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Old 03-10-2019, 04:00 PM   #4
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Join Date: Nov 2012
Location: Southeastern US
Posts: 717
First, you need to uderstand what focal length actually is: the physical distance between the lens and the camera’s image sensor. It’s indicated in millimeters, and is what determines the field of view of the lens. A short focal lenth means a wide lens (15mm, 24mm). A long focal length means a long lens (85mm, 135mm). A zoom lens is able to move across several focal lengths.

What you’re actually asking about is depth of field, which is how much will be in focus in front of and behind the subject. Wider aperture generally means shallower DOF.

Focal length enhances DOF based on aperture. For example, a 16mm lens at f/2.8 will still look to be relatively in focus throughout, but an 85mm at f/2.8 will have a very soft background behind the subject.

For wider interview shots, stick with the 24mm/35mm neighborhood. For closeups where you want to get more intimate with the subject and really blur out the background, you’ll want 50mm or even 85mm. Pick your aperture based on how soft you want the background, and light to that.

The example you linked is a medium angle with only a slightly soft background. You could get that with a 50mm. But be very careful shooting at extremely wide aperture. A lens at f/1.4 is going to be nearly useless because the focal plane will be so narrow that even the subject taking a deap breath can knock them out of focus. Stick between f/3.5 and f/5.6. And practice with whatever lens you get so you have a feel for the actual depth of field at f/3.5, f/4, and f/5.6.

Are you looking for just one lens to shoot single-camera interviews? If that’s the case, you’re better off getting a constant-aperture zoom that covers the range you want, so that you can push in a little when the conversation gets emotional. Zoom range gives you versatility, and constant aperture means you don’t lose light when you zoom in.

Tamron makes a great 28-75mm f/2.8 that’s available in Sony mount. That would be an excellent lens for interviews.

Last edited by AcousticAl; 03-10-2019 at 04:35 PM.
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