Noise apps = higher ISO settings?

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ETTR is based on the following principle: a sensor is linear, out eyes are not. That means that the sensor data have to be ‘gamma corrected’ to give the same effect as our eyes do. Because a sensor is linear however, half the number of shades will be in the first (brightest) stop, 25% will be in the second stop, etcetera. If you shoot a relatively dark scene, you may lose 50% or more of what the sensor could record, because you record nothing in the first stop. At the same time you will be struggling to get enough meaningful information in the darkest stops (read: to get a signal that is higher than the noise).

That is when ETTR makes sense. You overexpose the image, in order to push all the information up to the right of the histogram. The result is an increased signal to noise ratio everywhere in the image. In post processing you correct for this overexposure, of course. The result is a cleaner image, which is most obvious in the darkest parts. Unfortunately, this is not as easy as it sounds. You may blow highlights if you are not careful and do not understand when to use this and when not to use this. Many people think that ETTR simply means you overexpose every image and correct that in post, but that is nonsense. You only overexpose those scenes that have headroom to do this.
 
@Johan Elzenga

Yeah, I follow the theory. But this is reality. :) What is that trite phrase, in theory, theory and practice are the same, in practice they are not.

However I have never found a shot for me ever made ETTR make sense. Yeah, you push to the right until you get blow outs, with the theory that you get more details in the shadows. When I first got the Canon 6D, I spent a lot of time doing bracketed shots, seven of them separated by half stops.

For my old Canon, if the range was that dynamic, bracket shots worked much better (for obvious reasons). If I could not get bracket shots fore some reason, I cannot recall a single instance where ETTR would have worked better for me. It would have always caused blow outs, and most often the area with blow outs is the area I am interested in (e.g. family indoor holiday photos).
It could be that I never was in the perfect situation where ETTR would work better. However like I said I have taken bracket shots stepping a half EV. Everytime the negative shots worked out better or brackets were needed.

Tim

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I agree that there are far fewer situations where ETTR works well than some people think. The problem is that there are often small highlights that would blow out, even if most of the image is very dark. But because taking a digital photo is free, you can simply try by shooting multiple exposures.
 
Johan Elzenga said:
I agree that there are far fewer situations where ETTR works well than some people think. The problem is that there are often small highlights that would blow out, even if most of the image is very dark. But because taking a digital photo is free, you can simply try by shooting multiple exposures.
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And this multiple exposure becomes the principle behind HDR.
 
Johan Elzenga said:
The most important thing to remember about using ISO invariance is that it increases the effective dynamic range. Let’s say that a proper exposure of a scene would be 1/125 sec, F4 and ISO 6400. If you use the fact that your camera is ISO invariant from ISO 1600 onwards (assuming it is) and so you shoot at 1/125 sec, F4 and ISO 1600 (and correct for this underexposure in Lightroom), then you create two extra stops of headroom in your highlights before they’ll blow out.
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Is this approach the same as Expose To The Right?
 
Johan Elzenga said:
No, this is exposure to the left…
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Well, actually it isn’t either. The two techniques are very different. In the ETTR technique you do actually change the exposure, to utilise the headroom that the sensor has. You increase the amount of light that falls onto the sensor, and correct that in post production.

If you use the ISO-invariance of your camera, you do not change the exposure. The shutter speed and aperture remain the same, so the amount of light that falls on the sensor remains the same. The only thing you change is the ISO-setting, which is how much the sensor signal is amplified. Again, this is changed in post production, which is about the only thing the techniques have in common.
 
tspear said:
... I cannot recall a single instance where ETTR would have worked better for me. It would have always caused blow outs ...
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Not really, because ETTR by definition is setting the exposure as far to the right as possible without causing blowouts.
 
Johan Elzenga said:
Well, actually it isn’t either. The two techniques are very different. In the ETTR technique you do actually change the exposure, to utilise the headroom that the sensor has. You increase the amount of light that falls onto the sensor, and correct that in post production.

If you use the ISO-invariance of your camera, you do not change the exposure. The shutter speed and aperture remain the same, so the amount of light that falls on the sensor remains the same. The only thing you change is the ISO-setting, which is how much the sensor signal is amplified. Again, this is changed in post production, which is about the only thing the techniques have in common.
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So right now, I hate to admit it, I'm confused. How do I set the camera's metering, if it isn't Programmed (on Nikon cameras), Aperture Priority, or Shutter Priority?

Phil Burton
 
Neither. You will be in manual mode.
Well technically you could set the EV compensation and fix the ISO then control either the shutter or aperture, but that is a lot more convuluted.

Tim

Sent from my HD1907 using Tapatalk
 
For me the reason to use higher ISO is so my shutter speed can go high enough to freeze action in wildlife. I can see knowing the invariance ISO value that should be max ISO if shooting still images. That is good to know. For most of my shots I need a focused image with frozen action. That can drive the need for a higher ISO that might be OK for a still subject.
 
tspear said:
Neither. You will be in manual mode.
Well technically you could set the EV compensation and fix the ISO then control either the shutter or aperture, but that is a lot more convuluted.

Tim

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If my camera allows me to fix the ISO at just one value, then can I still shoot in some automatic mode? My Nikon D3 unfortunately does not have an ISO Priority exposure mode.
 
PhilBurton said:
If my camera allows me to fix the ISO at just one value, then can I still shoot in some automatic mode? My Nikon D3 unfortunately does not have an ISO Priority exposure mode.
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No, because then the camera would take the fixed ISO into account when setting the aperture and shutter speed, so you would change the exposure. The result would be a perfectly exposed picture (but possibly blurred because of the long shutter speed) that does not need to be corrected in post production, so you would not get the benefit of the extra dynamic range. This technique must be used with manual settings. ISO priority won’t work either. If you don’t want to use those or don’t know how, then don’t use this technique.
 
mcasan said:
For me the reason to use higher ISO is so my shutter speed can go high enough to freeze action in wildlife. I can see knowing the invariance ISO value that should be max ISO if shooting still images. That is good to know. For most of my shots I need a focused image with frozen action. That can drive the need for a higher ISO that might be OK for a still subject.
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I think you misunderstand how this technique works. There is no reason why it could not be used for action photography like wildlife or sport. If you would normally shoot a wildlife picture at say 1/2000 sec and F4, then you would use these same settings if you take the ISO invariance into account. You would still shoot at 1/2000 and F4!! The difference is that you‘d normally use perhaps 6400 ISO to get a perfectly exposed shot, and now you keep the camera at 1600 ISO and so you will get a two stops underexposed shot. That underexposure you then fix in Lightroom. Look at it as if you could change the ISO in post production.
 
PhilBurton said:
So right now, I hate to admit it, I'm confused. How do I set the camera's metering, if it isn't Programmed (on Nikon cameras), Aperture Priority, or Shutter Priority?
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Manual mode gives you complete control over Aperture, Shutter speed and ISO. Set the ISO to the setting that benefits you most and then the two Nikon dials can control shutter and aperture. The exposure meter is visible in the viewfinder to show you which way to move the dials for the exposure setting that you wish.
 
PhilBurton said:
If my camera allows me to fix the ISO at just one value, then can I still shoot in some automatic mode? My Nikon D3 unfortunately does not have an ISO Priority exposure mode.
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There are no benefits of shooting in some automatic mode. Manual IS automatic in a sense. ISO is adjustable (though not as easy as Aperture or Shutter Speed). In Manual Mode I set the ISO, then either set the shutter speed or the aperture depending on whether I need to freeze the action or maximize DoF. The I can move the other dial on the camera to "dial in " the correct exposure. Setting Aperture priority allows you to adjust the aperture and the Camera will automatically adjust the Shutterspeed. For Shutter priority, it is reversed. In order to force the camera to under expose or over expose, you need to adjust the EV.

Shooting Manual, you set the EV to zero. Adjust the ISO, then the shutter and aperture to under expose (ETTL) or over expose(ETTR). Each mark on the Viewfinder exposure meter is one EV increment ( EV increment can be set on 1/3 or 1/2 stops)
 
Johan Elzenga said:
I think you misunderstand how this technique works. There is no reason why it could not be used for action photography like wildlife or sport. If you would normally shoot a wildlife picture at say 1/2000 sec and F4, then you would use these same settings if you take the ISO invariance into account. You would still shoot at 1/2000 and F4!! The difference is that you‘d normally use perhaps 6400 ISO to get a perfectly exposed shot, and now you keep the camera at 1600 ISO and so you will get a two stops underexposed shot. That underexposure you then fix in Lightroom. Look at it as if you could change the ISO in post production.
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I intend to back into it. With my 90D, I get very manageable noise; and a large range of native ISO. I ran Johan's suggested ISO variations the other day and was very pleased with the results.
So I intend to still shoot at f/4 and ISO6400 (or what ever) where I might be perfectly exposed at 1/2000, and the change the shutter speed to 1/4000 where I will be clearly underexposed. But that underexposed shot is easily corrected in LR. It's the higher shutter speed that has concerned me before, and this discussion has relieved that "fear".
I like the comment "Look at it as if you could change the ISO in post production. "
 
Johan Elzenga said:
I think you misunderstand how this technique works. There is no reason why it could not be used for action photography like wildlife or sport. If you would normally shoot a wildlife picture at say 1/2000 sec and F4, then you would use these same settings if you take the ISO invariance into account. You would still shoot at 1/2000 and F4!! The difference is that you‘d normally use perhaps 6400 ISO to get a perfectly exposed shot, and now you keep the camera at 1600 ISO and so you will get a two stops underexposed shot. That underexposure you then fix in Lightroom. Look at it as if you could change the ISO in post production.
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So amplify the signal in camera using higher ISO setting or, amplify the signal in post production via Develop/ACR. So it is a question of which path gives the best signal to noise ration when completed.
 
mcasan said:
So amplify the signal in camera using higher ISO setting or, amplify the signal in post production via Develop/ACR. So it is a question of which path gives the best signal to noise ration when completed.
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No, it’s a bit different. There are different sources of noise. For some sources it doesn’t matter when the signal is amplified, for another source it does matter. ISO invariance means that the latter source has become so small, that it doesn’t really matter anymore when the signal is amplified. ISO Invariance Explained
 
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