Thank you, Alan. I was hoping DonB would answer, but the more the merrier 🙂
April 20, 2023
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i like to see my reasults in camera so i will increase iso 100% a sharp image with noise is better than a fuzzy image with less noise.
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That was pretty much my understanding before all these threads on noise, iso and dynamic range.
I no longer believe that is exactly correct for modern sensors.
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I use it to various extents on all images but it doesn't actually alter the exposure* because obviously you cannot adjust the amount of light that hit the sensor while the shutter was open.
The exposure slider adjusts the image lightness.
* exposure - amount of light that struck the sensor per unit area while the shutter was open
** optimal exposure - the maximum exposure* within dof and motion blur requirements without clipping important highlights.
*** under exposed - more exposure* could have been added with the DOF and blur constraints still being met without clipping important highlights. -
now reality, shooting a dance concert. with lights flashing every where. subjects highlighted then completely dark mixed lighting. you would go home with no keepers i can guarantee with your setting's.
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I think you misunderstand the scenario. I'm assuming here that the photographer has raised the shutter speed to get a sharp image. This has resulted in 4 stops of underexposure and a very dark image.
The question is what happens to the final image quality if we solve this problem in two different ways:
1) We boost ISO by 4 stops
2) We leave it at base ISO and simply deliberately underexpose by 4 stops, then brighten the image 4 stops in post.What effect do you think these two strategies will have on the noise level in the final image?
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My understanding has always been that if you have highlight headroom and you cannot increase exposure* then raising ISO at least to where the camera becomes iso-invariant will have visible noise reduction benefits in post. In my experience, especially in very low light scenes the noise reduction benefit is noticeable.
* exposure - amount of light that struck the sensor per unit area while the shutter was open
** optimal exposure - the maximum exposure* within dof and motion blur requirements without clipping important highlights.
*** under exposed - more exposure* could have been added with the DOF and blur constraints still being met without clipping important highlights. -
Which settings? Raising ISO or just brightening in post? I'd be grateful if you answer my original question directly, without obfuscation or changing the meaning or answering a slightly different question. I believe an honest answer will reveal precisely your real understanding of all this stuff.
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Nope, not true at all.
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I'm basing my new understanding on Jim Kasson's and Iliah's responses in other threads. I'll set it out once Don answers. We can quibble over details after that 🙂
C'mon Don, don't go silent on us now! This will be useful for all of us.
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Consider Nikon D850. Changing ISO setting from 400 to 25600 while keeping exposure doesn't result in any practical improvement of noise, but highlights clip earlier.
Pretty much the same story with Sony 7R M5, 400 to 12800. -
as i said you wont have a sharp image if its not in focus having a fast shutter speed doesnt give you a sharp image. if you shooting action and pan you need to see the image the evf and track it. what if your shooting video ?
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Fixed another post.
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understanding are you kidding ! do you shoot video ? underexposed at 4 stops ? my understanding is i never shoot at 4 stops underexposed period . what sort of photographer are you a hypothetical one ? shoot a black backdrop 4 stops under and its unrecoverable period.
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I am confused about what you mean because if the exposure* is maxed out and there is highlight headroom I would raise ISO only to just below highlight clipping so I still would not have clipped highlights.
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You are still not directly answering the question. Which of these solutions gives the lowest noise in this scenario. Come on, it's not a hard question to understand:
1) Raising the ISO by 4 stops to avoid camera shake
2) Leave the ISO at base, raise the shutter speed to avoid camera shake and deliberately underexpose by 4 stops, then brighten in post -
Your definition of underexposed is clearly different to what David meant by underexposed. Why am I not surprised...hmmmm...
This is typically what happens when people adopt a misconception of what exposure* actually is.
* exposure - amount of light that struck the sensor per unit area while the shutter was open
** optimal exposure - the maximum exposure* within dof and motion blur requirements without clipping important highlights.
*** under exposed - more exposure* could have been added with the DOF and blur constraints still being met without clipping important highlights. -
Danno
I'd like Don to answer the question in black and white. Depending on which answer he gives, we will have a clear statement as to how he thinks noise in generated and mitigated. I'm trying to stop him wriggling out of answering clearly (Don it's not a trap, just a diagnosis, please answer!), it would be easier if we can focus on this point for a bit.