I am currently looking to purchase 2 prime lenses for my Canon 600d to use alongside my Sigma 30mm. I decided not to go completely the Canon route in the first place as I don't have the budget for L glass and some of their other lenses are outclassed by other makes like Sigma, especially wide angle. I am looking at the Canon 85mm 1.8 but a friend of mine recommends sticking with one lens make as mixing and matching different makes, and even budget and expensive lenses has caused him headaches when colour correcting at the post production stage as the colours from each lens looks very different. My initial reluctance to go completely Sigma is the prices for some of their lenses are too much for me at the moment, their wonderful 85mm 1.4 is roughly £670 which I can't afford right now. The inevitable 3 week calibration to my camera body after purchase to correct front/back focus issues Sigmas are known for is my other reason and I've only just had my 30mm calibrated. What are your thoughts? Can I mix and match different lenses for video or should I just stick with one make?