Re: [diy_3d_printing_and_fabrication] Re: Projector Calibration/ Lens Distortion
- Graham Stabler wrote:
>Because of automatic contrast/exposure adjustment of webcams and digital
> you can buy a photodiode for a few dollars from any electronics
> supplier but then you need to build some electronics, not hard though,
> the webcam avoids that though it was just a thought.
it may be very hard to get repeatable measurements with them. Also,
with color wheels will be rapidly flashing cyan/magenta/yellow frames which
may give the camera a banded image. A photodiode (or even an LED) a
9 V radio battery and a DVM set to current mode may do much better in
giving a repeatable numeric result. You want to set up the diode in
photoconductive mode to get the most linear result, so the + of the
diode should go to the minus of the battery (providing reverse bias).
- On Wed, May 22, 2013 at 11:32 PM, Bhatt Himanshu <bhatthimanshu@...> wrote:
I read about ND filters and i think i can get it from local camera shop. Do i need diffuser if i use ND filter/filters properly.The reason I suggested a diffuser is because I was talking about converting a camera into a sensor so the "image" you get is actually an average of the light hitting the sensor. The idea of an ND filter is just to reduce the light levels though as I mention on another thread you can do this by projecting darker images anyway I think.I want to make it clear that I am not suggesting trying to measure the output of a specific pixel on the projector but rather to get the average intensity over a fairly small area (because crappy webcam sensors are tiny) and then use a grid of these measurements to produce a correction which should be fairly smooth if the aberration is only caused by the optics.Cheers,Graham