so basic of a question - fast lens?

[Pugs]

pretty n00b question here.. i understand what a stop is ie. stopping down the lens, exposing a stop more or less. but how MUCH is ONE STOP. i always undertood it as one unit of adjustment, like if i went from F2.8 to F3.2, or if i went from 1/200 to 1/250. these are all adjacent to each other when i adjust aperture or shutter speed. is there more to it then that?

A full stop is half or double the amount of light.

 

[ann]

a full stop would be going from 250 to 125 or 125 to 60; etc.

or 4 to 5.6, or 5.6 to 8

with modern cameras there are 1/3 available and so you may see a wide variety of numbers between full stops.

also, taking a photo of something at 125/f8 and the same image at 60/f11 will give the same exposure. the same amount of light enters but the results will be different with regard to DOF and/or sharpness of the photo.

 

[Josh66]

these are all adjacent to each other when i adjust aperture or shutter speed. is there more to it then that?

Your camera probably adjusts in 1/3 stops, maybe 1/2 stops (check your manual to be sure), so 3 (or 2, if you're only adjusting in half stops) clicks on the wheel would be a full stop.

 

[Pugs]

Man, I love this forum!

 

[Josh66]

Man, I love this forum!

?

 

[Pugs]

?

A newbie asks a question and people jump right in with good info. Follow-up questions are asked and more good info is given. No condescension. No arrogance. No pretentiousness. No snobbery. Just good solid info to help a new photographer get going.

What's not to love?!

 

[Josh66]

OK, lol. Just seemed a little strange...

 

[johan.sie]

well said

Yes, usually it is reference to the max aperture a lens is capable of.

For example, "EF 70-200mm F/2.8L IS" is faster than "EF 70-200mm F/4L IS" lens.

In other words, EF 70-200mm F/2.8L lens has a wider maximum aperture than the EF 70-200mm F/4L version.

With the wider aperture, the fast lens can use a faster shutter speed to obtain the same exposure with the slower lens with slower shutter speed (narrower aperture).

 

[stsinner]

If you think of the lens like a hose, light as water, and the "perfect" exposure as a bucket. The question is how long does it take to fill the bucket to get that "perfect" exposure. If the water (light) is flowing at a constant speed, the you can fill the bucket "faster" by getting a bigger hose.

SO, the lens maximum f/stop number is how "big" of a hose the lens is. Things are a little reversed so stay with me here. The smaller the f/stop number is, the LARGER the aperture opening is. So this means an f/1.2 is a LARGER aperture than an f/22.

Pugs, that was awesome! That cleared it up a lot!