View Full Version : Flickering image w/GL2

Jim Pfeiffenberger
August 26th, 2004, 05:34 PM
I recently shot some aerials over snowy mountains and the results were incredibly disappointing due to a subtle, but noticeable, flickering of the image. I was shooting in Av mode with the aperature set to 8.0. I then used the little exposure lock wheel to lock exposure at -2 to compensate for overexposed areas. What did I do wrong? Is the flickering a result of the camera changing shutter speeds rapidly--I thought using the exposure lock locked in the setting and shutter speed would not automatically change anymore? Could it have resulted from the vibration of the airplane? Anyone experienced this flickering before? I'm going to try to do frame by frame corrections in Premiere, but that's an awful lot of work....still, hate to waste a beautiful evening's flight...

Ken Tanaka
August 26th, 2004, 06:48 PM
Jim, how many times do we have to remind you that you really can't shoot through the propeller!

Welcome, Jim. Sorry, just couldn't resist the elbow.

It's nearly impossible to say what caused the problem, without seeing the footage. But I suspect that you're on the general track by second-guessing your choice of using Av mode. If you had to use any program mode assistance at all I would have recommended Tv, using 1/60 as your set shutter speed. After all, depth of field is not going to be an issue from thousands of feet; you're at infinity from the camera's perspective. It's puzzling why Canon offers the silly Av mode on video cameras at all. Shutter speed is a terrible tool for managing exposure on video cameras. It's really a hold-over from Canon's still camera designs.

Well, it looks like you'll just have to go back up there again...darn.

Good luck.

Jim Pfeiffenberger
August 27th, 2004, 10:11 AM
You know, it occurred to me that the propeller might have been if somehow the wash of air coming back from it was causing this, but I don't see how it could. Gues I'll abandon Av in favor of Tv next time. I tend to think like a still photographer since I have more experience with stills. Was thinking that since there was so much light, I would close the lens down...

Ken Tanaka
August 27th, 2004, 10:43 AM
I completely understand, Jim. Your challenge is to continue "thinking like a photographer" 30 times per second! The program modes on your GL2 operate essentially just like those on your SLR, but they'll do so very quickly as the frame changes. Flying over thick coniferous forests dotted with lakes and snowy mountains can certainly give any video camera a spas attack as it tries to adjust its free parameter.

My recommendation would be to practice using Manual mode on the ground by shooting subjects that closely represent the type of luminance variations that you'll see from the air. Set your shutter to 1/60 and find an aperture range that produces the most reasonable general exposure without blowing-out the highlights. Unlike film and good DSLR photography you really only have about 5 stops of latitude with that GL2. Experiment moving your shutter up to 1/100 but avoid going too much higher. Once you think you've hit a good range, use those settings with Manual mode on your next fly-over. I think you'll be impressed.

I know that many of us wish we could come with you to help!

Have fun!