ISO Versus EV Compensation

[ericgraig]

My new (to me) X-T1 will be arriving this afternoon and afer reading and aborbing Rico Pfirstinger's book on the camera I started to wonder what exactly is the difference between changing the ISO for a picture versus changing the EV compensation. The senor doesn't get anymore sensitive to light when you change the ISO. It's not like switching out a film back loaded with FP4 and loading one instead with  HP5. The camera simply amplifies the energy the sensor captures when you move from its native ISO (200 according to Pfirstinger) to something higher. I get that. But then what does the EV compensation dial do?

 

Suppose you're in manual mode and you need to use a specific shutter speed and aperture combination but at the same time you need another stop of exposure. Does it make any difference whether you move the ISO dial from 200 to 400 or instead add one stop of exposure via the EV dial.

 

I just don't get it.

 

Eric

 

eric-graig.squarespace.com

[bradsarno]

When in auto modes, the EV compensation dial will choose various combinations of aperture and shutter speed and ISO to increase or decrease the exposure. When in manual mode as you suggest, the only variable left for the EV dial to control exposure is the ISO. So in that case they are virtually doing the same thing, but only in that particular situation. If in aperture or shutter priority or fully auto modes, that exposure compensation dial will control more variables than just ISO. 

 

Also, I believe that in this case you describe, the EV dial will only have an effect if it's set to Auto ISO. If it's set on a particular ISO value putting you in FULLY manual mode, the EV dial will not do anything. 

 

 

 

B

Edited May 6, 2016 by bradsarno