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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 addition to quality differences, some lenses will have more features than others. Now quality should be your main selection benchmark, but you want to pay attention to other features as well. I've got a couple of zoom lenses here and there is an important difference in the way that they zoom. This lens has an internal zooming mechanism. When I turn the zoom ring, you don't see anything happening outside the lens. If I look inside though, I see all sorts of lens elements and things moving around. This lens has an external zoom mechanism. When I turn the zoom ring, the lens gets physically longer and shorter.
Now you now think that is much of a big deal and it may not be, but if you spend the lot of time in foul weather and rough environments, an external zooming mechanism like this could begin to wear out quicker, because dust and stuff can get on here and actually be carried down inside the lens mechanism. So an internal mechanism is definitely more durable and long-lasting than an external mechanism. These days most zoom lenses, even inexpensive zoom lenses, maybe even the kit lens that came with your zoom, come with stabilization features.
Optical image stabilization is an incredible technology. The way it works is the very last element in the lens that can be reshaped on-the-fly. So as you jitter the camera the lens can correct for that and stabilize your image. There is no substitute for a tripod. If you're trying to shoot from moving car, stabilization is not going to do you any good, but it will help counteract some of the handheld shake that you might experience and it's particularly useful for very long telephoto lenses. On this lens, I have here the stabilizer. I can turn it off and on. There are times when you want to turn off stabilization if your battery is running low especially, but also if you're working from a tripod, it's a good idea to turn off stabilization.
I also have two modes of stabilization. On this particular lens, I can have full stabilization or I can tell it to only stabilize on one axis, which is good when I'm panning. Stabilizers are rated in terms of stops. So a lens might have a 3-stop stabilizer. What that means is if I calculated my handheld shutter speed, while using the handheld shutter speed rule you can learn about in Foundations of Photography: Exposure, Once I've calculated that shutter speed if I have a 3 stops stabilizer I can actually shoot 3 full stops underneath that without having to worry about camera shake, at least that's what the camera manufacture will tell you.
Whether that's true or not kind of depends on how steady you are and how good their stabilization actually is. Stabilization is a great feature to look for. And if you're trying to decide between lens of equivalent qualities and one has stabilization and the other doesn't and you can afford both, you definitely want to go with the stabilization. Autofocus, all of these lenses are auto-focus. It can be switched on and off. Again on this lens I can turn a little switch here that says AF/MF. I've got the same thing over here. You might want to consider autofocus speed.
If you're a sports or a nature shooter, you want a lens that can focus very quickly. Autofocus noise is can also be an issue. If you're an event shooter you don't want a zzr-zzr-zzr sound interrupting a wedding or something like that. That's something to consider when you're shopping. You might have spent extra money on a camera that claims to be weatherproof, or not weatherproof but a little more weather resistant than another camera. That weatherproofing is only as good as your connection to the lens. So if you are again shooting in rough environments and you want to sure that the weatherproofing on your camera holds up, you want to be certain to get a lens that has weather sealing rings around its mounting edge here.
And it's just a little rubber gasket there basically. Lenses also have filter mounts. So there is threads right here for attaching filters. You can see on this lens, we've got a UV or Haze filter. These are worth putting on all of your lenses. They don't adjust the quality of your image at all, but they will protect your lenses. We're going to talk a lot about filters later. All filters have a thread size. If you've already got filters of a particular size, you might be interested in finding out whether the lens you're considering can use those filters. Lens markings.
This is kind of a touchy subject for me, because lenses just don't have the markings that they used to! You can see here that I've got focus markings here. These tell me where I'm focused. It's measured in feet and meters and so I can see right now I measure to 15 feet or roughly 5 meters it's saying. If you're lucky or if you're shopping for older lenses, you might find lenses that have aperture gauges and depth of field gauges on them and those were really, really handy. Particularly if you like to shoot manually. Most lenses these days don't have them. So if you're coming-- if you're an old- school photographer and you're looking for that, don't expect to find it.
Another thing you really see that differentiates one lens from another are coatings. You'll see that mention and I won't go into much detail about it. They might have some patented name about their coatings. If I tilt the lens at an angle, you may be able to see strange colors across it or interesting reflections or something. Those are because the lenses have been coated. Lens coatings are designed to reduce glare. As light goes into the lens, it might bounce around inside. That can lead to those circular lens flares that you see, or an overall loss of contrast, or diffusion of the contrast. Coatings can help prevent that.
As you're reading reviews you might see where expert reviewers are actually talking about the quality of a coatings and how good of job they do and that's definitely something to consider when shopping for a lens. I got these lens shades over here. A lot of lenses, particularly high-end lenses and especially wide-angle lenses, will ship with a lens shade. This is a 16 to 35 millimeter lens. It comes with this shade that I can just pop on the front here. And the reason that I really want to a lens shade with a wide-angle lens is that wide-angle lenses are especially susceptible to flare.
If I'm shooting into light, light coming at an extreme angle can again bounce around inside the lens and give me all sorts of awful artifacts. Having this filter on here you can see I've got stuff that bonk-- you know, that keeps the light from getting into the lenses way. So a nice lens shade is something to consider when you're shopping around. Finally lens mounts. If you're shopping for -- if lens shades are very important for wide-angle lenses, lens mounts are very important for really long telephoto lenses. This thing is heavy. It's pretty much solid metal on the outside and fortunately, it's got a mount for a tripod on the lens.
If I put this thing on my camera and put my camera on a tripod, I'm going to be putting a tremendous amount of strain on the mount of the camera. By having a tripod mount on my larger lens, I can give my camera a break and have a better balance when I'm trying to pan and tilt around. So those are a few of the really critical features that you need to consider when you're shopping for a lens, but again remember ultimately, it always comes down to image quality. You want the lens that's going to deliver the best quality. If you can get some of these cool extra features that's a definite plus.
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