Expert: John Oliverio - 7/24/2009

Question
I got a Olympus E-520 and it's my first "real" camera. The lens says it is f/4.3-f/5.6 (or whatever) and has no dial for aperture, it is all adjusted in the body. But the body aperture can go up to f/22. I don't understand, does the lens stay at f/5.6 no matter what the body says above that?

Tanks for your help.

Answer
Hi Andrew,

Thanks for the question.

The numbers on the lens express the maximum aperture of your lens.  The reason there are two numbers is that your lens changes aperture as you zoom out.  So, at the widest zoom setting, the lens is capable of an aperture of f/4.3.  When you zoom the lens out all the way, the lens is capable of only f/5.6.  Those numbers don't express the whole range of aperture settings; only the largest opening the lens is capable of.  The reason they put only the maximum aperture on the lens is so people know how much light (also called how fast) a lens is capable of transmitting.  

In case you don't understand f/ numbers....   The smaller the f/ number, the brighter the lens is.  So of course the larger the number, the darker the lens is.  f/4.3-f/5.6 is fairly average for an amateur lens.  To put the numbers in perspective, a pro lens would only have one number.  This means that the lens does not get darker as you zoom out.  Lenses that do this are called "constant" aperture lenses.  So a pro lens might be described as a 70-200mm f/2.8.  While an amateur version would usually be something like 70-200mm f/3.5-5.6.  

So, there is no "body aperture".  Most companies got rid of the ring that controls aperture in favor of a control on the body to cut costs and make the lens mechanically more simple.  When you set the aperture on the body, you are just telling the camera what to set the lens aperture to.  

Hope this helps.

John