ISO, exposing to the right and then correcting in post (ETTR) will improve noise further

That's all! (I won't mention ISO invariance ;))
 

mfturner

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@relic, I think you are describing a situation typical of mine, where the lighting is too dim to use base ISO for a scene once aperture and SS are set. You can set ISO to what the camera's meter wants, or a little above, or a little below. If you set it a little above or a little below, you then might have to adjust the image brightness in post processing to get it back to where you want the overall brightness to be.

If your camera's analog amplification circuitry is well designed, then it may not actually "add" much extra noise as you boost ISO, but instead it will only amplify the noise that is already in the image read out of the sensor (read noise in the sensor, photon shot noise, etc). If your camera's analog amplifier is not so well designed, then it may add additional noise of its own. That isn't so common now, amplifier designs are pretty good. Additionally, some noise will be added in the ADC circuitry (e.g. quantization noise in the shadows and clipping at both extremes, the idea of quantization noise in shadows drove a lot of the original ETTR discussion) how much depends on the design, and analog amplification before the ADC directly impacts this step.

So it isn't obvious, without testing, whether a camera's lowest noise result will be ISO=3200, SS=1/80, AV=f/4.0 for an f/4.0 lens, or to take the same image with ISO set at 5000 or 2000 or something else, and then adjusted back in post to match the ISO=3200 image. Post processing, even before trying any noise reduction software, has an impact on this - thus my comments about the S-curve and gradation settings impacting how visible the noise is in the resulting image. By reducing contrast in the dark end of the tone curve, I believe I am effectively making the shadow noise less visible. An ETTR advocate would say that my above example should have been taken at ISO=5000, SS=1/80, AV=f/4.0 and then pulled in post processing, which I have many images of with my old Canon with my EF 300 F4.0L IS lens, where 1/80th is about where motion blur appeared with the kids on-stage in concert band. But I'm unconvinced that this necessarily helps with my Olympus M10.3 and PM1 cameras, they seem to have similar noise behavior for a couple of stops either way in the shadows, and the highlights always risk being burned out (clipped by the ADC or any stage prior to the ADC) with increased ISO. So right now I am leaning towards setting ISO somewhere between where the camera meter wants it, or up to 1 stop darker (what you might call ETTL), depending on how contrasty the scene is (brightly lit white shirts and kids foreheads are the worst in HS concert band for me).
 

pdk42

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but then what I understand (or don't understand) from the reasoning above is that this would result in lower noise in the shadows once the exposure is brought down in post processing even though I used a higher ISO in shooting to obtain ETTR?
It probably won't. That's my basic argument with Siegfried's article. Over-exposing by one-stop ("+1" according to the camera's meter) at ISO 1600 will be very little different to a "correct" exposure ("0" according to the camera's meter) at ISO 800. The reason is that in both cases, the amount of light that the sensor receives IS THE SAME (same shutter speed and aperture). The photon wells will be filled to the same amount. All that will happen is that the extra noise added by the camera by using ISO 1600 will be negated by pulling it back in post-processing.

Where the over-exposure trick WILL work (i.e. ETTR) is if you do this at base ISO. In this case, you're actually filling the wells on the sensor properly, you're not adding ISO amplification, so when you pull the exposure back in PP, you'll get lower noise.

Also I don't see how one can increase exposure without increasing ISO if one started from the assumption that one is already using the largest appropriate aperture (given need for depth of field) and the slowest shutter speed (consistent with getting a sharp image) in order to be able to use the lowest ISO for the shooting conditions (light, movement). Again, sorry if I am being too naive.
No, you can't. You're not naive. The only way to increase exposure (so far as the sensor is concerned) is to give it more light (longer shutter, wider aperture, brighter scene). If you can do none of that and you resort to increasing ISO, all you're doing is amplifying what little the sensor is getting and that means noise.
 
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pdk42

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The really important point to grasp, which is easy to overlook, is that the ISO dial does not change the sensor's sensitivity. The ISO dial is effectively an amplification dial. At base ISO, the amplification is at its lowest. Anything above base ISO is adding amplification. You need to amplify if the signal is too weak from the sensor - that is, when the sensor didn't get enough light.

Just remember that however you set the ISO dial, the sensor gets what it gets. If it doesn't get enough to fill its wells, then the signal needs to be amplified by increasing the ISO and that means amplifying nosie too (and creating some of its own in the amplification process too).

Anyhow - I think this thread has done the topic to death - this post is probably just regurgitating the same stuff as it is ! Sorry :doh:
 

Matt Drown

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FYI, if you want to read even more, some google searching:
https://clarkvision.com/articles/iso/
https://www.abelcine.com/articles/blog-and-knowledge/tutorials-and-guides/iso-ei-and-gain-explained

If you are done reading, @pdk42 pointed out the instructions, with a minor modification I'll add:
IF you are concerned about NOISE in your final picture:
-shoot at the lowest base ISO (do not use "low/low2")
-shoot with the widest aperture, longest shutter that allows you to follow the previous instruction and still capture the shot you are shooting
-Adjust the histogram to the right, without clipping, re-adjust in post (image will potentially look overexposed in JPG and viewfinder unless you apply some adjustments)
 

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