on 1/23/04 2:44 AM, Brian Swale at bj@xxxxxxxxxxxxxxx wrote:
>
> Hi folks,
>
> Can somebody please answer this (probably stupid) question from me?
>
> When a lens test for macro refers to 1:2 and 1:4,
>
> which of these yields the greatest subject magnification on film?.
>
> I ask this because a lens test I was reading said the lens at closest focus
> 1:2 was 36 inches from the subject; yet they tested it at 1:4 as well.
>
> Brian
Magnification expressed that way (1:2, 1:4) refers to the size of the image
versus the actual size of the subject. So if you take a picture of a coin
(US 10-cent coin for instance) and then lay the actual coin on the negative
or slide and it is the -same- size, then you have achieved a 1:1
magnification. A 1:2 magnification would have the coin's image on the film
be 1/2 the size of the actual coin. The Zuiko 50/3.5 and the Zuiko 90/2.0
macro lenses both go to 1:2 magnification with continuous focus from
infinity.
Traditionally, the 'real' macro magnifications were considered to start at
1:4 or even 1:2, lesser magnification that that was just considered
'close-up'. I think the standard close-focus for most SLR normal lenses is
approximately 1:10 magnification. Many lens tests are done at 1:40
magnification, note that the distance between subject and film will be
different for different focal lengths to get the same magnification, which
is why you get more 'working distance' with a 90mm macro lens than with a
50mm...
--
Jim Brokaw
OM-'s of all sorts, and no OM-oney...
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