Bullet cameras are a popular lipstick-sized camera lens used in “active” environments where a full-size video camera may not be appropriate. I use one as the “head” in my racecar attached to a Mini-DV camera while other folks attach them to motorcycles, mountain bikes, or even R/C cars.
Because of the vibration in a racecar, mounting a Mini-DV camera to the rollcage will destroy the internals within a season of racing. Instead, my camera is mounted in a padded box on the floor of the car and the industrial-strength bullet camera is mounted to the roll cage providing a steady, fixed view (thanks to it’s much smaller weight).
In my prior racecar, there was enough ambient light inside the car that contrast between inside and out was not much of an issue. There were times when the picture would wash out but it was still intelligible.
In my current spec miata, the interior of the car is much smaller and less light makes its way into the car. As a result, there is a very strong contrast between inside and out. The bullet camera is not very good at deciding what to use for determining white balance and the result is that the windshield is horribly washed out, sometimes to the point of looking like you’re driving in a snowstorm.
I knew we needed some kind of polarized lens but nobody sells them for this camera and it is a non-standard size. This has been frustrating me for a long time and it wasn’t until I had my eyes dialated last year that I realized a potential fix. After my eyes were dialated, they gave me a set of plastic glasses while my eyes readjusted. It was flexible, polarized plastic that could be cut with scissors. Bingo!
My solution is decidedly low-tech but so far it is working great: create “sunglasses” for the camera. Cut a thin strip of a polarized (or probably any tinted plastic would do with clear optical properties) plastic, about 1/2″ wider than the bullet cam itself. Take about 1/4″ on each side and fold it back into a C shape so there are two “ears”.
Unscrew the bullet cam lens cap and remove the plastic lens piece. I sandwiched the tinted plastic between the cap cover and the plastic lens and screwed it back into place effectively locking it down. I got lucky on my first install that it was perfectly level and in the right position for my particular car. Remember, where you need the tint will depend on the shape of your windshield and the position of your bullet cam (close to the windshield needs more coverage, further back needs less probably).
Here’s a picture of the finished “product”. Ignore the dust everywhere, I just had the car repainted and it is really dirty inside. Initially I was worried that you would very clearly see the bright-dark-bright transition in the video but as it turns out, it works surprisingly well. With more refinement on the shape of the plastic, I don’t think you would be able to tell that it’s even there, other than your video is MUCH crisper and better balanced. I don’t know for sure that the plastic I have is polarized; if not that would be another improvement as it would take the sharp edges off of glare, further balancing out the photo. I would also think a good UV filter would improve it too.
I’m hoping some enterprising bullet cam vendor will produce a combination UV/polarized filter for these cameras, perhaps with a couple of different height bands of material for different cars/environments. In the mean time, hit up your optometrist and see what you can fabricate with a pair of scissors and about 20 minutes.
I’ll post some before and after video here soon to show the improvement.
All Categories from Feedburner
Mark Dadgar said:
on July 30, 2006 at 10:28 pm
Brian Ghidinelli, Super Genius. This worked PERFECTLY, so I no longer have to endure the horror that is washed-out in-car footage.
Strong work.
brian said:
on August 29, 2006 at 9:39 am
You can see some video with the fix in place on my JustRacing.com gallery. I will see if I can dig up some video pre-fix for comparison but trust me when I say it used to be like driving through a snowstorm at times.
Zack Steinkamp said:
on September 3, 2006 at 12:35 pm
Brian — Thanks for the tip / inspiration.
I just finished up a variation of this idea. What I did was to remove the protective glass lens and apply a semicircle of 20% window tint to the top half. Seems to work really nice… the only downside is aligning the semicircle when tightening the bezel back onto the camera to hold the lens tight can be tricky.
Zack Steinkamp said:
on September 3, 2006 at 6:28 pm
Here is a photo of the lens cover with tint applied.
brian said:
on September 5, 2006 at 7:55 am
@Zack: window tint is what professionals would use – nicely done. I’m curious to see how the entire top half will help/hinder the video. In the miata, we have a fairly small window port relative to the interior so my thin strip corresponds to the front windshield (with a bit of a fish eye lens to capture it all). This approach is great because you can customize it to the needs of each particular car.
Does the tint have adhesive already on it or how did you attach it?
Zack Steinkamp said:
on September 5, 2006 at 11:06 am
Heya Brian — Here are two images to compare no tint vs. a single layer of 20% tint:
Unless there is detail in the roof/headliner you want to capture, I think the half-circle would work fine.
The window tint does have an adhesive layer. On the tint I got from Kragen, there is a clear protective layer over the adhesive. Basically you clean the glass, cut the tint roughly to shape, spray it with water, remove the clear layer, wet it all again, position the tint, work out the air bubbles, let it dry (I used a hair dryer because I’m impatient
, then trim the tint along the edge of the glass with an x-acto knife or razor blade.
Email me if you’d like me to make you one or send you some tint. I only needed about 1/2 square inch, and I bought 25 square feet
.
brian said:
on September 5, 2006 at 11:53 am
@Zack – awesome pictures, really shows the difference. Although you have a lot of steering input in the first pic for what looks like a straight road.
The one case where the headliner area is of interest is when we want to capture the rear view mirror. It can be useful for studying racecraft or figuring out why you’re driving a crazy line when in fact you’re defending. Some of my best video has been captured in the rear view mirror!
Ultimately, a PnP setup would work best. Lance Leong (instructor and club racer) has a VCR and AC inverter strapped in his car with a 4-to-1 video converter IIRC so he gets four pictures at once: feet, head, windshield and rear view.
Zack Steinkamp said:
on September 5, 2006 at 12:30 pm
Whoa! 4 cameras + AC inverter + VCR = dedication
Unless the rear view mirror or rear window is tinted already, the tint filter on the camera lens should help with the image in the rear view mirror as well. Though the fact that you’ve arrived at the “strip” solution makes me think that you’ve already bee down that road!
Zack Steinkamp said:
on September 18, 2006 at 10:58 pm
Just wanted to follow up with a link to an in-car video from Thunderhill using the lens cover with a single layer of tint. Seems just right to me…
http://www.thenobot.org/video/watch.php?20060913-thill.mov