Over Exposure

[ChaosX73]

Hi! I am a member of team 2338. Our alliance won 2nd place at the Chicago Regionals. We had problems with our camera and we believe that this is due to over exposure. Because of the black curtains and large spotlights, when we ran the calibration for our camera, all that came up were small, very thin rectangles of coorsponding colors (please excuse my spelling). We have some ideas on how to fix this problem, but a little advice will help a lot. Can anyone help us?

[hillale]

We used sun glass lenses over our camera(s) a couple years back, That might help what I think you guys are having problems with.

[ChaosX73]

My dad was thinking of doing something like that, and it might work

[Vikesrock]

Check out the last 2 pages of this thread for some tips and procedures for working with the camera.

[Greg McKaskle]

As mentioned in the other thread, look to adjust brightness as the primary way to reduce glare. Because of light being in the frame, it was also necessary to lower the minimum saturation threshold value a bit.

As for sunglasses, the vision term they'd use is called a neutral density filter, it just means an uncolored filter that blocks some light without tinting the result. I haven't tried it explicitly, but I believe this will simply cause the camera to increase the exposure time further, causing more blur and slower response while still having too much glare on the targets. Of course if you try one out and find a good way to use it, I'd be happy to hear about it.

Greg McKaskle

[A_Reed]

May I suggest a polarized lens. Buy a semi-cheap pair of polarized sunglasses, pop out the lens and fit it to your camera. Rotate the polarization to the angle best suited for eliminating the field glare.

[Greg McKaskle]

This was a good idea. I finally got around to trying it, but without the cheap sunglass part. I used a directional polarizer for still photography, and it pretty much cuts everything evenly. Unlike sunlight, the floodlights aren't polarized. It turns out that the surface effect producing the glare is still unpolarized. That means that the polarizing filter acts as a neutral density and once the camera adjusts to let in more light, you still have glare.

Greg McKaskle

[Al Skierkiewicz]

In addition to the neutral density filters you can also try a method called "barn dooring" simply add shields to prevent the glare from entering the camera. If you go to a good camera shop or online store, you can ND filter material in a sheet film form. Simply cut the sheet in small pieces and add them in layers to the front of the camera until you get the desired effect. Search for neutral density lighting gel.

[Team 135]

Try a polarized piece of plastic over it. You can get polarized sun glasses for fairly cheap if you do not care about style.

[purduephotog]

Originally Posted by ChaosX73

Hi! I am a member of team 2338. Our alliance won 2nd place at the Chicago Regionals. We had problems with our camera and we believe that this is due to over exposure. Because of the black curtains and large spotlights, when we ran the calibration for our camera, all that came up were small, very thin rectangles of coorsponding colors (please excuse my spelling). We have some ideas on how to fix this problem, but a little advice will help a lot. Can anyone help us?

Does the 206 not allow you to set pre-programmed gain/offset information on it? (ie turn off auto-exposure).

[Greg McKaskle]

Since the 206 is a security camera, it has lots of auto settings, and has some ability for static setup, but typically no numerical values. For exposure you choose between auto and hold. This would technically allow you to set and hold the exposure, but you have no way to directly set or read the actual exposure time. You'd need a calibration procedure to "set" the exposure. I've done this for quick experiments, but it is not very repeatable. The gain control is referred to as exposure priority, and the choices are quality and speed.

Since the lighting changes so much as you pivot on the field, I don't believe a fixed exposure will work well.

See videos such as http://www.youtube.com/watch?v=xJnq-...eature=channel

for a robots eye view of the field. This was not taken with the Axis 206, but with some sort of hand held video cam.

As for the polarized sunglass idea, again, good idea, but that was what I was referring to. If the reflected light isn't polarized, they a polarizer won't seem to affect the glare any differently than the rest of the scene. It will simply darken the scene evenly by some amount. If in auto, the camera will then adjust the exposure and you are back to where you started. Barn doors can limit the direct view of the lights, but unfortunately, they cannot help with the reflected light from the targets.

I'm not trying to discourage investigation here, just giving results on things I've been trying. If anyone else has ideas I'm game. I'll gladly test it out and try to make it effective.

Greg McKaskle