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Old February 14th, 2008, 09:46 AM   #1
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Lens info

Is it just me (again), or does everyone experience the same: when the focus servo is enagegd, even in MF, the DOF indicator is extremely unstable and unreliable? I mean, just the indicator - the actual focus doesn't hunt, or pulsate, as much (if at all) as the indicator bar does...

It's only the Full Manual focus mode (servo clutched off), when the Lens Info indicator shows more realistic readings and is rock-stable, obediently following the focus ring movement.
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Last edited by Piotr Wozniacki; February 15th, 2008 at 08:11 AM.
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Old February 14th, 2008, 02:52 PM   #2
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Actually...
The auto focus does hunt as shown by the DOF indicator.
I've hooked up a 24" monitor via SDI and watched it closely.
You can even prove this by going back to manual focus and the DOF indicator is rock solid.
To have AF work ok, you need to use 50i or 60i. The progressive modes are to slow and hunt.
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Old February 14th, 2008, 03:08 PM   #3
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Perhaps you guys are using focus assist? I think it is turned on by default and focuses the camera to the nearest object after you manually focus. It is always disabled in full MF.
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Old February 14th, 2008, 03:13 PM   #4
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No...disabled. Never use it.

I don't think it's a great surprise the AF does not work well in modes like 24P.
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Old February 14th, 2008, 03:31 PM   #5
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The slower the frame rate, the slower the AF response... that's true for any camcorder.
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Old February 14th, 2008, 06:50 PM   #6
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But the problem that Piotr is describing happens in manual focus mode. The only "instability" in MF that I have seen is with MF assist mode.
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Old February 14th, 2008, 08:23 PM   #7
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I hear you now Eric. Maybe he has it on.
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Old February 15th, 2008, 01:30 AM   #8
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Quote:
Originally Posted by Piotr Wozniacki View Post
Is it just me (again), or does everyone experience the same: when the focus servo is enagegd, even in MF, the DOF indicator is extremely unstable and unreliable? I mean, just the indicator - the actual focus doesn't hunt, or pulsate, as much (if at all) as the indicator bar does...

It's only the Full Manual focus mode (servo clutched off), when the Lens Info indicator shows more realisting reading and is rock-stable, obediently following the focus ring movement.
Wait... If I understand right... the replies are talking about actual focus, whereas Piotr is talking about the Depth of Field Indicator.

If MF Assist is on, then it will actually hunt around to the points he's talking about.

If I understand properly, then this is entirely normal behavior. The indicator is showing what it thinks the focus should be (and thus the DOF) using what you actually focused on as its starting point. In other words it is telling you what "Manual Focus Assist" would do if you turned it on.

It isn't affecting your focus at all. (Unless you turn MF Assist on) There is a way to make it stop doing that... it was set up that way at the Sony booth at GV Expo, but I don't know how. I just turn the d@(n thing off and look at the focus marks on the lens.

I have yet to see any of my EX work projected, so I can't testify how accurate the marks are. When I stand on results on my monitors it looks fine... but that isn't the test: projection is.

I do know that the EX has a "focal plane" mark on the bottom which should be ignored if you are taping focus. You measure to the front lens element. This has tripped up some film 1st AC's I worked with.
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Old February 15th, 2008, 03:06 AM   #9
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Thank you all for the input. Indeed, I'm talking about the indicator being instable and not actual focus (though am only judging it by eye, so can't be sure it is not moving at all). Also, I have the MF* (assist) turned OFF.

Anyway, even when I switch to MF (not MF*), the indicator is moving withing a range that if the actual focus plane were changing that much, I guess I could see it on a 24" HD monitor!

Only in Full Manual focus is the indicator fully stable.

Edit: just did a quick test, and it's stable as a rock, even in AF not to mention MF :)

So, I should have added it is intermittent.
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Last edited by Piotr Wozniacki; February 15th, 2008 at 08:13 AM.
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Old February 15th, 2008, 08:34 AM   #10
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Piotr,
The bottom line is if you see the DOF wandering, so is focus. That's all there is to it.

I know this for a FACT. Again, I use a 24" monitor via SDI and can watch it hunt slightly in and out of best focus when using AF. Also, this hunting matches excatly what I see the DOF indicator doing. This problem does not happen all the time, but it does sometimes depending on image contrast conditions.

The bottom line for AF is use 50i, or 60i interlaced modes for best performance.
Like Chris said, this is nothing new.
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Old February 15th, 2008, 09:05 AM   #11
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Originally Posted by Steven Thomas View Post
Piotr,
The bottom line is if you see the DOF wandering, so is focus. That's all there is to it.

I know this for a FACT.
No Steven; when it's wandering, it's wandering - but I DEFINITELY have seen the indicator wandering without associated focus loosing its focal plane.

And this is what my enguiry is about; not the focus hunting per se that we all know so well, which I agree is worst in low-light and slow framerates.
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Old February 15th, 2008, 09:12 AM   #12
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Quote:
Originally Posted by Piotr Wozniacki View Post
but I DEFINITELY have seen the indicator wandering without associated focus loosing its focal plane.
Then you have something wrong with your camera.
All I'm saying is i'm not seeing it on mine.
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Old February 15th, 2008, 09:15 AM   #13
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Originally Posted by Steven Thomas View Post
Then you have something wrong with your camera.
All I'm saying is i'm not seeing it on mine.
Not necessarily - the focal plane might have been fixed, yet the DOF (and hence the indicator) unstable due to some "auto-iris hunting" rather than "focus hunting" (just a possibility; another one being what Alexander said about the DOF indicator telling you what "Manual Focus Assist" would do if you turned it on).

As I said, it's difficult to recreate but when I succeed, I'll report about the circumstances it happens in.
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Last edited by Piotr Wozniacki; February 15th, 2008 at 10:24 AM.
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Old February 15th, 2008, 09:20 AM   #14
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Piotr,
You're making this thread very confusing. You started the thread with:

"when the focus servo is enagegd, even in MF, the DOF indicator is extremely unstable and unreliable?"

Now you're saying:

"As I said, it's difficult to recreate but when I succeed, I'll report about the circumstances it happens in."

You started out saying how unstable and unreliable the DOF indicator displays. Now you're saying it's hard to recreate??????

I'm not sure what you expect for responses.
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Old February 15th, 2008, 09:22 AM   #15
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Quote:
Originally Posted by Steven Thomas View Post
Piotr,
You're making this thread very confusing. You started the thread with:

"when the focus servo is enagegd, even in MF, the DOF indicator is extremely unstable and unreliable?"

Now you're saying:

"As I said, it's difficult to recreate but when I succeed, I'll report about the circumstances it happens in."

You started out saying how unstable and unreliable the DOF indicator displays. Now you're saying it's hard to recreate??????
Yes Steven; I beg your forgiveness for upsetting you. Didn't mean to, really.

;)
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