Sigma 24-70mm F2.8 EX DG MACRO

I am unclear as the the MACRO label on this lens.

The lens has a minimum focusing distance of 40cm (15.7 inches) at all focal lengths and is capable of macro photography with a maximum magnification ratio of 1:3.8

What is meant by this ratio? A 1:1 ratio is kinda obvious but not sure one this one. Could you use extension tubes and would that bring it closer to 1:1.

I am just getting back into SLR photography after 6 yrs doing the unexciting P&S thing and never did do macro before but am quite interested. I am thinking about getting rid of my 17-85 and getting either this lens or the Canon lens as well as a 10-22.

Jim

It's basically a marketing point. The 24-70L, the Tamron 28-75Di, among others, are all "macros" in the same sense that they all have a MFD of about 15" and reproduce your subject at about 0.25 (or 1:4). They aren't technically "macro" lenses (1.0, or 1:1 reproduction), but for standard zooms, it gets by. If you use ETs (e.g., Kenkos 3-set AF is good), they will get you closer. In any case, the increase in magnification through the use of an ET is:

m'=m+(L/f)

Here, m' is the magnification with the extension tube in place, m is the magnification with no extension tube, L is the length of the extension tube (in mm), and f is the focal length of the lens (in mm).

The 24-70EX f2.8 is a very good lens. See my sig for tests. Hope this helps.

fStopJojo,

Thanks for that explaination. Makes things easier to understand and figure out.

What confuses me is how his lens qualifies as a macro, as it only has a .26 multiplication factor. What actually defines 'macro'?

I understand that using extension tubes works by changing minimum focusing distance. Is this directly proportional to the multiplication factor? How would one calculate this?

Thanks to all with the patience to help us newbies.

Jim

The closest focusing distance of the Canon 24-70/2.8 is 50 cm. Since the Sigma will focus closer at 40 cm it must meet someone's definition of macro. (Closer than a standard lens)

For those of us who make macro shots, that is not the definition we use. (1:1 image to actual)

Scott