If you ask the average photographer what the difference between a macro lens and a “regular” lens is, they will tell you macro lenses enable you to get closer to your subject than regular, or conventional, lenses. While this is true, the ability to focus close is only part of the story. The other part of the story has to do with an optical characteristic called “curvature of field,” of which there are two types—flat-field and curved-field.
All Photographs © Allan Weitz 2020
Most consumer lenses are curved-field lenses, and as you might have noted from personal experience, most consumer lenses are quite good at taking extremely good photographs.
With few exceptions, most macro lenses are flat-field lenses. The difference is that when you take a straight-on picture of a subject with a flat surface, be it a document, a painting, or other flat, two-dimensional subjects, the center of the frame is sharper than the edges of the frame when taken with curved-field lenses, most noticeably at wider apertures. If you want to bring the edges into better focus, you have to stop the lens down. How many stops? That depends on the lens.