Posted: 1/10/2016 6:44:28 PM EDT
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OK, we all know how to fiddle with exposure through shutter, aperture, and ISO. I've been playing around with the Exposure Comp feature of D7100, slightly overexposing (a few bars to the right of zero on my viewfinder scale).
What exactly is this function doing? Just HOW is it over/under exposing? Is the camera twiddling shutter/aperture/ISO and not really telling me? Or is it more fundamental than that? Seems if it is increasing sensitivity it's twiddling ISO, otherwise it ought to be twiddling shutter (so no change in depth of field). |
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OK, one answer I found was:
This depends on the mode that the camera is in, and whether your camera has Auto ISO enabled. Assuming no Auto ISO:
In Aperture Priority mode, exposure compensation affects the camera's choice of shutter speed. In Shutter Priority mode, it affects the camera's choice of aperture. In Program mode, the camera chooses on its own whether to implement exposure compensation using aperture or shutter speed. If Auto ISO is enabled, then the camera also has the choice of keeping shutter speed and aperture constant, and changing the ISO instead. Now, to me that's a little disappointing. That's saying that ExpComp is nothing more magic than what I could easily do myself with the shutter/aperture/ISO. |
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The quote you found explains the essential function of it fairly well.
How it makes that decision also depends on what metering mode you've selected. When I'm shooting in aperture priority (fairly common for me, really) I'll set either a fixed ISO or kick on auto ISO and either way I dial in about a stop of overexposure +/- a bit. Edit: I also edit the minimum shutter speed for auto ISO in the menu, that's a really cool feature. When I'm shooting in manual, if everything is set to fixed, EC doesn't do anything, but if I'm running auto ISO it will bump up the ISO a bit for me. Usually when I'm shooting in manual, I don't have auto ISO enabled but sometimes I know the aperture and shutter speed I need but the conditions are changing, so I'll kick auto ISO on to help balance things out. I generally run spot metering on my subject in one of the assisted modes, but every now and then I'll use center or full frame metering. |
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I posted this in pic o' the day thread but it's relevant here too
I'm not sure what camera you have but these tips apply to virtually all modern DSLR cameras. 1 - the meter lies. There are different metering modes (spot, center weighted, full frame) and each provides a different result and each has its uses but remember, the meter lies. 2) the screen on the back of your camera also lies. it is not a fair judge of exposure, and only slightly better at judging focus. c: the histogram is a far better way to gauge the overall exposure and detail content of the image. if the histogram is scrunched all the way to the left, it's underexposed. All the way to the right, overexposed. Balanced across the middle isn't entirely bad, but I prefer to have mine leaning towards the right. Learn how to read a histogram and apply it to your shooting. Learn what the metering modes are used for and it's OK to use it as a rough guide but don't trust it blindly. Also consider when you're in one of the aperture or shutter priority modes, the best way to adjust the exposure is with exposure compensation. Some cameras require a button press and a wheel turn for this, others can be set to adjust it by a wheel turn when in one of the applicable modes. Read this for more info http://www.ar15.com/forums/t_1_121/1804564_Let_s_talk_about_exposure___reasons_to_overexpose_your_images_and_why_high_ISO_isn_t_bad__new_pics.html You'll get there. 
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Quoted:
OK, one answer I found was: Now, to me that's a little disappointing. That's saying that ExpComp is nothing more magic than what I could easily do myself with the shutter/aperture/ISO. Quoted:
OK, one answer I found was: This depends on the mode that the camera is in, and whether your camera has Auto ISO enabled. Assuming no Auto ISO:
In Aperture Priority mode, exposure compensation affects the camera's choice of shutter speed. In Shutter Priority mode, it affects the camera's choice of aperture. In Program mode, the camera chooses on its own whether to implement exposure compensation using aperture or shutter speed. If Auto ISO is enabled, then the camera also has the choice of keeping shutter speed and aperture constant, and changing the ISO instead. Now, to me that's a little disappointing. That's saying that ExpComp is nothing more magic than what I could easily do myself with the shutter/aperture/ISO. Yes, there is no magic here; EC is just doing exactly what you could be doing manually. The point of EC is that there are times when your meter is being fooled by the scene and it is repeatedly off by a consistent amount. When this is the case, and you are using one of the auto or semi-auto metering modes, by dialing in the desired EC you then temporarily correct the "consistent mistake" by the metering system for that scene. If you are in manual exposure mode, EC will just bias the meter as you choose since you are making the actual exposure changes manually. The catch here is that if you are always zeroing the meter in manual mode, you might as well be shooting in one of the semi-auto modes since you are just manually doing the exact thing the semi-auto mode does, just manually. |