Confused about what aperture to use

[Richard Lane]

There are no dumb questions, only dumb answers.

There is something called Diffraction Limited Aperture or DLA:

As your aperture becomes too narrow, the incoming light gets diffracted or dispersed by the edges of the diaphragm blades, and it is this dispersion of light that can lead to a loss of resolution.

http://www.luminous-landscape.com/tu...fraction.shtml

In this example below you will see that as the aperture went from f/5.6 to f/16 there was a loss of resolution:

http://www.the-digital-picture.com/R...mp=0&APIComp=7

Usually with most higher-end cameras you should be pretty safe in avoiding diffraction if you keep your aperture between f/8 to f/11. Commonly referred to as the Diffraction Limited aperture (DLA). You shouldn't be afraid to use f/13, just be aware that the narrower you go, the greater the affect from diffraction.

Some people do feel that diffraction is a bit over-rated, namely the well respected Bryan Peterson in his book entitled "Understanding Exposure." He prefers the greater overall increase in DOF, over the pixel-peeping loss in micro-resolution. Personally, I wouldn't rule out the overall increase in DOF either, if the micro-resolution was considered less important for a particular image.

Diffraction is certainly more noticeable with pixel peeping. However, it is an accepted physical limitation.

I do think as long as you're aware of it and you don't shoot everything at the narrowest apertures then you'll be ok. It's also good to know what the DLA is for the particular camera and lens combinations that you'll be working with.

Here's another article:

http://www.cambridgeincolour.com/tut...hotography.htm

Check out the fabric example and DLA Calculator towards the bottom of the page.


Rich