question about my new lens

Hey, I just got a sigma 17-70mm macro. I dont know if this is a true macro but that is what it says. My question, as I zoom the lens in and out what do the numbers along the lens mean. For instance mine say things like1:2.3, 1:3.5 all the way down the lens. and then going around the lens are other numbers. Anyone have this lens that can tell me what all this means. thanks a lot

Hi demarco36,

These numbers refer to the magnification. 1:1 is life size. 1:2 is half life size. Substitute the : for a / and it'll make a bit more sense. So, 1:2.3 becomes 1/2.3, ie. roughly .43x life size. 1:3.5 becomes 1/3.5, which is around .28x life size. So, if a object (insect) is 5mm in length, it'll end up being either .43 x 5mm long (ie around 2.15mm on the sensor), or .28 x 5mm long (ie around 1.4mm on the sensor).

Does this make sense?

Dave

Yes somewhat. Will the insect image be bigger than actual size when I develop the picture? So as I zoom in and out that has to do with the macro function I guess? what about the numbers going around the lens that has the infinity symbol at the end. Is this for manual focusing? Thanks a lot for the help

Yes, those are the manual focus digits. Infinity means focussed to infinity, and the lower the numbers get the closer the lens is focused.

lens manufacturers use the term macro just to mean closeup.......In recent years, the term macro has come to mean being able to focus on a subject close enough so that when a standard 102×152 mm (4×6 inch) print is made, the image is life-size or larger.

The classical definition is photography in which the image on film or electronic sensor is as large or larger than the subject. Therefore, on 35mm film (for example), the camera has to have the ability to focus on an area at least as small as 24×36 mm, as this is the size of the image on the film. This is a magnification of 1:1.