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Old Jan 17, 2005, 6:40 AM   #1
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Ok, i am just wondering when on this site it says:
"Leica 12x optical zoom. The Leica DC Vario-Elmarit 12x zoom is equivalent to a 36 - 432mm zoom on a 35mm camera"

But is this excluding the 1.6x crop factor (or it would be 36-432mm plus the crop factor)? I am just trying to get a feel of what a 400mm focal length will be like (as i have only tryed a 10x zoom, which is equivalent to 380mm i think?)
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Old Jan 17, 2005, 7:09 AM   #2
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Basically the 12X optical zoom means 12X the shorter focal length, so if that is 36mm, then the maximum zoom would indeed be 432mm. My Dimage A2 is at 28mm multiplied by 7X equals 200mm (well actually 196mm).

But for the camera to see what the eye sees the lens needs to be at 50mm. So the 12X zoom would be 432mm divided by 50mm equals 8.64X zoom in the sense that it brings the image closer by 8.64X at the longest length, and not in fact 12X closer.In my case only 4X, that's why I bought a T-CON 17 which gives me a focal length of 340mm but only brings the image 6.8X nearer.....................I think !!

Hope this helps, if I am wrong somebody will tell me.


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Old Jan 17, 2005, 7:29 AM   #3
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The quoted equivalents include any multiplier. The true focal length rangefor the Leica lens on the FZ20 is 6mm-72mm.
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Old Jan 17, 2005, 8:18 AM   #4
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All that was said was right and to answer your question about cropping... When they say its 12x or that its 36-432, its only the optical zoom, meaning it excludes any form of cropping or digital zoom or interpolation.
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Old Jan 17, 2005, 8:46 AM   #5
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I'd ignore the 12x number. As Stevekin pointed out, that's only the difference between the widest and longest focal length of a zoom lens.

For example, a 35-105mm lens would be 3x, and a 100-300mm lens would also be a 3x. So, compare 35mm equivalent focal lengths instead to get an idea of the angle of view you'll have.

Consumer models typically point out 35mm equivalent focal lengths, but the actual focal lengths are sometimes included in their specs, too (if not, the lenses are marked with their actual focal lengths).

Because the sensors in consumer models like the Panasonic are very small, the crop factors (a.k.a., focal length multipliers) are much higher. For example, this factor is approximately 6x with the Pansonic DMC-FZ20 (6mm x 6 = 36mm; 72mm x 6 = 432mm).

Actually, I don't really like the term "crop factor" -- perhaps we should call it 35mm comparison factor. ;-)

I also don't like the use of the x factor for zoom (3x, 4x, 5x, etc.), since this has no meaning for magnification purposes -- it onlyit indicates how muchdifference you have between the wide and long end of a lens.

Virtually all lenses arecorrectly marked with their actual focal lengths, and consumer models usually include the "35mm equivalent focal lengths" in their specifications.

I think that the mainreason that you see the 35mm equivalent focal lengths of the lenses mentioned, and crop factors/focal length multiplierspublished, is so that users of 35mm cameras have a better idea of how the angle of view compares to the same focal length lens on a 35mm model.

The actual focal length of a lens is what is more important for determining things like Depth of Field.

You see the same types of differences when you go to film that's larger than 35mm, too. The actual focal lengths of the lenses are still marked on them. Yet, you'll have a widerangle of view for any given actual focal length compared to a 35mm model (versus a narrower angle of view like you'd have using the same focal length lens on a model with a smaller sensor or smaller film).

For example, a 45mm (actual focal length) lens on a 645 format camera would have a 35mm equivalent focal length of approximiately 29mm.

So, should we say that a 35mm camera has a "crop factor" compared to a 645 format camera, or a 645 format camera has a crop factor compared to an 8x10" view camera? The larger the film (or sensor), thewider your angle of view for any given actual focal length lens.

If 35mm models weren't so popular, there would be no reason to even mention a "35mm equivalent focal length".It's done for comparison purposes, since the actual focal lengths of the lenses are how they are marked.

What changes is the angle of view, depending on the size of the sensor/filma lens is being used with.

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