Is it "macro photography" or "micro photography?" Is there a difference? Let me tell you all about it.
There are photographers that feel there needs to be a distinction between "close-up" and "macro" photography. They say that photography at magnification less than 1:1 is a "close-up" (so even 1:0.9999) and anything at 1:1 or above is "macro".
Then there are photographers that say there needs to be a distinction between "macro" and "micro". They say that anything over 1:1 magnification is "micro," and anything below that is "macro" (so even 1:0.9999).
Finally, there are photographers who couldn't care less.
If we combine all of these statements, you get that either there is no such thing as "macro", and we only have "close-up" or "micro", or everything is just "macro." You decide which works better for you. Or if none of it makes sense.
The correct definition
I call the following "macro photography":
Genre of photography concerned with presenting small subjects at larger-than-life sizes.
The "presenting" part is of particular import, and let me demonstrate why it matters.
The image above was taken at 2:1 magnification. This is called twice-life-size reproduction ratio (or 2× magnification). Can you tell? Of course not. The only thing you can see is that it's (probably) larger than in the real life as seen on your screen.
With a twist of reductio ad apsurdum I reduce the size of the image to 40px tall. Now the bubbles should be less than the real life size on most screens. In fact, due to low resolution, you are not even able to see them.
The small image was shot at 2:1 magnification, which is "micro", or "true macro", or whatever else the Internet experts would prefer to call it, but the image fails to fulfill the intended goal of presenting the subject much larger than the real life. How the photo was taken doesn't really matter. It's what the viewers see that's far more important.
This is consistent with the definition offered by Wikipedia, which says macro photography refers to "extreme close-up photography, usually of very small subjects and living organisms like insects, in which the size of the subject in the photograph is greater than life size" (emphasis added). A photograph is the image we see on the screen or printed on a piece of paper, not the image captured by the sensor. The article further elaborates this point:
Apart from technical photography and film-based processes, where the size of the image on the negative or image sensor is the subject of discussion, the finished print or on-screen image more commonly lends a photograph its macro status. For example, when producing a 6×4-inch (15×10-cm) print using 35 format (36×24 mm) film or sensor, a life-size result is possible with a lens having only a 1:4 reproduction ratio. [emphasis mine]
The true macro lens myth
By extension of the definition seen above, the "true macro lens" nomenclature is also a myth. Any lens is a "true macro" lens as long your end result is "true macro", or larger-than-life reproduction of the subject.
I hope this settles, once and for all, the definition of macro photography. I'm just kidding. I know we're not even close. However, I hope this does show your two things: there's too much obsession with how we photograph over what we photograph, and how we photography doesn't matter that much as long as it results in what we intended.