Reply To: ISO Vs Exposure

Sudhir Shivaram

Hi Ritesh,

A small correction. when the subject is in shadow and the background is bright light, in matrix metering mode the camera will expose for the background and the main subject will get underexposed (not overexposed) as the camera meters for the 18% grey.

Now there are 2 different calculations you need to do for any scene to get the correct exposure.

1. You need to understand metering and use the exposure compensation based on the tonality and the metering mode. That is totally not connected to iso or shutter speed out aperture (of course those values will change when you play with exposure compensation depending on exposure mode).

2. Based on the above exposure compensation, you will see the final exposure triangle parameters. And if the shutter speed is less (in aperture priority mode) and you have hit the lowest f number supported by the lens, then you need to increase ISO to get a faster shutter speed.

So given any situation you may end up changing both Ev and the ISO. Hope that helps.