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#1 Varun Nayar

Varun Nayar
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  • India

Posted 02 March 2007 - 03:03 AM

Hi,

...I was reading a book by Nick Gordon. A piece on macro interested me. So I picked up the Z1 and D30 and was practicing on everything from newspapers, coins, miniature cars...etc...I found the Z1 easier to handle in macro than the Beta D30. Even though the Z1 took me quite close...is there any way to get closer....like a filter or so as used in photography.

The other question is what is the concept of maximum relative aperture of a lens and how do you calculate it.

Thanks...

Varun <|P.O.K.E|>
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#2 Michael Nash

Michael Nash
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Posted 02 March 2007 - 06:59 PM

Don't confuse close focus with magnification. As you may have noticed, many zoom lenses with macro elements can focus close enough to resolve dust sitting on the front element of the lens. You don't have to focus any closer than that! But if you want small details to appear larger (more magnified), you usually have to switch to a lens with a smaller front element. No matter how close you focus, image size is determined by magnification.

Without a macro element on the zoom, you would use a close focus diopter. This is usually a piece of convex glass that attaches to the front of your lens, letting you focus more closely. But it doesn't change the magnification of the lens you're using.

Maximum aperture just means the widest aperture a lens will open up to.

Relative aperture is just a way of noting that the stated maximum aperture is relative to the focal length, and that it's not a physical measurement of the entrance pupil. (Focal length/diameter = f). For example, a 100 mm lens with a maximum entrance pupil (iris) of 50 mm could be called f/2 (100/50=2). A 10 mm lens would be f/2 with a 5 mm entrance pupil. The longer the focal length, the larger the entrance pupil needs to be to pass through the same amount of light.

In the real world, the maximum aperture and relative aperture of a lens are usually the same thing.
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