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Old Aug 12, 2010, 12:34 PM   #11
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Originally Posted by Greg Chappell View Post
The 4/3rd's system, be it DSLR or these micro bodies, is a 2x factor, so a 50-200mm lens would cover an a equivalent range of 100-400mm, or 4x zoom.

The Pentax lens you mentioned above would not be a 16.7x zoom on that system. Not sure how you are coming up with that number. The Pentax system is either a 1.5 or 1.6x crop factor, so a 50-300mm lens would be, at most, the equivalent of a 160-480mm zoom, or 3x zoom.
To be fair, a 50-300 lens is 6x zoom regardless of sensor size. On Pentax (1.5 crop) it is 75-450 which is still 6x - if it were a 2x sensor, the ratio still remains 6x.

In the end though, that ratio is fairly meaningless - a 18-54 (if such a lens existed) and 100-300 are both 3x but completely different lenses
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Old Aug 12, 2010, 1:07 PM   #12
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[QUOTE=JohnG;1128720]To be fair, a 50-300 lens is 6x zoom regardless of sensor size. On Pentax (1.5 crop) it is 75-450 which is still 6x - if it were a 2x sensor, the ratio still remains 6x.

yeah, I caught that a couple of minutes after I posted it and corrected what I wrote. I was thinking 100mm, not 50mm, when I initially typed my response.
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Old Aug 13, 2010, 12:42 PM   #13
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Originally Posted by finja View Post
Those are some beautiful pictures... I think I would be very happy with an E-PL1.

Since I'm not familiar with dSLR, I am still confused about the "zoom" on the lenses though. For example, I believe that a Pentax K-x with a 55-300 lense would give a max zoom equivalent to 16.7X. So for an E-PL1 with a 55-200 lense would the max zoom be 14.3X or 22.2X?
This is the problem with 'x' zooms that are used to advertise P&S cameras. I The "x" only means the ratio of the widest angle of the lens to the most telephoto. It has basically no relationship to how far you're actually 'zoomed in.'

Some basics: On a 35mm film camera system, a 50mm lens is called a "normal" lens. In other words, it has approximately the same field of view as your human eye. http://en.wikipedia.org/wiki/Normal_lens "50mm" is usually the focal length of that lens.

Of course, on P&S cameras, you don't have lenses that have focal lengths that are 50mm long. (Most of the time they're in the single digits to tens of milimeters). So instead, we talk about "35mm equivalent."

For example, the Panasonic DMC-FZ35 (one of the favorite super zoom cameras around here), has a zoom lens with a focal length of 4.8 to 86.4 millimeters. But in the 35mm camera equivalent, that's 27-486mm. When you take 50mm to be a "normal" lens, that shows you how much that camera can zoom in!
http://www.steves-digicams.com/camer...ations-55.html

Now, this camera is advertised as an 18x zoom, because 486 divided by 27 is about 18, not because the lens is zoomed in times your normal vision. Other cameras are 3x zooms, but that doesn't really tell you what the focal length is. It could be a wide angle zoom -- say 15-45 mm equivalent, or it could be a portrait-style zoom-- say 50-150mm.

All of this is a long way to say that your "x factor" questions can't really be answered.

And then we have yet another complication-- the "crop factor." In big, super-massive digital SLR cameras, the imaging sensor that actually takes the picture is "full frame." Which means that the sensor captures all of the image that is focused by the lens. A 50mm normal lens on a Canon 1D produces the same photograph as if the lens were on a 35mm camera.
But cheaper dSLRs have physically smaller image sensors. So not all of the light focused by the lens lands on the image sensor. Thus, the image is "cropped" before it's even taken. The field of view is decreased.

In bigger, consumer-level dSLRs, the "crop factor" is 1.5x or 1.6x. Meaning that the image from a 100mm lens will be cropped down to capture the field of view that a 150mm lens would capture.

But the crop factor in micro four-thirds cameras is 2x. Meaning that the image from a 100mm lens will be cropped down to capture the field of view that a 200mm lens would capture. It's not really a zoom; light is just disregarded. But it looks like the image is doubly-zoomed in.

So, where are we? A long zoom lens, say 200mm, will appear to capture the field of view of a 400mm lens. So you get closer with shorter (usually lighter and cheaper) lenses. And that image would be about 1/8 of the field of view of your "normal" vision. Is that zoomed in 8x? Well, I'll let an optics person answer that question. But, if this lens was 65-200mm, it'd only be described as a "3x zoom."

So, in conclusion -- avoid talk of "X's." Think in rough 35mm film camera equivalents, and for all lenses you attach you a micro-four-thirds camera, double the focal length to get the equivalent in 35mm.

I hope this makes some sense. (And I hope I got everything right!)

Last edited by perdendosi; Aug 13, 2010 at 12:56 PM.
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Old Aug 13, 2010, 3:27 PM   #14
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Believe it or not, I think I actually understood that.

Thank you.
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