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Manual focus AND turning the display off

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Offline danielkun

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Manual focus AND turning the display off
« on: 13 / April / 2009, 09:36:27 »
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Hello,

I own a A720 and a A570 and I would like to make timelapses.

What I can't seem to figure out is, How do I set the focus to infinity AND turn off the screen to save power?

It seems like both these models reset the "focus mode" as soon the display is turned off. (By pressing the DISP button)

I have tried using the "Override Subject Distance Value" located in the "Extra Photo Operations" menu by setting it to 65535 and it seems to work. However, every time I take a photo I can hear movement in the lens, like if it's doing some kind of calibration. This "lens movement" is not audible when using Canons build-in MF setting. Altough it's not very long, the lens movement causes a short delay just before each shot is taken. I also assume focusing this way tears more on the lens ?

Another solution would be to plug the video cable into the A/V jack to turn the display off. I don't know if this is very efficent though. (Does it really save power?)

There are lots of great timelapses here in the CHDK forum, how to you guys set the camera focus mode?
I have searched the forum several times over without finding any answers to this.

Thanks in advance!

Daniel
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Offline peabody

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Re: Manual focus AND turning the display off
« Reply #1 on: 13 / April / 2009, 11:26:54 »
I have the same issue with the A590, so I assume it may be common to all Canons.  To use manual focus, it appears you need to have the display ON.  I'm not sure why this is the case.

I've tried two things.  The first is what you suggested - use manual focus and leave the display on, but put a plug into the AV socket.  I found this does save some power, but not nearly as much as having the display off.  It does have the added advantage of producing the least amount of mechanical noise as the picture is taken, and I assume (but don't really know for sure) that this minimizes the wear and tear.

The other option is to leave the camera in autofocus, turn off the display, and use the basic command set_aflock(1) at the beginning of the script to lock in the current autofocus setting.  This is done once at the beginning of the script before going into the regular loop.

sleep 2500
press "shoot_half"
sleep 2500
set_aflock(1)
release "shoot_half"

This works with the display off, and saves a lot on power.  But you have to make sure there's something at the target distance to focus on when this part of the script executes.  I ended up not using this because on my camera it generates a lot of mechanical noise, as though it was going through the autofocus operation each time and then resetting to the locked position.

I would appreciate it if you would let me know what you end up using, and why.  Particularly if you find something that combines turning off the display with little mechanical noise.  I haven't found that yet.

There's also a thread somewhere here on turning off just the display backlight.  I haven't had a chance to play with that yet.

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Offline fudgey

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Re: Manual focus AND turning the display off
« Reply #2 on: 13 / April / 2009, 16:04:33 »
Manual focus mode consumes more power compared to autofocus, which doesn't suit well with the battery savings aim of shutting down the display. This may be the reason for this unfortunate feature. Also, Canon may have thought that if you never see the MF sign, you may forget you had it enabled and shoot tons of out of focus pics trying to save battery life (although the same should apply to macro mode, shouldn't it... I don't think I've ever tried but I'm assuming you can take macro mode autofocus shots with display OFF).

And yes, the A/V plug method does save power. Not a whole lot, but it's been measured and the results are somewhere on this forum for a couple of cams. Just turning off the backlight saves a little bit more because the A/V plug also enables the video driver, which requires some power, but we can do the backlight trick only in scripts currently.

The reason display OFF reduces power consumption more than any of the above tricks is that it shuts down the entire sensor, because there's no need for live preview video stream from the CCD if both the LCD and the video output are disabled. It just seems that these cameras have sensor and focus mode tied together, and no way to override that has been found to my knowledge (not that anyone would have searched vigorously...).
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Offline danielkun

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Re: Manual focus AND turning the display off
« Reply #3 on: 14 / April / 2009, 10:23:22 »
Thanks!

Your answers were most helpful!
Just to simplify the possibilities I suppose we are limited to the following options:

1. Put a plug in the A/V socket (No mechanical noise)
2. Turn off the backlight while waiting (No mechanical noise)
3. Use the "Override Subject Distance" function (Mechanical noise)
4. Use BASIC command set_aflock() (Mechanical noise)
5. Increase battery lifetime

I'm still looking for other alternatives but at the moment a combination of #1 & #5 may be what suits me the most. (I'd rather avoid alternatives that increase mechanical operations in the lens)

This may be a little off topic but..
Both the A570 and the A720 have a plug for an external power (3.15V) source. I assume this power jack would work just as well with 2 rechargable batteries at 2.4V (2 x 1.2V)? Has anyone tried this?

This would make it possible to use the D sized rechargable batteries which have a capacity near 6000mAh. That would give 2.5 times the power compared to 2 AA batteries. By using 4 of these batteries (connected in parallel) that should in theory provide 5 times the power. Please correct me if I'm wrong.

I may have to get myself some new rechargable batteries
« Last Edit: 14 / April / 2009, 10:27:12 by danielkun »
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Offline peabody

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Re: Manual focus AND turning the display off
« Reply #4 on: 14 / April / 2009, 18:57:54 »
You should indeed be able to rig up an external battery pack.  For the A590, I found a generic replacement for the AC adapter somewhere online, and it said the connector was a 2.35 X 0.7 mm power connector, which should be a EIAJ-01 connector.  This connector used to be R/S item 274-1531, but alas, no longer.  However, it looks like this would work too for U.S. persons:

http://www.radioshack.com/product/index.jsp?productId=2062423

Or you could order an EIAJ-01 from Mouser, DigiKey or whatever.

I don't know if the same connector works for all Canon models.
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Offline danielkun

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Re: Manual focus AND turning the display off
« Reply #5 on: 15 / April / 2009, 20:12:32 »
Thanks!

I'll see what I can find at the electronics store this weekend.
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Offline fudgey

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Re: Manual focus AND turning the display off
« Reply #6 on: 25 / April / 2009, 10:51:45 »
Quote from: danielkun on 14 / April / 2009, 10:23:22
Both the A570 and the A720 have a plug for an external power (3.15V) source. I assume this power jack would work just as well with 2 rechargable batteries at 2.4V (2 x 1.2V)? Has anyone tried this?

I've tested my a570 from a lab PSU from the DC socket. It works in the same range as the batteries i.e. cam shuts down at about 2.0 V. Just make sure impedance from your voltage source to your DC plug is low!
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