When using my Sony A1 mirrorless camera, when in a dark studio I must set the Live View Display - Setting Effects to Off in order to have a bright enough EVF to see the model or item being photographed when using something other than a constant light source (i.e. strobe). With Setting Effects ON, I get a black or almost black viewfinder since the room (before the flash goes off) is quite dark. With Setting Effects OFF, I get a bright viewfinder that allows me to properly frame the image.

This works perfectly.

My question is - since the camera doesn't "see" thru the lens into the viewfinder like a DSLR (since there is no mirror), what does the camera do to give me the bright EVF? I know it works perfectly...I'm looking for HOW does it work.


  • \$\begingroup\$ What do you mean the camera doesn't see through the lens into the viewfinder? Where do you think the EVF gets its image? Or is that your question? \$\endgroup\$
    – osullic
    Nov 20, 2021 at 22:11
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    \$\begingroup\$ By that I meant - the EVF isn't seeing thru the lens. The EVF gets it's image from the sensor showing the settings you have dialed in, unlike the dSLR which allows the optical viewfinder to see directly thru the lens with the aperture wide open. \$\endgroup\$ Nov 20, 2021 at 23:15
  • \$\begingroup\$ @MichaelDavis How do you think the light falling on the sensor gets into the camera? \$\endgroup\$
    – Michael C
    Nov 22, 2021 at 6:31
  • \$\begingroup\$ this is a common critique of mirrorless vs dslr; what you see on the little screen might not be the same thing you'll see in the image, which is only true of very fast and long exposures on an optical viewfinder. \$\endgroup\$
    – dandavis
    Nov 22, 2021 at 10:44

1 Answer 1


The simplified explanation is: camera processor read from sensor the "image" and justify/amplify (as mentioned in to comment the amplification can happen before digitization of sensor information) the brightness to set the histogram in the limits (minimizing the lost in white and black areas). Eventually it also compress the dynamic range of read info (12-14-16 bits to 8 bits). And then it send it to display (viewfinder or back LCD)

  • \$\begingroup\$ by increasing temporarily the ISO? \$\endgroup\$ Nov 20, 2021 at 23:13
  • \$\begingroup\$ how does it amplify the brightness? \$\endgroup\$ Nov 20, 2021 at 23:13
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    \$\begingroup\$ @MichaelDavis: ISO is just a figure for the multiplication factor from light on the sensor to brightness of the display. Historically it represented the amount of light needed to expose film properly. Now it should mean that if you expose using a particular ISO, you will get about the exposure needed to expose film of that ISO properly. Yes, it increases the ISO used to drive the display. The ISO used if you take a picture may be different. \$\endgroup\$ Nov 21, 2021 at 3:22
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    \$\begingroup\$ Well, kind of. It may or may not actually amplify the analog signal prior to digitization which is, strictly speaking, what increasing the ISO setting does. It could also leave the sensor analog amplification set to the value chosen for image capture and multiply the signal after it has already been digitized to make it brighter (or dimmer). This would result in lower image quality in the VF due to quantization, but since the electronic viewfinder is typically so low resolution anyway, it isn't that noticeable. \$\endgroup\$
    – Michael C
    Nov 22, 2021 at 6:30
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    \$\begingroup\$ usually iso 200-400 has analog amplification, while the rest is indeed pure math. \$\endgroup\$
    – dandavis
    Nov 22, 2021 at 10:42

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