How about buying a set of extension tubes? They will cost a little more than rental, but then they're yours for always. Pop them between the camera and lens and presto, not a macro lens, but will get you nice a frame filling butterfly shot.
I assume that this will work as well for a Nikon lens as a Canon one.
Surely it will be cheaper and more productive to hire a quality macro lens for this one occasion rather than playing around with tubes?
The 70-300 is a big lens as it is, sticking tubes on the front will make it massive.
Not really, and considering tubes go on the back, I'm not too sure where that idea came from...

a bit left of centre,are these places sometimes quite Humid,

So without sounding thick you would say my 70-300 would be ok?
So without sounding thick you would say my 70-300 would be ok?
So sticking something on the back rather than the front doesnt make it longer???![]()
So without sounding thick you would say my 70-300 would be ok?
It was a slightly sarcy (and on hindsight, cheeky) comment to suggest that you weren't very knowledgeable in what extension tubes actually were.
12mm and 25mm tubes certainly aren't exactly that long - I use a 12mm tube on the back of my 85 quite a lot to overcome the lousy MFD of the lens (this is where crop factor would be good) and it is hardly noticeable - and the 85 is NOT a big lens.
Dedicated macro lenses are quite large anyway as they need all that extra glass and space to allow the range from macro to infinity. Look at the 100 macro for instance - much longer physically than the 100/2 or 85.
I know exactly what extension tubes are thanks, and they will cost a damn sight more than the £35 to hire a macro lens.