CA test and Lens?

P

Park Edwards

Veteran
I have a couple of questions. In order to tell if you have bad CA what kind of test can you to point it out right away. And lens, they're so confusing. If you have a certain mm lens how do you tell how far the subject/talent/object should be to shoot without having to put in front and hope they're in focus? That probably doens't make any sense.

-Rh
 
Q: In order to tell if you have bad CA what kind of test can you to point it out right away.

A: Try to shoot some footage of a tree against a bright grey sky - you might see some chromatic aberration in the form of reds and blues. If that's what you're referring to when you wrote "CA."

Q: And lens, they're so confusing. If you have a certain mm lens how do you tell how far the subject/talent/object should be to shoot without having to put in front and hope they're in focus? That probably doens't make any sense.

A: If you're asking about how to maintain focus - I've not yet had many problems just using the LCD - but many here would recommend a larger monitor in order to maintain proper focus.

If you're asking about how to set the lens the proper distance from the ground glass - just set the focus ring on your SLR lens to infinity and then move it closer or further until objects that are very far away are in focus.

Hope I understood you there.
 
Yes CA is Chromatic Abb. Thanks, I'll test that out. Secondly, the question about distance is I have a 28mm lens and wondering how far I should frame my shot. Feet, inches, mm's? Same with 50 and 85 and so forth. Does the mm tell you a certain distance you can shoot.
 
Car3o said:
Does the mm tell you a certain distance you can shoot.
Click to expand...

Not really. It's how wide a field of view you will have.

And some depth of focus differences, of course, but that's not the usual reason to buy a wide or long lens. (At least for me.)
 
Usually, the action decides the framing. If the shoot records movement (walking, etc) the framing should be looser (28 or 35mm lens) and the distance camera-action should give you the desired framing. If there is dialog (and not much body movement but facial expressions) you could go with a tighter lens (50 or 85mm) to get a nice portrait-type framing. Camera-action distance? Anything from 2 to 5 ft (depending on how you like the framing). Obviously, you could go the other way around just as well if that's what you want to see and record. There are tons of tight shoots of running/jogging people but the set-up is not that easy (tracking shoots from car/dolly) and focus is critical. The wider the aperture, the shallower the DOF. You can learn a lot more experimenting with different lenses without changing camera position or distance.
 
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