Sony Action Cam Flat Lens Cover

Lens cover for Sony HDR-AS200V with SPK2-AS2 waterproof case to address the blurry underwater images.
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updated August 31, 2023

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My daughter and I recently had the good fortune to go snorkelling with manta rays on the Great Barrier Reef, even had a humpback whale swim right below us at one point.  In preparation for the trip we dug out the old, barely used action cam that came as a freebie with the purchase of a laptop years earlier.  The battery was still good and the SD card had plenty of room - sorted!  

Sony sold two cases for this camera, the one I have which is waterproof to 5m and another one waterproof to 60m.  What they failed to mention is the 5m case is useless for underwater photography.  The 60m case has a wide, flat front cover, but the 5m case has a small, spherical front cover.  The different refraction angle in water makes images from the 5m case too blurry to be of any use.  I found an old forum thread where someone had posted the reply they received from Sony when complaining about the image quality.  The reply (which may have been a copy pasta from the fine print in the manual) said something along the lines of “note, underwater images may not be as sharp as usual”.  That makes it sound like they'll still be usable, just not as good as usual.  The truth is the images are rubbish.  At one point we found ourselves swimming in a school of hundreds of squid - well, they might have been squid, hundreds of dark blobs of some kind, you'll have to take my word for it :P 

I made a fully glued prototype with a polycarbonate offcut for the lens as a proof of concept and was delighted to find the lens cover makes the images as sharp as those from above water.  I included a couple of screenshots from video in a rock pool for comparison, first with the lens cover attached and then with it removed (you can just see my hand at the edge of the first shot reaching in to remove the cover)

I used a 60 x 2mm glass lens from Aliexpress.

Print the base, hood, ring and retainer in your filament of choice, 0.16mm layer height.   

Print the two seals in TPU, I used TPU95A because its all I have (softer might be better).  I recommend printing the TPU on a smooth build plate to get a smooth surface for a better seal (I use a G10 sheet) 0.28mm first layer, then 0.16mm, random z seam (to avoid one vertical seam that might allow water in).  The case seal has a small lip one layer thick on the inner edge, kind of like a small brim, its meant to stretch and fold as the lens cover is pushed onto the case to help get an even, watertight fit.  I have uploaded two versions of the case seal with slightly different inner tolerances.

Super glue the base into the hood. (Before gluing you might want to check the fit of the base and case seal onto the case).  Then insert the seals, the lip on the case seal should face the back of the lens cover.  The smooth face (from off the build plate) on the lens seal should face forward to be in contact with the glass.  Insert the glass and screw the ring on tight.  Carefully fit the assembled cover onto the case, ensuring the arrow marker is pointing straight up, then slide the retainer clip into place. 

Happy filming.

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