Old rule of thumb

Hi, I am interested in your comments on an old rule of thumb on strobe positioning. It says that the distance between the strobes should be the same as the camera distance to the subject. Of course here are strobe positions and supermacro conditions where this rule does not work. However, if the rule generally still holds it would make live easier.  What do you think?

Yeah, could be.

But rules are meant to be broken otherwise all the images look kinda the same. In addition, the angles of the strobes and their orientation are as important, eg 9-3, 10-2, slightly turned outwards, or upwards.

If you can, get your hands on Alex Mustard's book, "Underwater Photography Masterclass". There's a good section on strobe positioning. ISBN 978-1-78145-222-6

Think of it as a starting point rather than a rule and mainly for wide angle photography, it sort of breaks down when you start to get close to your subject.

I think of it as the distance between the lens and a strobe (instead of what was stated above) with the axis of both being in parallel thus forming a square and thus 45-45-90 isosceles triangles when thinking of the strobe's light output. Double the 45 to 90, thus a strobe with 90 degrees coverage will reach the lens' optical axis i.e., the center of the frame. A wide angle strobe will do more thus one can use the feathered edge of the strobe for illumination. Do the same for each strobe when using two strobes - distance between them will vary according to their "clock" position. Use this as a starting point adjusting the strobe angle to point outwards if so desired as Tim mentions above.

I like Tom's 'mathematical' answer that shows that the 'rule' better fits the lens-strobe distance. It shows that in the original rule there would be a very strong overlap of the light of both flashes in the central area, counteracting the even distribution of light. And  yes, it's just a starting point for wide angle photography, it should not hamper creative ideas.