I have been experimenting with some new equipment ready for my trip next week back to Sri Lanka.  My 500 4.5 Sigma Lens is back with the manufacturer for repair so I needed to think of a way of getting good shots while I am there.  I have a very good Pentax 300 prime lens which I use sometimes with a 1.4 extender, this gives me the equivalent of 420mm. This is fine for birds and wildlife when it is reasonably close but I may be struggling with distant subjects. I have been experimenting by stacking with two 1.4 extenders to get more reach for distant subjects. It has worked quite well and as long as the camera is on a tripod then it will auto focus and give me almost 600mm but I have to say that I haven't got the technical expertise to say exactly what the magnification is.  You would expect there to be quite a degrading of quality in the images but I am pleased to say that this does not appear to be particularly noticeable and I am very happy with the results.

I took the lens in to the garden late this morning to do some tests and I was joined by a Robin.  In the garden this can be a very confiding species that is attracted to humans to feed on any small invertebrates that are disturbed by gardeners. This is a behaviour that is thought to have evolved when they followed herds of deer and wild boar in a forest environment. Blackbirds (turdus merula) is also a species with this behaviour. Anyway, I am pleased to say that the little bird gave me the chance to put my equipment to the test with very satisfactory results.