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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.
One of the kind of annoying things about digital cameras is that if you come from a film background, especially if you were shooting with film before there were digital cameras, you regularly find yourself wanting to say, "You know back in the film days we did it like this." It's really hard to resist. So I'm not even going to try. You know back in the film days we used filters. These days "filter" usually means a small bit of plug-in code that you run inside of Photoshop or some other image editor, but filter used to refer exclusively to a piece of glass that you put in front of your lens.
Now it still means that, but these days you don't typically use filters as much as you used to, because most of what you use to do with filters can now be done in post-production. But there are still some filters that are valuable and that can be pretty handy. This is an example of a graduated filter, you can see that it's darker at the top than at the bottom. We've talked about the limited dynamic range of your camera compared to your eye, how it's difficult for it to capture bright sky and dark foregrounds. This is something you could put in front of your lens and actually dim the sky while preserving the background.
This is a big square filter. It's for a particular type of camera. For most of the lenses that you'll put on your SLR, you'll be just using round filters that screwed onto the end. Your lens should have threads and the filter just screws in. There are number of different kinds of filters. The one you should be most concerned about or that you should be most indulgent in is simply a UV filter, sometimes called a skylight filter. It sits on the end of your lens and it's there just to protect the end of your lens.
It doesn't alter the light at all and so it's going to help protect the lens from scratches. I have actually dropped lenses before and they have landed like that. I've dropped my entire camera, it's landed like that, shattered the filter, the lens has been fine. So it's really, really worth it to protect your investment and your lenses by investing in some UV or skylight, sometimes called haze filters. You go out and you spent a $1000 on a lens, don't buy a cheap filter to put on the front of it because that can actually degrade the quality. You want to get a filter that is multicoated.
That means it's going to have special chemical coatings that will help reduce flare as light passes through the filter. Another handy type of filter which happens to be on this camera right here, note we've got two filters. I've got a UV filter and on top of that I've got a circular polarizer. You can stack filters. And what I've got here is a circular polarizer. It's actually screwed onto the front of the lens, but I can turn this front element and as I do I can change the polarization of the light that's entering the camera. There are two things I can do with the circular polarizer. I can increase contrast, particularly in skies, clouds especially.
I can also use it to eliminate reflections. If I'm shooting even the surface of a table like this that is very shiny, I can use a polarizer to just dial that reflection away. I can dial a certain amount of reflection out of windows. So if you're shooting through glass a circular polarizer is very handy. Circular polarizer is one of those filters that you cannot simulate digitally. So it's a good investment. Filters come in different sizes and the end of your lens will list on it a filter size and I've got that right here. This little symbol, it's a circle with a vertical slash through it and then it's a 72mm.
That's telling me that the filter size for the end of this lens is 72 mm. So I want to get a lens that is that size. They come in lots of different sizes and as you would expect, the bigger they are, the more expensive they are. So your fast lenses like this one 0.250, which always have a wide diameter, it's going to cost lot of money to start putting filters on those. Some other types of filters I have here and this happens to be a 72mm filter. This is an infrared filter. It filters out all the light except for infrared. And as you can see it's almost appears to be completely opaque.
Infrared photography is possible with digital cameras. It's a bigger topic than we want to get into here, but I screw this onto the end of my lens and then I'm going to be able to take infrared photos like these. There is a lot of work to get a good infrared photo, because this filter is blocking out so much light. There are actual modifications that some people make to their cameras to make them work better as infrared cameras. Like these images here. Infrared images have a very distinctive look and it can be worked to get a good infrared picture with a digital camera, both because of the opaqueness of the infrared filter and because your camera itself is not really set up for infrared shooting.
Some people actually modify digital cameras specifically for infrared shooting. So you've got the power of your post- production image editor and you've also got filters that you can put on your lens to achieve different effects. When you go filter shopping you'll find filters that can create starburst effects around highlights, that can change the color of things. That can add diffusion. That can enhance skin tone, on and on and on. When should you use a filter to get an affect and when should you use post-production? If you are working in an environment where you need a really quick workflow, maybe you're shooting a wedding or something and you've got to get home and get those images out to the client as quickly as possible.
If you want the type of affect you can get from the lens filter that you can also get from an image editor, maybe it's better at that point to use a lens filter. You won't have to do as much post-processing. Personally, I prefer to shoot my images as clean as possible, as close to just reality as I can, because then I can have a lot of different options later. If you've already filtered an image to say make it more diffuse or to put a starburst pattern on specular highlights, things like that, I can't take those effects out later. So shooting a more neutral image that I can filter in post-production gives me more flexibility if I want to repurpose those images for something else later.
Still, filters, especially circular polarizers, are very valuable effects and absolutely put UV filters on the end of all of your lenses.
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