Auto focus help

boomstrikevideo

boomstrikevideo

Active member
One of the things I have been struggling with all summer is the autofocus on the HVX. I do my best to optimize settings (high frame rates and shutter speeds) to minimize the problem. Most clients want us to shoot 24 frames which has been a real problem. I do my best to convince them to use something closer to 60 frames. I would love to use manual focus but there is a slight problem with my set up. The HVX is attached to a large remotely piloted helicam. The camera operator can remotely control focus, iris, zoom etc. but views what the camera is shooting via a 2.4 ghz DV video downlink to a 9" LCD monitor. This image isn't nearly of good enough quality to make focus decisions.

Any suggestions on a different approach would be greatly appreciated?
 
whats the problem with the focus? Do you have a pola or any glass dome infront of the lens? Can you just set it at infinity and be done with it?
 
I don't know much about your set up but the bottom line is you need to improve your signal from the helicopter to the receiver and monitor. You are not going to be able to rely on auto focus in this situation or pretty much any situation with this camera shooting HD.
Jim
 
When there isn't much difference in contrast in the shot the autofocus hunts. The main advantage of the helicam is the ability to get in tight and fly close to/around/over objects. Infinity doesn't work in these situations.

I only have a UV filter out front.
 
24p and autofocus don't go well togethor... I was going to say infinity, but you just said that doesn't work well for your situation.

But, just to be sure... when you try infinity focus are you rolling the focus ring to infinity or flipping the auto/manual/infinity switch to get infinity focus? The reason being is that the HVX actually will hit infinity on the focus ring and then focus beyond that to an extent... if you just use the switch, you may find it to provide more acceptable results, if you are not already.
 
Jason,
That's a good idea. The only thing is he can't see the picture clear enough to tell if the focus is sharp.
Jim
 
I have the ability to adjust focus in flight now. My video transmitter takes the SD video out (yellow RCA plug) and sends that signal to a ground based receiver that outputs to the LCD display. The quality of the transmitted signal isn't good enough to tell if you are in focus or not. What I am really looking for is a system that can transmit/receive in HD.
 
He's using a helicam -- a wired lens controller won't work. There are wireless ones, but you still have the problem of needing to be able to accurately see what is going on,

I would avoid 24P for anything with lots of motion and deep DOF. I would try 30P or even 60P to allow for better AF performance, and then drop every other frame in post. Use an aperture that gives deep DOF to make accurate focus less critical.
 
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