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Defining 'correct exposure'

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hjulenissen said:
DSPographer said:
To me correct exposure means that the elements of the image that you want to capture are within the dynamic range of the camera. Now that means for some image and camera combinations there is no correct exposure- since the image exceeds the DR capability of the camera (Bracketed exposures are allowed but might not be appropriate for a dynamically changing image). In other cases there is a range of exposures that meet my criteria. In that case you might as well optimize the quality of the image. For a still subject that may mean getting the most light possible, but for a dynamic scene it may mean trading off between DOF, motion blur, and noise.
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Seems that you are talking about "capture exposure". For the total end-to-end exposure (including brightness on print), one might want to do high-key or low-key presentation. Depending on how the artist plans to present the print, it might make sense to adjust capture exposure accordingly.
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Indeed.
hjulenissen said:
If you capture images of fireworks at night, a "perfect" AE will probably fail miserably. Rather, you want to keep the small, bright sources of light within the sensor saturation point, and live with large parts of the background landscape being drowned in sensor noise.
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Yes.
hjulenissen said:
If, on the other hand, you are taking photos of your kid playing at the beach with harsh highlights in the waves or directly into the sun, it might make sense to allow them to clip while placing the kid sensibly within the DR window of your camera.
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Bingo.
hjulenissen said:
Which is to say, expose (in camera) so as to maximize the quality of the parts in the image that is going to be most critical in the final print/display. If that is easy, concentrate on avoiding clipping and noise for the less important image extremes. Adjust final brightness to taste and according to the capabilities of your printer/display (assuming that you use raw format).
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Right on the money. You two have given the perfect response!
 
FrankyM said:
Correct exposure is when mid grey in the image is exactly where the photographer wants it to be.
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Assuming canned processing (eg, cellphone camera), otherwise mid grey is where it is placed in processing (of course, if you want to preserve detail in the mid grey of scene, you create an exposure range that allows that).
 
A photographer's exposure is never over. Nor is it under. He exposes precisely what he means to.

I can think of two general types of "correct exposure": one is the exposure that achieves the subjective creative goals you intended, and the other is one that follows a sort of technical correctness (e.g. 18% percent gray is such-and-such digital value in the resulting JPEG).
 
Daniel Browning said:
A photographer's exposure is never over. Nor is it under. He exposes precisely what he means to.

I can think of two general types of "correct exposure": one is the exposure that achieves the subjective creative goals you intended, and the other is one that follows a sort of technical correctness (e.g. 18% percent gray is such-and-such digital value in the resulting JPEG).
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Both these types assume canned processing. Without you own photographic lab (and in particular with slide film), canned processing was common enough in the film days. With digital, in particular, raw photography, assuming canned processing is like tying on arm behind your back.

Why do still so many people assumed canned processing when thinking about exposure? It is like riding a bike with multiple gears but only using the middle one because twenty years ago when you learned riding a bike, it did not have any gears.
 
Daniel Browning said:
A photographer's exposure is never over. Nor is it under. He exposes precisely what he means to.
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Yes.
Daniel Browning said:
I can think of two general types of "correct exposure": one is the exposure that achieves the subjective creative goals you intended, and the other is one that follows a sort of technical correctness (e.g. 18% percent gray is such-and-such digital value in the resulting JPEG).
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How is the other "technically correct "? What makes "18% percent gray is such-and-such digital value in the resulting JPEG" more "correct" than 18% gray with some other digital value in the resulting jpg?
 
Great Bustard said:
How is the other "technically correct "?
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By conforming to whatever arbitrary standard that it is correct for.

For example, f/8 might conform to the manufacturer's idea of correct exposure for a certain analog gain, raw converter, and settings, while the exposure I chose may be two stops over (or under) that, to achieve whatever goals I had in mind (less noise, more headroom, etc.)

--
Daniel
 
noirdesir said:
Daniel Browning said:
I can think of two general types of "correct exposure": one is the exposure that achieves the subjective creative goals you intended, and the other is one that follows a sort of technical correctness (e.g. 18% percent gray is such-and-such digital value in the resulting JPEG).
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Both these types assume canned processing.
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No, only the second type does. Here is an example of how the first type does not assume canned processing. If my goal is to minimize noise in a scene that needs very little headroom, I may shoot with only 1 stop between 18% gray and clipping and then reducing brightness in post (not canned processing), then that would fit the first type of correct exposure.
noirdesir said:
With digital, in particular, raw photography, assuming canned processing is like tying on arm behind your back.
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You are assuming that the photographer strives only to achieve "correct exposure". If they were, then they would definitely be tying one arm behind their back. But that is not necessarily the case.

For example, one may define the lawfully correct speed limit as 55 MPH and yet still choose to drive 70 MPH anyway. Similarly, one may define correct exposure according to some certain arbitrary standard and yet not use it in chosing exposure. For example, I don't see any problem with either of these statements:
  • My meter told me that f/8 was the correct exposure, but I deliberately underexposed to f/16 because I wanted more headroom than the meter is programmed for.
  • My meter told me f/8, but the correct exposure was f/16, because f/16 gave me the headroom that I needed.
noirdesir said:
Why do still so many people assumed canned processing when thinking about exposure?
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I blame film. People are still learning methods (e.g. exposure triangle) that went obsolete when film died. Drives me nuts to see ISO 12800 shots with tons of blown highlights that would have looked fantastic at ISO 3200 with non-canned processing (e.g. +2 stops nonlinear digital gain).
noirdesir said:
It is like riding a bike with multiple gears but only using the middle one because twenty years ago when you learned riding a bike, it did not have any gears.
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Agreed.
--
Daniel
 
Member said:
If your photo comes out as a perfect black rectangle, and that's how you visualized it and intended it, then that's the correct exposure...
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Well, that's it, isn't it? GB's images are exposed 'correctly' for the subjects, and he lets the highlights blow out, which is a perfectly reasonable artistic choice... don't they call it 'high key' in fashion work? To me, same as the above post, a correct exposure is if you get what you wanted to get...
 
Daniel Browning said:
noirdesir said:
Daniel Browning said:
I can think of two general types of "correct exposure": one is the exposure that achieves the subjective creative goals you intended, and the other is one that follows a sort of technical correctness (e.g. 18% percent gray is such-and-such digital value in the resulting JPEG).
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Both these types assume canned processing.
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No, only the second type does.
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Apologies for assuming incorrectly what you meant.
Daniel Browning said:
Similarly, one may define correct exposure according to some certain arbitrary standard and yet not use it in chosing exposure. For example, I don't see any problem with either of these statements:
  • My meter told me that f/8 was the correct exposure, but I deliberately underexposed to f/16 because I wanted more headroom than the meter is programmed for.
  • My meter told me f/8, but the correct exposure was f/16, because f/16 gave me the headroom that I needed.
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Generally, I would use the term 'better exposure' for such situations. Our evaluation of headroom is rarely very precise. I would say f/16 was a better exposure because it gave me a headroom that was much closer to what I needed. But that is splitting semantic hairs.
Daniel Browning said:
Daniel Browning said:
Why do still so many people assumed canned processing when thinking about exposure?
Click to expand...
I blame film. People are still learning methods (e.g. exposure triangle) that went obsolete when film died. Drives me nuts to see ISO 12800 shots with tons of blown highlights that would have looked fantastic at ISO 3200 with non-canned processing (e.g. +2 stops nonlinear digital gain).
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I grew up with film and did not fully realise what ISO meant in the digital world until a few years ago when I learned about it here in these forums. But once you think about it, it is very easy to adjust your mind to it. It has made exposure so much easier in artificial light, don't worry about precise exposure anymore, worry more about f-stop and shutter speed.
 
all the JPEGs you require for any normal HDR exercise,
again, it's a post exposure thing.

--

 
Daniel Browning said:
Great Bustard said:
How is the other "technically correct "?
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By conforming to whatever arbitrary standard that it is correct for.

For example, f/8 might conform to the manufacturer's idea of correct exposure for a certain analog gain, raw converter, and settings, while the exposure I chose may be two stops over (or under) that, to achieve whatever goals I had in mind (less noise, more headroom, etc.)
Click to expand...
But does it makes sense to use the word "correct" to refer to an arbitrary standard? I understand what you're saying, but unless the term "correct exposure" is well-defined somewhere, I'm thinking it's just sloppy language that leads to a very poor understanding of what exposure is.
 
Great Bustard said:
But does it makes sense to use the word "correct" to refer to an arbitrary standard? I understand what you're saying, but unless the term "correct exposure" is well-defined somewhere, I'm thinking it's just sloppy language that leads to a very poor understanding of what exposure is.
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I agree -- it is pretty sloppy and does contribute to misunderstandings. Personally I can't think of any field or endeavor with more common misconceptions than photography. Scientology, perhaps.
--
Daniel
 
Great Bustard said:
Daniel Browning said:
Great Bustard said:
How is the other "technically correct "?
Click to expand...
By conforming to whatever arbitrary standard that it is correct for.

For example, f/8 might conform to the manufacturer's idea of correct exposure for a certain analog gain, raw converter, and settings, while the exposure I chose may be two stops over (or under) that, to achieve whatever goals I had in mind (less noise, more headroom, etc.)
Click to expand...
But does it makes sense to use the word "correct" to refer to an arbitrary standard? I understand what you're saying, but unless the term "correct exposure" is well-defined somewhere, I'm thinking it's just sloppy language that leads to a very poor understanding of what exposure is.
Click to expand...
To borrow from the jargon of some more rigorous disciplines, a more apt terminology might be 'canonical exposure'.

--
emil
--



http://theory.uchicago.edu/~ejm/pix/20d/
 
'correct exposure' means that it captures what you want to capture - I choose to use Bryan Peterson's definition, as opposed to some arbitrary clinical 'correct' - there are a number of 'technically correct' exposures for each situation, but only one or two that capture what your eye sees... to my eyes, on my calibrated MacBook, your samples are 'creatively correct' - they show and capture what YOU were looking to capture.

yes, this is a philisophical subject...

cheers,
S.
--
beam me up captain, there's no intelligent life down here!
 
ejmartin said:
Great Bustard said:
Daniel Browning said:
Great Bustard said:
How is the other "technically correct "?
Click to expand...
By conforming to whatever arbitrary standard that it is correct for.

For example, f/8 might conform to the manufacturer's idea of correct exposure for a certain analog gain, raw converter, and settings, while the exposure I chose may be two stops over (or under) that, to achieve whatever goals I had in mind (less noise, more headroom, etc.)
Click to expand...
But does it makes sense to use the word "correct" to refer to an arbitrary standard? I understand what you're saying, but unless the term "correct exposure" is well-defined somewhere, I'm thinking it's just sloppy language that leads to a very poor understanding of what exposure is.
Click to expand...
To borrow from the jargon of some more rigorous disciplines, a more apt terminology might be 'canonical exposure'.
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that would cause problems with all the nikonical, pentaxical, sonycal and olympusical folk :).

Edit: the one I tend to use when referring to the exposure defined in the ISO EI standards (or in the case of REI, not defined) is 'nominal exposure'.
--
Bob
 
Daniel Browning said:
Great Bustard said:
But does it makes sense to use the word "correct" to refer to an arbitrary standard? I understand what you're saying, but unless the term "correct exposure" is well-defined somewhere, I'm thinking it's just sloppy language that leads to a very poor understanding of what exposure is.
Click to expand...
I agree -- it is pretty sloppy and does contribute to misunderstandings. Personally I can't think of any field or endeavor with more common misconceptions than photography. Scientology, perhaps.
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As you should be well aware, "correct exposure" will offset the negative energy of the thetans and is The Way to Happiness. Unfortunately, the 20% of us who are suppresive persons interfere with the social personalities who maintain and promote the objective nature of "correct exposure".

You should mind what you say before you are called by the Ministry of Love for some of the doubleplus good electroshock. Oh my! Now see what you've made me do? I've gone and switched metaphors with no apparent reason! ;)
 
well, the easiest way to put it is that the term "correct exposure" is simply relative. it's relative to the scene you want to capture and it's relative to the photographer's idea of how he is planning to capture that scene.
 
absentaneous said:
well, the easiest way to put it is that the term "correct exposure" is simply relative. it's relative to the scene you want to capture and it's relative to the photographer's idea of how he is planning to capture that scene.
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Correct, and interestingly enough it is also scientifically relative, because of adaptation and how our psycho-visual system works. That's why when shooting raw it is not important to have an absolute correspondence between luminance at the scene and a specific recorded raw value. Leaving artistic considerations aside for a moment, what is important on the other hand is that there is a relative correspondence between DR/TR we can perceive at the scene (1), DR/TR the camera is able to record (2) and DR/TR we can display after PP (3).

So set up (2) to record the most relative information possible in (1) and adjust (3) to taste.

Jack
 
noirdesir said:
FrankyM said:
Correct exposure is when mid grey in the image is exactly where the photographer wants it to be.
Click to expand...
Assuming canned processing (eg, cellphone camera), otherwise mid grey is where it is placed in processing (of course, if you want to preserve detail in the mid grey of scene, you create an exposure range that allows that).
Click to expand...
I must admit I have some difficulty in understanding you. However, let me explain. It has nothing to do with processing being 'canned' or not. Exposure is correct when mid grey is where the photographer wants it to be.

Post processing allows you some latitude to adjust, which I suppose is what you're trying to explain with preserving detail on the mid grey. However, that latitude is limited and so it comes back to what has always been true - i.e. exposure is correct when mid grey is where the photographer wants it to be.
 
Much of the time that the phrase "correct exposure" is used, it would be better replaced by "optimal exposure", but of course, what is assumed to be correct exposure may not even be optimal. "Correct exposure" is only meaningful when your goal is to meet a certain exposure standard, such as shooting a grey card at ISO 100 with a certain amount of light falling on the sensor sandwich (or other interceptor, such as a semi-transparent mirror) per unit of sensor area.

We could use "correct exposure" when talking about ISO performance comparisons, such as those used by DPReview, Imaging-Resource, and DxOMark. When one camera gets 1/500s for a test at an ISO, and the same scene and lighting gets 1/640 with another camera, we can then say that at least one of them was not exposed correctly (correctly only in terms of our standard).

--
John

 
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