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Arriving at the best exposure for a photo is part science and part art. In Foundations of Photography: Exposure, Ben Long helps photographers expand their artistic options by giving them a deep understanding of shutter speed, aperture, ISO, and all other critical exposure practices. This course covers the basic exposure controls provided by all digital SLR cameras, as well as most advanced point-and-shoot models. Learn how to master a camera's metering modes, how to use exposure compensation and bracketing, and much more. By the end of the course, you'll know how to develop an "exposure strategy" that will allow you to effectively employ your exposure knowledge in any shooting situation.
We are going to harken back now to those wonderful days of yesteryear when men were men and women were women, and photographers didn't have light meters. Now, think about that. Not having a light meter, everything we have done so far in our exposure exercises has been built around the automatic light meter in our cameras. We half-press the shutter button; the camera meters the scene for us and tells us a shutter speed and aperture. What would you do if your camera wasn't doing that for you? Well, you can find out, and you can play with it yourself, and have this wonderful anachronistic feeling of shooting the way people used to shoot.
But doing this is also a really great way to go a little bit deeper into exposure theory and really nail down a couple of important ideas. I have got my camera in manual mode, and I am going to shoot a picture of this stump right here. So where do I begin? Now, I could just follow my light meter, because even in manual mode, my meter is still doing something. As you have seen, when I half-press to expose, I get a little meter that tells me whether I am over- or underexposed. I am going to ignore that though, and I am going to do things away the way I used to be done. I am out here in bright sunlight. Now, as with film, with your digital image sensor, there is a starting point for your daylight exposures, and that's something called the sunny 16 rule.
And that goes like this. If I am at F16 then my shutter speed should be one over film speed, or one over my ISO, to get a good exposure. I am shooting at ISO 100, so if I put my aperture at f16 and my shutter speed at 1/100th of a second--that's one over my ISO or 1/100--and take a shot, I get a decent exposure. So right off the bat, great. I am manually exposing here. I am out in the wild just surviving photographically on my wits, thanks to the sunny 16 rule.
But what if this isn't the picture I want? That's given me a good overall level of illumination, but I would prefer to have shallow depth of field in this shot. I would like the mountains in the background to go out of focus. So, I need to get my aperture open, because f 16 is very small, and that's going to give me very deep depth of field, so I want to open it up all the way. This lens can open all the way to F4. So I am going to change my aperture. So I am using my manual controls here, and I am going from f16 to f11. That's one stop. And if you are not sure how I knew that was one stop, its very simple: I have just memorized the whole stop aperture increments, which is that something either you need to sit down and expressly do, or that you will just learn over time working with your camera.
So, that's one stop. From f11, I am going to go to f8. That's two stops. From f8, I am going to go to 5.6. That's three stops. Again, I am just going in whole-stop increment and from f5.6, I am going to go to f4. So, I have opened my aperture four stops. If I take a picture now, still at 1/100th of a second, I am using that same shutter speed but my aperture is much wider, four stops wider than it was before--that's four doublings of light, which means my image is going to be way overexposed. So I need to compensate for that larger aperture by speeding up my shutter speed by the same amount, by four stops.
Shutter speed is a lot easier to deal with. It's just straight doublings. So I am at 100 right now, 1/100th of a second. I am going to go to 200. That's one doubling or one stop. From 200, I am going to go to 400. That's two stops. 800. That's three stops. And one more, to 1,600. That's four stops. Now, if I take a shot, I still get a good exposure, and I have got shallower depth of field. The mountains are a little blurry back there. But as I am looking at it, I am recognizing that--and it's a good place to stop; I am happy with my image, but I just want to be safe about what I am taking home.
I am going through kind of a same process I would if I was shooting in program mode, which is I am looking at my scene going, "There is a lot of dynamic range there. I have got these kind of darker tones in the foreground, and I have got bright sky full of white clouds. And they are not real well-defined clouds. They are just kind of wispy, almost solid white. I really don't want to loose any detail in there. I feel like I should underexpose that shot a little bit." I am at 1/1600th of a second. I need a faster shutter speed. A faster shutter speed is going to cut a little bit of light out of there and get me a little bit of under exposure.
My camera right now is set up to change in 3, a 3rd-of-a-stop increments. So I don't want to go a full stop under. I think that's going to darken things too much. I just know that from experience. I am going to go one click on my dial. That's going to be a 3rd of a stop, and that gets me to 1/2,000th of a second. So 1,600 to 2,000 is 1/3rd of stop. I know that just from reading my little dial here. Now I take a shot, and I have now got slight underexposure, and that's protecting the clouds a little more. I don't go out and shoot this way, particularly in a situation like this, particularly when there are bugs flying around that I am swallowing.
It takes a long time. What's nice about it is doing a little practice like this is going to help drive home some of these exposure theory concepts. It's also going to give you a feeling of what it's like to really stop and slow down and take your time taking a picture. That's how people used to have to work. And it makes you a lot more thoughtful about what you are doing. It makes you really look at the scene more. It makes you think more about what kind of exposure you want in terms of depth of field, in terms of what's my dynamic range, and what do I want to capture. It's a very good exercise for learning how to slow down and get into a very present place, which is where you need to be both to see to be even able to pay attention to what's going on around you and to nail the technical aspect of things.
So, put your camera in manual mode and go think through these reciprocal steps like I did just here. It is some good practice.
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