I'm trying to figure out what camera to buy for photographing coins, should my current camera go bad. I've read I need a macro lens with a magnification ratio of 1:1, 2:1, 3:1, etc., as opposed to 1:2, 1:3, 1:4, etc. Is this correct?
I just use a regular lens and shoot at a very high resolution then use a photo program to zoom in and crop. It works for my needs, but I don't know your specific needs.
A macro lens, which will be very good to have, is defined to be a lens that lets you focus close-up. Like 12" away from the coin, or even closer. The magnification of the lens usually isn't part of the equation for macro.
For coins a dedicated macro with a 1:1 ratio is best. You can get possible photos with other lenses, including zoom. It all depends on what you want as far as clarity of devices and fields.
No, dedicated macro lenses are categorized by magnification -- the ratio of an object's size (at minimum focus distance) to the size of its image on the camera sensor. (Of course, you can then project that image onto the side of the Grand Canyon if you want.) Traditionally, a "macro" lens was one that produced at least a 1:1 magnification. Canon used to make one that would go up to 5:1, but they discontinued it last year. With that one, a full-frame camera image at top magnification would cover a object a little more than a quarter-inch wide, and a bit less than a fifth of an inch high. With a 1:1 true-macro lens, a quarter would not quite fit vertically into the camera view at its closest focus. Of course, you can shoot larger coins by just backing further away. There are also extension tubes you can use with an interchangeable-lens camera to get closer focus. You put one or more tubes between the lens and the camera body to hold the lens further from the camera, and that lets you get closer to the subject. But it also darkens the image, and usually trashes auto-focus. If you want to get closer than 1:1 for coin photography, you're probably just focusing on small marks or features, and you're likely better off with a microscope.
You are correct. I was commenting as to needs related to typical photography of coins, but wasn't clear on that.
Some cellphones these days have a Portrait, Landscape and a feature to take shots at 4cm or closer for things like this. One such phone is the Moto G stylus.
1:1 magnification would mean that the size of the sensor and the size of the section of the coin you are photographing are identical. 2:1 magnification would mean that the size of the sensor is twice the size of the section of the coin. Thus a macro lens will make it difficult to photograph the entire coin.
