Westminster fountain at sunset

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Reading this thread I got to think of why there are no DSLR bodies with protective curtain that extends (and by doing that spans over the entire mount) while changing lenses and then retract afterwards. I guess this could be made fairly small and would certainly help preventing dust getting into the camera.

Does anyone know why?

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2  
Unless it stayed in place all of the time (and the Sigma SD1 Merrill has such a barrier), it would only change when dust could get into the body as a result of changing lenses. –  user2719 Jan 29 at 8:06
    
To amplify what Stan said: If you allow air in the space between where the lens is mounted and a movable protective curtain you also allow dust in that space. An air lock used to eliminate dust in a "clean room' only works if you evacuate the air from outside and replace it with the air from inside (or filter the air from outside) after closing the outer door and before opening the inner door. –  Michael Clark Jan 29 at 8:35
    
@StanRogers and MichaelClark Didn't know about the Merrill's barrier, then it already exists. Btw I wasn't thinking an tight airlock, rather something preventing larger specs from falling into the camera. Thanks –  Hugo Jan 29 at 9:06
    
@Hugo - the Sigma SD1 Merrill has a GLASS element, not quite what you were referring to... –  Darkcat Studios Jan 29 at 9:38

3 Answers 3

up vote 4 down vote accepted

For two reasons:

  1. It would add to cost, complexity and chances of the camera failing. What happens when the mechanism fails and the curtain stays closed just before you shoot the crucial shot of a sports match (which you had to change lenses for)?

  2. It wouldn't work. As stated in my answer to the question you linked to, camera bodies aren't manufactured in a clean room environment, there is already dust inside the camera body before the curtains are fitted! Not only that but the lens mount is not always dust proof, and guess what there's dust already inside the lens and on the back of the rear element, so as soon as the curtains open it will find its way onto the sensor.

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Not only would the curtain be expensive and ineffective as pointed out in the other answers - it would also add to the problem of dust. Whenever you have moving parts, abrasion creates tiny dust particles. With your curtain you just introduced a new source of dust in your camera.

From this point of view mirrorless cameras should have less of a dust problem than traditional SLRs.

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Because its basically an expensive and pointless thing to do. You might gain a Very, VERY minimal amount of protection from air-borne dust while changing lenses, but what about the dust that is already on the back of the lens?...

Secondly any dust that lands on this shutter arrangement whilst the lens is off would still end up inside the camera body...

Also to make something like this would take up a lot of room internally, as well as being hard to design. And of course it is "Something else to go wrong"

The old Hasselblad V series camera bodies do infact have such a protective mechanical curtain, BUT this is on the BACK of the body, so to stop dust getting in when changing the back (it doesn't really work)

ETA: Damn, beaten to it by 5 seconds @matt Grum!

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