Can't get Tv or Av Modes to work at DVinfo.net

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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 July 15th, 2008, 09:17 AM   #1
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Can't get Tv or Av Modes to work

I've had my XH G1 for about a week and think I have most of its functionality figured out except the Shutter or Aperture Priority modes.

If I'm in the Av mode and I close the iris then my understanding is that the camera should decrease the shutter speed, thus allowing more light into the camera to keep the exposure constant. However when I close the iris in this mode nothing happens except the scene darkens. The same happens in Tv mode when I increase the shutter speed.

I fairly certain that it's something I'm doing or not understanding as when I went and tested out another XH A1 it did exactly the same thing.

Everything works as expected in Manual mode and I don't have the AGC on.

This has me really puzzled - would really appreciate it if any kind soul that could enlighten me.

Cheers

Hugh
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Old July 15th, 2008, 03:04 PM   #2
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Sounds like you pressed the exposure lock button before turning the dial. So what you actually did was change to under-exposure.

In TV mode, you just need to turn the shutter dial to change the shutter speed.

In AV mode you just need to turn the aperture/iris ring.

But if you press the exposure lock first, you change the exposure because you've locked the shutter speed (in TV mode) or the aperture (in AE mode).
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Old July 15th, 2008, 03:12 PM   #3
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Agreed -- from the description, it sounds like the Exposure Lock button was pressed...
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Old August 2nd, 2008, 03:27 AM   #4
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Thanks to you both for the replies - Have been away in Singapore for the last two weeks so haven't had a chance, until now, to try your suggestions.

Unfortunately I don't think it's related to the exposure lock. Here's my sequence of events.

1) I turn on the camera directly to Av mode (if I had the the exposure lock on it would have E. Lock displayed on the screen - which it doesn't).

2) The screen has displayed Av F1.6 which means it's wide open.

3) I turn the Iris Ring until until it reads F3.7 and the display is noticeably darker which implies to me that the shutter speed hasn't changed (ie giving me a slower shutter speed to let in more light).

Also re the Exposure lock - my understanding of its functionality is to allow you to adjust both the Shutter and Iris while in A Tv or Av mode without having to go to Manual mode. Kinda like, 'ok lets see what the camera reckons the exposure should be for this scene, and then tweak it to your liking after pressing the Exposure lock'. Am I in the ball park?

Thanks in advance for any advice.

Last edited by Hugh Calveley; August 2nd, 2008 at 06:32 AM.
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Old August 2nd, 2008, 04:47 AM   #5
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Hi Hugh. Your understanding of the exposure modes and exposure lock button is correct. I'm wondering if it's just that there is not enough light for the exposure to be adjusted properly, and that's why the image darkens? Can you try it outdoors with the ND filter switched off? Or maybe just add 6db of gain and see if the same thing happens?

Richard
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Old August 15th, 2008, 11:28 PM   #6
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Problem Solved!

I tried it out in daylight with no ND filters on - and kept flicking the Exposure lock on so I could see what the camera was actually doing

In Tx mode it worked exactly as expected - as I increased the shutter speed it opened the Iris to compensate.

However in Av mode it will never go below a shutter speed of 1/50 (which I guess kinda makes sense - although often scenes can be shot fine on 1/25) and will just let the scene go dark (this is what caught me out when first testing it) however it will increase the shutter speed as you open the iris.

So great to know that I don't have a defective camera and many thanks to you all for the great advice.
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Old August 22nd, 2008, 02:23 PM   #7
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Av mode

Hugh, I bought a XHA1 a couple of weeks ago and noticed the same thing. I signed up on DVInfo but have only just been approved to post here, so I could not get in touch with you earlier. Maybe they thought I was the "other" David Usher.

I needed to decide if this was a "feature" of the XHA1 or whether my unit was faulty and should be returned. Fortunately I was able to contact Bill Pryor by phone and he did some tests and told me that his camcorder behaved in the same way. So I'm glad to say that I kept the A1.

Mine not being the PAL version, Av mode will not automatically adjust the shutter to a slower speed than 1/60 sec. It turns out that there is also a limit on the other end. If I am in Av mode and start opening the iris, the shutter will not automatically go any faster than 1/1000 sec, so the picture can get way over-exposed.

Off topic: I used to live in Wellington, Eastbourne actually . . .

David
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Old August 22nd, 2008, 11:49 PM   #8
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Hi David,

Good to know that I wasn't the only one confused :-) And thanks for the 1/1000 tip.

Ahhh Wellington - worked there for 2 years - lovely little city with houses that seem to cling to the hills!

Hugh
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