What does it mean...

[robb01]

When looking at lens reviews, and lens shopping, and seeing the "f/4" for example. I don't understand what that means, I get the focal range obviously, but I thought the f stop was set by the camera body. Stupid question im sure :blushing:

 

[Juice]

Aperture.

 

[reznap]

When looking at lens reviews, and lens shopping, and seeing the "f/4" for example. I don't understand what that means, I get the focal range obviously, but I thought the f stop was set by the camera body. Stupid question im sure :blushing:

Probably the lenses max aperture. The 50mm f/1.8 for example has a max aperture of 1.8, meanwhile the 18-55 kit lenses typically only open up to f/3.5.

We set the aperture on a DSLR with buttons on the body usually.. but it's really changing the aperture blades inside the lenses via electrical contacts. Check out some older film camera lenses with aperture rings to see what I mean.

 

[ballr4lyf]

That's the maximum aperture for that lens. I.e. you can go down to f16 on a f4 lens, but you can't go up to f3.5.

 

[robb01]

That's the maximum aperture for that lens. I.e. you can go down to f16 on a f4 lens, but you can't go up to f3.5.

Simple and easy to understand. Thanks

 

[tirediron]

To expand on Juice's reply, it refers to the maximum aperture of a lens or the largest opening (most light) which pass through the iris. You may also see zoom lenses listed as f3.5-5.6 (example numbers only). This is refers to a type of zoom lens knows a variable aperture zoom which means that at its widest end (we'll assume that this is a 20-80mm lens for example's sake) or the 20mm end of the zoom range, the lens has a maximum aperture of f3.5, but when you get to 80mm it's maximum zoom decreases to f5.6. This is done to simplify the design and reduce the cost of a lens, and is common on consumer-grade lenses.

You will also hear lenses referred to as fast or slow. Fast(er) lenses are ones which have larger maximum apertures (small f #s). This is desirable as it means that more light will be let in, and allow the use of faster shutter speeds.