Under what situations would you purposely underexpose a photo?

[Brownbear]

In most cases, I usually up the exposure compensation in my photos. However, I think I have deliberately underexposed photos of white birds and ended up using center or spot metering to get around problems with over exposure in parts of the photo.

I've also used it in landscape shots with white fences and in sunset shots, but again just adjusting after viewing in the view finder.

That said, I just realized that I should know more about this, so my question(s) is (are)..

Why and in what situations (or for what purposes) would you deliberately underexpose a photo using exposure compensation?

How does matrix, center and spot metering come into play in this situation?


Thank you

[Geoff F]

I regularly underexpose my photos whenever there are bright areas which risk over exposure.

Evaluative (matrix) metering works well on fairly large general areas but there are often important spots which will be missed so they become over exposed. Or under exposed.

Centre metering, in various forms, can occasionally be useful but I tend to find this is neither one thing nor the other.

Spot metering can work well but you need to use it carefully and think about the scene. I often spot meter around a scene to locate any potential hot spots and notice the exposure readings.

Then I calculate my actual settings based on these readings.

But I usually switch to manual before actually shooting.

Using centre or spot metering can cause problems if you are using any form of meter and recompose methods because the reading can change when you recompose.

For example, select and hold the focus (pressing the shutter button halfway) then recompose the scene. But the exposure can change and you don't notice it.

Another case where I meter then go manual.

[Mike Buckley]

I'm confused about your terminology, Christina. Using the exposure compensation button to a value lower than zero doesn't necessarily mean that you are underexposing the scene. So, are you asking when to underexpose the scene or when to adjust the exposure compensation to a value that is lower than zero?

[Brownbear]

Why does everything have to be so complicated? Thank you Geoff, much appreciated. I will print and study and keep learning.

[Brownbear]

I guess, I'm confused too. I am speaking about adjusting the exposure compensation, in most cases to get the right exposure, by decreasing the exposure. But in the case of sunsets, I would mean deliberately underexposing the photo to enhance the colours. So I guess, I'm asking both.

Thank you.

[Mike Buckley]

I am speaking about adjusting the exposure compensation, in most cases to get the right exposure, by decreasing the exposure.

I have a very simplistic approach to this. I always check the histogram and/or the blinkies after shooting. If either indicates substantially lost highlights, I adjust the exposure compensation. If I'm shooting something that doesn't allow me to reshoot it after checking that stuff, I use my best judgement and try to err on the side of underexposure. That's because underexposure can be compensated for during post-processing whereas lost highlights can be lost forever.

But in the case of sunsets, I would mean deliberately underexposing the photo to enhance the colours.

I don't shoot sunsets enough to comment about that.

However, if I see a scene that I want to capture as a low-key image (defined as mostly mid-tones and dark tones with relatively little contrast), I would deliberately underexpose in the sense that the histogram would indicate underexposure.

I almost always use matrix metering. That's because I would be so bad at using spot metering that I would have to adjust every single exposure after taking the first shot. I occasionally use center-weighted metering but only when I'm dealing with some backlighting that I don't want the meter to take into account. So, my choice of metering doesn't have anything to do with how I want the exposure to be.

[Manfred M]

Carefully said Christine, I wouldn't call using exposure compensation as either over or under-exposure; but rather correct exposure. The light meter in your camera will be fooled by a very dark (night - camera tends to lighten things up too much) or very light (snow or white sand on the beach - camera tends to darken the shot) scene, so your exposure compensation will actually give you the "correct" exposure. In those cases, I will increase / decrease my exposure as required to get a correctly exposed image, based on my read of the histogram or the "blinkies" where I have blown out highlights.

I tend to only use matrix and spot metering. Centre-weighted metering is really a fairly ancient technology that has been built into cameras for decades; I really think it is just there for some old-timers that grew up with it and haven't made the leap to a more sophisticated metering mode. I can't think of a single case where I would use it, rather than matrix metering. Spot metering is something I will use in unusual lighting situations, but will almost always use the meter readings to set up manual exposures and will tweak and bracket as required. I also use a hand-held incident light / flash meter for some of my shooting, especially for portraits and flash work.

[Shadowman]

1. Daylight photos.
2. When the light source is in the image.
3. Daylight portraits.
4. Some night photography, brightly lit strore front.
5. Astrophotography.
6. Too make colors pop.

[Brownbear]

Thank you Mike and Manfred. Truly helpful and appreciated.

Mike would you have a sample of a low key image that you could post for me to see?

I was under the impression from my readings that Center weighted meter is generally used for portrait shots of people and birds, etc, and that spot metering would be used for insects ie; macro shots? An oversimplified generalization?

[Brownbear]

1. Daylight photos.
2. When the light source is in the image.
3. Daylight portraits.
4. Some night photography, brightly lit strore front.
5. Astrophotography.
6. Too make colors pop.

Thank you John... Can you clarify #2 for me?

[tclune]

A classic way to understand when you would intentionally use +/- EV is through the zone system. There is a very nice simple discussion of it here: http://www.luminous-landscape.com/tu...e_system.shtml FWIW

[Brownbear]

Thank you Tom

[Dave Humphries]

There are a lot of good replies above Christina,

Why and in what situations (or for what purposes) would you deliberately underexpose a photo using exposure compensation?

How does matrix, center and spot metering come into play in this situation?

I was under the impression from my readings that Center weighted meter is generally used for portrait shots of people and birds, etc, and that spot metering would be used for insects i.e.; macro shots? An oversimplified generalization?

Possibly - I think it is important to separate the different issues at play.
As I see it, the metering method is not directly relevant to getting correct exposure!

To help you separate these two things, let's try an analogy;
Think of two builders; to comply with statutory 'building regulations', they each build houses with a standard ceiling height and a standard light switch height.
One builder always measures the light switch from the floor up, the other from the ceiling down, they are two different measurements, and yet both builders do comply with the regulations, they just approach it from a different direction! It isn't a perfect analogy, but I hope it helps.


A given 'correct' exposure can be arrived by many means;

matrix metering
average metering
spot metering
centre weighted metering
separate ambient light metering
or even guessing

Usually we'll apply an offset to the meter reading, based on experience and/or chimping the histogram and blinkies, using + or - EC, to get the 'correct' exposure.
Which way that is, + or -, depends upon the tones of the subject, background tones and the relative size of the subject in the frame and which metering method we're using.

Which suits me (or you) depends upon the subject, my/our experience of shooting that subject, etc. - but ultimately, it is no more than personal preference for many of us. It is whichever way allows us to quickly mentally re-assess the scene when it changes and apply an appropriate amount of EC to capture it with the 'correct' exposure. Shall we measure up or down to get the switch in the correct place?

... and what is that 'correct' exposure?

Well that depends upon the subject;
if you shoot a scene, say a pale skinned model, and "expose to the right" (ETTR) so the brightest tone in the shot is pushing the blinkies (i.e. you make it 'white' as far as the camera is concerned), you're very likely to need to reduce the exposure in PP to make it look right and that may not even be possible because if you were too far to the right (of the histogram), you'll have gone into the non-linear part of the sensor's photo-receptors.

This is a prime example of when you might say you would be 'under exposing', but you're not really, you are getting the correct exposure. To further complicate things, depending which metering mode you were using, that absolute exposure might have been achieved with either + or - EC on what the meter said.

I will try to shoot some example pictures to demonstrate what I mean, as this is a question that arises quite often and it'll be useful to have some.

I hope that helps, rather than confuses,

[Brownbear]

Thank you.. Very helpful, as is every single reply to my posting. I'm still learning so sometimes it takes a while for me to digest all the terminology. Cambridge is a wonderful learning tool. Thank you everyone.

[Mike Buckley]

Low-key and high-key photographs (understanding one will make it easier to understand the other) can be seen here

For me, the epitome of a low-key or a high-key image is one that has little contrast. The CiC tutorials don't address contrast or lack of it in their definition of low-key or high-key. If you're willing to accept their definition, they do provide a good discussion of the two types of photography

[Dave Humphries]

For me, the epitome of a low-key or a high-key image is one that has little contrast.

I'm not sure I agree with that Mike, but I'm equally not sure it came out the way you intended.

For me the epitome would be a picture where say > 95% of the area of an image has tones in the image were below a certain low level, or above a certain high level, so the histogram would be predominantly on the left or the right, but I do think that such images need a good contrast range, so the remaining 5% of pixels will be at the other end of the histogram. Think of a high key portrait; we'd still expect the pupils of to be a good black, not a wishy-washy light grey

Looking at the examples in the first link you gave, only the rose really matches what you said, the rest do have small areas of good white or black tones in them.

I have to say that while the histograms in the CiC tutorial sort of demonstrate what I mean (above), I have seen better example images of these genres.

Still friends?

Cheers,

[revi]

I'm not sure I agree with that Mike, but I'm equally not sure it came out the way you intended.

For me the epitome would be a picture where say > 95% of the area of an image has tones in the image were below a certain low level, or above a certain high level, so the histogram would be predominantly on the left or the right, but I do think that such images need a good contrast range, so the remaining 5% of pixels will be at the other end of the histogram. Think of a high key portrait; we'd still expect the pupils of to be a good black, not a wishy-washy light grey
(...)

I think that that expectation is why we want some blacks in certain high-key images: we 'know' that certain objects are always black (like eye pupils). As there are no such zones in the
rose image, the absence of black there is accepted. Vice-versa, we expect high-lights to be light, so low-key that's only dark grays look under-exposed.

[Inkanyezi]

I cannot remember any instance of under-exposing on purpose, as I always try to get it right. However, many people refer to exposure compensation as under- or over-exposure, which is incorrect. And by the way, I never shot a sunset.

My photography teacher in school was an artist, painter and sculptor, and the first thing we had to learn was the zone system, and still I think in terms of the zone system, even though it is applied somewhat differently in digital than back in film age. When I visualise and evaluate a scene, I subconsciously place the various areas of it in zones according to the zone system, keeping in mind that important highlight tones should not be blown. Only at very rare occasions would I use spot metering, to make sure that I don't blow highlights. In those cases I use spot metering with +2 compensation for the highlight where I wish to keep structure. This is a tried-out value for my camera and the way I process, yours might be different.

Usually I use integrated measurement and apply compensation according to the scene. For a scene with much snow in it, compensation of +1 often is my choice for the first shot, which I then evaluate in the histogram to see if compensation should be tweaked a bit. If most of the tones of the scene are very dark, I apply minus compensation. Chimping with highlight blinkies will tell me whether my compensation was correct, so I can change it for subsequent shots. Mostly I allow blinkies at minute areas.

My definition of under-exposure is when there is important detail in dark areas that won't come out, and the histogram piles up to the left side with a substantial part of the right side flat at the bottom. In such a case, I would adjust compensation in the plus direction to get more shadow detail, even if the scene is very dark.

Ideally both ends of a histogram should slope down to the baseline, which should be met very close to the lower corners each side, but the left side is not as important in this regard as the right. The right side of the histogram usually should not have a substantial portion to the right flat at the bottom, unless there are small highlight areas that won't appear in the histogram, which should not be blown. I never pay much attention to the left side of the histogram, but I check the right side and blinkies when I evaluate my exposure. The real time histogram and highlight blinkies in cameras that read the image from the sensor is a very valuable tool for checking exposure before shooting.

So in essence, I always try to get my exposure right from start, and I often use the histogram and blinkies in real time to get it right. I have more than one camera, and they are different, so the approach with one that does not have real time histogram is to guesstimate compensation and check afterwards, or at rare occasions use spot metering with compensation, usually taking a highlight with +2 compensation.

[Shadowman]

Thank you John... Can you clarify #2 for me?

Hi Christina,

If I have either a reflection or the actual source, such as the sun or a bald light bulb, in the image i would underexpose to reduce the flair from the source.

[GiacomoD]

A classic way to understand when you would intentionally use +/- EV is through the zone system. There is a very nice simple discussion of it here: http://www.luminous-landscape.com/tu...e_system.shtml FWIW

Thanks Tom, a very interesting and useful link.

It looks to me that the zone system provides a quite clear procedure to evaluate the major elements of a composition and their contribution to the final "as more as possible" correct exposure. I think it is an excellent learning tool for training our eyes to read and interprete the reflected light.