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Old Feb 10, 2007, 4:17 AM   #5
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Join Date: Nov 2005
Location: Hassleholm, Sweden
Posts: 3,437

mtngal wrote:
Oh, wow! Kjell - lovely shot.

Kjell - let's see if I got this right - you took it with a macro lens and extension tubes? What does the extension tubes give you that you don't get from a macro lens (I'm confused, as usual). I thought that extension tubes didn't change the lens ability to magnify, just its ability to focus closer and made the DOF smaller. A dedicated macro lens can already focus pretty closely (my cheapie100mm can focus as close as I'm willing to get to my subjects, sometimes closer) so by adding additional extension tubes, you'd be right on top of your subject, wouldn't you? Or do I have this all wrong (like normal).
Even macro lenses differ from each other. The Vivitar gives, as I understand it, a magnification of 1:1. My Pentax 100 mm "only" allows 1:2. I guess the difference is that the Vivitar is built to allow you to get closer to the subjectthan with the Pentax, when using shortest possible focussing distance. The closest I get with my lens is 45 cm (1.48 feet). But with extension tubes attached, I can get closer also with the Pentax, thus getting that 1:1 ratio, or even more.Of course, with the extension tubes attached, I can't focus the Pentax to infinity. Somehow that has never been a problem when shooting macro.:-)

As I understand it, the main difference between dedicated macro lenses and other lenses is not the magnification factor per se, but that the macro lenses give you a flat field with less distortion at the edges. That can be of importance when taking photos of things like stamps. Any lens can magnify with extension tubes.

Roy and Hogrider, help us out here. Does the extension tube really give less DOF at the same aperture, or is it just because you focus closer that it appears like that?

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