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Author Topic: Triggering and Camera Questions  (Read 7616 times)

gtarplyer

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Triggering and Camera Questions
« on: August 28, 2014, 07:35:19 AM »

Hi all,

I've done my share of reading the forum (there's too much to read!), but I'm still unclear on some things, and, hey, doesn't hurt to rethink past answers as technology progresses.  ;)

I'd like to build a high quality rig for face / head scanning.

*  I was thinking of using Sony a7 (24 MP) or a7R (36 megapixel) mirrorless full frame cameras. Mainly because I hear they're lighter than DSLRs and just as good pixel quality.

* Simultaneous triggering has always been the mystery to me.  I've heard people talking about Pocketwizards as the way to go, then Esper Shuttercell.   Which is the best way?  I trust cables more, and I think its cheaper too.  Is that all I need? Shuttercell and some cables?

* I think 16 cameras is plenty for face/head capture, no? One Esper Shuttercell should do, right? I'm not quite sure how to hook things up. At the end is it just one cable with a button at the end you physically push to trigger all 16 cameras at once?

* I've heard that USB 3.0 triggering is also an option?  How do you trigger the cameras? Just put them into a USB hub, then what? The Breeze Systems software to trigger the USB?   I heard that USB doesn't really trigger all the cameras at the same instant, is that true?   

* If I went with Esper Shutter cell, I don't need the Breeze software, correct?  Just push the button and bang! Right?

* And finally: Lighting.  How many light umbrellas do I need? Any recommendations? The top 3 products on Amazon are the LimoStudio 600W system for $38.    Then the CowboyStudio for $59, and the FAncierstudio 2000 Watt for $174.

I've got a bunch more questions about Photoscan settings (go with default?) , etc, but I'll leave that for another day.

Thank you!

 8)

mala

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Re: Triggering and Camera Questions
« Reply #1 on: August 28, 2014, 01:47:28 PM »
Hi gtarplyer,

I can answer a few questions for you  :)

The Sony cameras are great and very fast, but I would not advise you use them for this application, the problem is Sony's proprietary connectors for triggering and Breeze or Smartshooter currently do not support downloading of images from Sony cameras (Sony are very guarded with all their SDK info that would be required to make this happen)
I would recommend Canon DSLRs for ease of finding trigger cables/adaptors (simple 2.5mm stereo jack) and cheap PSUs...... the best at the moment in terms of cost versus quality is probably the 100D.

Triggering via USB is not a good idea as, yes as you mention it is not possible to trigger all shutters at exactly the same time.

The ShutterCell I can of course give you plenty of info about  ;)
There is a ShutterCell info sheet here: 

http://www.esperdesign.co.uk/assets/manual-_sc.pdf

If you used one of our ShutterCells you would need something to trigger/switch the input, most people use one simple radio remote for this such as the Pocket Wizard, this means you can be anywhere in the room (or in the middle of cameras for a 3D selfie) and trigger all the outputs without getting tangled up with the cable.
You could of course just use a simple cabled remote into the input if desired, but beware any that have half press AF function, as even if you have AF turned off on the cameras(as you should) the signal can disrupt some cameras and lead to unreliable shutter control.

For large camera rigs it would be cheaper to use the ShutterCell rather than one PocketWizard for every camera, plus you don't have to worry about batteries on the PocketWizards.

You will still need Smartshooter(cheaper) or Breeze to download the images to your attached computer unless you don't mind taking memory cards out to copy the images over, though this is time consuming and risks moving your cameras.

Hope that helps,
mala

gtarplyer

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Re: Triggering and Camera Questions
« Reply #2 on: August 28, 2014, 07:01:11 PM »

Thanks Mala, that was really helpful. I'll probably get the ShutterCell in the near future.

Regarding the cameras: Reading back through some of the posts, I see there was some discussion about noise in the models.  Lee was saying "use more cameras" and/or use the full frame Canon Mark 5D III .   Big difference in price per camera.   What is the current thought on that?

I don't want to spend time in ZBrush smoothing models. I would like the system to just produce good models requiring minimum cleanup.

Thanks. :)


mala

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Re: Triggering and Camera Questions
« Reply #3 on: August 28, 2014, 07:43:31 PM »
I'm probably not best placed to answer the question regarding noise in the built models, as I'm mostly focused on hardware nowadays.
But from past experience I would say that to an extent more cameras will help, provided your images have as little noise as possible (low ISO) and a sharp focus through a wide depth of field.

Though even if you do keep image noise to an absolute minimum there will still be some fine noise in the built mesh (from my experience) this appears to be inherent in the agisoft process and there have been in the past various requests for an in application smoothing function.

A lot of people here at the forum are using agisoft to then 3D print models or produce medium resolution assets which may not suffer so much from this fine noise, as I don't know your intended end application for the models I can't say if this will be a problem for you or not.

I think Lee (Infinite) maybe the best person to throw some light on the best way to deal with this fine noise problem really, as he has far more experience with this software and Zbrush when producing very high quality models for various end uses.

mala

Digitage

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Re: Triggering and Camera Questions
« Reply #4 on: September 01, 2014, 05:11:35 PM »
Hi gtarplyer,

basically to obtain good results and a minimal noise in your PS results, you have three sliders to control what you do. You want to have a small pixelsize, good quality crisp pictures, and good camera coverage so that  each point of your model is present on as many pictures as possible.

When you want to improve the quality and lower the noise, it is a good rule of thumb to improve these parameters at the same time.

For instance, it would not be really useful to get a better set of cameras if you don't improve your lighting (if it was not perfect yet) at the same time; or if you don't improve camera coverage and/or or zoom level.

Then again, it is always a questin of how much you can invest in your rig   :-\

FLuca

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Re: Triggering and Camera Questions
« Reply #5 on: September 02, 2014, 03:52:39 PM »
Regarding the noise issue, i have allready bought raw models from infinite, and they are quite noisy even with 110 cams. Infinite advantage with such quantity of cams is to have a great coverage of the subject. He even show himself how to get rid of noise with zbrush in its famous tutorials.

From my modest experience, noise quantity really depends on the subject and its skin quality.
With children with very smooth and spotless skins, the result is very noisy with big holes in the point cloud, while with old skin full of moles and wrikles the result are much more precise.

You can also notice the quality difference between skin and clothes. The later are always better defined due to their more detailed textures (with mat fabric of course).

It is not a mystery that PS is requiring images with lots of distinctive features and skin is not the ideal material (and can be very shinny). Hair are even worst.

It is also very important to have the largest depth of field possible (high aperture number thus lots of light) as blur on the subject is very detrimental for the model quality.

Good luck with your rig
Fred Lucazeau - Body Scan - www.another-me.fr
Sketchfab gallery: https://sketchfab.com/fredlucazeau