I'm about to purchase an 85mm Prime Lens to use to film interviews using my Canon C100mk2. I've been searching for some reviews and comparisons between the Sigma 85mm f/1.4 DG HSM Art lens and Canons EF 85mm f/1.4L IS USM lens for video. There are some great videos and articles that compare the two for still photography but I couldn't find anything for video. So far the best thing going for the Sigma 85mm Art is it's price point but before I go ahead and make the purchase, I thought I'd ask for some advice from users of these Primes and the Canon C100mk2. I've only just stepped up into using an interchangeable lens camera so still have a lot to learn.
I'm purchasing the Prime Lens for recording "talking head" interviews, shot indoor with a three point lighting setup. I do travel a bit to the homes of the people I'm interviewing and don't always have the option of checking out the location until I get there. This means I'm not always able to get the exact dimensions of the room that they are happy for me to set up all my kit in. This can be a problem when getting a good amount of distance between the interviewee and the background in order to achieve a short depth of field. From tests with an 85mm Prime, I was able to achieve a nice bokah effect that is more to my taste than what I can achieve with the Sigma 20-75mm F/2.8 DG OS HSM Art Lens that came with the camera bundle I purchased.
I would really appreciate some advice on what considerations I should take into account before choosing the Sigma 85mm Art Lens over the Canon 85mm Prime. I'll always be using a tripod so IS isn't a problem. However, I would like to use the Face AF on the C100mk2 and I haven't been able to find out if either of these lenses are compatible with this function.
Any help with this question or advice/tips when shooting with an 85mm Prime Lens and the C100mk2 would be most appreciated.
85mm is pretty long on a Super-35 sensor. It's perfectly usable, but you'd better make sure you have lots of space to do your interviews, because if you want to show more than just a head, you'll have to pull way back from them. If your interviews are going to be in tighter spaces, you might consider dropping down to a 50 or 60mm lens. Ultra thin DOF is just going to ensure that part of their face isn't in focus; your 75mm lens at f2.8 should be more than enough to get you good background separation.
As for comparing the two; rent 'em both and see which one you like more.