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Author Topic: How much light is needed?  (Read 17187 times)

EMULAT3D

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How much light is needed?
« on: December 17, 2013, 11:14:21 PM »
Hey Guys,

I have been doing some experiments with two studio flashes (360w) to illuminate face captures. However, I have been only able to capture at 1/8 shutter speed, with an ISO of 200 and an aperture of 13 (to minimize DOF). My question is, how are some capturing at 1/10,000?! Even with 1/1000 I have a close to black image, how much light is actually being fired into to the scene for illumination? Any insight would be greatly appreciated.  ;D

Thanks,
Corey

fabberlounge

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Re: How much light is needed?
« Reply #1 on: December 18, 2013, 12:11:07 AM »
Hi,

we are working with 4studioflashes (250Ws each), our setting is Iso100, aperture13, 0,5sec. shutter speed... as the cameras and flashes are synchronized, the shutter speed is not important, as our studio is quite dark. so the shutters are open, and the 4 flashes give enough illumination for sharp, bright photos. We are running a multicamerastudio with 48 DSLRs, scanning humans and pets. The biggest challenge was a shadow free light setting, we have experimented a lot with different flash positions, a combination of reflecting walls, white floor, indirect positioned flashes and a closed system does the job now without any light problems or black images...

all the best, good luck, Andreas from fabberlounge
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Exhale

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Re: How much light is needed?
« Reply #2 on: December 18, 2013, 01:00:35 AM »
Hi ,
Andreas,   do you have mostly 1100D?

fabberlounge

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Re: How much light is needed?
« Reply #3 on: December 18, 2013, 01:16:18 AM »
Exhale, we have 12 Canon 1100D ( for the floor area) and 36 Canon 600D (face, hands, ), mostly 35mm, but as I mentioned in a previous post, its a mixture of cameras, focal length,... Agisoft PS does the job! a great thanks to the people behind it.
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EMULAT3D

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Re: How much light is needed?
« Reply #4 on: December 18, 2013, 06:58:22 AM »
Hey Fabberlounge,

Thanks for the information! I really appreciate it! I guess as long as there isn't any serious motion I can keep the shutters open longer. Plus 2 additional back lights and a few reflectors would definitely help. :)

Thanks again!

Exhale

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Re: How much light is needed?
« Reply #5 on: December 18, 2013, 11:56:54 AM »
Andreas,  What do you think about 50x 1100D setup?

fabberlounge

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Re: How much light is needed?
« Reply #6 on: December 19, 2013, 01:17:21 AM »
Emulate3D, motion is no issue as the studio is ( nearly) dark, so you can jump, dance hold kids and pets (see also a screenshot attached) with Iso100 and fstop13, you get a sharp picture just because the flashes are the only light source...

Exhale:50x1100D,  I think it would work fine, depending on the quality you are expecting. with a fixed lense objective instead of the 18-55mm, you can compensate some quality issues... I am using my 12 Canon 1100D for the leg area, and I dont have any troubles to align photos and get a decent texture out of it. ( but I am only using it for 3D prints, with a resolution of about 0,1mm, max. printing size 350mm) My standard export parameters are about 200-300K mesh and a 2K texture map, that does the job .
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EMULAT3D

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Re: How much light is needed?
« Reply #7 on: December 19, 2013, 05:27:00 AM »
Wow! I was sure that .5 second shutter speed would have introduced motion blur. I am going to have to give this a whirl! So what would be the benefit of capturing at a much higher shutter speed?

Thanks again fabberlounge!  :D

meshmixup

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Re: How much light is needed?
« Reply #8 on: December 19, 2013, 07:25:38 AM »

Exhale:50x1100D,  I think it would work fine, depending on the quality you are expecting. with a fixed lense objective instead of the 18-55mm, you can compensate some quality issues... I am using my 12 Canon 1100D for the leg area, and I dont have any troubles to align photos and get a decent texture out of it. ( but I am only using it for 3D prints, with a resolution of about 0,1mm, max. printing size 350mm) My standard export parameters are about 200-300K mesh and a 2K texture map, that does the job .

Hi Andreas,
I am using 24mm to avoid any part missing (e.g. with legs stretching) and more picture overlapping. But from your experience, it seems 35mm gives better details which I wanna try too. May I know do you encounter any problem with 35mm in capturing a pose with some body part moving out of the camera view?
Jim

fabberlounge

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Re: How much light is needed?
« Reply #9 on: December 19, 2013, 09:37:44 AM »
Emulate3D, The only reason for a longer shutter speed is a more reliable synchronisation of the cameras. I am using the 2.5mm connector and some triggerboxes with a Pocket Wizard to send the signals, with a 0.5 sec. speed I do not get any black images anymore, meaning all shutters are open before the flashes are activated. (it works also with 1/8, but 0.5s is more reliable, and there is no qualty difference)

Meshmixup: I have also tried 24mm, it works, but I had a bit more problems with the texture map... so instead of 24mm I would rather increase the distance to the object, if possible. my studio is about 3.5mx3.5m, thats the limit. And yes if you miss some parts of the person, that is a big problem, for some poses I still change the setting for some cameras to 24mm.

all the best Andreas
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Exhale

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Re: How much light is needed?
« Reply #10 on: December 19, 2013, 11:31:45 AM »
Hi,

Andreas,
Yes you are totally right with the shutter lag. I did an experiment and shutter lag is between 50-100ms depending the camera vendor. Canons usually have around 50-60 , Nikons 70-80 and some models have higher shutter lag. It sometimes changes even in the same model camera. 5-8 ms but it doesn't make a big impact.
 Also I think, 1100D setup would be enough in your case. Have you ever tried to position 1100D for head and body capture instead of legs? You said "depending on the quality you are expecting" do you believe the quality won't be good for print like you do?  Have you also tried decreasing 600Ds' quality to 12mp and see the result ? Can you give a go like this and let me know please :)

fabberlounge

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Re: How much light is needed?
« Reply #11 on: December 19, 2013, 05:26:59 PM »
Hi Exhale,

I also believe that the Canon1100D would be good enough, there are some advantages like the display can be positioned in a way that I can see the live picture, while focussing (esp. for my small studio a big advantage, as the cameras are placed very close to the walls). I have used the 1100D also for face, hands,... the output is good enough, so yes I think it will work with 1100D`s only. I could have saved some money (about €100 each), and spend that on more cameras, which would give better results in the end... that is the hard thing about trial and error, and the good thing to follow the Agisoft community :-)  all the best, happy XMas to all of you, as I will be on Skiing holiday for the next 10 days (no cameras, no ZBrush overnight sessions,...)
Yes, we scan !

Exhale

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Re: How much light is needed?
« Reply #12 on: December 19, 2013, 08:08:26 PM »
Thnaks for sharing your exp. with us.
Cheers buddy. Happy Xmas to you.! Don't get hurt :)

neo93

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Re: How much light is needed?
« Reply #13 on: January 05, 2014, 04:04:45 PM »
Do You think studio flashes with 100watts Could be enough?

fabberlounge

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Re: How much light is needed?
« Reply #14 on: January 06, 2014, 09:57:36 AM »
Hi, if you accept a higher ISO setting, or decrease your f-stop... even a 100W lighting is of course possible... all the best
Yes, we scan !