PMW-EX1 Auto Focus Slow?

[Bob Grant]

Steven,
sorry mate I thought we'd already determined that your camera was performing much the same as everyone else's.
I just did a pretty quick and sloppy test as I don't have a good set of sticks at hand and it's getting dark. However what I did notice was panning along the edge of a table at an angle so the distance to focus slowly increased the AF would suddenly loose the plot and go through a complete refocus.
First time I tried I had Macro on, turning it Off seemed to help but it still did the same dance just not quite as dramatically. I was panning quite slowly but hand held, perhaps someone with a good tripod and better setup should repeat this test but I'd say you certainly cannot rely on the AF to do a rack focus for you. The speed to find focus was around 2 seconds and I didn't notice any hunting once it'd found focus but that wasn't under good test conditions but certainly nothing unlike what you'd encounter under gun and run where you just have to get the shot and anything can happen.

My slightly better times might be because the camera was in 50i.

[Steven Thomas]

Thanks Bob,

This is why I am interested in the test I posted.
My camera when stationary and staring at high contrast objects in good light will nail focus for 1 second and then start to slightly move in and out
as if it did not find it. It should disable servo when it finds its peak.

While it's auto focusing, I can see where the peak is using the peaking function. I'm not sure why it does not disable servo once it rolls over the peak. I understand the camera should continue to adjust AF if the camera is moving across a different focus plane, but in this case it's stationary.

You're not seeing this, so this is starting to confirm my original thoughts that there's a problem with my camera.

[Steve Mullen]

"I suspect the slow autofocus is simply the price we have to pay for having a true mechanical lens - it's got to be much easier to make a fast, smooth and quiet autofocus when you don't have to have the lens elements coupled to gears meant to be turned by a large outer ring."

This is the reason I suspect. Most all the other AF cameras use an inner-focus system. Think of a lens carried within a speaker voice coil. Near instant response because there's almost no mass.

The question of the INDICATED hunting -- perhaps the VF read-out shows the sensor output. But, also perhaps, this signal is not being sent directly to the lens servo. Perhaps a "damped" version is sent to the servo. So, when you see the "hunting" do you see the mechanism moving? Or, do you see the focus change on a monitor?

Assuming it does hunt -- then the Push-to-Focus button is the key. I tend to hold it down for a second or two. The other is to use the Assist function to rapidly get close and manually find the final focus.

[Steven Thomas]

Steve,

On the EX1, I've never seen the outer focus ring move with the AF, regardless on how far focus was off. I'm assuming this is all done via an interval servo driven optic?

Well,
After more experimentation using all image modes, I did find that 1080 60i was the most stable. I was under the assumption, since the AF is time sampled based and needs a high frame rate that 720 60P would be sufficient.
Well, I was wrong! 60P hunts and rarely locks.

This is odd, when I tired the SAME tests yesterday, 1080 60i seemed also unstable; although, most of my testing was on 720 60P.
So I guess the bottom line is you can not use progressive, even at 60P when using AF mode?
From previous AF cameras I know this is true, but I sure thought 60P would of worked well enough.

[Tom Roper]

...but I want to confirm Steven Thomas' EX1 focus hunting behavior on my camera.

On a tripod, if I move the small switch to manual focus, the dof display is stable. If I thereafter press the AF button, the DOF display hunts continuously. I was expecting a one-time movement from this.