Using an automatic exposure camera is pretty cool most of the time. You can play with composition and not really worry about if the image will be exposed correctly.
There are some situations however, when the auto settings just don’t quite work to get the image you want. The first two are the most common;
1. Dark subject with a bright background.
2. Bright subject with a dark background.
In the first case, the camera sees a LOT of light and adjusts the exposure such that the dark subject is a featureless silhouette against a drab background.
The second case the camera sees very little light and adjusts the exposure such that the subject is a featureless bright blob against a drab background.
Some cameras are pretty smart, so they decide to “fix” the situation for you. If your auto camera does this then you should still read this, because even though the camera may know how to fix this, it cannot know what you really wanted to do. Maybe you really wanted a dark silhouette. 🙂
You should take some test shots to see if you have a smart camera, or a dumb camera.
If you have a dumb camera, then what you need to do to fix the first case, is tell the camera that you want it to increase the amount of light it records by setting the EV higher than zero. Most auto cameras let you adjust the EV setting to +2 in 1/2 increments.
In the second case, adjust the EV setting down to below zero, again most cameras let you set the EV to -2 in 1/2 increments. This decreases the amount of light your camera records.
In the old days with film cameras using manual settings, we could adjust the aperture and shutter speed to control exposure. If we had a scene with a dark subject and a bright background, with the camera telling us to use f8 aperture and 250 shutter speed, we could adjust the aperture to f5.6, and the shutter to 125, (=EV +2).
I want to note here, that all this fiddling around has NOTHING to do with focus or zoom, those are used for composition, NOT exposure.
So, what if you have a smart camera that “fixes” this for you, and you don’t WANT it to fix it??
You want a silhouette, but the camera gives you detail. In this case, you decrease the EV setting.
If you have a camera that allows you full manual control of aperture and shutter speed, then don’t bother trying to mess with EV settings, change either or both of the aperture and shutter settings to increase or decrease the light you are recording.
Here is the strange part. To INCREASE light, LOWER the setting. I really think they did this on purpose, because they did not want just anyone to be able to take good photographs!
If your camera tells you that correct exposure is f8 and 250, and you want to BRIGHTEN your subject, then decrease the setting, Use f5.6, or set 125, or both. To DARKEN your subject, you can increase the aperture to f11, or shutter to 500 or both.
Now here is where the shutter speed and the aperture can affect composition.
Lets assume, for a moment that you want a picture of a flower, fairly close up picture. You set up the camera on a tripod and the camera tells you a correct expose would be f16 with a shutter speed of 60. You do not have a bright background, or a dark background, so the exposure will be good just as it is.
You take the picture and download it on your huge monitor, and it really looks good, ahh, wait, you did not notice that one petal that is somewhat wilted, and kinda makes the whole thing look bad.
If you could make that one petal out of focus, no one would notice that it is wilted and you would be happy with the picture. Sooo, you set up everything again, and try to adjust the focus, but find that if you adjust the focus, such that the wilt is not noticeable, then the parts you want in focus are not.
ARRGGHH.
What you need to do is adjust the depth of focus! If you could change the length of good focus, then you could have the wilt out of focus, while keeping the rest of the flower in good focus!
YOU CAN DO THAT!! Yep, because changing the aperture changes the DEPTH OF FOCUS!
If you increase the aperture setting from f11 to f22 you INCREASE the depth of focus, and if you decrease the aperture setting you DECREASE the depth of focus. That is what you wanted to do, right?
Now, you know that you can defocus that wilted petal, by decreasing the aperture setting. OOPS, if you change the aperture, you also mess up your perfect exposure! The cool part is that you have TWO settings that control exposure, if you decrease one, you can simply increase the other!
If you decrease the aperture setting by 2 clicks from f11 to f5.6, then INCREASE the shutter setting two clicks from 60 to 250. Remember that those settings control the amount of light, they BOTH control the same amount of light. So if you change one, to keep the same exposure, change the other one in the opposite way!
Let’s try a different picture, a child riding a bicycle past you. The amount of light is the same as your flower picture, so you know that f11 and 60 will give you a good exposure. You snap the picture and then go look at it on your huge screen. Oh NOOO, the picture is all blurry!
Well, maybe you moved the camera, so you set up the tripod and ask the kid to ride by again, he does, you snap, and oh no, it’s STILL blurry. The kid is just too fast!
It sure would be nice if you could somehow freeze time. Well, guess what? You CAN!!
You can adjust the shutter speed, such that the light does not have time to get jumbled up in the camera, you can change that shutter speed, from 60, to 250, or 500! Remember that now you have to DECREASE the aperture setting to get correct exposure. From 60 to 125 is one click, then to 250 is another click. That is two clicks, (or stops as the professionals say), from 60 to 250, so you need to decrease the aperture 2 stops, from f11, to f8, and then to f5.6! Poof your exposure is correct, and now that kid is not fast enough to blur!
For good pictures, you need good exposure settings, (even if the camera thinks it knows what it’s doing, it prolly does NOT know what YOU want to do!), and good composition.
People find it easy to understand that composition is the creative aspect of photography and they may not want to deal with the technical aspects of exposure. However, controlling exposure can change the mood of an image, and being able to choose what area of focus is displayed, and being able to control motion blur are all creative tools that allow you, the artist to create not just a snapshot, but a stunning, provocative image!
I wrote this for my Niece Rachel, because she has my Ricoh film camera that has NO auto settings at all!! LOL.
Hugz, 45 Mike
ps, There are only two factors that affect depth of field, focus distance and aperture.
AND I know that some purists will claim, correctly, that depth of focus is not the correct term. Yep, so what. It makes sense to the person reading an intro to basic concepts.