I bought a used Olympus OM-1. The previous owner drilled two holes in the top plate to attach a custom hot shoe with screws. Now I want to remove the hot shoe and the screws that are holding it, and then cover the holes with electrical tape, but I am afraid that it won't be lightproof. How critical for the top late of an slr to be lightproof?

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Light entering through the holes above the pentaprism may affect the light meter if it is located within the pentaprism compartment (as MichaelC notes). However, the compartment is isolated from the film compartment, so light entering the holes will not affect film exposure itself, as long as there are no other light leaks in the camera.

Even if the light meter is not affected, light entering the holes may affect your view through the viewfinder, so you may still want to cover them anyway. You can use gaffer tape, which should be sufficiently light tight. You can also screw a metal plate over them, as rackandboneman suggests.

See also Should I use the rubber viewfinder cover?

  • 2
    There are screws already ... you are a 3mm drill, tinsnips and a bit of tinned sheet metal away from a posh solution :) Feb 4 '19 at 11:56
  • 2
    "However, they may affect your view through the viewfinder." If the view via the viewfinder is affected, metering will also be affected if the light meter is located in the pentaprism area as it is with most SLRs.
    – Michael C
    Feb 4 '19 at 16:45
  • @MichaelC Updated answer to add that light meter may be affected.
    – xiota
    Feb 5 '19 at 8:49
  • There's almost always a miniscule amount of light leaked around the edges of the mirror when it is up. It's not normally enough to affect typical photos, but very long exposures in dark environments can be affected if there is a light source behind the camera shining through the viewfinder (or through holes in the roof of the prism housing).
    – Michael C
    Feb 5 '19 at 17:53

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