Lens advice

ab1385

ab1385

ab1385

Associate
Joined
25 Apr 2006
Posts
53
I get most of the stuff about apertures etc, but I wanted to check a point - is it such that F/2.8 allows in exactly twice the amount of light as F/5.6, or is it not as linear as that?

The reason I ask is that I'm thinking of getting some prime lenses - I want them to be sharp - probably a 50mm ('cause I seem to be going to quite a few weddings at the moment!) and and another in the region of 75-100mm for sports. I like the idea of having a lens with a wider aperture so I can manage faster shutter speeds, but how much real world difference does having f/1.8 or f/2.8 make over f/5.6?

Any reccomendations for either of the above? I'm assuming the Canon 50mm f/1.8 is going to be quite popular? I'm looking for eBay (or anywhere else!) bargains really - maybe £50ish for the 50mm, and maybe £100 for something around 85mm f/1.8 or f/2.8...
 
Try here for a good explanation.

f/2.8 will let in four times the light that f/5.6 will as there is f/4 s a "full" stop in between. Reading the link above will explain it....

Having a good quality fast lens is always a good idea. 50mm (about 70mm on a non-full frame dslr) is ideal for indoor photography of people and places where being able to use natural light often needs f/1.8 or f/1.4.

I know that the 50mm canon f/1.8 is highly regarded around here and seen as a bit of a bargain.

Depending on the sports you want to photograph, consider a 70/300 lens as it will let you get closer to the action.
 
Thanks :)

For sports I really wanted a faster lens rather than longer - I'm quite often going to watch Cardiff play rugby and getting close enough isn't really the issue - I have the Sigma 70-300 APO, but it's just too slow. Still, will probably stick to that for the moment, and just get the 50mm f/1.8 - what I really want is a 70-300 f/1.8 with IS for under a hundred... oh well! :)
 
Bold = Full stop
Normal = 1/2 stop

F1.0
F1.2
F1.4
F1.8
F2.0
F2.5
F2.8
F3.5
F4.0
F4.5
F5.6
F6.7
F8.0
F9.5
F11
F13
F16
F19
F22
F27
F32

A full 'stop' is double the previous two full 'stops'. i.e. F32 = F16x2, F2.8 = F1.4x2 (hope that makes sense)
Shutter, aperture and ISO all work together so it's possible to use a combination of settings that let the same amount of light to sensor/film.

e.g. - All of these settings produce the same exposure.

Aperture F1.4, Shutter 1/250, ISO 100
Aperture F8.0, Shutter 1/30, ISO 400
Aperture F16, Shutter 1/15, ISO 800

It's up to the photographer to decide if a faster/slower shutter speed is required, or, a larger/smaller aperture for less/more depth of field etc


ab1385 said:
what I really want is a 70-300 f/1.8 with IS for under a hundred... oh well! :)
Click to expand...
Join the back of the queue :p
 
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