F Stop lens question...

[Big]

I was wondering why lenses will say f/3.5-5.6 but when you read the specs, it goes all the way to 22 or such...I know what f-stops are but this has been something that has me confused. :scratch:

Thanks -BIG

 

[JamieR]

I believe it's the maximum aperture. SO say you have the Canon EF-S 18-55mm f/3.5-5.6, the maximum aperture at 18mm would be the f/3.5, and the maximum aperture at 55mm would me f/5.6.

I'm sure someone will correct me if I'm wrong, i only own a prime lens!

 

[Christie Photo]

I believe it's the maximum aperture.

That's exactly right.

-Pete

 

[Big]

Thanks guys. I guess that's why when I'm in manual mode on my P&S that when I zoom in the aperture is automatically raised making me have to use a slower shutter speed... I just thought that if 22 was the max aperture that it would say f/3.5-22 instead of just to 5.6.

 

[JamieR]

22 in the minimum aperture.

 

[Big]

22 in the minimum aperture.

Thanks haha I get it confused once in a while... :banghead:

 

[bigboi3]

22 is the minimum aperture.

+1

 

[Dwig]

22 in the minimum aperture.

Thanks haha I get it confused once in a while... :banghead:

One way to keep it straight is to always write the number correctly. F/stops should always be written as either fractions (f/32) or ratios (1:2.0) since that's what they are.

The "f" in the fraction notation means "focal length" and "f/8" means the diameter of the effective aperture (not necessarily the mechanical iris) is equal to the focal length divided by eight. And as everyone who passed 4th grade math knows, one quarter (1/4 or f/4) is smaller than one half (1/2 or f/2).

The confusion comes when people write only the denominator of the fraction (8 or 22) instead of the whole fraction (f/8 or f/22), either out of laziness or when space is limited (digital camera displays or f/stop rings). They should never be written with the "f" capitalized, except at the beginning of a sentence, or without the slash, "/".