Good God this subject always generate some pretty bizarre opinions!
The scientific and medical community etc are quite clear on the definitions of what constitutes macro photography and photomicroscopy. We tend to be quite specific about things! To suggest that 'there is certainly nothing universally agreed' as to what constitutes macro photography is frankly ridiculous. When I'm looking at images of histological slides, for example, they weren't just taken in some sort out slapdash fashion - they are professional quality images produce to recognised standards. Unlike camera lens manufacturers we don't tend to use words like macro and micro on a whim, we tend to use them to mean specific things!
That's all very well, but you don't tell us what those "recognised standards" are.
If it is so concisely defined can you please point me to the ISO definition of Macro photography?
The point is that "Macro" means different things to different people, although these days a 1:1 or greater reproduction ratio is widely accepted as the starting point of macro working, but as proven by this discussion, just because something is widely accepted does not constitute a definition, especially a correct one.
As someone who has had an interest in macro photography, years ago, in the days of film, I purchased a Focal press book titled "Macro Methods" by Arnim and Ingeborg Tolke.
This was first published in 1965 an in the text it says (about macro) "... (there is)
the fascination of photographing minute objects "big", with quite astonishing results. Photographs of this kind are commonly divided into two categories - close-up and macrophotography - and it would be better if such indefinite terminology could be replaced by a clear-cut definition based on the technique employed."
So it seems the definition of "macro" has been undefined for quite some time.
Just because camera manufactures stick 'macro' on a lens barrel instead of 'close-focusing' doesn't change the definition. Just because lots of people into macro photography like to shoot pictures of insects, doesn't mean the definition changes to encompass any picture of a friggin' ant! Just because a picture of something taken on a FF dSLR fills the frame more than something taken on medium format doesn't make one more macro than the other!
NO NO NO NO NO! What if that image is being taken for the purpose of forensic photography in a study on the tensile strength of that brick and someone wants an image generated to those specs? Think a bit beyond photography being simply about making pretty pictures. Just because the macro images you're used to seeing are of butterflies that doesn't mean a photo of a house brick is 'silly' FFS.
The only way to provide a "forensic" reference in a photograph is to include a scale of some kind, (although I'm not sure how you measure tensile strength with a photograph.)
Otherwise you are reliant on the image always being reproduced to the same scale, which is never the case with a print, which can obviously be made any size, without reference to the original.
Just because it was macro (1:1) on the original imaging device (be it film or digital) does not mean it will be 1:1 in the final print.
In fact it is very unlikely, since I don't know anyone who makes 1:1 prints at image sensor size, even a large format one.
Without providing us a reference to a defined standard you are expressing an opinion just as "silly" as some of the other posts.