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Old Oct 28, 2004, 7:00 AM   #1
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A while back I asked about some basic definitions and people were very helpful providing the answers, well I'm back and tad confused. I'm sure there's a logical explanation.

One of my questions was focal length and how to tell the magnafication (or zoom) of a lens.

A couple of people said "multiply it by two, then take off the zeros...so, a 300mm lens would be (x2=600-00=6x) 6x"

Using that logic a 50mm lens will be 1x. Simple enough

I also got a link to dpreview
and that glossary says "if you divide the maximum focal length by the minimum length of a zoom lens you get the optical zoom or magnification factor, e.g. 280mm/28mm = 10X"

Now I just purchased the 70-300mm f/4-5.6D ED AF Zoom-Nikkor lens. (Seems good by my uneducated eyes) Well if I use the first method to determine the zoome its a 6x lens but if I use the second 300/70 = 4.3x which coincides with what Nikon advertises.

So why the difference, what I am doing wrong?
When should I use the first over the second method to determine zoom?

By the way I was really contemplating not getting the lens and using the stock lens that came with the nikon for last night's lunar eclipse. I'm so glad I went with the larger lens. Probably not the best that you seen but I'm happy with the results. Plus iPhoto reduced the quality as it reduced the image size when I published it to the web.
Lunar Eclipse

Thanks
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Old Oct 28, 2004, 8:15 AM   #2
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Ignore the zoom factor: its only purpose seems to be to say, "Mine is bigger than your's!". Much like making a big issue of going from 3Mpixels to 3.1Mpixels.

What matters is the field of view. Does it fit the subject? Is it wide enough to capture your entire garden? Is in narrow enough so a wild turkey in the garden fills the whole frame? The zoom factor does not answer those questions.

Since a lot of folks are familiar with 35mm lenses, the field of view tends to be stated in terms of 35mm equiv, i.e., the same field of view (ignoring the difference in aspect ratio).
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Old Oct 28, 2004, 9:29 AM   #3
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Thanks for the info, but to be honest thats all greek to me.

The zoom is a good point of reference for me until I can get on my feet.
My confusion has to do with which method to use in looking at lenses and why are there two methods, am I not understanding somthing.

Mike
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Old Oct 28, 2004, 11:18 AM   #4
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Let me throw out another explanation of why you should ignore this 'zoom factor' - it in no way tells you how good a lense is. Take 2 lenses - one a Sigm 100-300 f4.0 the other a Quantaray 100-300 4.5 - 6.7. By either definition, both lenses would have the same 'zoom factor' - however these two lenses are LEAGUES APART. The Quantaray is trash and the Sigma is a very highly regarded lense. Now let's take the same Quantaray (trash) lense and compare it to the Sigma 70-200 2.8. Your first definition would rate the quantaray higher - again a BIG mistake.

To Drew's point, you need to decide what type of lense best fits your needs. An SLR is not the place to find a one-size-fits-all lense. If that is your wish, stick to point-and-shoot cameras. They can produce some very great photos. The benefit of an SLR is that you can get lenses to fit your specific needs. If your need is primarily to shoot landscapes or architecture then a 300mm max zoom lense is wasted. If, however, you shoot wildlife or sports then a 100mm max zoom is wasted (regardless of the zoom factor). There are some wonderful, experienced people on this site that can help you with some suggested lenses - if you let them know what type of photos you are interested in taking. I agree with Drew - the zoom factor is wasted. It is an advertising gimick for point-and-shoot cameras and really doesn't have a useful purpose in SLR lenses.
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Old Oct 28, 2004, 11:23 PM   #5
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maflynn wrote:
Quote:
A while back I asked about some basic definitions and people were very helpful providing the answers, well I'm back and tad confused. I'm sure there's a logical explanation.

One of my questions was focal length and how to tell the magnafication (or zoom) of a lens.

A couple of people said "multiply it by two, then take off the zeros...so, a 300mm lens would be (x2=600-00=6x) 6x"
I can see why you are confused...that doesn't make any sense in reality. The x factor on digital cameras (and camcorders) is the difference between the widest part of the zoom, and the tele part of the zoom. BOTH 35-105mm AND 100-300mm are 3x zooms because the difference between the wide and tele extremes are 3 times.

BTW, 50mm is about the same as the human eye. 300mm is 6x the magnification of 50mm (300/50=6)...but digicam lenses are quoted in the difference between wide and tele.
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Old Oct 29, 2004, 7:12 PM   #6
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maflynn wrote:
Quote:
Thanks for the info, but to be honest thats all greek to me.

The zoom is a good point of reference for me until I can get on my feet.
My confusion has to do with which method to use in looking at lenses and why are there two methods, am I not understanding somthing.

Mike
[b][size=4] No, the zoom factor is NOT a point of refernce, it is a silly marketing number. It tells you nothing usefull whatsoever. Ignore it.
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Old Nov 2, 2004, 11:22 AM   #7
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I think BillDrew is pretty firm about his opinion, don't you ??
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Old Nov 2, 2004, 11:48 AM   #8
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Yes - he very concisely summarized my rambling two paragraphs into 2 sentances:-)
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Old Nov 2, 2004, 12:58 PM   #9
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Wow, pretty strong responses.

Being a newbie, there's a lot for me to learn about photography. What I try, is to use what I already know as a jump off point to increase my knowledge. It seems people here have some pretty strong feelings regarding this issue. All I'm trying to do is learn.

My question seemed to innocuous enough. I go on to dpreview and they have a glossary which mentions zoom, Nikon, canon, sony all of them use zoom and the lens I purchased (70-300mm f/4-5.6D ED AF Zoom-Nikkor) from Nikon they mention the zoom on their website when they describe the lens.

My original thread had people post replies that in essence had two different ways to calculate the zoom factor - all I wanted was some clarification on the issue. I got that but not the answer I expected.

Mike
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Old Nov 2, 2004, 2:06 PM   #10
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There are two things being talked about there. I'll try to cover them both.

Those two calculations are calculating different things. one is measuring the zoom range (how much "zoom" there is in the lens) the other is measuring the amount of magnification the lens is giving you compared to what the human eye sees.

I mentioned this in the other thread.

The question of a "zoom range" is really only useful for marketing. Please quickly forget about it. What exactly does it tell you? As I said in the other thread a 20-40mm zoom is "2x" and the 200-400 lens is "2x". But they are completely different lenses. The 20-40 is a wide angle lens you'd use to take pictures of buildings and other large things. The 200-400 is a large telephoto lens that you'd use to take pictures of distant things like sports players or wild animals. But they are both 2x? You see what I mean... 2x tells you almost nothing useful.

So to answer you question of "When should I use the first over the second method to determine zoom?" the answer is (as BillDrew said so loudly) don't use either. "determining zoom" tells you almost nothing useful. What is useful is what type of zoom lens it is. Is it wide angle (less than 50mm) is it a telephoto? How much? That is useful.

So hopefully I have clarified the issue and taught you something more. Now you know how the meaning of both pieces of info you calculated and that they are of little value.

Eric
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