heres the couple of ways to achieve the effect
1) on any reflex viewfinder (where what you see is actually the image THROUGH THE LENS. Example, if u get a kodak disposable camera, the viewfinder isnt what the LENS sees, its a seperate piece. The reflex viewfinder reflects light intermittenly from the lens to the viewfinder so that you can correctly compose the shot) lemme start again..ON ANY REFLEX VIEWFINDER, if you remove your eye from the eyepiece while the sun is at your back, light can enter the viewfinder and into where the film is exposed, so that for a brief period, the film is overexposed and the emultion takes on those trippy colors
2)obviously it isnt from not loading in a dark bag. While this can occur, ever notice in ski movies its almost always timed perfectly with the end of a trick? its like a transition from one clip to another in most instances. You can create this look digitally, overlay a previous instance of 'burn', or remove your eye from the eyepiece and purposely let light into the eyepiece
basically, its really never ACCIDENTAL when you see it, maybe one out of 20 occurances would be accidental. If your good with a super8/16mm camera, you can create the effect while shooting.
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