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Old Dec 24, 2005, 1:07 PM   #1
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I see lens posted as 18-200 macro and others that don't say macro. What is the difference?
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Old Dec 26, 2005, 9:52 AM   #2
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RP33 wrote:
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I see lens posted as 18-200 macro and others that don't say macro. What is the difference?
For a lens to be a true macro lens, it must have a 1:1 magnification factor. This is the ratio to the actual size of the object being photographed in relation to the image being delivered to the sensor.

And unfortunately, lens manufacturers do not conform to the guideline. There are many lenses out there from all major manufacturers whose lenses say "macro" on the barrel or on the box, but they are not really macro lenses. You can check the "maginification" in the lens specifications. Many near-macro lenses will be 1:2 for example, but like I said it's not real macro, and in some cases it's not even close (Although 1:2 is pretty good for a non-macro lens, actually). The worst example of this is on my Canon 17-85IS. It says "MACRO 1.2 ft" or something like that on the barrel. It is simply saying that to get a "closeup" shot, you can get as close as 1.2 feet from your subject with this lens (which isn't really close at all).

A good way to find a true macro lens is to look at dedicated prime lenses. The two best that come to mind are Canon's 100mm 2.8 macro and the Sigma 150mm macro. These lenses have a true macro maginification factor of 1:1. Also, these lenses serve other purposes as well. For example, the Canon 100mm is also a good portrait lens while the Sigma is a 150mm telephoto as well. I don't think there is such a thing as a true macro zoom lens, by the way.

Finally, the focal length of a macro lens dimply determines the len's "working distance" You have to get closer to your subject with the 100mm versus the 150mm, but the resulting subject will be the same size in the frame (because the maginification factors of each lens are both 1:1 I believe). This increased focal length/working distance is useful when shooting bugs, for example (unless they are dead)...

Hope this helps.

Chris M
www.imagineimagery.com
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Old Dec 26, 2005, 10:01 AM   #3
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So with that said then 100mm1:1 lens verse a 1:2 lens the 1:1 allows you closer for the same picture is that right?


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Old Dec 26, 2005, 11:35 AM   #4
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RP33 wrote:
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So with that said then 100mm1:1 lens verse a 1:2 lens the 1:1 allows you closer for the same picture is that right?

Well, not exactly. True, you will be able to get closer with the 1:1 lens, but the picture will not be the same. The 1:1 lens subject will be twice as large in the frame as the 1:2 lens (magnified by 2). If you want to get into real macro photography, simply look for a prime lens with a magnification ratio of 1:1 and you'll be in business. The Canon 100mm 2.8 Macro is highly regarded.

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Old Dec 27, 2005, 9:12 PM   #5
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> For a lens to be a true macro lens, it must have a 1:1 magnification factor.

Almost - dedicated macro lenses can certainly have a higher magification factor than 1:1 - for instance, the MP-E 65 can have up to a 5:1 magification, so you're filling your film/sensor plane with an object 5x smaller than the sensor's dimensions.


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Old Dec 28, 2005, 9:32 AM   #6
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sjburges wrote:
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> For a lens to be a true macro lens, it must have a 1:1 magnification factor.

Almost - dedicated macro lenses can certainly have a higher magification factor than 1:1 - for instance, the MP-E 65 can have up to a 5:1 magification, so you're filling your film/sensor plane with an object 5x smaller than the sensor's dimensions.

Yes, of course, a lens must have a magnification factor of AT LEAST 1:1...

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