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Old April 6th, 2002, 05:29 AM   #1
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Lens designation

Dear all,

I have a newbie question: On my camcorder (Panasonic MX300) lenses the following designation is engraved:

Leica Dicomar

43 mm, f=3.55 ~ 42.6 mm , 1:1.6

I assume that:
- Leica Dicomar is the manufacturer and the lens series, respectively.
- 43 mm is the (maximum) focal length (and these are "zoom" lenses ?)
- "f=3.55 ~ 42.6 mm" denominates the maximum aperture at the max. focal length (??)
- Third is the image magnification ratio (???!!)

I have a basic understanding of lens notions and terminology (focal length, aperture, depth of field, etc.) but i cannot find anywhere a description on lens designations i.e. how to decipher those engravings on different lenses. Pointers highly appreciated (the best one I could find so far on the web is the Cannon "EF lens 101" glossary).

Thanks in advance,

Florian
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Old April 6th, 2002, 11:11 AM   #2
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Hi,

From what I can figure the lens is a variable apperature zoom lens. The apperature varies as you zoom from wide angle to telephoto. If I remember correctly it is a 12x optical zoom. That makes it a 3.55mm to 42.6mm lens. the apperature at 3.55mm is F1.6, it's largest or greatest light gathering apperature. The F number is a ratio. That's why a numerically small number is the largest opening of the lens. This ratio is expressed 1:1.6 The 43 I am guessing is the filter size of the lens (43mm).

I hope that helps

Jeff Donald
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Old April 9th, 2002, 02:43 AM   #3
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Another newbie lens question

Hi Jeff,

First, thanks a lot for the info. I really should have read the manual first, it would have spared me the embaressment of asking about focus lengths: they're written big and clear all over the specs and since the lens manufacutrer is Leica they sure do remind you every now and then about that :)

The initial reason for me asking was that I initially thought that lens designation is uniform/standard across lens vendors to give you a way to compare different lenses. AFAICT it varies quite a lot and each manufacturer have their own little variations in the way they designate lens.

On a related issue: I've seen a lens engraving (on a Nikkon SLR camera, don't remember the exact model, looked prosumer) designating the apperture as "1:3.5 (22) - 5.6". If I understand correctly 1:3.5 - 5.6 is the maximum apperture and within brackets is the min. apperture (i.e. f/22). What does intrigue me is why the min apperture is designated as a range (f/3.5 -- f/5.6). I've seen this designation also on some Cannon EF lenses, with the max aperture engraved as "1:4 - 5.6".

Thanks once again,

Florian
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Old April 9th, 2002, 02:50 AM   #4
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Typos

Sorry for the typos and missing commas, I've posted the msg w/o any preview. Obviosuly I ment "Nikon SLR camera" and "Canon EF lens" :-)
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Old April 9th, 2002, 08:44 PM   #5
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many of the newer lenses are varying the ninimum aperature also. So, at 70mm it might be F22 , but at 300m it is F29. it si easier to design lense with variable min and max aperatures so it cost less to build them.

Jeff
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