How to Understand Focal Length in Digital Lenses

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Just because you're working with digital lenses doesn't mean you can ignore focal length. Understand focal length in digital lenses with help from a filmmaker and freelance editor in this free video clip.

Part of the Video Series: Filmmaking & Camera Tips
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Video Transcript

Hi guys. I'm Justin Z. I am an independent filmmaker living in Los Angeles and I am a freelance editor for the entertainment industry. I've been getting some basic questions about filmmaking including this one how to understand focal length for digital lenses. So focal length basically means the distance between the camera and the subject that is in focus. So when you have shallow focus that means only a small part of the image is in focus. When you have wide focus that means a larger part of the image is in focus. This can vary depending on lens and depending on the choices of the camera man and the director. So there are different types of lenses out there. There are two different types actually. There are zoom lenses like this one and there are prime lenses which are not zoom lenses. They have a fixed focal length but with both lenses you can change the distance or length of focus. The general idea first of all is you want to have the subject in focus. The second idea is that you want to determine the length of focus depending on how much light you are getting. If you have a lot of light, then usually you can get a very shallow depth of field which is another term for how much focus you have. If you have a wide shot or a subject where you have a lot of information in the shot such as a landscape, then you want to have a very low depth of field, or in fact everything should be in focus. If you have a very tight closeup, then you want to have a very shallow depth of field or a long focus and that means that only the subject is in focus and the foreground and the background are out of focus. It actually is meant to imitate the human eye where if you concentrate on a single object, then you'll notice out of the corner of your eye that the other objects behind it and in front of it are out of focus. A lens works exactly the same way, only you have total control with the aperture over how this works. So, I'll go through that again, a wide shot such as a landscape should have pretty much infinite focus, nothing should be out of focus and a closeup should have a very shallow focus so you can only see that subject and everything else is out of focus. It's important that you do this especially for closeups so the audience can pay attention to that particular subject. So that's the basic idea behind focus on digital lenses. If you have any questions, feel free to ask.


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