A lot of modern auto-focusing lenses have a very short through, which helps the autofocus motors achieve the focus quicker for photography needs, however for video this is actually a big downside, so good old manual lenses are so much better for manual focusing. They also have hard stops, which are important if you use a follow focus and focusing marks. Again, some modern lenses, Canon EF in particular don’t have any hard stops.
I keep telling people that the reason why modern lenses are so much more expensive that the old glass is not only because they have great optics, but also because they have great, fast auto focusing motors, which obviously makes a massive impact on the price. After all, these are photography lenses made for modern sophisticate cameras with fancy auto focusing systems. I said it before and I’ll say it again: if you are only doing video work with you DSLR then there is really no need to buy modern Canon, Nikon, Panasonic, etc glass. You can get so much more for your money if you invest into manual lenses and they don’t have to be as cheap as this Helios. Even very popular manual Nikon and Zeiss lenses will cost so much less that a modern equivalent which will not necessarily be better for video work.
If you are on a tight budget though, I highly recommend this Helios 44-2 58mm lens. It is a great mid/close up lens and it is so cheap that anyone can afford it.
I have 2 of them and I will be giving away one shortly. Stay tune for more details.