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DPChallenge Forums >> Tips, Tricks, and Q&A >> Lens mm info and zoom?
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Showing posts 1 - 11 of 11, (reverse)
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02/07/2005 05:34:39 AM · #1
Ok, I am totally confused. Is there a correlation between mm range on a lens and it's capacity to zoom?
Let's say I am looking at the Canon 28-135 IS 3.5-5.6, how would I know how many times over it will zoom on an object. 3X, 5X, 10X, etc?

Going to the Canon website and looking at lenses has confused the hell out of me! An EF 28-90mm f/4-5.6 II USM is considering a zoom lense, but how does it compare to telephoto zoom lens like the EF 75-300mm f/4-5.6 IS USM?

Is there any direct way to figure out zoom magnification from the given lens info?

Thanks for your help in advance!



Message edited by author 2005-02-07 05:42:43.
02/07/2005 05:49:16 AM · #2
I'm not sure what you mean. The 28-135mm lens is almost a 5X zoom (135/28) but if you are talking about how much magnification the lens gives it is a bit more complex. If a 50mm lens is a 1X on a full frame (36x24mm) camera, then a 31mm lens should be a 1X lens on your 300D. So the 28-135 is about 0.9-4.3X zoom on the 300D.
J.
02/07/2005 06:33:39 AM · #3
If it sounds like I'm not sure what I mean, that's because that is exactly the case! Lol.
But I think you managed to decipher my main question a bit.
Basically, how do you know the 28-135mm lens is 5X zoom? Did you calculate it using those numbers somehow? What mm range should I be looking for if I want a lot of zoom?
02/07/2005 06:41:26 AM · #4
Originally posted by crank2o:

If it sounds like I'm not sure what I mean, that's because that is exactly the case! Lol.
But I think you managed to decipher my main question a bit.
Basically, how do you know the 28-135mm lens is 5X zoom? Did you calculate it using those numbers somehow? What mm range should I be looking for if I want a lot of zoom?


What are you asking, what lens has the greatest range between shortest and longest focal length?

jonr gave you the numbers for how he came up with 5x - 135/28. All this tells you is the focal length range of the lens. A 75-300 would be 300/75 or 4x. Does this mean it has less zoom than the 28-135? Less range yes, less zoom I think not.
02/07/2005 06:51:33 AM · #5
If you mean magnification as opposed to zoom then just look for the longest focal length in your budget.

bazz.

Message edited by author 2005-02-07 06:52:13.
02/07/2005 08:50:04 AM · #6
Magnification is roughly the focal length in mm divided by the diagonal dimension (in mm) of the image sensor. In the case of the 20D/10D/300D that is about 27.3 mm (based on the published effective sensor size of 22.7mm x 15.1mm).
02/07/2005 03:06:45 PM · #7
i think what he's asking is how to correlate an SLR lense's range in comparsion to a P&S cam that has a spec such as "3x zoom lens".
02/07/2005 03:58:01 PM · #8
Originally posted by jxpfeer:

i think what he's asking is how to correlate an SLR lense's range in comparsion to a P&S cam that has a spec such as "3x zoom lens".


So far we've all been just guessing so maybe he'll pipe in and let us know what he's really asking.
02/07/2005 04:01:24 PM · #9
It is simple, you divide 135 by 28, the longest FL by the shortest.
This give a zoom range of 4.82 to 1.
02/07/2005 04:09:31 PM · #10
On point and shoot cameras, there is typically a 3x lens. This doesn't refer to how long it is, it simply tells the range.

For SLRs, The 17-85 lens is 5x. The 100-400 is 4x. The 100-400 is much longer than the 17-85, but it has a smaller range--it can't zoom out very far.

With point and shoot, a 3x lens can be 28-84 or 37-111 or any other length like that. a 28-84 would give you nice wide angles, but you wouldn't be able to zoom in all that far. A 37-111 would not be very wide, but it'd have a better telephoto than the 28-84.

Hope that helps a little.

Message edited by author 2005-02-07 16:09:59.
02/07/2005 09:19:14 PM · #11
Sorry for not responding earlier to the questions that were posed about my own question! I am currently studying abroad in Australia so right about when you guys were waking up to respond to my inquery I was going to sleep :)
Anyway, you seem to have answered my question about the the zoom capabilities of the lense. It depends on its range ratio. The reason my question was so difficult to decipher was that I was probably asking it in point-and-shoot camera jargon.
The main reason I asked this question was because one of my friends was telling me about how he used to have a lense on his SLR that had a 50X optical zoom or some ridiculous number like that. So in theory, if what he said were true, the range would have had to have been something like 17-850 or some other number range with that ratio(if that's even possible?).
What do you guys generally find as an adequate range to capture candid shots of people or animals from a distance?
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