Focus issue solved, faulty camera now replaced

[Michael Mann]

Alex, meanwhile I have noticed, that my A1 shows the very same zoom focusing problems like the ones you described in this thread. (I can upload a short file for documentation if anyone is interested.)

Please let me/us know whether you new camera gets rid of this problem. Thanks in advance.

[Alex Leith]

Hi Michael. Until about half an hour ago I thought that my new camera had fixed *all* the issues that the previous camera had.

However, after reading your message I tested the "focus-pulsing-during-zoom-with-auto-focus-on" problem on this camera... and I can confirm that it does display it too.

I certainly don't have any of the other AF and IAF issues that I had before (AF and IAF are now quick, stable and pretty reliable). But it does have the focus pulsing. It's much less pronounced - I would say almost unnoticable through the viewfinder or LCD, especially on faster zooms. But it's there.

I suspect this may be a weak point in the design of the camera...

[Philip Williams]

Originally Posted by Alex Leith

Hi Michael. Until about half an hour ago I thought that my new camera had fixed *all* the issues that the previous camera had.

However, after reading your message I tried a test of the "focus-pulsing-during-zoom-with-auto-focus-on" problem... and I can confirm that this camera does display it too.

I certainly don't have any of the other AF and IAF issues that I had before(AF and IAF are now quick, stable and pretty reliable). But it does have the focus pulsing. It's much less pronounced - I would say almost unnoticable through the viewfinder or LCD, especially on faster zooms. But it's there.

I suspect this may be a weak point in the design of the camera...

Hi Alex, thanks for the update. Quick question, are you seeing the pulsing in 24F, 30F or 60i? If you haven't tested that out yet, try to compare 24F and 60i on the same subject/environment...

[Alex Leith]

Originally Posted by Philip Williams

Quick question, are you seeing the pulsing in 24F, 30F or 60i?

Interesting...

I tried the test again (I'm in Europe, so it was at 25F and 50i).

At 25F the pulsing is slight but noticable on out-of-focus portions of the image during slow zooms at the long end of the lens. It pulses at around 4x per second at ZS 1 and gets faster on quicker zoom speeds. By ZS 8-10 you can't really see it because the image is moving too quickly.

At 50i the pulsing turns into a much slower oozing! You probably wouldn't notice it if you weren't looking for it, but it slowly pulses once every 2 to 3 seconds at ZS1. Again at faster zoom speeds it oscilates faster, but it becomes more or less imperceptible by ZS 4-6.

[Raymond Toussaint]

And its gone with manual focussing and zooming. Zoom in -focus - zoom out -start shot - zoom in. Like you do with all the professional lenses.

[Philip Williams]

After I noticed this phenomena a couple of weeks ago I did some testing. I found that situations that are challenging for auto focus cause a pulsing focus when zooming in or out in 24F mode. The exact same shots and zooms in 60i were fine (I was watching live output on a 42" display to watch any focusing issues). As Raymond just mentioned, setting the lens to Manual Focus elimates the pulsing altogether.

If I had to guess, I'd say this pulsing is related to auto focusing issues that most (all?) 24P camcorders have. The XH A1 actually finds focus fairly quickly in 24F mode, probably much faster than many other 24P camcorders. Perhaps the downside to this faster focusing at slower framerates is the focus pulsating back and forth as it tries to compensate for zooming? It would be interesting to compare the XH auto focus to some of the other 24P camcorders in a controlled test.

In any event, I think Raymond is pretty much right on. Especially in 24F, I'm just going to shoot manual focus only. The focus ring is pretty decent, the lens holds focus well and the distance readout plus peaking makes it pretty much bullet proof.

[Michael Mann]

Originally Posted by Alex Leith

Hi Michael. Until about half an hour ago I thought that my new camera had fixed *all* the issues that the previous camera had.

However, after reading your message I tested the "focus-pulsing-during-zoom-with-auto-focus-on" problem on this camera... and I can confirm that it does display it too.

I certainly don't have any of the other AF and IAF issues that I had before (AF and IAF are now quick, stable and pretty reliable). But it does have the focus pulsing. It's much less pronounced - I would say almost unnoticable through the viewfinder or LCD, especially on faster zooms. But it's there.

I suspect this may be a weak point in the design of the camera...

Alex, thanks for your fast reply.
You can download two short native demonstration clips here (25F, fast auto focus mode):

http://www.filefactory.com/f/f5656740836b15ad/


The problem only occurs in either of the two auto focus modes. If I switch to manual focus, the problem is gone.

Since I use manual focus in most cases I really can live with this "problem". But sometimes - when doing snapshots for example - I just have no time to focus manually, and then the "pulsing" results are very annoying (see clips above).

By the way, my HV10 shows a similiar focus pulsing when zooming.

Chris, I suggest to change the title of this thread again, since this focus pulsing issue does not seem to be solved at all.

[Alex Leith]

Originally Posted by Philip Williams

The exact same shots and zooms in 60i were fine (I was watching live output on a 42" display to watch any focusing issues).

Personally I think I *could* see the effect in 50i too - but it was extremely subtle because it changed from a pulsing to a much softer undulation.

Originally Posted by Phillip Williams

The XH A1 actually finds focus fairly quickly in 24F mode, probably much faster than many other 24P camcorders. Perhaps the downside to this faster focusing at slower framerates is the focus pulsating back and forth as it tries to compensate for zooming?

If it is trying to compensate for zooming then it's a fault with the design of the camera. The back-focus on the lens should be setup in such a way that as you zoom in an out the focus stays the same (and in fact it does if you turn AF off).

I personally think it's more likely to have something to do with the mechanical aspect of using a single motor for zoom and focus - especially as the rate of pulsing seems to increase as the speed of the zoom increases.

Either way, you and Ramond are correct. The best way to work is with AF off. I wouldn't normally have it on - but regardless, this effect demonstrates some sort of a design flaw if it's being seen across multiple units.

Thanks for sharing these clips Michael. You can clearly see the pulsing effect. It's fairly pronounced and makes AF effectively useless to be left on. I guess we've found (one) of the camera's Achilles heel's!

[Brad Tyrrell]

Originally Posted by Alex Leith

I personally think it's more likely to have something to do with the mechanical aspect of using a single motor for zoom and focus.

- but regardless, this effect demonstrates some sort of a design flaw if it's being seen across multiple units.

Not sure "design flaw" is the right description for 1 motor instead of 2. Probably a financial decision there. The A1 boys seem to have done a pretty decent job of "two things at the same time" for one motor, - just not perfect. I bet that for more bucks ...

[Alex Leith]

I think you're right Brad, that Canon have generally done a pretty good job with the A1. But personally if something doesn't work properly by design, I'd call it a design flaw - even if the underlying root of that flaw is one of providing a cheaper product.

One expects certain things from a product for it to be considered of "merchantable quality" - and one of those things (in my opinion) is that the advertised features work, and can actually be used.

I think we can see from Michaels clips (and my own experience with two A1s) that the auto-focus cannot be used on slow speed zooms towards the long end of the lens.

To me that's a design flaw. Just because it's a feature that isn't left "on" by most professional videographers, or just because we can be "understanding" of the problem because we're getting something at a certain price point, doesn't mean that the manufacturer can then go on to advertise it as a revolutionary new instant AF system... and not mention that you can't use it whilst zooming.

Having said all that, I am happy with my A1, even with its flaws.

[Brad Tyrrell]

Originally Posted by Alex Leith

Having said all that, I am happy with my A1, even with its flaws.

Me too. Even if I can't use the lens on "full-wide" because of the barrel distortion.

Annoyed me at first, then kinda realized what I was asking. A wide angle on a zoom lens on a wide format HD video cam with no fish eye at the edges for less than $4000. Jeesh.

On-the-other-hand, just a little off full-wide and it's very usable. Of course since I don't think anyone claimed no distortion, it's not really a "design flaw". (This probably belongs in a different thread anyway.)

[Michael Mann]

Alex, do you think Canon is or has got aware of this problem or did they just try to get you satisfied, without going deeper into it? Did they give you any plausible comment on this "pulsing problem" or did they just send you a new A1 in exchange? Thanks.

[Alex Leith]

I didn't actually get any commentary from Canon except for them to say that the camera was "definitely faulty" (they weren't specific as to which faults they were addressing).

My dealer brokered the repair on my behalf, so I was sent a replacement from the dealer's stock. I gave it a quick test when I received it, and it didn't appear to display the pulsing or other focus problems that I had with the first unit. As you know, I've now checked more closely, and the focus pulsing is still there on this unit - albeit less noticable.

Whether Canon knows about this or not... I don't know. It would seem like something that should have been picked up at the prototype stage. Perhaps they didn't notice it; or perhaps they were constrained by their budgets to use mechanical systems that are already in other Canon camcorders - which they just couldn't get to work "perfectly" in this form factor; or perhaps they noticed it too late to make changes to the design before it shipped out; or perhaps they hoped that no-one else would notice the problem; or perhaps it's a software problem... I don't know.

Either way, I feel it's something that Canon *should* fix given that it means you can't use the AF whilst zooming - which is something that I feel you would expect of a merchantable quality AF system. I know AF isn't perfect, and can *sometimes* have problems maintaining accurate focus, but this pulsing looks like a mechanical flaw, and is not something that one would expect of any AF system.

Whether they will fix it, or just update it with the next model is another matter entirely.

[Tom Roper]

Originally Posted by Alex Leith

The back-focus on the lens should be setup in such a way that as you zoom in an out the focus stays the same (and in fact it does if you turn AF off).

Wrong!

If you video something moving away from you, (picture kids sledding down a hill), as you zoom so that the object continues to fill the frame while the subject distance is moving away from you, you would not want the focus locked on the first position of the sled when it was just a few feet in front because it would go out of focus as it draws farther away.

Canon gives you the option to turn autofocus off. That's enough. If it worked as you described in auto, you could only maintain static focus on a constant camera-to-subject distance while you zoom.

[Raymond Toussaint]

Q. The focus issue Alex described is repaired and gone. That is his word.
Q. Zoom and focus in AF together the same time (how often do you want that? or work that way, but that is another question, I never do)

Focus is on subject in center of the screen, if you zoom, the image information in the center of the screen is changing, so is the focus. An object that was only for a small percentage in the center becomes the whole image. In 24F and 25F Canon has a very speedy AF compared to others.

The Canon has a Manual and TWO Autofocus systems, you can work with one of them or with two combined.

1. You can manually focus and zoom together.
1a.You can manually focus and zoom together and use Push Focus button on subject.

2. You can set focus on automatic end choose in menu:
a) AF normal autofocus (TTL)
b) IF instant autofocus (TTL and sensor, two way, fast)

If you choose for autofocus with (a)
You can focus and zoom together and hold the focusring during zoom.(override) and release if your zoom is finished.

If you choose for autofocus with (b) the system needs to recalculates faster the focus. You zoom and focus together. There is some "computerwork" but you can override the focus system by using the manual focus ring.

Normally always set everything on manual and use the push focus button if needed. Or if you want to use AF, not in the same time during the zoom, set cam to AF for easy focussing on moving object.