Thanks for that, the information is very useful and that lens would be within my budget. Regarding the lighting - I had not heard of the Flash Bender, but having looked at it i don't think it would be a practical option in the operating room - there has to be absolutely no risk of contaminating the surgical site, so the 'sail like' nature of the flash bender would be a concern i think. Is anyone aware of ring-flash options that might work or any other potentially better options given the filter size of the 24-70 zoom is 77, so I don't see how i could attach a MR14 EX, and even if i could, would the flash housing being attached directly to the front of the lens cause image cut off/vignetting with an APS-C sensor?

Thanks for everyone's time - nothing seems to be straightforward!