# Exposure Compensation VS. Shutter Speed



## Rosshole (Feb 19, 2010)

I am sure this is going to come off a a very n00b question, but I am getting myself confused.  Ex Comp. and Shutter Speed have a similar effect on your image.  A faster shutter speed coupled with a higher ex comp will end up with a similar image as a slower shutter speed and a lwer ex comp.

Is this correct?  If not, what is the real difference between the two?

I am curious as I am thinking about ways to manipulate the cameras settings...

Please help me clarify what these two different settings/adjustments actually do.

Thanks!


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## IgsEMT (Feb 19, 2010)

Ok, b4 going into details first things first
EXPOSURE. EX:  ISO 400, 1/125sec, f/8 = ISO 200, 1/125, f/5.6 = iso 400, 1/60, f/8

Ev ON CAMERA controls global 'compensation' +/- meaning if you have a flash 30* camera right at ttl and you add +1 EV your OVERALL image will be brighter (both right and left sides) vs +1 EV on FLASH will be more concentrated where the flash is firing at.



> Ex Comp. and Shutter Speed have a similar effect on your image. A faster shutter speed coupled with a higher ex comp will end up with a similar image as a slower shutter speed and a lwer ex comp.


Based on value I given you above, exposure is the same but EFFECTS will vary. 1/60sec to 1/125 sec you might not notice greater difference is motion, especially with flash, but if you want to shoot a running water, let's say at 1/10sec then effect you'd get at exposing it at 1/10 will be MUCH DIFFERENT then you'd get at 1/125.
Similarly for aperture - you'll get correct exposure, let's say, at f/2.8 at iso 100, 1/60 AND same exposure will be at f/5.6 1/60 iso 400 *BUT* effects will be different.



> I am curious as I am thinking about ways to manipulate the cameras settings...


So I got this book by Joe McNally called Hot Shoe Diaries, *very* interesting read. This guys shoots 90+% in Aperture and he uses EV (on camera) a lot for overall exposure.

I shoot manual (camera) and AA on flash. So when I play with EV values on camera I actually control flash power output. For me, its faster to do that way rather then pressing up/down buttons on the flash. WHEN I'm shooting ALL MANUAL, then EV value is useless.

Hope that clarifies and helps.


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## Overread (Feb 19, 2010)

There are 3 things in the camera that make an exposure - the Aperture, shutter speed and ISO. When using either auto or one of the semi auto modes (eg aperture or shutter priority mode) the camera is attempting to meter the scene and expose the shot correctly. However it might be that the light is that little bit to strong and you have highlight problems or that you are shooting action and want a little more shutter speed - at these times exposure compensation comes in. 

This tells the camera to either under (negative compensation) or over (posetive compensation) expose the shot. You can do the very same if you go to manual mode and dial in the settings and watch the little exposure meter in the viewfinder. A "correct" exposure is when the needle is in the middle but you can move it to the left (under) or right (over) as you wish if you need specific settings that the camera won't give you alone. 

If you want more info I strongly recomend the book Understanding Exposure by Bryan Peterson


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## NateWagner (Feb 19, 2010)

The exposure compensation only really changes shutter speed for sure in Aperture priority, and most of the time in auto. In Shutter priority mode, changing the exposure compensation would affect the aperture.

The exposure compensation, as Overread stated, merely affects the camera's attempt to over/under expose an image. 

If you are in aperture priority mode, then yes the camera will over/under expose the image by adjusting the shutter speed, because it's basing it's exposure on what you choose for your aperture (thus when you dial in exposure comp it will change shutter speed)

However, in shutter priority, the camera will over/under expose by changing aperture, because it is basing it's exposure on what you choose for the shutter and the ISO (hence shutter priority)

In auto I think it decides what it thinks is best.


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## Rosshole (Feb 19, 2010)

Ok, this is what I am understanding from your responses...

Exposure Compensation is there to fine tune the auto metering in the camera to your ideal exposure.

Close?  or was my conclusion too simple?


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## IgsEMT (Feb 19, 2010)

> Ok, this is what I am understanding from your responses...
> 
> Exposure Compensation is there to fine tune the auto metering in the camera to your ideal exposure.
> 
> Close?  or was my conclusion too simple?


If you put it that way, yes


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## Rosshole (Feb 19, 2010)

IgsEMT said:


> > Ok, this is what I am understanding from your responses...
> >
> > Exposure Compensation is there to fine tune the auto metering in the camera to your ideal exposure.
> >
> ...


 
I didn't mean to dumb it down too much, but thank you very much.  That helped a lot guys!


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## NateWagner (Feb 19, 2010)

yeah, pretty much.

that is true, the problem is that shutter speed can do the same thing, which is why rather than just explaining what the purpose of Exposure Comp is we also explained what it does and when.


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## gpardo64 (Feb 20, 2010)

As Overread mentioned, I also recomend reading the book Understanding Exposure by Bryan Peterson. You'll understand that even though a combination of settings can give you the same exposure, the end result can be dramatically different. Is just there where your creativity starts.


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