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Many of the creative options available to a photographer hinge on an in-depth understanding of lenses. In Foundations of Photography: Lenses, Ben Long shows how to choose lenses and take full advantage of their creative options. The course covers fundamental concepts that apply to any camera, such as focal length and camera position, and shows how to evaluate and shop for DSLR lenses. The second half of the course focuses on shooting techniques: controlling autofocus, working with different focal lengths, and managing distortion and flare. The course also examines various filters and contains tips on cleaning and maintaining lenses.
In this course I've been assuming that you're already comfortable with basic auto focus, a topic that we covered in some detail in the Foundations of Photography: Exposure course. So, you should already be habitually pre-focusing and you should understand what the focus points in your camera's viewfinder are. You may have already encountered times when auto focus was difficult or more complicated or just outright impossible due to weird lighting or complex composition or moving subject matter. Fortunately, your camera probably has features for dealing with all of these issues.
Now, like the Exposure course, we're keeping this course camera agnostic. I am not going to talk about specific camera controls or features. But no matter what type of camera or lens you have, you're going to see features that are very similar to what we're seeing here. So, you'll just need to look those up in your manual to understand how to work what I'm doing here on your particular camera. Also, here you're seeing something new. You're seeing our mighty smart board, which is plugged into the output of the camera. So, what you're seeing here is what my camera would show in its live view display mode.
That is what it would show on that rear LCD screen when I activate live view. It's also a pretty good simulacrum of what I see when I look through the actual optical viewfinder. So, you're going to be able to follow along as I do stuff here. Now I have a pretty simple set here. I have three lenses, one each at a different distance. I want to shoot a shot of this scene and I want this lens to be in focus. Now I am working with kind of shallow depth of field here, because I'd like for the rest to fall out of focus. So I am going to half press the Shutter button. As you should already be familiar with, because this is kind of the default mode on most cameras, it has automatically chosen a couple of focus points on what it thinks the subject should be.
And it's great, because it agrees with me that the subject should be this lens right here. So it has chosen those two points and it's focused the lens to this distance. Remember, focus is always about distance to a particular plane. A certain distance from the lens. But I've changed my mind now. Looking at that picture, I think, "Oh, It would be much better if that middle lens was in focus." Great! I'll have pressed my shutter button again to auto focus, and it's no good. It's still deciding that this is the subject. Now, each one of those little boxes is a potential place that the auto focus system can focus on.
Your camera will have maybe a different number of them and they might be arranged in a different pattern. Fortunately, with most cameras you can choose the point that you want to focus on. So, what I am going to do here is bring up a control that allows me to manually select a focus point. Now what you'll see is I can move around to pick precisely which point I would like to focus on. So, I am going to put this on right there, on one of the points in the center. I am going to put it down a little bit lower. I'll put it up there.
I am looking for a point that's got some contrast in it. I am going to half press the Shutter button to focus and sure enough, now my center lens is in focus. This one has fallen out of focus because of my shallow depth of field and that one back there is still out of focus. So, that's looking pretty good. But yeah, the more I look at it, the more I think it's that far lens that's the subject of this image. So, I want to focus back there. So, I am going to bring up again my focus point display. Then I am going to move the little lighted box over to a point on that lens, and uh-oh, I got a problem here.
Because there is no point with this particular number of focus spots that falls on that thing, which is what I want to be my subject. However, if I put the spot right there, it's still choosing a point on the table that's at the same distance as the lens. So, it doesn't matter that is not actually on that object. It's on a point that's at the same distance as that object. So, when I half press auto focus, it's still in focus. So, remember focus is about distance. Now, if it was really low light in here, my camera might have trouble focusing.
A lot of auto focus mechanisms need contrast in the scene to be able to focus. Others use something called phase detection. Either way, like your eye, they need some light to be able to see what they're doing. If it was darker in here, when I half-press the shutter button, this particular camera has something called an auto focus assist lamp. It's a little light bulb right here that it can turn on to shine light into the scene to try to create enough light to focus with. Your camera might have something similar. And if you've ever wondered why sometimes in low light, it starts shining a light in your subject's eyes or it pops up the flash and flashes it a bunch of times even though you didn't want flash.
That's probably an auto focus assist mechanism. Most cameras that have them also allow you to turn them off. This can be essential if you're shooting in a museum, at a wedding, somewhere where it's not appropriate to have these odd lights shining around. So, you want to turn that off. If you then get back into low light and a place where it's okay to have that, remember to turn it back on. There is another option that I can use for focusing here. And that's manual focus. The way we used to do it before we had auto focus mechanisms. This camera has on it, like most SLRs, there is a switch that says AF and MF.
If I switch it to MF, I can manually focus. And for that, there is just a ring that I can turn. There is the center lens in focus, there is the front lens in focus, and there is the rear lens in focus. This is much easier to do when I am looking through the viewfinder. I've got a more accurate eye on focus. Most live view modes let you zoom in if you need to, to really double-check your manual focus. Also, fancier lenses have just a manual focus override built into their auto focus mode. So, I've switched this camera back to auto focus.
So, as you can see, it's still auto focusing. But without having to flip that switch, I can just grab the manual focus ring and move it over. Don't forget about your manual focus feature. It can be very, very, very handy. Particularly, if you're needing to work quickly. Your auto focus is not getting what you want, you can just grab that ring and try and focus. A lot of times, manual focus is a better way to work if you're shooting fast-moving subject matter. You can ride the focus to follow your subject as it moves around. There're a couple of other solutions to this particular type of focus and auto focus problem.
And we're going to look at the next one in the next video.
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