I know that on single lens reflex cameras the exposure sensor array is placed up near the pentaprism and a beam splitter is used to cast the image onto the array.

Since a mirrorless camera has no pentaprism, where is the exposure array located and how is light diverted to it?


1 Answer 1


Modern mirrorless cameras use the uncovered image sensor to measure the amount of light entering the camera. Since the sensor must be exposed to the light entering the camera for compositional purposes, the signal from the main sensor can also be measured to provide a 'meter' reading.

  • \$\begingroup\$ This is very slow method, because low dynamic range of the sensor compared to DSLR exposure sensor. I have not seen mirrorless yet I can point to different light and shoot in split second. With professional DSLR it is common practice, exposure metering instant, AF instant, aperture moving instant, lens moving instant. What I have seen with mirrorless, the camera just changes shutter time or iso to guess light level, it always takes time and if i get my rx100 from dim pocket, it always 100% fails to measure correct exposure. With 5dII it was even 100% hit in such case when lens was directed tow \$\endgroup\$
    – user69362
    Commented Oct 23, 2017 at 19:15
  • 1
    \$\begingroup\$ You are comparing a pocket camera to a pro-grade DSLR and are surprised that it fails? \$\endgroup\$ Commented Mar 7, 2020 at 23:34

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