Maximum number of continuous mode shots

74prof

Re: Maximum number of continuous mode shots

« Reply #10 on: 05 / August / 2013, 18:57:28 »

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My subjective estimate of high speed vs low speed was the sound of the clicks (the shutter?) and the flashes of the light to the left of the optical view port.

No idea of whether I actually have 2.5 frames per second in high speed.

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74prof

Speeding up continuous ( burst) mode on A540

« Reply #11 on: 07 / August / 2013, 18:28:38 »

I am using continuous mode for stop motion video on the A540. With the liveview screen turned off, the largest jpegs slow down after about 20 shots. I can shoot indefinitely at the M size. RAW plus jpeg seems to be about 1 shot per second.

Not sure what else I can do. I am using a 133X sd card. Some sources suggest card speed does not matter.

I have used both chdkcam gui and ptcamgui, but I assume that saving directly to computer via usb would be slower than to sd card.

I have a couple of 4gig sd cards, but some sources here suggest size does not matter.

The Magic Lantern and the Nikon hackers to shoot raw video seem to be bypassing the shutter and using live view feed to get bursts of 30fps in raw. Is that relevant to the chdk coders?

I was surprised that a camera (A540) that does not directly save pictures to internal memory does have a buffer for temporary file storage.
Another off the wall wonderment: could coders alter the buffer size in software and thus speed up file capture?

Of course Canon states the predicted fps, so one assumes they have hard-wired it so that once I have continuous shots, smaller file size, or faster cards will not matter.

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waterwingz

12132

Re: Speeding up continuous ( burst) mode on A540

« Reply #12 on: 07 / August / 2013, 18:34:01 »

~~Didn't we already discuss this here : http://chdk.setepontos.com/index.php?topic=10488.0 ??~~

Edit : comment redacted - admin merged this thread with the old one I linked

« Last Edit: 07 / August / 2013, 23:41:08 by waterwingz »

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Ported : A1200 SD940 G10 Powershot N G16

74prof

Re: Speeding up continuous ( burst) mode on A540

« Reply #13 on: 07 / August / 2013, 20:42:25 »

What I have stumbled upon since the last discussion is issues as to whether the A540 does have a buffer for photos or directly writes to the sd card. Also a debate as to whether card speed matters even in continuous mode.

Some sources say they can't find the listing of buffer size. Others state that there is no buffer on the A series cameras.

I am wondering whether Powershot live views can at least in theory send their feed directly to the sd card electronically without firing the shutter. This is apparently what Magic Lantern and Nikon hackers are doing to get very fast raw bursts.

But yes, I did raise the issue in general before.

Sorry if I raised these points elsewhere and forgot.

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waterwingz

12132

Re: Speeding up continuous ( burst) mode on A540

« Reply #14 on: 07 / August / 2013, 21:06:03 »

Quote from: 74prof on 07 / August / 2013, 20:42:25

What I have stumbled upon since the last discussion is issues as to whether the A540 does have a buffer for photos or directly writes to the sd card. Also a debate as to whether card speed matters even in continuous mode. Some sources say they can't find the listing of buffer size. Others state that there is no buffer on the A series cameras.

Links ?

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Ported : A1200 SD940 G10 Powershot N G16

reyalp

13880

Re: Speeding up continuous ( burst) mode on A540

« Reply #15 on: 07 / August / 2013, 22:19:29 »

Quote from: 74prof on 07 / August / 2013, 18:28:38

I have used both chdkcam gui and ptcamgui, but I assume that saving directly to computer via usb would be slower than to sd card.

The only one that would have a chance of being faster would be chdkptp remote capture in continuous mode. I would expect a fast SD card to be faster, but haven't measured it.

Quote

The Magic Lantern and the Nikon hackers to shoot raw video seem to be bypassing the shutter and using live view feed to get bursts of 30fps in raw. Is that relevant to the chdk coders?

No.

Quote

Another off the wall wonderment: could coders alter the buffer size in software and thus speed up file capture?

Not likely. If buffering is a significant factor, it's likely that Canon already uses as much memory as they reasonably can.

Quote

Of course Canon states the predicted fps, so one assumes they have hard-wired it so that once I have continuous shots, smaller file size, or faster cards will not matter.

I wouldn't assume that. Those specs almost always have a "may vary" footnote.

edit:
Since these two threads are discussing exactly the same subject, I've merged them.

« Last Edit: 07 / August / 2013, 22:22:00 by reyalp »

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reyalp

13880

Re: Maximum number of continuous mode shots

« Reply #16 on: 07 / August / 2013, 23:15:01 »

OK, how about some actual data:

On my a540, using chdkptp remoteshoot with some timing code added.
shooting mode: manual 1/30, F2.6, ISO 80
Focus:Manual
jpeg: Super/Large

rs -cont=60
finishes in 30.1577 seconds, meaning almost exactly 2 fps.
The timing code records the time taken between image downloads completing. Two shots were around 0.72 sec. All the remaining shots were between 0.42 and 0.49. There is no discernible slowdown, the two outliers are shot #3 and shot #27 (edit: though this is measuring time between downloads completing, not actual shooting times)

This doesn't quite meet the spec of 2.3 fps, but seems like a pretty good result to me.

I did get an "invalid offset" error from chdkptp on one run, so it may not be completely stable...

« Last Edit: 07 / August / 2013, 23:24:54 by reyalp »

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74prof

Re: Maximum number of continuous mode shots

« Reply #17 on: 07 / August / 2013, 23:25:59 »

FWIW, forums.whirlpool.net.au/archive/520047
says that Canon p&s cameras write at least the videos directly to sd cards (ie not to buffer)

http://www.dslreports.com/forum/r18965537-Re-SD-card-question

Seems to say that the A line Canons have either tiny or non-existent buffers.

Of course they may be as expert as me

I did find a suggestion that ISO speed could affect speed of shots.

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reyalp

13880

Re: Maximum number of continuous mode shots

« Reply #18 on: 08 / August / 2013, 00:05:55 »

Quote from: 74prof on 07 / August / 2013, 23:25:59

I did find a suggestion that ISO speed could affect speed of shots.

I know this has been observed before, I'll see if I can dig up a relevant post. Also, on old cameras like the A540, it has been observed that smaller images sizes can actually be slower than full resolution.

I ran another test, continuous shooting to card rather than using remote shoot. The attached script shoots in continuous mode and records the time when the exposure count increases.

Except for the second exposure, 60 shots all came out at 0.48 seconds.

This is using an OCXZ 2gb "150x" card. The card was not freshly formatted. All camera settings were as in the previous test.

So I don't observe any "buffering" in these conditions. The images with my test scene come out to about 1 mb. Since this cameras only has 32 MB of ram total and much of it is used for other things, we can be sure that it's not all being buffered.

The image size will vary greatly depending how much detail there is in the scene, which will likely affect saving times.

cstest.lua (0.84 kB - downloaded 40 times.)

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74prof

Re: Maximum number of continuous mode shots

« Reply #19 on: 08 / August / 2013, 06:23:29 »

My experience as stated I think above, is that with the screen off, maximum resolution images force the continuous mode to slow down after about twenty shots. If I drop one step to M size, high speed seems to go indefinitely.

I do not know however whether those 20 very fine images are being shot more quickly per picture than the indefinite number of M shots. My impression is that the clicks are at the same speed.

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