Tips on improving shooting speed with remote synced cam's

arsenix

47

« on: 11 / March / 2016, 16:24:31 »

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I am building a multi-camera rig with four synchronized cameras. They are A4000 IS's, using the "precision sync" code, with triggering through the battery temperature third terminal. It is actually working quite well, with good synchronization results (a hundred test photos yielded a max timing spread of about 2mS, which is probably within my measurement error).

My problem is I need to get the cameras able to capture faster. Right now, I can only take about 10 photos a minute (one every 6 seconds). I have tweaked the settings to try to reduce it:

No flash[/size]
Manual white balance[/size]
Focus locked (AFL)[/size]
Exposure time minimal (1600ISO)[/size]
All "intelligent" features disabled (blink detection, red eye, focus lamp)[/size]
Review on 0 s[/size]
IS settings do not seem to effect the capture time.[/size]
JPG compression settings also don't seem to impact[/size]
RAW disabled (this adds a few more seconds).[/size]

Any other tips on how to improve things? In continuous mode, the camera when configured this way can take about 30 pictures a minute, so this is probably the fastest it can do. If I can get it to a reliable 20 photos/minute I will be happy.

Are there some excessive delays in the precision sync mode I could try shaving down maybe? I was thinking I could try altering the precision sync remote triggering code to use continuous mode and just hold the shutter until triggered?

I am using a Sandisk Ultra SD card, which according to my benchmarks is decent, but not the fastest card for these. Think bumping to a faster SD card will help things?

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waterwingz

12138

Re: Tips on improving shooting speed with remote synced cam's

« Reply #1 on: 11 / March / 2016, 17:04:56 »

I suspect the ISO 1600 setting is causing most of your problem. Try testing at speeds below ISO400.

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Ported : A1200 SD940 G10 Powershot N G16

arsenix

47

Re: Tips on improving shooting speed with remote synced cam's

« Reply #2 on: 11 / March / 2016, 22:20:52 »

Interesting. I had assumed the ISO1600 would make it faster because of faster shutter speeds.

You are correct that it shoots much faster in ISO200. Even in a fairly dark room, I shot 44 pictures in 60 seconds in continuous mode (compared to 29 in 60 seconds at ISO1600). Why is this? Does the light evaluation take longer because of the noise?

I'll have to play with this a bit more. I need some brighter lights. This is an outdoor application so shooting at ISO200 is fine, but in my dark lab the exposure times are currently too long. My initial "cave test" got me to 17 shots in a minute, but only with one of the cams, the others lagged a bit.

Thanks for that tip waterwingz!

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reyalp

14080

Re: Tips on improving shooting speed with remote synced cam's

« Reply #3 on: 11 / March / 2016, 23:42:34 »

Quote from: arsenix on 11 / March / 2016, 22:20:52

You are correct that it shoots much faster in ISO200. Even in a fairly dark room, I shot 44 pictures in 60 seconds in continuous mode (compared to 29 in 60 seconds at ISO1600). Why is this? Does the light evaluation take longer because of the noise?

The camera does more noise reduction processing at higher ISO. This probably goes in distinct steps, so for example ISO 100-200 would be fastest, 400 would be slower, 800 would be even slower etc. These numbers are just made-up examples, you would need to test your specific camera model to find out where the actual changes are.

CHDK scripting lets you set ISO in 1/96th stop increments, so if you find it gets slow at say ISO 400, you could use something like 397 instead.

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arsenix

47

Re: Tips on improving shooting speed with remote synced cam's

« Reply #4 on: 12 / March / 2016, 14:30:03 »

That makes sense. I wouldn't have thought the noise reduction would take so long. It is pretty clear when you try the different ISO settings. There is a "busy" text that comes up for longer and longer at the higher ISOs. At ISO100 it doesn't come up at all.

This is a good sign since I plan to shoot at lower ISO's anyways. We'll see if I can get the cams fast enough without modifying the chdk code further. There is a significant difference in speed between continuous mode shooting and "full release" of the trigger. If I shoot with "half shoot" held indefinitely this seems similar in speed to continuous mode (it may be functionally equivalent).

I have implemented a new remote shoot mode where half shoot is held after the first trigger, but I have not yet gotten that to work with the precision sync. It should be possible but some digging into the sync code is necessary.

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waterwingz

12138

Re: Tips on improving shooting speed with remote synced cam's

« Reply #5 on: 12 / March / 2016, 14:42:50 »

Quote from: arsenix on 12 / March / 2016, 14:30:03

I have implemented a new remote shoot mode where half shoot is held after the first trigger, but I have not yet gotten that to work with the precision sync. It should be possible but some digging into the sync code is necessary.

There is a "flag" ( usb_sync_wait_flag ) that you need to set in your usb shooting module to tell the sync code to go active on the next shot. It's reset internally after each shot so your module needs to set it each time.

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Ported : A1200 SD940 G10 Powershot N G16

arsenix

47

Re: Tips on improving shooting speed with remote synced cam's

« Reply #6 on: 14 / March / 2016, 15:57:56 »

I'll check out that flag.

I did some additional testing with SD cards too and surprisingly the SD card speed really doesn't impact write speed, at least moving from a "decent" speed card (8500Kb/s) to a fast one (14000Kb/s). Seems like SD card writes are cached (which is good!). FYI for others trying to speed things up.

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waterwingz

12138

Re: Tips on improving shooting speed with remote synced cam's

« Reply #7 on: 14 / March / 2016, 17:40:17 »

Note that you might also get an occasional delay of a few additional seconds periodically as the card reorganizes itself. I posted some test results here last year for one card. YMMV.

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Ported : A1200 SD940 G10 Powershot N G16

arsenix

47

Re: Tips on improving shooting speed with remote synced cam's

« Reply #8 on: 14 / March / 2016, 17:50:27 »

That is interesting. I'm sure that varies significantly by the type of card too. I'll watch for that as I do more testing. Since my triggered capturing is essentially "open loop" that would make me skip a capture or two.

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arsenix

47

Re: Tips on improving shooting speed with remote synced cam's

« Reply #9 on: 17 / March / 2016, 20:38:50 »

Ah. Dug in here and have the sync working with my half shoot held mode. I modified action_stack.c to add some new shoot scripts.

The minimum "setup time" ie the time the remote needs to be in half_press state is now extremely short (I can't reliably measure it but I'd say 100ms tops, as we'd expect since in half shoot mode everything should be ready to shoot). I'm at 26 shots/minute now, so getting a lot closer to my 30 shots/minute target.

I assume the delay between remote full state and shutter close is set by the sync code? Seems to be about a half second right now, which is not bad and a small part of my 2s/shot time budget.

There seems to be still a fairly long time between the shutter close and when it is ready for the next trigger event (about 2s). Much longer than when shooting in continuous mode. Any ideas how I might trim this down? In my special action_stack shoot script I removed the retry functionality and the delay that was in there to wait for the jpeg to be saved. This helped, but I'm not sure where else to trim time out.

If I can't get things working fast enough in this mode, maybe I should try to build a remote trigger mode that is based on continuous mode? I could just hold down full shot and then use the sync code to hold the shot between trigger events?

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