I recently acquired a new macro lens, the Sigma 150mm 2.8. A macro lens is one that is able to reproduce the subject at a “life size” ratio. This means that the object in real life is the same size as it is on the film or digital sensor. This means REALLY BIG. It also tends to mean up close, though that is a side-effect, not a requirement.
There are many zoom lenses out there that claim to have “macro” capability but that really means it can focus closer than perhaps others, but can only produce something that is 1/4 or 1/5 of life size. Not true macro.
The thing about this new lens is that I get more “working distance.” Shorter macro lenses put one almost right on top of the subject – literally inches away. I can be almost a foot away (maybe 8-10″) and still be at or near life size. This gives me a lot more freedom, to say the least, and gives me more natural lighting (I am less likely to block the light myself, etc).
This also means that standing at any normal distance from a subject is getting really close to life size, which means focusing is really tough. This is one of maybe 25 photos of this flower that came out with reasonable sharpness. And as you can see, while that petal on the right side is probably not more than 5mm in front of the stamen, it’s blurry and out of focus.
I am extremely happy with this lens, though it will take some getting used to. It is extremely sharp, easy to handle, and produces very rich colors with nice saturation and contrast. It opens up new options as far as macro photography, which is a wonderful thing to have.