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EF 500mm f/4L IS USM

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EF 500mm f/4L IS USM

EF 500mm f/4L IS USM

FAQ ID: 51427
Last modified: 10-Jun-10


FAQ: Why do I get blurred photos when I use closed diaphragm?

Helpful Information:

This problem is known as diffraction. Diffraction flare is produced when using a small aperture of diaphragm (F22 - F32).
This phenomenon is caused by the wave-like nature of light. Light rays are diverted in several directions when they graze one thin sheet.
This phenomenon is more frequent in macro photography.

Solution:


The aperture value must be at least F16.
The lens works better using medium diaphragm values.

The formula for the optimum aperture is the following:


Kf = optimum aperture
u = circle of confusion
= wavelength
m = magnification power

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