macro lens question

starky987

So I'm new to photography and had a few macro questions. First is about the lens itself. i don't understand what makes a good macro lens. When I look to purchase a lens I look at how 18mm-200mm measurement. (obviously I'm very new to photography) If a macro lens says 50mm why am I able to take pictures that are incredibly close up? Couldn't I do that with my normal camera lens? I'm also very interested in getting macro lens and was recommended to get the sigma lens. Once I purchase the lens am I ready to hook it up to my camera and start shooting or do I have to do other stuff before I can take good macro shots? I'd really just like to learn about macro photography b/c I am very interested in it. Any help would be appreciated and please don't think I'm a complete idiot, I'm still learning about photography as I go. Thanks

Icebear

starky987 wrote:

I'm very new to photography

Run away! Run away! Now, before it's too late!

OK, don't say I didn't warn you. The fundemental difference in a dedicated macro lens and a "normal" lens is in the way the lens is constructed. A macro lens has the ability to focus on a subject that is much closer to the "film plane" than a normal lens.

You can make a normal lens act much like a macro lens at close focusing distances with the use of extension tubes that move the lens away from the film plane (sensor). One big advantage of a dedicated macro lens is that it is also able to focus at more "normal" distances, up to and including infinity. Can't do that with a lens mounted on extension tubes.

Extension tubes are an economical method of getting into photographing the world of the small. It's addictive though. That's why I warned you to run away.

starky987

I was also wondering what is accomplished by reversing the lens or whatever people are talking about in here? does it provide an even greater magnification? Just looking to get into macro photography and thought I'd gather some info before starting.

thanks

Lord Vetinari

True macro prime lenses allow you to focus close enough so that at minimum focus 1cm of subject will give 1cm of image on the sensor (be it film or electronic) and thus give 1:1 magnification. Some zoom lenses claim macro capability but this is not normally much better than 0.3:1 magnification. The different focal length macro lenses have different minimum focus distances so a 180mm macro lens achieves 1:1 magnification further from the subject than say a 50mm macro lens.
Reversing a lens onto the camera body has a similar effect of reducing the minimum focus distance of the lens such that the kit lens you get with DSLRs can actually achieve upto 3:1 magnification when reversed like this.

Brian V.