Messages

61

Face and Body Scanning / Re: LED arrays

« on: May 03, 2014, 01:58:14 PM »

Yeah i agree that i wont be able to find it for a cheap price too. However turning them of/off is not a problem at all.

The "moving arm design" is definitely cheaper in my opinion, buying the equivalent in fixed cameras is : about 25k euro... plus cables filters... etc. I havent spent more than 10k right now in development, it will be even cheaper in later stages. Also for the future, it is cheaper to buy 8 cameras than to sell 48+ cameras and buy another 48. But this is another topic!

I will probably use Cree COB LED's or another cheaper solution from ebay... taking account that each LED takes 75v and 1800mA, finding a power supply that gives +40a and 75v is the hard thing.

- Using more LED's to achieve the same lumens is better in one way: the light is more diffuse since the area of emitting light is more evenly distributed, the downside is that the CRI of the cheaper and less bright LEDs could degrade the texture.

62

Face and Body Scanning / Re: LED arrays

« on: May 01, 2014, 12:40:41 PM »

My lumen output was just a very rough approximation, i'll implement the LEDS from less to more until i have the exposure i need.

If you have 320 x 700 that is around ~220k for 0.5ms. For my exposure time which is 1ms it would be  440k lumens, which is just 1 stop more, not much for the camera.

Im using polarizing filters too, not on the lights though. I have around 1/2 stop less light because of them. Since my subject is very near to the light source, you may be right that 440k lumens is too bright, i'll need to test it since this is very complicated to calculate on theory basis. 

What i need to find is a high power LED strip, with decent CRI for a low price, this seems to be impossible  , because wiring each LED could be a nightmare.
Have you wired those 320 LEDs ? could you suggest any good company for high power LED strips ?

Thanks for your response mala!
Cheers,
Manuel.

63

Face and Body Scanning / Re: LED arrays

« on: April 30, 2014, 02:36:43 PM »

I understand,

- About those LED's, the problem is that it doesnt specify the CRI, for LEDS its usually +80 but it may be less... color rendering a thus texture in agisoft might be very color innacurate. (It is not easily fix-able in post prod as well)

http://en.wikipedia.org/wiki/Color_rendering_index for those who dont know what it is.
- On the other - more expensive - LEDs model CRI is certified to be "Available in 70-, 80-, 90- and
93-minimum CRI options"

However as you say, the price for the cree LED's is too high to buy more than 20. Which is what i need. 

64

Face and Body Scanning / Re: LED arrays

« on: April 30, 2014, 12:14:38 PM »

Thats amazing Eildosa!  I'd love to see scanning outputs of your system if possible.
Lots of thanks for the capacitor white paper i?ll have a look into it with my colleague.
(I got electroshocked with a capacitor from a flash, so im quite respectful to them) 

You could alimentate your cameras with wired fake batteries to a power source. (just make some moulds of the original ones) or maybe they may even sell them.

- About the LEDs, i was thinking about the CREE LEDS because their luminous flux is about 18k at 1800mA, the ones i saw in ebay were about 5k, so i'd need a ton more if i use those ones. But maybe someone knows another cheaper brand that delivers that luminous flux ?

This is getting interesting 

65

Face and Body Scanning / Re: LED arrays

« on: April 30, 2014, 11:24:35 AM »

Thank you a lot for that information Magnus! 
Cooling as you said is not an issue since the temperature generated in ~1ms pulse is close to nothing.

Thing is that your exposure time is 1/60, my "exposure time" should be 1/1000 at f.16 (i need it to be that fast because my cameras shoot in movement), i need a huge amount of light (flash light).
I would use a flash, but i cannot since all of them are too big for my needs.
As a record i tried to build my own mini-flash from flashlightbulbs webpage, but its too dangerous for someone that doesnt perfectly know it. (You can even die from a flash capacitor discharge on you)

It would be wonderful if mala could share its experience!

Regards,
Manuel.

66

Feature Requests / Re: Photoscan Professional "Artist" Edition

« on: April 29, 2014, 02:58:50 PM »

+1 with normal median denoising

67

Face and Body Scanning / Re: LED arrays

« on: April 29, 2014, 02:51:10 PM »

Sorry i didnt specify my shooting conditions:

- Im shooting at f16 plus polarizing filter reducing almost 1.8 stops
- Lights should be at 60cm from subjects face

** Bear in mind  that im not using LEDs as constant illumination, but just with a pulse width of 20 ms or less... (like the flash one).

From what i've read flash output at full power equals to almost a crazy million lm's ... since i dont need full power at that distance.. (i need about 1/8) that is about 320k lms. If each LED has about 15k at 1500ma ... i'd need about 20 of them. Is this correct ?   

http://parts.arrow.com/item/detail/cree/cxa3590-0000-000r00cd0e3#yRQQ

Thank you for your response Eildosa 
 

68

General / Re: Prepare Models For 3D Printing

« on: April 28, 2014, 11:05:42 AM »

Wow, thank you a lot FoodMan, very usefull tutorial! 

69

Face and Body Scanning / LED arrays

« on: April 28, 2014, 01:26:49 AM »

Dear all,

Does anybody have any experience with high power LEDS ? in arrays if possible... im planning to shift from flash to LEDS for space purposes!

I was having a look at those ones : http://www.cree.com/LED-Components-and-Modules/Products/XLamp/Arrays-NonDirectional/XLamp-CXA2530

70

General / Re: TUTORIAL - Request

« on: April 19, 2014, 03:19:04 PM »

A good tutorial about the basics of photogrammetry and understanding some of the algorithms behind the functioning of Agisoft would be amazing as well. 

71

Face and Body Scanning / Re: Face scanner - Prototype

« on: April 17, 2014, 05:11:28 AM »

Not yet... i was planning to build a head stabilizer like on the old photographic times. (more ergonomic ofc...) but just seeing my tests i dont need it, it is useful for placing the head "on the recording volume" however.

72

Face and Body Scanning / Re: Face scanner - Prototype

« on: April 16, 2014, 03:32:49 PM »

Building is perfect, no misalignments.  (for neutral faces) i dont know for expressions that are hard to hold... I can post results when i attach the flashes next week.

In theory : If the pixel resolution used by Photoscan for building is less than "the resolution of the movement" then no building error should occur. Since when using "High" the image is down-sampled to 50% (i think?) the movement is not noticeable in pixels. (Alexey correct me if im wrong) 
Anyway building looks good.

The only critical thing in this system is DOF and not blinding the subject with the so-close flashes. I might change to super-luminescent LEDS used like a flash, but i dont have enough budget for that yet.

- Of course its never better than instant system, but just cheaper... 

73

Face and Body Scanning / Re: Face scanner - Prototype

« on: April 16, 2014, 03:13:55 PM »

https://www.dropbox.com/sh/3mj3f4k1z5wx2fv/1ssE0x86tM

  - Movement takes 3 seconds right now - for testing purposes, it will be 2.2 seconds soon.
Flashes are not in position, i was building my own micro flashes, (with just the bulb and the capacitor) but i got electroshocked, never manipulate a flash if you dont know perfectly what youre doing! ... so im using comercial ones at the moment ..

74

Face and Body Scanning / Re: Face scanner - Prototype

« on: April 16, 2014, 12:39:17 AM »

Out of curiosity: why do you rotate the cameras up/down like this? I would expect that it would be mechanically much easier to rotate them around your subject (from left to right)? (with the pivot of the arm located above your head).

- Well thats a good question, at the first stage of the prototype i thought that the gravity force could help the system... so i would just need some kind of hydraulic brake... But things got more complicated so i decided to use a servomotor, i might change it on the near future... (I have another concept drawing made on solidworks ready)


* Yeah its just for a demonstration for a surgery convention in Prague.
* we've developed a laser scanner as well, if you're curious have a look at www.factum-arte.com all the work we're doing is mainly for restoration and conservation purposes.

75

Face and Body Scanning / Re: Face scanner - Prototype

« on: April 16, 2014, 12:34:06 AM »

Lee - It does indeed, someone from my work mentioned this today dont miss me if someday i disappear...

I will prepare a home made video of the working system, tomorrow im going to test the optic sensors for triggering...

Wow thats an amazing panoramic robot marcel! i have a CLAUSS system on my home, but its WAY too expensive for what it does...
- Personally i dont know much about about automation systems, just the basics:
Im using a programmable inverter to control de servomotor, with an angular encoder attached. Its way too complicated for this task i know ^^. Im not the best person you can ask about the stepper motors. (I know that Maxon is a good servomotor manufacturer although).

- indeed Lambo, im just aiming for functionality right now, getting the most out of the cameras speed has been complicated for me as well as programming the logic of the micro controller, (im still a beginner in this field  )