Right Lens for DSLR
I have just recently jumped into the world of DSLR. I have been working with all different kinds of camera throughout my 10 years of production. I honestly held off on dslr because I didn't want to reconfigure all my equipment for a dslr. But now I am starting on my path and I am having a hard time finding a correct lens to use for the rig. Basically I find I cannot move in close or away when recording w/o focusing annually. Is there a lens that works more like an auto focus? I got a nikon d7100, just to start out and try. Thanks for any help on this.
This is very close to my other post on the issue.
The Dx000 series Nikons are all pretty much the same sensor wise, only the video processors and resolution are different. The actual Dxxx series are the higher end full frame models. Getting "DX" lens are the matched lens for the DX cameras. The N series Nikon lens are much higher quality lens with more resolution. You can use a full frame lens on a DX camera with a crop factor. The older manual 35mm lens will work with DX cameras in manual mode and likely have better resolution. The DX sensor is basically 1:1 with motion picture frame size, where as the full frame sensor matches 35mm still. This is due to one 35mm format running vertically vs horizontally.
What you are experiencing is one of the realities of filming video with DSLR cameras. While some lenses and camera combos do have autofocus capability many are very slow and will hunt and seek before picking something to focus on. There are a few camera bodies that are recognized for having especially very good autofocusing capabilities - these are sometimes known as dual pixel auto focus systems but can go by other marketing names as well, names vary by brand.
Cinema lenses are almost defined by NOT having any autofocus capability at all, they are totally manual focus. In cinema circles auto focus is almost looked down upon; "a true cinematographer would never allow the camera or lens to try and focus their shot for them" is a common idea. When you have larger crews and maybe even a very skilled someone whose whole job it is to focus the camera for you (a "focus puller") then the camera operator does not have to worry about focus - most of us don't live in that world.
DSLR lenses in particular are notorious for being very very sensitive when it comes to getting focus, just a small turn can result in big focus changes - hence the popularity of follow focus gears (again too pricey for me right now but would love to have a setup like that)
So if you are filming with a DSLR and maybe have a full frame sensor and very shallow depth of field, then it can be quite the task to keep the subject in focus and that's on top of keeping an eye on everything else. Camera or external monitor firmware that offers nice things like focus peaking are very nice to have, perhaps along with a follow focus unit on the side of the camera.
So you may have to make a choice, playing it "safe" with deep depth of field on subjects that are prone to move around and then saving the shallow depth of field stuff for your beauty shots where you have more control and things are more static. (Either that or train yourself to get very very good at nailing focus, perhaps by filming cats or children or children playing with cats)