What makes a macro lens a macro lens?

[Socrates]

You don't need to know the focusing capabilities. The 24-135 macro at 100mm will not focus as close as a prime 100mm macro.

Obviously you do need to know the focusing capabilities - you've described those capabilities in the second sentence.

Btw on your earlier comment. How BIG are your hands! Your thumbnail doesn't fit on a DX sensor at 1:1 ????

I'm frantically searching for a ruler to measure my thumbnail! Let's see, DX is 24mm X 16mm, which in my language is 0.9 inch X 0.6 inch. I'm staring at my thumbnail and it appears to be a tad more than a half-inch by a half-inch so I guess the correct comment is that it would "just barely fit."

 

[JerryPH]

Be reminded that the desired end result is the size of the image relative to the actual physical size of the subject. (Read my previous post as well as the ones that followed from Chris and Helen B.) The focal lengths and focusing distances are nothing more than the means to achieve that end.

Also, the focal point size makes a practical difference. To get to that 1:1 macro size, with the 60mm you will practically need to shove the lens up the poor insect's nose (lol). A 105mm (in comparison), with let you get that same 1:1 picture but be about 12 inches away.

There are macros in the 50-150mm or more range, but the longer lenses let you get that macro shot without infringing on the subject's space. This becomes a consideration, especially of you are shooting living subjects (insects, etc...). A flower is not going to mind if you stick the lens into it, but a wasp or Brown Recluse spider may have a thing or two to say about you infringing on their territory.

Also, as Socrates said... primes rule. In the world of macros, if you are wanting to get serious about your results, you will take the time to save up for the best lens that you can afford to get the results you want.

In my case, I chose the 105mm F/2.8 Sigma for several reasons:
- It is a FX capable lens that works on my DX sensored D200.
- 105mm is a near perfect range for outdoor portraits
- The lens is incredibly sharp both in macro and normal modes
- Excellent bang for the buck based on the quality
- The 105mm was the perfect compromise between needing to get too close to a subject in macro mode and needing to be too far from a subject when making portraits.



Not quite into macro mode, but a good example of how sharp this lens can get.

A macro shot of an ordinary memory chip (computer RAM):


It's not perfectly sharp, but for the example, close enough.