Lens Question(s)

[b00]

Relatively new to digital SLR photography, always had a point and shoot of some sort, but wanted to step it up. Bought a DRebel and love it so far, except for the action shots. Read a few of the threads on recommendations of lenses, but still had questions...

If i'm shooting at 250 or 500 or whatever shutter speed, will it be a huge difference to have a f1.8 or f2.0 lens? Should I just pick up a 50mm f1.8 and the 100mm f2 and that'll be my compliment of lenses for any sporting event where I have access to sidelines/courtside? Or just drop a $100 on the 50mm f1.8 and see where to go from there?

[Pekka]

Large apertures (small aperture numbers) help a LOT with shutter speed.

Check out this table from http://www.chem.helsinki.fi/~toomas/photo/ev.html (other one in http://home.pcisys.net/~rlsnpjs/minolta/ev%20lv%20asa.html )

a p e r t u r e v a l u e
1.0 1.4 2.0 2.8 4.0 5.6 8.0 11 16 22 32 45 64
s 1 0 1 2 3 4 5 6 7 8 9 10 11 12
h 2 1 2 3 4 5 6 7 8 9 10 11 12 13
u 4 2 3 4 5 6 7 8 9 10 11 12 13 14
t 8 3 4 5 6 7 8 9 10 11 12 13 14 15
t 15 4 5 6 7 8 9 10 11 12 13 14 15 16
e 30 5 6 7 8 9 10 11 12 13 14 15 16 17
r 60 6 7 8 9 10 11 12 13 14 15 16 17 18
125 7 8 9 10 11 12 13 14 15 16 17 18 19
s 250 8 9 10 11 12 13 14 15 16 17 18 19 20
p 500 9 10 11 12 13 14 15 16 17 18 19 20 21
e 1000 10 11 12 13 14 15 16 17 18 19 20 21 22
e 2000 11 12 13 14 15 16 17 18 19 20 21 22 23
d 4000 12 13 14 15 16 17 18 19 20 21 22 23 24

The numbers in the middle are EV's which is a value describing shutter/aperture combination for same exposure (e.g. 1/4 @ f16 and 1/15 @ f8 are both EV 10 so they capture same exposure).

So, if you need to expose to EV 11 and your largest aperture available in your lens is 5.6, then you have max. shutter speed 1/60. If you had lens with aperture 2.0 you could have shot with 1/500 and would have gotten exactly the same exposure.

EV tables are usually ISO 100 by default. Of course you have also a possiblity to crank up ISO: each ISO step up doubles the shutter speed.

[b00]

Thanks for the excellent reply. The chart was very informative. I believe i'm going to start with the f1.8 50mm Canon lens. I read through the list of various vendors thread up in this forum and found a couple good new USA ones for under $100. I'll order that and my journey as a digital photographer will take yet another step forward :)