OT: Shooting a laser pointer?

farss wrote on 4/18/2008, 6:13 PM

I'm sure you know the things I'm talking about, the red ones presenters use with their PPTs out of video projectors.
Here's my problem. The camera doesn't seem to see them. I'm wondering if I give the presenters a different coloured laser would matters improve? Maybe the SD cameras do see them but the dot is so tiny they mostly get lost between the pixels in the camera.

I don't plan on using the footage in the finished product, shooting off the screen the results are horrid. However running another camera just pointed at the screen so I've got a reference to what they were pointing at would make the task much easier in post. Pointless exercise though if I can't see the damn dot.

Bob.

Comments

Chienworks wrote on 4/18/2008, 6:43 PM

Red is troublesome for DV since red sampling only has half the resolution. Maybe a green laser would be enough to do the trick. Zoom in as close as you can on the screen.

I've seen some laser pointers with diffraction grating inserts to change the point into various shapes like cirlces, lines, stars, etc. That might work, though it might also look a lot less professional.

MH_Stevens wrote on 4/18/2008, 6:50 PM

Before we had lasers we had batons.

Why not do it in post with a big frog shooting a long red tongue at the point of focus?

johnmeyer wrote on 4/18/2008, 7:15 PM

I was intrigued enough to pull out my laser pointer and try to photograph it against a brightly lit white wall. If I zoom in enough, I can pick it up, but when zoomed out a long way, it sure is tiny.

While I didn't capture the result, my next step would be to use secondary color corrector to create a mask, and then increase saturation and/or change the luma value. Given that the color is pure and single frequency (the nature of a laser), this part is dirt simple. If you can find even a pixel or two that can be tracked accurately with the color corrector, you should be able to use this tracking mask to do all sorts of things.

As to getting a better capture in the first place, I got better results using the "spotlight" function on my Sony camera. This led me to try simply underexposing, but that didn't seem to help. If your camera has any sort of gamma adjustment, I'd play with that.

farss wrote on 4/18/2008, 7:48 PM

Thanks guys.

Part of the problem might also be the nature of the screens used with video projectors. I might get a cheap green laser pointer and try that. I guess at the end of the day though getting the presenters to use my pointer could be a problem as the red laser is typically built into the wireless mouse gizmo. Asking them to have two devices in their hands could be too big an ask.

Bob.

TGS wrote on 4/18/2008, 10:11 PM

If it's built into the wireless mouse, it probably is too much to ask.
I went through numerous Cat-toy lasers at about $9 a pop, but they would hardly last more than a couple of months. The On/Off button was cheesy. After going through 4 of them, I walked into a Radio Shack one day and saw a nice Pen shaped laser for about $30. (US), about the size of a Sharpie, but flat on the ends. It has a nice bright red light and runs on 2 AAA batteries. It's now about 3 years old and works as good as new. (I really only remember changing the batteries twice in this time)
Although I've never purposely tried filming it for the sake of capturing a laser, especially on a lit screen, I have noticed what I have filmed, this one is much clearer and brighter than the old Cat-toy ones.
Yeah.... I know,.....useless info.....

farss wrote on 4/18/2008, 11:17 PM

"Yeah.... I know,.....useless info..... "

ALL info is usefull, maybe or maybe not in the current context BUT it's amazing what one digs out of the memory banks at times.

Bob.

ushere wrote on 4/19/2008, 3:32 AM

hey bob, i hope the police aren't monitoring this - you might be suspected of flashing aircraft.....