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Author Topic: Synchronizing different DSLR cameras  (Read 15327 times)

Andrew

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Synchronizing different DSLR cameras
« on: July 04, 2013, 05:23:16 PM »
I just bought Camera Axe with Multi Flash Plus to solve different shutter lags on different camera models I have laying around (old Canon 550D, two 600D's, Nikon D3200 and Nikon D7100).

I set all cameras to Manual mode, set all zoom lenses to Manual Focus, made sure all cameras use same settings (ISO 100, F5,6, same WB), disabled any image altering shenanigans (like Active-Dlighting and some such), pointed all cameras at digital stopwatch and triggered them all simultaneously with Camera Axe/Multi Flash. I used no stobe lights to keep things simpler.

What I expected was evidence of consistent (down to 1-3ms) shutter lag, letting me adjust trigger times on Multi-Flash Plus unit, to achieve near-perfect sync.

To my surprise, I only observed consistent shutter lag on Nikon D7100 and Canon 550D. The two 600Ds would either sync perfectly with 550D or be quicker by 43ms, while Nikon D3200 would either sync perfectly with 550D or be slower, curiously by the same 43ms value.

All camera settings look the same, but perhaps there is something I'm missing, something that causes D3200 and 600Ds to sometimes pause and think before taking photos? Any ideas?

Cheers,
Andrew

andy_s

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Re: Synchronizing different DSLR cameras
« Reply #1 on: July 04, 2013, 06:16:33 PM »
Very interesting Andrew.

Have you used the camera-axe to test shutter lag [and it's variability] on each individual camera ? [by using a flash like this http://www.techphotoblog.com/tpb-13/ ]

Maurice Ribble [the Axe designer] sometimes replies directly to email queries or requests you open  a new forum topic here: http://www.dreamingrobots.com/forums/viewforum.php?f=8 .

I'd be interested to hear more. 

Update: I see you posted on Maurice's forum already - if you don't get any feedback please try Maurice directly.
« Last Edit: July 04, 2013, 07:23:40 PM by andy_s »

andy_s

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Re: Synchronizing different DSLR cameras
« Reply #2 on: July 07, 2013, 12:58:24 PM »
Hi Andrew, i'm pleased that you found a workaround. I hope you don't mind my sharing it here [for the possible benefit of others on this forum].

See http://www.dreamingrobots.com/forums/viewtopic.php?f=8&t=1902

"...I finally got around to improving my testing methodology and was able to both measure individual shutter lags for my cameras, AND figure out where the occasional delay was coming from. The Multi-Flash Plus pre-focuses cameras to get them ready for shortest possible shutter lag but that pre-focus command is not re-issued every time I trigger Camera Axe. I haven't noticed that before because it doesn't make virtually any difference on Nikon D7100 (one speedy camera), but for the other cams, it does, big time. So each time I am about to trigger cameras, I toggle 'ready' button on Multi-Flash Plus... A bit messy but works..."

PS Andrew - I don't remember how advanced "mrniemand" had become for the multiflash boards using his "remote control the CA via pc (better way to set CA values)" - but it may be something you'd like to investigate further ?

http://www.dreamingrobots.com/forums/viewtopic.php?f=8&t=1689
« Last Edit: July 07, 2013, 01:06:23 PM by andy_s »

andy_s

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Re: Synchronizing different DSLR cameras
« Reply #3 on: July 07, 2013, 03:48:35 PM »
Hi again Andrew.

Would you mind sharing the individual shutter lag / variability that you found for your Canon 550D, two 600D's, Nikon D3200 and Nikon D710 ?

Andrew

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Re: Synchronizing different DSLR cameras
« Reply #4 on: July 07, 2013, 07:49:30 PM »
Hey there, glad you shared my post from the other forum, it was way past 2am when I concluded my testing, felt too tired to post here as well :)

As for the details of my testing - yes, I did test shutter lag for individual cams by placing them directly in front of flash unit and adjusting flash delay until I got uniform illumination of entire frame, just like Maurice did in his blog post. The strange thing is - whenever he saw his camera's shutter partially open, he would get a photo where there was clearly defined border between lit part of the frame and black part obscured by shutter. In my testing though, I never got this crisp border - I would always get images slowly emerging from darkness, as I was increasing flash delay by each millisecond. Instead of border, I would get dark gradient lifting from the frame. Could it be because of my cheap studio flash? Perhaps it isn't as quick to fully light up as Maurice's small speedlight?

Now my findings: Nikon D7100 understandably wins by a large margin - shutter lag was fast and consistent, around 54ms if memory serves. The other Nikon, D3200 landed last, and I mean last (145 or 150ms I believe), but it too was rather consistent. Canon 600D's were in the middle (90ms I think), while 550D was a tad slower (94-95ms), and a whole lot less reliable. You can get some black images or dark gradients as the shutter is dragging its feet.

I tightened my timings only to a point where I was able to shoot 1/100s with these 4 cams and flash units, with only occasional problems caused by 550D.

Andrew

andy_s

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Re: Synchronizing different DSLR cameras
« Reply #5 on: July 08, 2013, 12:24:53 AM »
Thanks [again] for the info Andrew - that covers my major contenders  ;) [other than these new Samsung Android types  ::)]

My memory is the flash Maurice used was a Yongnuo with light produced over about 40microsec [at the power setting he used] - that could be anywhere up to a tenth the duration of your studioflash ?
 

Andrew

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Re: Synchronizing different DSLR cameras
« Reply #6 on: July 08, 2013, 06:11:43 PM »
I just dug up useful article testing flash duration for various speedlights as well as two studio flashes.

http://www.gock.net/2012/01/flash-durations-small-strobes/

Yongnuo YN560 at its weakest setting emits light in 43 microseconds, while "Mystery" Ebay light (probably close to the cheap Chinese gear I got), takes 7120 microseconds to flash :) That's a cool 165 times slower, wow! No wonder I wasn't able to measure lags with too much precision :)

andy_s

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Re: Synchronizing different DSLR cameras
« Reply #7 on: July 08, 2013, 08:15:04 PM »
wow Andrew !  i sent you a pm as well...

Magnus

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Re: Synchronizing different DSLR cameras
« Reply #8 on: July 11, 2013, 09:17:48 PM »
Hello!

Thanks a lot for this info! Very interesting to see the different lags, hehe.

Best, Magnus.

tommyboy

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Re: Synchronizing different DSLR cameras
« Reply #9 on: January 14, 2014, 05:00:21 AM »
Now my findings: Nikon D7100 understandably wins by a large margin - shutter lag was fast and consistent, around 54ms if memory serves. The other Nikon, D3200 landed last, and I mean last (145 or 150ms I believe), but it too was rather consistent. Canon 600D's were in the middle (90ms I think), while 550D was a tad slower (94-95ms), and a whole lot less reliable. You can get some black images or dark gradients as the shutter is dragging its feet.

Just coming across this issue in our testing, wanted to see if you had a similar experience with your Canons.  We are testing 600D x 6 using Maurice's methodology, and noticed wildly varying shutter lags between all cameras, from to 0.112 and 0.1430, and these values were inconsistent from shot to shot even for the same camera.  Interestingly, once we enabled mirror lock up, timings got very consistent at around 0.083 for all cameras.  However some in the forums here have said that MLU increases shutter lag, which we're not seeing, can someone confirm this?

We also tested Nikon D5200 x 6, which don't support mirror lock up, and found them to be quite consistent at around 0.090.

This was using pre-focus for both camera models.

fabberlounge

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Re: Synchronizing different DSLR cameras
« Reply #10 on: January 14, 2014, 09:21:27 AM »
Hi all to you,

may I ask why are you so interested in perfect synch. when you can use the flashes for exposure? My cameras are set to 1/2 sec. even 1sec. or more would be ok, as long as I am working with ISO 100 and F 11-13 in a quite dark studio. ( not completely dark, enough light to see what you are doing). Also with optimized flash positions (4-6 and 250W each), I get good sharp shadow free images.
Is there any other reason for perfect synch., other than not having the possibility for a studio setting ?
Maybe I have missed something really important, but for the purpose of scanning dynamic poses it is a realiable working solution ( I am running the 48camera studio since 4months now, did a lot of scans and 3D prints, kids, pets, people jumping and dancing... , no synch. or ligth issues)

thanks for an answer,

Andreas, fabberlounge.com
Yes, we scan !

Infinite

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Re: Synchronizing different DSLR cameras
« Reply #11 on: January 14, 2014, 02:36:39 PM »
The 550D's are terrible. They have a huge amount of inconsistency. I've tested 38x together. The 600D's are much more reliable 100+ but this is at slow shutter speed 1/4 - 1/10 over 1/10 you will start to get black images or visible curtains in the shots..

The goal is to acquire 100% image capture, 100% of the time. No black images.

You could also try mirror lock-up, this way you can use faster speeds.

I would also personally say stay a way from Nikon cameras. They are not suited for photogrammetry. They have a nasty yellow / orange tinge to the images, bad noise, soft output and on the more expensive cameras you can get oil spots. I've tested on D5200 (4x), D3200 (28x) and D800 (8x) + D800E (1x). Bad cameras for photogrammetry IMHO. Their only benefit is the build quality. There was barely any discernible different between standard D800 and E. Don't believe the hype  :(
« Last Edit: January 14, 2014, 02:41:36 PM by Infinite »
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tommyboy

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Re: Synchronizing different DSLR cameras
« Reply #12 on: January 15, 2014, 12:29:39 AM »
Thanks Lee and Andreas for your great responses.  The reason for being so interested in perfect sync, is that I am trying to figure out a nice way to do two stage capture (noise projection + texture), with as small a time difference between them.  I figured if I can get two camera models that have different shutter lags, yet are consistent within that model, I can fire them from one trigger, and time the flashes such that the noise projection is captured by one set of cameras, and regular images are captured for textures by another set.  Unfortunately this does leave very little room for error as far as shutter speeds, my process certainly is not free of black frames even with the small set of cameras I've tested so far.

Has anyone tried this, or other techniques for two-stage capture that are simpler/more robust?  Or should I just use the extra cameras to improve coverage and forget about noise projection?

Infinite

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Re: Synchronizing different DSLR cameras
« Reply #13 on: January 15, 2014, 03:04:11 AM »
What you're trying to do is very complicated. The problem is shutter speed. The only way to do it is with a gap between each capture 1,2 seconds. We just can't synchronize cameras fast enough. What works with 8 cameras and all looks good, can break down when you then go to 16 or 36 when doing multiple captures. I've seen it happen. It depends how many cameras you want to use. You could also use 2 banks of cameras, one set for noise, one set for colour. Or go InfraRed.

Really they need to firing synchronized at a split second. Very hard to do.

It's complex problem to solve. I've spent many hours on it, for some occasions it's useful. Others not so much. The trick is getting that fast capture between each set. Tricky.
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fabberlounge

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Re: Synchronizing different DSLR cameras
« Reply #14 on: January 16, 2014, 12:00:52 AM »
...Has anyone tried this, or other techniques for two-stage capture that are simpler/more robust?  Or should I just use the extra cameras to improve coverage and forget about noise projection?...

Hi again,

There are unfortunately certain textures, where you really would need a noise projection... so if there is anyone out there with a reliable solution, I would invite them for a nice weekend in a 5star hotel in the centre of Vienna, including diner and a visit in Viennas best winebar (actually run by my wife.. ;) )

So go for denim, leather, tweet, and you really avoid a lot of mesh building problems....

regards, andreas

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