Messages

31

General / Re: Test Renders - Camera Calibration Settings

« on: January 15, 2014, 02:16:50 AM »

Thanks, we are just using the Maya software render as we have a copy lying around already, no VRay (yet).  Will give Lens Correction a try in Photoshop.

Any ideas on the pixel size?  PS seems to be doing a pretty good job by just supplying the lens length, although sometimes it has greater success than others.  For example it calculates the cx,cy as being quite right of center, while other times not, is that a problem?

32

Face and Body Scanning / Re: Synchronizing different DSLR cameras

« 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?

33

General / Test Renders - Camera Calibration Settings

« on: January 14, 2014, 11:37:05 AM »

As suggested by others on these awesome forums, we have been working on Maya-based renders to test camera positions and coverage, lens lengths, and use of noise projection.  There are two aspects that are unclear though, regarding camera calibration:

1) What is the pixel size for these renders, since there is no real sensor?

2) Because Maya's renders are 'perfect', there is no lens distortion to undistort, and the diminishing effects of wider lenses like 24mm cannot be accurately simulated.  Does anyone have a Photoshop or Nuke script that can recreate the lens distortion using the same Brownian model that PS uses to remove it?

Any other tips for making accurate simulations?

Thanks!

34

Face and Body Scanning / Re: Synchronizing different DSLR cameras

« 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.