Good luck educating beginners with this complicated theory without confusing them. I would rather tell them "High ISO make your picture 'look' brighter, but in expense of possible reduction in DR, adding noise bla bla" and "the best ISO is the lowest, around 100-200, but avoid 50 bla bla" without the ISO-less sensor theory behind it. That's easier for them to chew. They are beginners after all. If they want to dig deeper, I'll recommend this series to them ( Is ISO part of exposure? Vol 1,2,3 and 4).
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Poll: should we lie to beginners? II
- Thread starter Andre Affleck
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bobn2
Forum Pro
The right theory is actually simpler than the one people use. The one people want to use makes dealing with exposure a three variable problem rather than a two variable one, and the graphic they use to illustrate it (the triangle) is completely meaningless.
Andre Affleck
Senior Member
Of course it should be described accurately, but the question is, must it be? It was claimed by quite a few members that if you didn't understand the true essence of ISO, your photography would suffer. In fact one member said:moving_comfort wrote:
I ran into a situation related to this with my neighbor last year.
He had been told that shutter speed, aperture and ISO formed an exposure 'triangle', in that each was equally 'tweakable' to get more light on the sensor. (Thanks, National Camera Exchange clerk!)
He was basically under the impression that there was no downside to being lazy with aperture or shutter speed, because it could be made up with an ISO adjustment - that all three variables affected 'exposure'.
(In his defense, he wasn't really being lazy about aperture, he just had the consumer kit zoom and usually didn't have a lot of aperture range to work with.)
After I had a talk with him, he bought a Tamron 17-50 2.8 to get more aperture range to work with - and he started to notice noise, more, after that (he had upgraded from a P&S so he thought the noise he saw before was still 'pretty good'.) He also bought a used 35 1.8G later.
I think there are a lot of shooters who have more of a clue than he did, and have been informed that you should perhaps carefully choose your SS and aperture first, and then let ISO make up the difference, but they know that because what's really happening with ISO has been partially described to them - which begs the question, if you're going have to partially describe it anyway, why not entirely, accurately describe it?
It is worse than wrong, it is misleading.
The problem is that the wrong understanding of what exposure means results in wrong decisions while shooting, and suboptimal results.
So far no examples of such.
People seem to come to the same conclusion and make the same decisions regardless, using the exposure triangle method. You may think this is trivial, but the implications are significant. This is why Human Factors engineers are never unemployed. Scientists, in their brilliants, often loose site of the prize. And we have 800 posts to prove it!
The implications may also help explain why some taught it that way, especially in the film days.
Photography is not a science like photometry. It's part art, part skill, and part science. Artists are often not good scientists. If they have a hard time with science, I say give them something tangible that they can use.
Andre Affleck
Senior Member
Bingo!
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Great Bustard
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- The exposure is a function of the amount of light falling on the sensor, and is determined by how bright the scene is, how wide the aperture is, and how long the shutter is open.
- The less light that falls on the sensor, the more noisy and dark the photo will be. For a given aperture, shutter speed, and/or flash power, to increase the brightness of the photo in-camera for the desired LCD playback / OOC jpg brightness, raise the ISO.
- On the other hand, if you're letting the camera decide the aperture, shutter speed, and/or flash power for you, then the camera will figure in how many stops underexposed you choose to be on the basis of the ISO setting you've chosen.
Great Bustard
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Well done.
Then you are of the opinion that exposure is unimportant.
Both were underexposed. If you'll recall, ISO is not part of exposure.
Yeah -- that.
Andre Affleck
Senior Member
Why is this so hard for you to understand? I am *postulating* that if one did not understand this to be true, the same conclusion is drawn. Agreed?
Andre Affleck
Senior Member
It depends how it's presented. Look here at a link that was referenced before as being flawed. It's is definitely flawed, but it gave the reader the general concepts. Now look at what you wrote as a comment to the author:
Sorry Nasim, this article is wrong in several fundamental ways. ISO is not ‘the level of sensitivity of your camera to available light’ and the sensitivity of a digital camera’s sensor never changes. The ISO Exposure Index, which is its proper name, only describes a relationship between scene brightness and final image brightness, and has no connection to the sensor’s ability to collect light. A sensor does not have an ISO rating at all. By increasing the ISO setting on your camera, you do not enable it to capture more light. In most, you don’t change the way it captures light at all, all you change is the way the raw file is converted into an image (JPEG) file. In some, raising the ISO results in less electronic noise being added to the image. The noise you see in images taken in low light is not caused by the ISO setting, it is caused by the small number of photons making up the picture.
Bob.
I asked a friend of mine last night who is trying to learn photography to read the article, then read your comment. His exact words were, "now I'm completely confused".
Andre Affleck
Senior Member
PhilPreston3072
Senior Member
So wouldn't you get the same 'brightness' by using the exact same ISO in camera that you used in post?
From what I see, for any given shutter and aperture combination, you require an appropriate value of ISO to have appropriate exposure/brightness.
bobn2
Forum Pro
Since ISO maps exposure to brightness, by definition if you have the same exposure and brightness, you have the same ISO. Or vice versa.
For every exposure (shutter, aperture, scene illuminance) there is an ISO which will give you the normalised ISO brightness. That simply comes from the definition of ISO, above - ISO is a function of exposure to brightness.
Bob has done nothing of the sort Sammy; it is your reaction to what you simply refuse to understand & learn that is "rubbishing" these forums.
It is you who is going "personal", give it a rest already.
This exactly what you are doing. How……"nice" of you
Your posting history proves the contrary; but it doesn't matter to you anyway.
Sammy don't take it personal just because somebody is trying to rectify habitual errors (yours & other persons of course) in exposure technique; learning starts when you open your mind to the possibility that you are wrong; & when realising your knowledge on a subject is limited, choosing to learn instead of mud-slinging.
bgD300
Senior Member
and if you don't understand the craft you won't be much of an artist. Creativity is stretching or outright breaking the rules to achieve something.
Using selective DOF as an element in an image is one thing, just having an OOF image because you don't understand shutter speed vs. aperture is quite another.
Using selective DOF as an element in an image is one thing, just having an OOF image because you don't understand shutter speed vs. aperture is quite another.
moving_comfort
Veteran Member
Like:Andre Affleck wrote:
Of course it should be described accurately, but the question is, must it be?...moving_comfort wrote:
I ran into a situation related to this with my neighbor last year.
He had been told that shutter speed, aperture and ISO formed an exposure 'triangle', in that each was equally 'tweakable' to get more light on the sensor. (Thanks, National Camera Exchange clerk!)
He was basically under the impression that there was no downside to being lazy with aperture or shutter speed, because it could be made up with an ISO adjustment - that all three variables affected 'exposure'.
(In his defense, he wasn't really being lazy about aperture, he just had the consumer kit zoom and usually didn't have a lot of aperture range to work with.)
After I had a talk with him, he bought a Tamron 17-50 2.8 to get more aperture range to work with - and he started to notice noise, more, after that (he had upgraded from a P&S so he thought the noise he saw before was still 'pretty good'.
I think there are a lot of shooters who have more of a clue than he did, and have been informed that you should perhaps carefully choose your SS and aperture first, and then let ISO make up the difference, but they know that because what's really happening with ISO has been partially described to them - which begs the question, if you're going have to partially describe it anyway, why not entirely, accurately describe it?
Photography is not a science like photometry. It's part art, part skill, and part science. Artists are often not good scientists. If they have a hard time with science, I say give them something tangible that they can use.
"Upping ISO is not affecting exposure, it's adding brightness to the image artificially after the image is captured and before it is saved. That is why... (add your usual instructional caveats/warnings to increasing ISO that you normally would give them here...)"
How could it get any simpler? This ^^ at least points in a more accurate direction, and would help them with the underpinnings of 'exposure'.
.
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bobn2
Forum Pro
The word 'artificially' is redundant. A raw file has no brightness, it's brightness depends entirely on how you process it - so all processing choices are as valid as each other, the only question is which one of those choices ends up with the output looking realistically 'bright', on the understanding that the amount of light entering the eye from the reproduced image bears no direct relation to the amount of light that would have entered from the original scene.moving_comfort wrote:
Like:Andre Affleck wrote:
Of course it should be described accurately, but the question is, must it be?...moving_comfort wrote:
I ran into a situation related to this with my neighbor last year.
He had been told that shutter speed, aperture and ISO formed an exposure 'triangle', in that each was equally 'tweakable' to get more light on the sensor. (Thanks, National Camera Exchange clerk!)
He was basically under the impression that there was no downside to being lazy with aperture or shutter speed, because it could be made up with an ISO adjustment - that all three variables affected 'exposure'.
(In his defense, he wasn't really being lazy about aperture, he just had the consumer kit zoom and usually didn't have a lot of aperture range to work with.)
After I had a talk with him, he bought a Tamron 17-50 2.8 to get more aperture range to work with - and he started to notice noise, more, after that (he had upgraded from a P&S so he thought the noise he saw before was still 'pretty good'.
I think there are a lot of shooters who have more of a clue than he did, and have been informed that you should perhaps carefully choose your SS and aperture first, and then let ISO make up the difference, but they know that because what's really happening with ISO has been partially described to them - which begs the question, if you're going have to partially describe it anyway, why not entirely, accurately describe it?
Photography is not a science like photometry. It's part art, part skill, and part science. Artists are often not good scientists. If they have a hard time with science, I say give them something tangible that they can use.
"Upping ISO is not affecting exposure, it's adding brightness to the image artificially after the image is captured and before it is saved. That is why... (add your usual instructional caveats/warnings to increasing ISO that you normally would give them here...)"
How could it get any simpler? This ^^ at least points in a more accurate direction, and would help them with the underpinnings of 'exposure'.
PhilPreston3072
Senior Member
Therefore ISO (or gain in video terms) still has its part in determining the final brightness/exposure.
Which means that even if I alter the shutter or aperture parameters, I can still obtain the same final brightness/exposure by altering ISO accordingly. Isn't that how the exposure triangle works?
bobn2
Forum Pro
No, because ISO maps exposure to brightness. So, you can't just write 'exposure/brightness'. Different ISOs will give you different brightnesses from the same exposure. So, ISO determines which brightness you get from a given exposure.
You've conflated 'brightness' and 'exposure' again.
Great Bustard
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I apologize if I'm misinterpreting. Could you restate the point you are trying to make? Thanks, and sorry for missing the point.
gollywop
Veteran Member
Pretty much so. The only problem is that you don't know the ISO that you would find best during processing at the time you're taking the shot. So there's a danger that you would set the in-camera ISO too high. That's one of the real advantages in doing the brightening during processing.
In a very loose (broadly interpreted) sense of ISO that is correct. If your desired exposure at base ISO is not ETTR, and the resulting image would be darker than desired, then some ISO must be added somewhere, ether in-camera or during processing. If, on the other hand, you have an acceptable ETTR exposure at base ISO that is too bright, then you are going to want to shoot at that exposure and apply "negative ISO," i.e., reduced brightening during processing.
The latter case is the one that originally brought attention to ETTR, a concept, however, that has more general applicability and advantage.
I am assuming above, by the way, that one is shooting raw and that a "desired exposure" is one having a desired f-ratio and SS, and that an "acceptable exposure" is one whose aperture and SS are within acceptable values.
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gollywop
moving_comfort
Veteran Member
.
I think he's saying that if you witness the sun moving across the sky it doesn't matter if you think it revolves around the earth or if the earth is turning on it's axis, you can come to the same conclusion - that you will see it again, in roughly the same place and almost the same time, the next morning.
He's also implying that to most people, there's no practical reason that they need to know the difference between the earth rotating on it's axis and the sun revolving around the earth - the observable effects, as far as everyone is concerned, are the same.
There is a minor point there. It's an odious, depressing point that rewards irrationality and ignorance... But it's a point.
However it doesn't strictly apply to this argument, as keeping ISO as a full light-gathering member of the exposure triangle (or whatever) can lead to misconceptions that can bite you in practical ways.
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Here are a few of my favorite things...
---> http://www.flickr.com/photos/95095968@N00/sets/72157626171532197/
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