Manual Focus in Ultra Intervalometer

adamp101

3

« on: 25 / March / 2011, 23:29:21 »

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I just got a used A570 and I'm excited to try out some time lapse shots.

I've got the Ultra Intervalometer running (on a A570), but I've noticed some jitter in my time lapses that looks like the lens is slightly zooming in and out. Upon further inspection it looks like it's actually due to changes in focus. This is not so surprising, because it's happened during shots that were the center of the shot was in the sky, and sometimes there were contrasty clouds to focus on, and sometimes the center of the frame lacked contrast.

So my next step was to run the script with manual focus mode on, with focus set at infinity (mode dial is at Av). For some reason, even though it's in manual focus mode, when the script is running it still runs auto focus before each shot. Can anyone help me get it to stay at infinity focus? Also, if anyone has guidance on how to run manual focus with the display off, that would also be very helpful because I'd like to conserve battery during these sequences (in my failed manual focus trial I left the screen on because I've read that the camera reverts to autofocus if the display is turned off).

I also have one other little question. The Ultra Intervalometer documentation warns that caution should be used with unlimited sequences. What could go wrong, and what should I do to avoid problems?

Thanks for your help!

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peabody

167

Re: Manual Focus in Ultra Intervalometer

« Reply #1 on: 26 / March / 2011, 12:40:42 »

I use an A590 with my own script, so may not be able to give you a definitive answer.

I set the camera settings so that absolutely everything is manual. So I'm shooting in M mode, and set the shutter speed and aperture I want. I use Custom white balance and manual focus. IS is off. Review is off. But the display has to be on.

With these settings, the camera just trips the shutter to take a pic, with no motor stuff at all. To save power, I insert a plug into the A/V port, which blanks the display, but not really. It's doesn't seem to save much juice. For reasons that are not clear, it appears that on all Canons the display must be on when using manual focus. I don't use them, but in other threads you will find ways to turn off the display backlight, which should provide some power savings.

If you are getting motor noise using manual focus, I don't know what it would be. Try changing from Av to M and see if it still does it.

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adamp101

3

Re: Manual Focus in Ultra Intervalometer

« Reply #2 on: 26 / March / 2011, 19:10:06 »

Thanks for the response.

After fooling around with the camera for a while I think I've found the problem. Switching between M and Av did not make a difference. The problem was a rookie mistake: I had "Safety MF" enabled.

For anyone who runs into a similar problem, this is a standard Canon option accessed by pressing menu while in shooting/record mode. It allows you to manual focus, and then the camera attempts to "fine tune" the focus with its AF mechanism. In my case it was sometimes making it go slightly out of focus.

In playing around with this I came across an option that may be useful for maximizing battery life for time lapse. I haven't tested this for time lapse yet, but the main CHDK menu allows you to over-ride the subject distance. This should allow you to leave the camera in AF mode with its display off during a time lapse, but keep the focus locked at infinity (or wherever). According to power consumption measurements made by user bugsplatter ( http://chdk.setepontos.com/index.php?topic=3872.msg36569#msg36569 ), it seems like this option of staying in AF mode with the screen off would offer significant power savings over staying in MF mode and using the A/V plug trick or the backlight off command. The only possible downside to this that I can think of is if you're doing a super long sequence and want to minimize mechanical wear on the focus motors/components.

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peabody

167

Re: Manual Focus in Ultra Intervalometer

« Reply #3 on: 27 / March / 2011, 12:38:33 »

There's also the AF lock command. You take an initial exposure using AF, then lock the result in. It will stay that way for all subsequent shots even though AF is still on. This does work with the display off, and it does save a lot of power.

However, the only way I've found to stop all the motors is to use manual focus. And I think that's important if you're going to be using a camera a lot for time lapse. The shutters last a long time. The motors - maybe not so much.

But I would be interested in knowing if the distance override works for you. The potential problem is that the camera may not return the focus to exactly the same place every time.

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fudgey

1705
a570is

Re: Manual Focus in Ultra Intervalometer

« Reply #4 on: 28 / March / 2011, 16:19:22 »

Quote from: peabody on 27 / March / 2011, 12:38:33

There's also the AF lock command. You take an initial exposure using AF, then lock the result in. It will stay that way for all subsequent shots even though AF is still on. This does work with the display off, and it does save a lot of power.

AFAIK, a570 doesn't have that... or it does, but it's just another way of entering manual focus if display is on. If it does, please tell me how to work it

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peabody

167

Re: Manual Focus in Ultra Intervalometer

« Reply #5 on: 28 / March / 2011, 18:31:46 »

If it works on my A590, it should also work on an A570. So you enter alt mode with autofocus turned on, and the display turned off. Then start the script running, working blind kinda.

The script first does a half-press, waits a bit for autofocus to finish, then locks in that setting using AF lock. Of course you have to be sure the camera is pointing at the right thing to focus on when you start the script, otherwise it will be out of focus thereafter.

Then the script goes into the loop for taking pictures, but doesn't revisit the focusing part, so the locked AF value stays in effect until you end the script. This does save a lot of power because the display really is turned off. But you do still get the focus motor activity. Apparently it goes though the motions of doing the autofocus, then disards the result and goes back to use the locked value.

Well, here's the script:

@title Peabody AFlock Intervalometer
@param a Delay 1st Shot (Mins)
@default a 0
@param b Delay 1st Shot (Secs)
@default b 0
@param c Number of Shots
@default c 1
@param d Interval (Minutes)
@default d 0
@param e Interval (Seconds)
@default e 4
@param f Interval (10th Seconds)
@default f 0
@param g Endless? No=0 Yes=1
@default g 1

p=a*60000+b*1000
t=d*60000+e*1000+f*100
if c<1 then let c=5
if t<100 then let t=100
if g<0 then let g=0
if g>1 then let g=1
if p<0 then let p=0
z=t*c
y=p+z
h=1

print "1 Cycle Time:", y/60000; "min", y%60000/1000; "sec"

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

goto "interval"

:interval
if p>0 then gosub "pause"
for n=1 to c
if g=1 then print "shot", h else print "shot", n, "of", c
click "shoot_full"
sleep t
next n
h=h+1
if g=1 then goto "interval" else end

:pause
n=(a*60)+b
for m=1 to n
q=n-m
print "Intvl Begins:", q/60; "min", q%60; "sec"
sleep 930
next m
return

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adamp101

3

Re: Manual Focus in Ultra Intervalometer

« Reply #6 on: 12 / April / 2011, 16:52:55 »

A few updates:

The subject distance override that I described above seems to be working consistently for keeping focus locked while in AF mode, which allows you to keep the display off to conserve power. For what I'm doing now, I'm always working at infinity focus, so this subject distance override is preferable to peabody's AF lock method, because this way I don't need to worry about it missing the focus in the first frame. I can see how if you were working with a closer subject using the AF lock would be more convenient.
fudgey: I have not tried AF lock on the A570 yet, but it is mentioned in the manual (pages 45-46: http://gdlp01.c-wss.com/gds/5/0900001215/02/PSA570ISCUGad_ENg.pdf ).

Another thing that I've started playing around with is a script that just shoots in continuous mode. (see: http://chdk.wikia.com/wiki/UBASIC/Scripts:_A_fast_%22intervalometer%22 )

This addresses peabody's concern of avoiding wearing out the focus motors, since it does not refocus between shots, and you can run it in AF mode (I still use the subject distance override), which allows you to turn off the display. The only downside here is that you have less control over the time between shots. You can still control it to a certain extent by using longer shutter speeds. I'm thinking about buying a dense ND filter for this purpose.

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fudgey

1705
a570is

Re: Manual Focus in Ultra Intervalometer

« Reply #7 on: 15 / April / 2011, 12:35:06 »

Quote from: peabody on 28 / March / 2011, 18:31:46

If it works on my A590, it should also work on an A570. So you enter alt mode with autofocus turned on, and the display turned off. Then start the script running, working blind kinda.

Ah, I thought you meant a Canon feature, not CHDK override.

What I figured would be desired for intervalometer use is locked focus that keeps the focus mechanics at a fixed state, possibly giving longer camera life time (and I mean camera, not battery).

Quote from: adamp101 on 12 / April / 2011, 16:52:55

fudgey: I have not tried AF lock on the A570 yet, but it is mentioned in the manual

The AF lock chapter describes the way I usually enter manual focus (AF lock is just another way of entering MF). But as you can see in the manual, it instructs you to power on the LCD first. When the LCD is shut down (and video out is disconnected?), focus is lost and MF cannot be entered until LCD is powered on again.

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