Flicker while zooming: video + low light

[mikeydvx]

OK. This video is about as horrible as they come but it's only to illustrate the problem:

http://www.vimeo.com/5342846

Has anyone else noticed the flicker (bursts of exposure change) while zooming in low light? It's not the aperture changing because it happens even when you lock aperture. As I said, this video is lousy but it does illustrate the problem. It doesn't happen in bright light but it does happen even when the light is better/more than the above. BTW, this is visible in the original MTS file, even on the camera.

Anyone else seen this? I figure it must be the camera changing ISO, shutter speed, or something?

Mike

[mikeydvx]

Here's a better example:

http://www.vimeo.com/5343115

If I shoot out into the yard where it's sunny: no problem. Turn the camera 90 degrees and shoot in the shade, and the flicker is back. There's plenty of light in this shot, so the flicker seems to rear its ugly head whenever the light isn't extremely bright. Anyone else notice this: could someone run a similar test?

Mike

[PappasArts]

Here's a better example:

http://www.vimeo.com/5343115

If I shoot out into the yard where it's sunny: no problem. Turn the camera 90 degrees and shoot in the shade, and the flicker is back. There's plenty of light in this shot, so the flicker seems to rear its ugly head whenever the light isn't extremely bright. Anyone else notice this: could someone run a similar test?

Mike

The aperture adjusts from f4 to f5.8 while doing this zoom. This is normal!

Definitely need a sticky for this. Kinda reminds of; "" my dvx100 is broken, it's clicking when I tilt it "" posts from the past!

[mikeydvx]

The aperture adjusts from f4 to f5.8 while doing this zoom. This is normal!

Definitely need a sticky for this. Kinda reminds of; "" my dvx100 is broken, it's clicking when I tilt it "" posts from the past!

That's what I thought too, but I already covered that above: it isn't the aperture changing. Even if you go to manual mode and lock aperture to f6.3 it does this.

Mike

[Ken7]

OK. This video is about as horrible as they come but it's only to illustrate the problem:

http://www.vimeo.com/5342846

Has anyone else noticed the flicker (bursts of exposure change) while zooming in low light? It's not the aperture changing because it happens even when you lock aperture. As I said, this video is lousy but it does illustrate the problem. It doesn't happen in bright light but it does happen even when the light is better/more than the above. BTW, this is visible in the original MTS file, even on the camera.

Anyone else seen this? I figure it must be the camera changing ISO, shutter speed, or something?

Mike

Yup! I get precisely that effect Mike and I posted it somewhere else on this board. It was suggested that it was the ramping of the lens, but I did exactly what you did, I locked the aperture and it still did it. But as I understand it, lens ramping can still occur in low light even with a locked aperture. Your locking of the lens to an aperture smaller than the 'ramping aperture' would seem to indicate it may not be the ramping issue. As you said, I see it only in dimmer lit areas.

One thing's for sure, it aint pretty.

[mikeydvx]

Yup! I get precisely that effect Mike and I posted it somewhere else on this board. It was suggested that it was the ramping of the lens, but I did exactly what you did, I locked the aperture and it still did it. But as I understand it, lens ramping can still occur in low light even with a locked aperture. Your locking of the lens to an aperture smaller than the 'ramping aperture' would seem to indicate it may not be the ramping issue. As you said, I see it only in dimmer lit areas.

One thing's for sure, it aint pretty.

You're right about that. In some conditions it can be quite distracting. I did a little more experimenting last night. Even when locking the aperture I could still hear the lens making those faint clicks like it makes when it changes aperture and the clicks seemed to match the times that the video flickers. Like you, I wondered if the lens was still changing aperture even though it was locked. I set the lens to f22 where I knew I could see the depth of field change if the aperture (lock) was being overridden. I still saw the flicker and heard the little clicks but it looked to me like it was locked at f22 as specified the whole time.

I has a similar problem with my 5D Mark II and it seemed like the flicker occurred even when the aperture was well above (smaller) than the max of the lens. It's almost as if there is a mechanism in the lens that changes as you zoom regardless of whether or not the aperture is locked and that somehow affects exposure. I guess it's possible that the lens has some sort of "stop" that keeps adjusting as you zoom no matter what aperture you are currently at, and adjusting that stop is causing some sort of interference. Maybe the firmware of the lens can be updated to stop this?

Mike

[bebu]

Hello,
I noticed the same problem. Iris (6.3), shutter, ISO, focus set to manual, "Intelligent exposure" to off, but it flickers during zooming.


I have some examples on youtube:
http://www.youtube.com/watch?v=2Q9eftFelxc
http://www.youtube.com/watch?v=7WfamcEX3xg
http://www.youtube.com/watch?v=PMr834opi_Q
http://www.youtube.com/watch?v=do54SFXqlt4


Filmed in 720p50 and converted to 720p25 (european version of the GH1).


Bernd

[mikeydvx]

I noticed that on both the 5D Mark II and the GH1, the lens continues to "click" at certain points while zooming even when you are sure the aperture is locked. My theory is that there is some sort of servo in the lens that moves an aperture stop at certain points. While the aperture isn't being changed, the "stop" still moves so that the lens is physically unable to go past the stop IF it is commanded to do so. My theory is that whatever mechanism is used to keep updating the max aperture stop is binding momentarily with the aperture, causing the aperture blades to "flick" to a smaller or larger aperture for a fraction of a second.

Notice in all the videos the video momentarily gets brighter when zooming in and darker when zooming out. While this is the opposite of what you might expect, it could easily be reversed depending on how the mechanism is designed... and I think it at least proves that the aperture or aperture stop mechanism is what is causing this. I think it might be possible to fix this via lens firmware. The solution would be to not change the aperture stop if the camera is locked at an aperture smaller than the max aperture of the lens.

Mike

[Chibs]

People seem to forget that, by locking the aperture to f/6.3, it still needs to physically change during the zoom. The aperture needs to be wide open when fully zoomed in, yet slightly stopped down when wide. This may cause these flickers, though it does not explain why this would happen in bright light. Is the camera on full manual?

[mikeydvx]

People seem to forget that, by locking the aperture to f/6.3, it still needs to physically change during the zoom. The aperture needs to be wide open when fully zoomed in, yet slightly stopped down when wide. This may cause these flickers, though it does not explain why this would happen in bright light. Is the camera on full manual?

Sorry. That's simply not correct. If you set it to manual exposure video and set the manual exposure mode to "A", an f/6.3 aperture will remain f/6.3 through the entire zoom range. I've verified that two ways. The aperture in the EVF will show the change if it changes (and it doesn't). Also, you can set the aperture to f/22 and watch the depth of field as you zoom: it doesn't change yet the flicker still occurs. Also, you have it backwards above: when you zoom in, the aperture stops down (smaller). As you go wider, the aperture opens up (wider). But... that's only if you are in the zoom's max aperture range: f/4 to f/5.8. If you are smaller than f/5.8 and you are in aperture manual mode, the aperture will never change.

Mike