What happens if you attempt to operate a Sony SLT (pellicle mirror) camera with the mirror up? Does the camera detect this condition? Will the camera shoot? What happens to autofocus--can the camera fall back to contrast detection? Is the increase in exposure value accounted for?

  • \$\begingroup\$ Are you sure that it can be operated with the mirror up? I thought the whole point of these cameras was that the mirror never moved. That said I don't own one and can't find the manual for one online to check. \$\endgroup\$
    – Dan
    Jan 6, 2012 at 9:36
  • \$\begingroup\$ The mirror must be moved manually, there is not motor to move it but it is movable by hand so that the sensor can be cleaned. It is a wonder why they did not simply produce a completely sealed unit which would prevent dust from reaching the sensor. I suspect the issue be with the sensor-shift stabilization system but that is just a guess. \$\endgroup\$
    – Itai
    Jan 6, 2012 at 17:41
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    \$\begingroup\$ Keep in mind that the focal-plane shutter is a mechanical part which may generate dust behind the mirror. This is probably the reason the unit is not fully sealed. \$\endgroup\$
    – bwDraco
    Jan 6, 2012 at 17:44

1 Answer 1


The SLT-A55 at least no longer focuses but everything works, even with the mirror removed which you can do without too much difficulty. Exposure is off by about 1/3 EV.


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