Thanks for the advice Agiel - will try rendering tiles - is this using 'select render area'? Only problem with this is it will only render to screen so I have to render in small tiles - but this may be my only option The render selected objects option is a problem because it always renders the sky as well the object and so takes a long time. I haven't worked out how to render isolated individual objects with the correct lighting without the sky (this would be very useful)! Peggy - I was definitely overwriting previously failed renders, so maybe this was a problem? i have included a low res version of the image in case anyone has any other advice john