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[OM] Repro ratios, was Fame at last - perhaps ;-)

Subject: [OM] Repro ratios, was Fame at last - perhaps ;-)
From: Moose <olymoose@xxxxxxxxxxxxx>
Date: Thu, 02 Oct 2003 14:59:23 -0700
Reproduction ratio is the linear relationship between the size of the subject and the size of its image on film. A 20mm long image on film of a 100mm subject is a repro ratio of 1:5. They are useful for several things. For folks like me, they are most important as a measure of how 'close-up' a lens will focus independent of focal length. For example, a 200mm lens at a close focus limit of 4 feet will give the same size image on film as a 50mm lens with at a close focus limit of 1 foot. To avoid doing math making comparisons of different lenses, one can simply compare the maximum reproduction ratio. A 35mm and a 135mm lens that have repro ratios of 1:5, for example, are the same in magnification of the subject at their close-focus limits (although they will give different perspectives).

It gets more complicated with zooms. A lot of zooms call themselves 'Macro' with ratios of 1:4, which is no better than many regular lenses. Some others have quite good macro capabilities. The Tamron SP 60-300 at 1:1.55 and Tokina AT-X 50-250 at 1:1.4 are exceptional and the Tokina AT-X 35-200, at 1:3.3, not bad. The Zuikos are generally not that impressive in this particular regard, with the 'close-focus' setting on the 35-105 giving 1:5 and the 35-70/3.5-4.5 at 1:6. Still better than the otherwise wonderful Tamron Asp 35-105/2.8 at 1:7.3.

Another thing with macros is working distance. A 50mm at 1:2 is much closer to the subject than a 100mm at 1:2. This difference is important in various ways, depending on subject, lighting, etc. Again, this is different with different zooms. The Tokina and Tamron mentioned above achieve their close macro through internal adjustment at their widest focal lengths and the front of the lens gets very close to the subject. The Zuiko 50-250 only achieves a 1:5.8 ratio, but does it at 250mm, giving a working distance of 1.53m.

As to quality, the Tamron SP 60-300 and Tokina AT-X 50-250 are amazingly good within their limits. They are excellent with typical natural 3-D subjects where the central parts of the image are often all that is in focus. If used for flat subjects with straight lines and detail over the entire frame, the will likely disappoint. For that, you need genuine macro prime lenses with flat field and minimal linear distortion.

Moose

Boris Grigorov wrote:

&Bill Barber advised me that the 60-300 had a pretty good macro&

OK, I have to ask the elementary question:  What do you mean by macro range?  I 
never used the macro setting on my lens (the Sigma I recently acquired and 
wrote to the list how happy I am with it).

As far as I understand, macro setting allows to focus closer.  Never bothered 
to understand what 1:1, 1:4 etc. means, but now I am curious.




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