hello i want to do video interviews in regular indoor lighting (without additional lighting) - i guess i need a fast prime portait lens to do that. (typically a 50mm f1.8 on 1.5 crop factor) but there is not such a 35 to 40mm prime lens in the panasonic family of lens what are my options from other brands (i would like to keep the Continuous AF / AE Functionality is it possible)? is the option of the Lumix 20mm f/1.7 x 2.6=52mm using the ETC crop mode a possible solution that will give me a good video image quality? thanks for your help.
The Panasonic 20mm f1.7 is effectively a 40mm lens in "full frame 35mm" terms because of the crop factor of the smaller Micro 4/3rds sensor. So the 20mm lens is already in the ballpark of a 50mm lens on a full-frame DSLR, just a little on the wide side. If you're comparing against a 50mm lens adapted onto a micro 4/3rds camera, that's something else altogether. Then yes, using the ETC crop would be getting you into that general range.
The 20mm is not that good for video, mainly because it's noisy (as in audio, not image quality lol). If you're using a "remote" microphone (away from the camera body), you can probably get away with it. But still even with that issue aside, I think 20mm is too wide for interviews. If you're doing just "sit-down" interviews, I think you can get away with manual focus. If you're ok with MF, get yourself a legacy lens and adapter. You can find a good fast 50mm prime + adapter for $100 or less.
Get a C-mount adapter and a nice cine lens. 35mm is not uncommon in that format, like how about a Fujinon 35mm f/1.7, or a Zeiss 35mm f/1.4? Or maybe get an adapter for a G.Zuiko 38mm f/1.4 or something? Lots of options...
tripod of course but even with a sitting interview, the person might lean forward and get out of focus (on a f1.7 the focus zone is very short) so autofocus is really a plus.
I'm not aware of a single M43 AF lens that is both fast enough AND silent focusing to meet your needs. As a matter of fact, the only silent focusing lens that I am aware of for M43 is the 14-140 F4.0-5.8. So if you really want a fast lens for this, be prepared to record your audio separately and merge in post. More to the point, I'm not sure if I would trust the camera to be able to keep focus sharp at F1.7 without some focus hunting and/or lag as the camera tried to keep up with the subject. I've dealt with the issue of a moving subject by not shooting wide open. Very often I'll shoot at F2.8-F4.0 even though my lens is faster than that. I do that to make sure that even if the subject moves, I'll have a fighting chance that they stay in focus. Here's a shot I did with a Pentax DA70 F2.4: {} Still from Kenney Interview by john m flores, on Flickr I set the focus manually and then kept it there as he spoke. IIRC I was at F4.0 or thereabouts, but the background was far enough away to still be blurred. If you click through you will see the lights that I had. Nothing fancy, but it helped make the shot. Which leads to my next question - what is your aversion to supplemental lighting?
sound is not a problem as for interviews i use lav mic (once it is clipped they forget they wear one), my aversion to supplemental lighting is like not wanting to put my camera too close to the person interviewed, i want them to be comfortable and forget that i am filming them. so if you did not use the 2.6x crop mode with the 20mm, how far was your camera from the people's faces ?
There you go. The lavalier wont pick up sound from the lens. Or a good quality wired mic. Never underestimate the value of quality sound in video production. Way more important than shallow DOF. Then again - I don't trust AF for production video - unless I'm using a real video camera. It'll hunt on you when you least want it to. Pulling focus with a manual lens is pretty easy with a little practice.
so if autofocus on the gh2 (who is supposed to be the fastest on a camera) cannot be used then does it means that shallow depth of field must never be used for an interview ? ( otherwise you'll be forced to correct your manual focus each time the person sitting is leaning forward or backward, how can you speak to the person you are interviewing while checking in real time if your focus is ok) ? the person who did this interview ([ame="http://vimeo.com/20343716"]Summit Awards 2011 - Pikes Peak Council on Vimeo[/ame]) on gh13/20mm, did use AF(AF locked) and it seems ok.
