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Old Feb 18, 2004, 7:00 PM   #1
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Default How do you calculate the Zoom factor of a lens?

This is probably a realy silly question, but how do you work out the zoom factor of a lens?

18-55 = ? zoom
or
28-135 = ? zoom
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Old Feb 18, 2004, 7:50 PM   #2
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Default Re: How do you calculate the Zoom factor of a lens?

Quote:
Originally Posted by scata
This is probably a realy silly question, but how do you work out the zoom factor of a lens?

18-55 = 3.0555... zoom
or
28-135 = 4.8214... zoom
Simple ratio. And a largely useless one. I saw a preanouncement for a 3x zoom camera that went from 200 to 600mm (equiv) - it was built by one of the telescope manufacturers who had lashed a CCD and LCD onto one of their scopes. That 3x zoom outreaches any 12x zoom digicam that I know of.

Pay attention to the range of focal lengths, not to the zoom factor. If it goes wide enough and long enough to suit your purposes (none ever do), that is what you want to know. I will never purchase a camera that does not have a short focal length. Long is nice to have, but I really want short. Not what is being sold widely though.
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Old Feb 19, 2004, 6:42 AM   #3
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Thanks Bill,

What would you recomend lens wise as a general walk about lens?

I am about to get a EF 28-135mm f/3.5-5.6 IS USM to compliment my other lens:-

EF-S 18-55mm f/3.5-5.6 (Kit Lens with 300D)

Filters : UV/SoftMat/Polarizing PL-C
(Note to self : Need to get a 58 - 72 converter, or new filters)

also have you ever used the EF 25 Coverter?
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Old Feb 19, 2004, 7:48 AM   #4
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With your 1.6 focal length multiplier the 28-135 will behave like a 45-216 and that's ok. With a 0.5m close focus and image stabilisation as well it sounds like a nice lens.

My walkabout lens is a Nikon 28-105. It focuses closer than the Canon but not as much reach and no IS.

Regards,
Graham.
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Old Feb 19, 2004, 10:18 AM   #5
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Same my perfered general walkabout is a sigma 28-105.
Although lately I've been on a wideish kick and taking a 19-35 on my walks instead.
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