Please help us improve our service by completing a short survey based on your experience of the Canon Support website.

Yes, I would like to join Topic

No, thank you Topic

Do not show again

EF 500mm f/4L IS USM

Find FAQs

Print  Print this information

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.


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

Click here to view all applicable modelsClick here to close the applicable models list

Did this article answer your question?