|
| Author | Thread |
|
|
04/02/2009 06:58:43 AM · #1 |
So I've got two questions for you:
First does
Canon EF 70-200mm f/4.0L USM
work on my camera? 1000D Rebel XS? I believe so right? I know it takes the EF lenses but isn't this one made for the Full Frame cameras? What will be different on mine versus it being used on a full frame?
Not buying it anytime soon anyways but more just for learning purposes
Second
Canon EF-S 18-55mm f/3.5-5.6 IS
Does that mean that at wideangle on the zoom I get 3.5 for my F/stop?
Third(I guess that's actually 3 questions)
If I have a lens that is 75-300mm 4.0-5.6. Assuming 4.0 is the best I can get in terms of F/Stop at the widest angle, is 4.0 in a 75mm-300mm lens less light then a 18-55mm 3.5-5.6 at 3.5? or is that the just a relative measurement for the lens itself? In practical terms, I shot a hockey game with my 18-55mm. Had it set at close to the widest aperture(Fstop 3.5 i Believe). I had an ISO of 1600 and I had it taking shots at 1/250th to 1/320th. If I had the 75/300mm 4.0-5.6 at, say 75mm I would have an F-Stop of 4.0. Since that's smaller then 3.5 in terms of aperture, does that mean I wouldn't get away with the same exposure at 1/250th or 1/320th? I would have loved to be able to shoot a little bit faster to stop the action. I have this uncanny feeling you're going to tell me I have to get a faster lens like a 2.0 or 1.8 or something along those lines.
And is 4.0 half the light 2.0 is? So at 4.0 you shoot at 1/250 and at 2.0 you can get away with the same exposure at 1/500th?
|
|
|
|
04/02/2009 07:08:21 AM · #2 |
In short:
Yes the EF 70-200 fits on your camera and should work well. Yo won't notice it was originally made for FF cameras. But if you can afford that, why don't you get a FF body (say used 5D)?
The EF-S 18-55 will give you an aperture of 3.5 at the wide end (which is, considered the crop factor of your camera, not really wide - about 29 mm), but that's a lens you won't get happy with.
I think yes, f/4.0 always lets less light into your camera than f/3.5, no matter which lens you use.
4.0 is not half the light of 2.0. It is half the light of 2.8 (one f/stop smaller). Full f/stops are usually 2.8 - 4.0 - 5.6 - 8 - 11- 16 - 22 and so on. Meaning that if you go one f/stop smaller, you need double the time.
 Bear_Music will give you complete answers soon :)
Message edited by author 2009-04-02 07:13:45. |
|
|
|
04/02/2009 07:15:53 AM · #3 |
Originally posted by drewhosick:
So I've got two questions for you:
First does
Canon EF 70-200mm f/4.0L USM
work on my camera? 1000D Rebel XS? I believe so right? I know it takes the EF lenses but isn't this one made for the Full Frame cameras? What will be different on mine versus it being used on a full frame?
|
The difference is the angle you cover - with a full frame you have a broader angle than with the one you have at the same focal length.
As you would need a longer focal length on a full frame camera for the same angle (200mmx1,6) this is sometimes referred to as Brennweitenverlängerung (don't know the english one, focal length extension?), but that is technically not absolutely correct. For practical purposes it's good enough, though.
Yes
Originally posted by drewhosick:
Third(I guess that's actually 3 questions)
If I have a lens that is 75-300mm 4.0-5.6. Assuming 4.0 is the best I can get in terms of F/Stop at the widest angle, is 4.0 in a 75mm-300mm lens less light then a 18-55mm 3.5-5.6 at 3.5?
|
Yes
Originally posted by drewhosick:
In practical terms, I shot a hockey game with my 18-55mm. Had it set at close to the widest aperture(Fstop 3.5 i Believe). I had an ISO of 1600 and I had it taking shots at 1/250th to 1/320th. If I had the 75/300mm 4.0-5.6 at, say 75mm I would have an F-Stop of 4.0. Since that's smaller then 3.5 in terms of aperture, does that mean I wouldn't get away with the same exposure at 1/250th or 1/320th?
|
Yes.
The f-stop sequence goes 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32 - on every step you have half the light and need to double the exposure time when there is no change in the lighting and ISO.
That means that in your example you would need a somewhat longer exposure, but not really double (as 3.5 is halfway between 2.8 and 4).
Originally posted by drewhosick:
And is 4.0 half the light 2.0 is? So at 4.0 you shoot at 1/250 and at 2.0 you can get away with the same exposure at 1/500th? |
It's a quarter and you would get away with 1/1000th.
|
|
|
|
04/02/2009 10:49:32 AM · #4 |
Yes, you need a faster lens. Not many zooms are faster than f/2.8, and I don't know of any for Canon that are faster. But 2.8 isn't all that much faster than 4, its only one f/stop, so you'll get half the shutter speed. And most zooms are not at their sharpest at f/2.8. Prime lenses will make a world of difference. Remember, the wider the aperture, the shallower the DOF. Depending on how far away you are, the 50 f/1.8 is a good and inexpensive lens.
A newer body with faster ISO, or even a 5D, will give you at least an extra f/stop. (that is, you can bump the iso to 3200 and either stop down one f/stop, or increase your shutter speed.)
Another solution is to pan with the action.
You were questioning zoom vs wide angle. IMO, metering will be a bigger difference than the difference between f/3.5 and f/4 -- that's 1.143. With a wide angle lens, you may get lights, shadows, and the ice on the hockey rink etc in the image. With telephoto, your metering may not have these extraneous elements. I don't recall if the 1000D has spot metering, but it will help.
Note that f/stops are about 1.4 apart -- 1.4 is about the square root of two. Rather than memorize the f/stops, I calculate them in two series: 1, 2, 4, 8, 16, 32, ... and 1.4, 2.8, 5.6, 11, 22, ... each number in each series is two f/stops apart.
Message edited by author 2009-04-02 10:50:27.
|
|
|
|
04/02/2009 12:37:43 PM · #5 |
Originally posted by eyewave:
Bear_Music will give you complete answers soon :) |
Bear_Music has nothing to add to what's already been posted :-)
Except to go off on a slight tangent and explain what an f/stop actually IS: it's a ratio, calculated by dividing the focal length of the lens by the physical diameter of the aperture. So an aperture of 25mm gives f/2.0 on a 50mm lens, f/4.0 on a 100mm lens, and f/8.0 on a 200mm lens. The reason the "f/stop" is used instead of he actual aperture is because it represents a constant that takes into account the fact that light intensity falls off by the square of the distance traveled. So the "f/stop" essentially does your calculating for you. An indicated f/stop of 4.0 delivers the same amount of light to the lens regardless of the focal length it is appended to. Which, of course, makes metering/exposure calculation a whole lot easier, assuming you bother to do it for yourself (which you should) instead of letting the camera do it for you.
R.
|
|
|
|
Current Server Time: 12/26/2025 01:21:58 AM  |
Home -
Challenges -
Community -
League -
Photos -
Cameras -
Lenses -
Learn -
Help -
Terms of Use -
Privacy -
Top ^
DPChallenge, and website content and design, Copyright © 2001-2025 Challenging Technologies, LLC.
All digital photo copyrights belong to the photographers and may not be used without permission.
Current Server Time: 12/26/2025 01:21:58 AM EST.
|
