BetterPhoto Q&A
Category: New Answers

35mm (film) aperature settings

To obtain a narrow depth of field - I need a large aperature?

To obtain a blurred motion I need a slow shutter speed with a high aperature?

To obtain a stopped action - I need a high shutter speed with a low aperature?

This is basically 4 questions.

Thanks so much!

Rose Howland

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February 05, 2007

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February 05, 2007

You got it right! Congratulations:

Just a few fine points:

To obtain a long depth of field where everything from foreground to background appears to be in focus - I need a small aperture?

Right on –- It’s the tiny lens opening that does the trick that’s f/22 and f/16. These small apertures broaden the depth-of-field span. These larger f/numbers translate into very tiny lens openings.
To obtain a narrow depth of field - I need a large aperture?
Right again – Large aperture (wide lens openings) like f/4 or f/2 reduce the span of acceptable focus thus depth-of-field becomes shallow.
To obtain a blurred motion I need a slow shutter speed with a high aperture?
Right – However, its slow shutter speed that gives rise to blurred motion. The aperture is not a contributor. Using a slow shutter speed allows the exposing light to play of the film or the digital chip for an extended duration. This increased dwell time often results in over-exposure. We often must counter by using a tiny lens openings like f/16 or f/22.
To obtain a stopped action - I need a high shutter speed with a low aperture?
Right in principle, a high shutter speed is a quick blink that reduces the time allowed for the exposing light to register on the film or digital chip. Its the fast action that arrests motion. Because a fast shutter reduces the time the exposing light is allowed to play of the film or chip, under exposure is a danger. Therefore we often need to compensate by using a wide lens opening like f/5.6 or f/4 or even f/2 etc.
Good for you Rose!
Alan Marcus
ammarcus@earthlink.net

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February 05, 2007