Exposure compensation
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LOL. The thing is... there was no need for exposure compensation before the Pentax ME. That was the first Aperture Priority Camera and with no other modes at all and it was a minor miracle at the time.
In Manual Mode there's no need for Exposure Compensation at all, if you need to give more or less exposure, you just adjust the shutter speed or aperture to give the desired bit more or less, ignoring the fact that the viewfinder display isn't showing the indicator right in the midway point of the scale, where the camera puts it when it 'decides' what the exposure should be.
However, with any automatic mode (AV, TV, Programme) the camera is designed to take a meter reading and set the exposure. Regardless of how much you adjust the shutter speed or aperture to different combinations, it will always maintain that same exposure value. If you took a shot at every possible combination the pics would all come out looking identical as far as exposure is concerned anyway - because they would be!
So that's how the Exposure Compensation Dial was born to Pentax and the ME. There was no shutter speed dial anyway. Pentax decided in their wisdom that togs might not always want to trust the onboard silicon overlord, so provided us with the Exp Comp Dial in 1/3 stop increments and it's pretty much stayed that way since with all the other manufacturers who quickly followed suit.
There was a way round the problem of course and that was just to adjust the ISO (ASA as it was then) up or down to give the desired amount of adjustment, but I suppose it was asking too much for us always to remember to put it back.
As to how it actually works - y'know I've never really thought about it, but try setting some exp comp and see if the aperture or shutter speed changes. I don't think the display changes but that doesn't mean one or the other hasn't changed anyway, but they just don't see the need to tell us. It would be equally easy for the system to just make changes to the ISO.
In this digital era though it's just as possible( even more likely) that the exposure compensation is being set deep down in the bowels of the camera at sensor/processor level. :shrug:
In Manual Mode there's no need for Exposure Compensation at all, if you need to give more or less exposure, you just adjust the shutter speed or aperture to give the desired bit more or less, ignoring the fact that the viewfinder display isn't showing the indicator right in the midway point of the scale, where the camera puts it when it 'decides' what the exposure should be.
However, with any automatic mode (AV, TV, Programme) the camera is designed to take a meter reading and set the exposure. Regardless of how much you adjust the shutter speed or aperture to different combinations, it will always maintain that same exposure value. If you took a shot at every possible combination the pics would all come out looking identical as far as exposure is concerned anyway - because they would be!
So that's how the Exposure Compensation Dial was born to Pentax and the ME. There was no shutter speed dial anyway. Pentax decided in their wisdom that togs might not always want to trust the onboard silicon overlord, so provided us with the Exp Comp Dial in 1/3 stop increments and it's pretty much stayed that way since with all the other manufacturers who quickly followed suit.
There was a way round the problem of course and that was just to adjust the ISO (ASA as it was then) up or down to give the desired amount of adjustment, but I suppose it was asking too much for us always to remember to put it back.
As to how it actually works - y'know I've never really thought about it, but try setting some exp comp and see if the aperture or shutter speed changes. I don't think the display changes but that doesn't mean one or the other hasn't changed anyway, but they just don't see the need to tell us. It would be equally easy for the system to just make changes to the ISO.
In this digital era though it's just as possible( even more likely) that the exposure compensation is being set deep down in the bowels of the camera at sensor/processor level. :shrug:
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Aperture priority (a/v) =shutter speed changes when dialling exposure compensation.
Shutter priority = aperture changes.
Shutter priority = aperture changes.
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Cool. That's why you have that silly stupid little rubber eyepiece blind attached to your camera strap, unless you've binned it. When your eye isn't actually at the viewfinder in any of the auto modes, the light entering the eyepiece is often enough to change the exposure setting. Why they can't fit a proper blind.?..
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i prefer to think of exposure compensation as program shift as your just moving it over one way or the other away from what the chip thinks.
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Good advice there from The Reb. You really do need a good understanding of the basics and there's no better way than doing it from a book. And get an exposure meter - doesn't have to be expensive as long as it preferably does incident and reflected readings. Just playing around with that and comparing the results with your camera meter will teach you a lot. 
chuckles
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Programme Shift is not the same as exposure compensation.....
Compensation does what it says on the tin.... compensates for something or other. In the instance of exposure, the compensation is for making allowances for inordinately bright or dark subjects. Something for which the camera's built in algorithms can't handle..... Strange thing is in quite a lot of expensive kit comes the ability to handle bright snow or beach scenes - without having to dial in an amount of overexposure. (This was something Nikon addressed quite successfully about 16 years) Dark scenes have proven to be a bit more problematic however.
Program Shift, however, takes the given exposure and the tog adjusts/shifts either the shutter speed or the aperture to a different value, but the exposure value stays the same. Eg, 1/250 @ F8 shifts to 1/125 @ f11, or if you shift the aperture to f5.6 the shutter will alter to 1/500. It allows the tog to have a form of aperture or shutter priority without having to change the Mode with a simple flick of the thumb and without taking the eye from the viewfinder (if you know where your controls are!). It is most certainly not a compensation.
As for whether exp. comp. shows the changed shutter or aperture values in the viewfinder - it certainly does in all the Nikons I've owned, can't say about other makes though.
Compensation does what it says on the tin.... compensates for something or other. In the instance of exposure, the compensation is for making allowances for inordinately bright or dark subjects. Something for which the camera's built in algorithms can't handle..... Strange thing is in quite a lot of expensive kit comes the ability to handle bright snow or beach scenes - without having to dial in an amount of overexposure. (This was something Nikon addressed quite successfully about 16 years) Dark scenes have proven to be a bit more problematic however.
Program Shift, however, takes the given exposure and the tog adjusts/shifts either the shutter speed or the aperture to a different value, but the exposure value stays the same. Eg, 1/250 @ F8 shifts to 1/125 @ f11, or if you shift the aperture to f5.6 the shutter will alter to 1/500. It allows the tog to have a form of aperture or shutter priority without having to change the Mode with a simple flick of the thumb and without taking the eye from the viewfinder (if you know where your controls are!). It is most certainly not a compensation.
As for whether exp. comp. shows the changed shutter or aperture values in the viewfinder - it certainly does in all the Nikons I've owned, can't say about other makes though.