Wide(r) Angle View for Your Old ATC2K Action Cam

Some time ago the ATC2K action cam was launched. it can record 30 minutes of video on a flash card, intended to film action sports and waterproof up to 3 meters (I dove to 7 meters with it before I modded it..)

Generally it is a very nice cam, but for the extremely narrow angle of view. This is even worse under water. The manufacturer since created the ATC-3k and ATC-5k with a wider view. If you want a
new wide(r) angle cam, buy these. But if you still have an old ATC2K, this is for you.

Several action sports people have modded their atc2K to have a wide angle lens. These mods generally ruined the waterproofing and used large/expensive/professional wide angle lenses

This is my mod of the ATC2K, preserving the waterproofing of the cam, and keeping it small.
This was important for me as my hobby is building and driving R/C model submarines
(have a look at http://www.subcommittee.com if you are curious). We strap the
cam on the back of a submarine.

Step 1: What to Get ?

The trick is to buy a so-called "JellyLens". Specifically, the wide-angle jelly lens. these can be had for 5 dollars/euro's plus shipping. buy two, just in case...
These things are intended as a stick-on lens for the camera in your mobile.
good clean fun.

next to this you will need a sturdy screwdriver with a reasonably sharp edge, a phillips screwdriver,
a solvent-based plastic glue, some silicone glue, and a strong, flat and clear piece of plastic.
futhermore a small round file and sanding paper.

Step 2: Disassemble the Front of the ATC2K

First, take a moment to remember the good old days when you still had warranty on your ATC2K.
Those days will be gone now.

then take a sturdy screwdriver and pry loose the frontal rubber cap of the ATC2K by stabbing between and under the side of the rubber cap.
the cap was only attached to the rim in my case. stay away from the center of the cap.

when the rubber cap is removed you'll see a round plate with the square cam window.
it is fixed in place with three phillips screws. unscrew and remove the plate.

now the glass in front of the actual cam is exposed. it is lying in a rubber cup.
turn the cam upside down and gently let the glass and the cup fall out.
Keep these clean! The rubber cup is what makes the watertight seal. damage or debris
will cause leaks.

Step 3: Attach the Jelly Lens to the Front Plate of the ATC2K

Now we attach the lens to the front plate. I did it like this :
- remove the Jelly from the lens, it detaches easily. what is left on that side of the
lens is a plastic rim about the thickness of the frontal plate. perfect !
- take a washer with an inner diameter close to (but smaller than) the size of
the rim and draw or scribe that circle. The washer enables you to center the circle nicely.
- on the front plate, file out the square window until your hole is about round and of the
drawn/scribed diameter. This should be smaller that the rim on the lens.
- Now carefully sand the hole wider (I used a pen so the sand paper would sand
a reasonably round hole) until it thightly fits that rim on the jelly(-less) lens
- after a fit is reached, be sure to remove burrs and crumbs of plastic from the
underside of the frontal plate.
- clip and file off the extending bit of the lens floor plate.

For good measure, I glued the outside of the lens where you can see it is made out of two parts.
it is important that no water enters the lens.

Step 4: Optional : Make the Lense Work Under Water

Basically, you are done if all you want is shoot film above water.

But if you want a sharp image under water, you need to do some more.

The lenses in this Jelly Lense are designed based on the assumption that
the light always goes from air to plastic and vice versa. The light is bent slightly dfferent on water-to-plastic boundaries. this results in a fuzzy image under water.

What needs to be done is to put a clear window in front of the jelly lense. I did this by simply gluing
a bit of polycarbonate (i think..) to the front of the jelly lense. I used a solvent based glue.
First time around (yes, that is why you buy two lenses..) I used CA,. but this attacks the polycarbonate, giving it a white hazy coat and ruining your work. Do not use CA.
between the jelly lense and the actual ATC2K there should also be air, not water. we come to that
with the re-assembly of the ATC2K.

in the photo, the outer two pieces of plastic are just to protect the lense/window combo from the
clamp. you can still see the CA-induced white haze on the upper piece of plastic.

Step 5: Reassembly

put the rubber cup back in the ATC2K. put the glass back in the cup.
you will notice the whole assembly is slightly higher than the ATC2K casing.

Now screw on the frontal plate again, evenly.
It pushes the glass into the cup, sealing the slit between glass and cup. at the same time, it seals the cup against the housing of the ATC2K.
Note that we have not done anything to this seal. As long as these components are clean,
it will be waterproof again. If you wish you could consider greaing the rubber cup with silicon grease.
beware that other greases may attack the rubber ! Next to that, you risk smearing the glass.

Now, you have your original cam back, minus the rubber front cap.

push the jelly lense into the frontplate. you can choose to glue it on. Mine has a decent fit of it's own, so I left it for now. If you do glue it on, keep the glue from the actual lenses !

If you go for bonus points you can now cut a larger hole out of the rubber front cap, and stick or glue it on again as well.
I cut the rubber with a sharp hobby knive. The cut is irregular but it still looks nice when I put it on the cam. Be sure the hole is slightly smaller than the lense is wide.

Step 6: Evaluation

I tested the cam in a large black bucket.
From a standard distance I shot video of a ruler. Then I counted the amount of millimeters on the ruler in the video.
distance between the cam and the ruler is 240(ish) mm

in air, no lens : 135 mm seen

in air with lens : 225 mm seen

in water, no lens : 105 mm seen

in water with lens : 150 mm seen

if my math skills are still intact I guess this is a viewing angle of
15 deg.
25 deg
11 deg[
17 deg
respectively.

I calculated the angle between the center of the picture and one of the sides.
you could argue the angles should be multiplied by 2 (i.e. measured from side to side)

a very nice improvement for a 5-dollar lens...

and just for fun :
jellylens without cover in water :