The Outdated Fuss About Exposure

[JohnMM]

If you dial in compensation and the aperture and speed stay the same then the amount of captured light stays the same. Whether or not the ISO changes is irrelevant.  ISO has no effect on the amount of light captured - if the aperture, shutter speed and scene luminance stay the same.

[Ann]

John is absolutely correct.

However, I do push my cameras' ISO settings because i find it helpful to let the camera do the preliminary brightening so I can actually see a JPG preview in the LCD on the back of the camera and also in the Finder and file-browser before I actually process my RAW NEFs in ACR.

[Nikkor Shooter]

[Matthew Currie]

I should have added "and the right body" cause they all don't share
the same menu nor the same features.

When I dial in a compensation value, aperture and speed stay as they
are, the ISO is taking it.

I guess it does vary.  Both the D7100 and the D3200 behave differently. On the D7100 (and the D3200 as far as I've bothered to test it), exposure compensation never varies the ISO unless it is set to Auto ISO.  In  A mode it only varies the shutter speed.  In S mode, only the aperture.  In P mode, it varies aperture first and then shutter speed when it runs out of apertures.  In M mode it varies nothing at all except the meter recommendation. 

When Auto ISO is on, it varies only ISO in M mode, and in other modes changes ISO last, after other options are used up.  So it will change shutter speed down to 30 seconds in A mode, aperture to the extreme in S mode.  In P mode it will do aperture, then shutter, then ISO.  The D3200 and others of its ilk use the compensation button with the control wheel to change aperture in M mode, and thus allow no compensation in that mode even with Auto ISO.

I'm a little surprised if other cameras do it differently, as this setup seems nicely predictable.  With the rather noisy DX cameras I have been using I'd be unhappy if the compensation cranked up the ISO without warning, especially on the D3200, which informs the user of Auto ISO choices only in the post shot EXIF file.

[Nikkor Shooter]

I guess…

I see you've done your homework, Matthew!

When shooting wildlife, typically with the 600 ƒ4 + D850 combo,
It is for me critical to control both aperture — systematically at ƒ8,
and the shutter speed — depending on the action.

I am often dialling in a EV -4 in situations where I needed absolutely
to protect the whites.

[Airy]

I used to shoot slides (E6 or Kodachrome) and, as others said, exposure was everything. The Canon T90 was a perfect camera for that purpose, thanks to the multispot metering: I could measure 8 different spots on my subject, check that they were in the +/- 2 EV range compared to 18% grey, and forget about the rest.

With DSLRs and especially my current Df, I still find it desirable to have 1) a properly exposed subject; 2) if possible, no blown highlight, in that order. The reverse order would be relevant to e.g. single-shot HDR shooters.

So techniques like "Exposure to the right" (popular with earlier generations DSLRs and noisy sensors) do not serve my purposes, while exposure principles dating back to film times are still somewhat relevant to me, albeit much less critical than during my slides time.

Significantly, in PP, I do not fiddle much around with exposure compensation (usually, at most +/- 1/2 EV), while I'm using lots of it when shooting (using the full range: +/- 3EV). With modern sensors, you could do the contrary, i.e. not caring while shooting and do lots of corrections in PP. It's just that I like to "catch the atmosphere", so the overall brightness of the scene and the brightness of the subject are essential and if I do not settle these at shooting time, I have the impression that I did not do a proper job. You may call me old-fashioned