EX1 Inherent Autofocus Problem?

[Simon Frances]

I’ve tried four different cameras and I’m getting the same results with all four cameras.

Here are the settings:

PAL, 35 mbps (VBR), 25p, 1920 x 1080, the shutter was set to on, at 1/50th, iris set to manual around f/4 – f/5.6, gain set to -3, manual white balance, and set to autofocus.

The picture profile I used was “PP4TC2 C3” but I don’t believe it makes any difference which profile is used.

If anyone wants to give it a go, here is the SETUP.SUR file (rename to SETUP.SUR), which I got from the Picture Profile Recipes thread (Thanks Bill, great profiles), albeit I changed it to PAL.

An easy way to replicate the problem is to point the camera at an object with a bright light behind it, like some trees as per my example.

If the same is happening with your camera, you should get a pulsating rhythmic light flicker in the bright areas around the trees and the image will go in and out of focus in time with the rhythm; sounds weird I know!

Here is the Link to the clip.

Regards,
Simon

[Alex Leith]

Wow! That's pretty scary! I thought my Canon A1 had AF problems... but that's nuts! When zoomed in the whole image seems to change color balance as it pulses.

Tree branches are a pretty tough target for any AF system, especially with bright light coming from behind, but I wouldn't expect it to fail with such ugly results.

[Michael Mann]

Yes, that does not look like what I would expect from a pro-cam at all.
Has anyone else noticed such behaviour? Can anyone reproduce these results?

[Bill Ravens]

more than you ever want to know...
http://www.dvinfo.net/conf/showthread.php?t=113933

Bottom line:
1-the slower the frame rate, the longer it takes to AF
2-this is an amazing camera. yes, it has its weaknesses, learn to avoid them
3-in full AF, the focus will hunt, which is why you're seeing a pulsating. It's coincidental that it pulses to the music....LOL

[Piotr Wozniacki]

Originally Posted by Bill Ravens

more than you ever want to know...
http://www.dvinfo.net/conf/showthread.php?t=113933

Bottom line:
1-the slower the frame rate, the longer it takes to AF
2-this is an amazing camera. yes, it has its weaknesses, learn to avoid them
3-in full AF, the focus will hunt, which is why you're seeing a pulsating. It's coincidental that it pulses to the music....LOL

Even though I have no idea why you have linked to "my" thread, Bill, I agree with all 3 points.

However, I have never seen the AF pulsating that bad on my unit. If Simon didn't say he could reproduce it on 4 units (which is hard to believe), I'd say the camera was broken.

[Michael H. Stevens]

Piotr: I think Simon IS saying he CAN reproduce it on all four cameras. Every review I've read of this camera says to avoid the auto and focus assist function. Also Doug Jensen in his video says the auto focus will only work well if the center 25% of the frame area is filled with the subject.

[Piotr Wozniacki]

Yes Michael - I'm just saying that I find the autofocus quite usable with my unit, and each time I need it (not often of course), I can actually use it with good results. All my walking shots, for example, are done with AF on. Also, when the camera is stationary but my subject' s moving, the AF can follow quite well.

The MF assist is another story, and so far I didn't find it useful at all.

[Steven Thomas]

I'm not sure you will find many AF fans here, regardless how well it works on any camera. Unless you get lucky enough to have it lock onto your intended subject, AF will focus where ever it can.

AF has never worked that great on many progressive cameras, including the HVX200.

[Piotr Wozniacki]

If one knows how and when to use it, it can be used on progressive cameras with no problems. I've used it a lot when run'n'gun shooting with my V1E, and also in 25p. While not being the "mode of choice" with the great manual lens of the EX1, it can perform no worse at all.

Just use it when needed, and don't expect too much - you'll be fine.

[Simon Frances]

Thank you everyone for your comments, much appreciated.

I would just like to point out the following; the timing of the pulsating effect is the same in all the footage I’ve shot under the same conditions. I've seen many times a lens that is hunting but nothing like this. In my experience a lens hunting for focus is quite distinctive and when doing so, doesn’t change the color or cause the light to flicker in a particular section of the scene i.e. where there is a dominance of light.

I do believe this is an inherent problem with the EX1 given the shots taken of scenes like the ones I’ve shot. As stated above, I've been able to reproduce this phenomenon on four separate cameras, three of which were largely spaced apart by way of the serial numbers.

Here is a LINK to a sequence I put together to more easily compare. In the first shot you’ll notice the light bulbs on the side of the Harrods building, in the second shot, not only is the light flickering and the shift in color around the trees but notice a focus problem with the building on the right.

Has anyone done these quite specific tests, it would be interesting to see the results.

Regards,
Simon

[Michael Mann]

Originally Posted by Simon Frances

I've seen many times a lens that is hunting but nothing like this. In my experience a lens hunting for focus is quite distinctive and when doing so, doesn’t change the color or cause the light to flicker in a particular section of the scene i.e. where there is a dominance of light.

I agree, this does not look like a usual focus hunting at all, it looks defective to me, especially the shifts in color temperature. Never noticed such a thing with the AF of my FX1 or HV10 before - and these are consumer devices.
Simon, have you already spoken with Sony about this?