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What is EV value
I understand ISO, Shutter speed and amperture. ISO is the sensitivity of the CMOS/CCD. Shutter speed is the speed of the shutter. And Aperture is the size of the opening..

When the EV value is changed, what is setting does the camera change, ISO, shutter speed, or aperture? Or none of the above?..

Comments (5)

Pigxel wrote:.

When the EV value is changed, what is setting does the camera change,ISO, shutter speed, or aperture?.

One or more of the above. Which is changed depends on the camera exposure mode setting..

For example some cameras in Auto mode are able to change any or all of ISO or Shutter or Aperture. In Program mode, the ISO is fixed, but the either or both Aperture and Shutter may be changed. In Aperture priority mode, only the Shutter speed may change. Similarly, in Shutter priority mode, only the Aperture may change..

See "Exposure Compensation here: http://www.dpreview.com/...n/?/Glossary/Exposure/Exposure_Compensation_01.htm.

Also "Exposure Value" here: http://www.dpreview.com/learn/?/Glossary/Exposure/Exposure_01.htm.

Regards,Peter..

Comment #1

Ok, thanks Peter.

So, +1 EV or -1 EV is one F stop. Is this correct?..

Comment #2

Pigxel wrote:.

I understand ISO, Shutter speed and amperture. ISO is thesensitivity of the CMOS/CCD. Shutter speed is the speed of theshutter. And Aperture is the size of the opening..

When the EV value is changed, what is setting does the camera change,ISO, shutter speed, or aperture? Or none of the above?.

It depends on:1. What program mode you have2. What focal length you are using3. The internal computer of the camera.

Example: In Sports mode, the camera will try and maintain a fast shutter at the sacrifice of depth of field. (maintain shutter speed, use a larger aperture (smaller f/stop)).

In Landscape, the opposite is true. The camera will try and maintain a small aperture an bias towards a slower shutter (to a point of course).

Same with using Shutter Priority- The camera will ALWAYS use the shutter speed you dial in, and open/close the aperture by one EV. Likewise in Aperture priority - Use the selected aperture , vary the shutter speed..

Of course, some cameras have an option to Auto ISO (increase the ISO) that will raise the ISO under certain conditions.

Finally, a longer focal length means the computer will try and maintain a faster shutter speed, and for shorter focal lenghts, the computer will bias towards a smaller aperture in order to maximize DOF..

Of course each camera has it's own algorithms. This is why many experienced people tend to not use the "P" mode, and rather use "A", "S" (Tv), as well as "M".Contrary to what you might think, "P" does NOT stand for "Pro" - LOLWarm regards,DOF..

Comment #3

Interesting question..

In 30 seconds, I ran an 'experiment' that answers your question ... at least for my Nikon D40..

I ran the experiment in both P, S and A modes..

I framed a subject and allowed the camera to meter the light and determine aperture and time. As I turned the EV comp up +1EV, it doubled the shutter time. So there you have it 1EV = 1 Stop..

For my camera, it changed the *shutter time* (in modes P and A).In S mode, it changed aperture exactly one stop..

[For 1 stop unit of change, the amount of light is either doubled or halved.].

Is there any flaw in this logic?..

Comment #4

Pigxel wrote:.

So, +1 EV or -1 EV is one F stop. Is this correct?.

Yes. That is correct...

Comment #5

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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