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03/06/2004 03:59:12 PM · #1 |
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03/06/2004 08:04:26 PM · #2 |
It's so hard to resist buying that... I need a fast lens though, and all I have is crappy EF 28-90mm 4-5.6
Hey answer me this if you don't mind... How much of a difference is there between each step, like say a 4 to a 3.5? I've been looking at a Tamron 24-135/3.5-5.6 and I was curious what kind of difference I'll see or how much better it will be shooting action at lower light!
Message edited by author 2004-03-06 20:07:16.
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03/06/2004 08:21:29 PM · #3 |
| Opening is proportional to the speed , something like if F2.8 gives you 1/500 sec,F 5.6 will be 1/250 sec... |
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03/06/2004 08:24:36 PM · #4 |
The difference between a "full stop" is 1/2 (or double) shutter speed, depending on which direction you go.
e.g. from small to wide open: 8 -> 5.6 -> 4.0 -> 2.8 -> 2.0 -> 1.4 -> 1.0
if f/8 gave you 1/10s, theoretically you will progress something like this:
1/10 -> 1/20 -> 1/40 -> 1/80 -> 1/160 -> 1/320 -> 1/640
So... the difference between f/3.5 and f/4.0 may or may not be any different depending on the situation and what sort of shutter speed that you are trying to achieve.
Sometimes it's a life saver, giving you just the slight extra speed needed to handhold properly, and sometimes it doesn't make any difference at all.
:)atwl
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03/06/2004 08:26:24 PM · #5 |
Each full f-stop increase allows you to decrease your shutter speed by half or decrease your "film" sensitivity (ISO) by half.
So, for example, with your current lens, if you are shooting at ISO 400, f/5.6 and in a certain lighting situation the camera needs a shutter speed of 1/30th of a second to get a proper exposure, going to:
* f/4 will allow you to go to ISO 200 at the same shutter speed, or stay at ISO 400 but increase your shutter speed to 1/60th of a second
* f/2.8 will allow you to go to ISO 100 at the same shutter speed, or stay at ISO 400 but increase your shutter speed to 1/125th of a second
* f/2 will allow you to go to ISO 100 and increase your shutter speed to 1/60th of a second, or stay at ISO 400 but increase your shutter speed to 1/250th of a second
* f/1.4 will allow you to go to ISO 100 and increase your shutter speed to 1/125th of a second, or stay at ISO 400 but increase your shutter speed to 1/500th of a second
(f/2 is a third of a stop slower than f/1.8, so the 50mm/1.8 would be able to shoot at 1/320th of a second, for example).
So as you can see, moving from f/5.6 (1/30th of a second) to f/1.4 (1/500th of a second) is a huge difference in shutter speeds.
Since most indoor lighting is quite abysmal for stopping the "action", you can understand the desire for "fast" lenses (I consider anything with an aperture of f/2.8 or better to be "fast", although I'm beginning to realize the value of "fast primes" like the 85mm/1.2, 135mm/2 or the [discontinued] 200mm/1.8...)
Message edited by author 2004-03-06 20:34:15. |
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03/06/2004 08:46:31 PM · #6 |
These lenses are being released in small quantities by Canon, and B&H get them in stock from time to time but don't have any dates to give out. It's best to just put down an order and wait for the next batch. The last time I saw it in stock they were sold out the same day.
Mine is somewhere on the way as I type, along with its big white brother
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03/06/2004 10:02:32 PM · #7 |
Thanks guys, I feel like I just learned a lot of usefull info... Grasshopper is now wiser!
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03/07/2004 09:27:06 AM · #8 |
Wow... buydig is $10 more expensive than B&H for that lens and charges $13 for s/h! Anyone have experience buying buydig?
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