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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old June 22nd, 2009, 08:55 AM   #1
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auto focus questions

I come from a still camera background where the spot that the camera is auto focusing on is clearly marked in the viewfinder. I use that spot to lock in the focus then recompose to put the subject where it compositionally makes sense.
What exactly does the canon auto focus on? the center,? the closest object? Can it follow, if I center on object in the middle and it moves towards me?
Yes I know that it's best to use manual, zoom in focus then reposition or hit the af instant button, but every once in a while I need to run and gun, want to set it on auto but would like to know what it's using as a criteria to auto focus on.
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Old June 22nd, 2009, 09:34 AM   #2
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Hi Roy. I thought I should reply to this, since I'm the only guy in the DVInfo forums that sometimes uses autofocus, everybody else is too pro for that. :)

The autofocus always tries to set focus on the centre of the screen. You can display a cross on the EVF/LCD to mark the centre via one of the menu options.

Yes the autofocus will try to track a moving object at the centre of the image. One reason it's best to avoid autofocus if possible is that it is a bit unpredictable. Sometimes the focus will drift off, especially when the object is moving too fast, or if the light is low. Using IAF at very close range is also not a good idea, because there is a parallax shift or something that prevents it locking on nearby objects.

Richard
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Old June 22nd, 2009, 04:22 PM   #3
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Richard, you are not the only autofocuser, I'm a lazy sod and when I pay thousands on a camera I expect the 'auto' aspects of it to work well in most situations - and I'm pleased to say the with a few exceptions I've been very pleased with what has come out.

And just to throw an example of excellent autofocus, I was filming some stocks shots today - a poppy field - I deliberately wanted a wide aperture but sharp image. I shot in both auto and manual focus and auto won hands down because of wind blowing the flower stalks I couldn't track that manually, but the autofocus did a fine job
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Old June 22nd, 2009, 05:27 PM   #4
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I also use auto focus. The XHA1 is a very smart camera and does certain jobs on its own very well. Although I shoot in manual mode, I always let the camera control the sound and focus. It controls sound quite well on its own. NOw I should also say that I usually shoot under very controlled conditions.
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Old June 22nd, 2009, 06:03 PM   #5
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Quote:
Originally Posted by Richard Hunter View Post
... since I'm the only guy in the DVInfo forums that sometimes uses autofocus, everybody else is too pro for that. :)
Richard
Nope. You got company here.
I use it when I'm pretty sure that its degree of unpredictability
will be lower than the resolving power of my eye
(i.e.: quite often, especially w/ Push Focus)

Vasco
(one-eyed & very shortsighted;
should I give up shooting just because of that?)
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Old June 22nd, 2009, 06:11 PM   #6
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Hi Roy...............

If you dive into the menu in a shooting mode and select [DISPLAY SETUP], then [MARKERS], then [GRID], the camera display will show a grid of horizontal and vertical lines.

The centre box of this grid pretty well outlines the focus area the camera works on, not perfect, but with a bit of practice it is suprisingly close.

An added benefit is that it makes setting the horizon so much easier and helps prevent that "leaning tower of Pisa" effect with verticals.


CS
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Old June 22nd, 2009, 09:28 PM   #7
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I will add that I have found that the autofocus on the XH-A1 is excellent, and it works very well for on-the-go documentary type shooting.

One note, the autofocus is sometimes a bit sluggish in 24p, but in 60i it is very responsive. I don't know about 30p.
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Old June 23rd, 2009, 10:13 AM   #8
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My camera has auto focus?!

Really, I use AF 90 percent of the time when hand-held. The other 10 percent I use push auto. When using a tripod, I'll normally use push auto. Either my eyes, the viewfinder, or the LCD (or all three) are terrible at getting sharp focus manually. There is just too much going on to accurately focus manually while hand-held. I'll only use full manual focus when I have the time to compose shots. You know...artsy stuff, B-roll, etc.

The grid is always displayed on my camera when shooting. I've had too many "leaning" shots in the past when hand-held, due to the CG of the camera. Why didn't Canon make the camera balance properly using the handle?
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Old July 2nd, 2009, 12:46 PM   #9
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"I use autofocus" - does that mean

"I use auto to find focus"

or

"I leave focus in auto"?
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Old July 2nd, 2009, 02:41 PM   #10
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The xh-a1 is not a good camera to manual focus, unless you use the peaking aid which helps but still. I only switch to manual when I zoom in but as long as the lens is wide autofocus does a really good job. I find it very hard to focus when the lens is fully wide because the xh-a1 screens are too low rez for my vision.
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