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04-03-2013, 04:35 AM   #1
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Any difference between exposure when shot or in PP

Question assumes I am shooting RAW. Is there any difference in getting the exposure right when you take the picture versus modifying it in PP (e.g. Lightroom) afterwards?

For example, say I want to shoot at low ISO but for my desired aperture or shutter speed the pic would be quite dark. Am I doing anything wrong by just taking a dark picture and then using Lightroom to increase the exposure? Would I actually end up with a better quality image then if I used higher ISO? Or is there some reason why you really need to focus on getting the right exposure when you take the picture.

Sorry if I've got some of the terminology wrong but hopefully my question will make sense to someone... This is all just part of me trying to figure out what stuff I really must get right when I take the picture, versus stuff that can be fixed afterwards if need be.

04-03-2013, 05:33 AM   #2
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FWIW, I think it's better to err on underexposed since it's easier to recover dark areas than blown highlights. Ideally, you should be able to get close to perfect exposures if you watch your settings.
For me, shutter speed is high priority when in the field, since you don't want blurred subjects. Then it's aperture, to keep a good DOF and third is ISO since the K-5 gives a pretty broad usable range.
04-03-2013, 05:38 AM   #3
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As long as your photo is at low iso, it won't be too much problem to bring it up a stop or two in post. If you are working at high iso, exposing to the right is helpful, even on a camera like the K5 -- iso 3200 is kind of my max, but I don't see a big difference between shooting at iso 3200 and under exposing a couple of stops and then shooting at iso 800 and bringing it up in post -- noise levels are pretty similar either way.
04-03-2013, 06:56 AM   #4
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When you say "exposing to the right" do you mean over exposing? Why is this useful for high ISO scenarios? If high ISO means you are over exposing, wouldn't you be better using lower ISO? Just trying to learn what you mean as this is all a bit new to me. I have always seen ISO as something you want to be as low as you can get away with to get your desired shutter speed or aperture.

04-03-2013, 08:00 AM - 1 Like   #5
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QuoteOriginally posted by thechumpen Quote
Is there any difference in getting the exposure right when you take the picture versus modifying it in PP (e.g. Lightroom) afterwards?
There are two senses of the word "exposure":

1. Visual exposure - when the final image appears, more less, to match the naked eye's perception of the original scene's light level.
2. What I call, for the lack of a better word, "Data Exposure". That is the level of exposure that is optimal for capturing the maximum amount of editable data.

For myself I always shot RAW and ETTR. ETTR is simply always pushing the right side of the hgram to the very limits of the sensor and letting the shadows fall where they may. This is exposure in the second sense. Then later in PP I worry about getting a proper visual exposure.

So to answer your question - yes there is a big difference. In one you are trying to expose for a final visual image right out of the camera and in the other you are exposing in order to give your PP software maximum optimal data to work with at the back end of the process.

I hope this makes some sense - it's still early in the day for me.

Last edited by wildman; 04-03-2013 at 08:22 AM.
04-03-2013, 08:21 AM   #6
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Thanks Wildman. It is the second option I am interested in learning more about. I have done some wikipedia'ing and understand it much more now. Interesting as I thought you were best doing the exact opposite and under exposing more so that you don't blow your highlights.

What is the correct technique for this then? E.g. could you use AV mode and just set exposure compensation to the right or do you ideally need to be using manual mode for this technique?
04-03-2013, 08:25 AM   #7
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Look at your curve and keep turning the EV setting more and more negative until you have a no exposure at the right side of the curve. In some circumstances it will be -3 EV.
04-03-2013, 08:37 AM   #8
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QuoteOriginally posted by thechumpen Quote
When you say "exposing to the right" do you mean over exposing?
Over exposing = losing detail.
ETTR = maximizing detail.

Big difference.

04-03-2013, 08:47 AM   #9
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QuoteOriginally posted by wildman Quote
There are two senses of the word "exposure":

1. Visual exposure - when the final image appears, more less, to match the naked eye's perception of the original scene's light level.
2. What I call, for the lack of a better word, "Data Exposure". That is the level of exposure that is optimal for capturing the maximum amount of editable data.

For myself I always shot RAW and ETTR. ETTR is simply always pushing the right side of the hgram to the very limits of the sensor and letting the shadows fall where they may. This is exposure in the second sense. Then later in PP I worry about getting a proper visual exposure.

So to answer your question - yes there is a big difference. In one you are trying to expose for a final visual image right out of the camera and in the other you are exposing in order to give your PP software maximum optimal data to work with at the back end of the process.

I hope this makes some sense - it's still early in the day for me.
Wildman, I know about ETTR but havent practiced it. This explanation is very good. I like the "Data exposure" concept to name it somehow.

Here is another doubt: Suppose I am using the biggest aperture available (f/2.8) and my shutter speed is limited to 1/60 to avoid blur. For an indoor shot, this happens often with my A24/2.8 or F28/2.8. My F50 goes down to f/1.7 but it lacks wideness.
Back to the excercise: my only choice to ETTR is to increase the ISO. if I am using ISO 400 to achieve a "Visual Exposure" is it ok to increase to ISO 1600 (taking care no or minimal highlights are blown) to achieve "Data Exposure"?

Am I not loosing Dynamic range? Adding noise? Will there be more data available for PP anyway?
04-03-2013, 08:47 AM   #10
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OK, I'm confused now so maybe I am misunderstanding. Norm, you seem to be suggesting I turn to the left to "under expose" slightly. Wildman seems to be suggesting turning to the right to "over expose" slightly (all within limits of course).
04-03-2013, 09:10 AM - 1 Like   #11
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The sensor has one base ISO and all the other values involve some analog or digital amplification. When you move the exposure slider in Lightroom, it's digital amplification. I have read a few discussions about where the camera uses analog amplification and where it uses digital. They always turned into an academic argument - they were talking about math and histograms but no photos. I'm not sure who was right, but I suspect if I really wanted to know, it would be easier to set up a test scene, take a few shots and see what you get.

I find it is easier to have one shooting habit because you have other things to think about when shooting. I do what Wildman does, expose just short of getting blinking highlights (overexposed areas). Sometimes those brightest areas are unimportant, so I can raise exposure even further. (I am careful about overexposing pure reds and blues in my main subject, like in a flower shot. The camera meter can be fooled here. Look at the RGB histogram if you are not sure.) Then I have enough information to process the shot. I do it all the time even when it isn't an important shot.

If I start to need higher ISOs, I worry a lot less about using the lens at its sharpest aperture. I would rather have a shot at f4 and ISO 800 than f8 and ISO 3200.

Shutter speed is one reason to break the habit. You may have a situation where you need a minimum shutter speed to capture a moving subject. In that case, I would consider taking an underexposed shot with that minimum shutter speed and increasing exposure later in processing.
04-03-2013, 09:58 AM - 1 Like   #12
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Increasing ISO will always increase the overall noise and decrease the dynamic range; the actual amount will depend on the sensor. Increasing the exposure in PP will also increase the noise, especially in the dark areas where noise is more visible. Depending on the situation and especially the kind of de-noise techniques used, either one can produce good results. The best way is to experiment and compare the final images, remembering that in most cases a correct in-camera exposure will probably be better in close scrutiny.

Noise is one of several parameters in an image, that include dynamic range, overall brightness, motion blur, depth of field, etc. Taking a photograph is a balancing act on desired final image, e.g. stopping motion, blurring motion, maximizing DOF, intentionally over/under exposing, etc.

In a controlled environment (e.g. studio) you simply set the proper parameters (aperture, speed, ISO) for the desired effect and adjust your lighting for correct exposure. In uncontrolled environments, you have to compromise some of the variables, like loosing DOF to get more speed, increasing noise (using a higher ISO) to get both speed and DOF, etc. Which one is right will depend on what is more important for the particular image.

Modern DSLR capture 12 or 14 bit data that theoretically can provide 12 or 14 stops of dynamic range. If a scene has less than that, exposing to the right, essentially slightly overexposing without blowing the highlights, gives you some insurance that you can correct the exposure if need with less visible effects, since in most cases you will be decreasing it and with it decreasing the noise also.
04-04-2013, 06:41 AM   #13
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QuoteOriginally posted by demp10 Quote
Increasing ISO will always increase the overall noise and decrease the dynamic range; the actual amount will depend on the sensor. Increasing the exposure in PP will also increase the noise, especially in the dark areas where noise is more visible. Depending on the situation and especially the kind of de-noise techniques used, either one can produce good results. The best way is to experiment and compare the final images, remembering that in most cases a correct in-camera exposure will probably be better in close scrutiny.

Noise is one of several parameters in an image, that include dynamic range, overall brightness, motion blur, depth of field, etc. Taking a photograph is a balancing act on desired final image, e.g. stopping motion, blurring motion, maximizing DOF, intentionally over/under exposing, etc.

In a controlled environment (e.g. studio) you simply set the proper parameters (aperture, speed, ISO) for the desired effect and adjust your lighting for correct exposure. In uncontrolled environments, you have to compromise some of the variables, like loosing DOF to get more speed, increasing noise (using a higher ISO) to get both speed and DOF, etc. Which one is right will depend on what is more important for the particular image.

Modern DSLR capture 12 or 14 bit data that theoretically can provide 12 or 14 stops of dynamic range. If a scene has less than that, exposing to the right, essentially slightly overexposing without blowing the highlights, gives you some insurance that you can correct the exposure if need with less visible effects, since in most cases you will be decreasing it and with it decreasing the noise also.
Thanks, this makes it pretty clear. I did some more digging and found this interesting article: ChromaSoft: Why "Expose to the Right" is just plain wrong
Basically, ETTR will only show a noise advantage when shooting at base ISO and with disadvantages regarding color shift.
Copy-paste conclusions:


QuoteQuote:
1. There is no advantage to image quality from ETTR that can't be duplicated by selecting a lower ISO, if a lower ISO setting is available. In some situations, such as where there is in-camera noise reduction, ETTR actually increases noise. That's what the practical tests show, and the theory of the case confirms the practical results to be correct.
2. The only situation where there is an advantage to ETTR is if you're already at the lowest ISO setting your camera, and you use ETTR to synthesize a lower ISO. However, given the noise performance of most modern cameras, that advantage is often very small. The test I did here - a small sensor high pixel count camera - is the best possible scenario for seeing an improvement. Using a modern DSLR, the improvement would be marginal at best.
3. Any kind of ETTR brings significant disadvantages in the shape of color and tone curve shifts that will have to be repaired in post processing. While these shifts are small, they are easily the equivalent in effect of changing profiles. So, in effect, ETTR negates the advantages that modern raw developers such as Lightroom bring with them.
Bottom line - ETTR offers improved image quality in only one specific situation - where you can use a lower ISO setting than your camera has. In all other situations, ETTR will only ever decrease image quality.

Update : see my later post here as well, as well as the subsequent two ETTR posts, the last one of which adds another situation in which ETTR may be useful. For some cameras, if you're willing to overexpose by four (yes four!) stops.
04-04-2013, 11:30 AM - 1 Like   #14
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QuoteOriginally posted by carrrlangas Quote
Thanks, this makes it pretty clear.
Have a look at this and make up your own mind about what would work best for you:

Digital Exposure Techniques
04-04-2013, 05:00 PM   #15
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QuoteOriginally posted by wildman Quote
Have a look at this and make up your own mind about what would work best for you:

Digital Exposure Techniques
Haha, that is my "go to" guide when in doubt. I was already reading it.

So, in the end, it depends on the situation, what you want to achieve, personal workflow.
Thanks again
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