Exposure compensation ... I'm confused

[snapsnap1973]

On my D3200 (Nikon_) there's a button on top with a + and a -. This is the exposure compensation button correct?

In order to compensate the exposure though you either have to change the aperture or the exposure speed correct?

For example, when I hold down the exposure comp. button and use the wheel on back of my D3200 I change the shutter speed.

I thought though that the exposure compensation button change the gain of the sensor?

confused.

 

[Overread]

In a DSLR there are 3 variables that change the photographic exposure.

Aperture
Shutter speed
ISO

There are not other settings that will change the final photographic exposure. Exposure compensation thus kicks in when you have modes where the camera controls one or more of those three variables. It tells the camera that when it meters the scene and selects the settings that it should over or under expose from the meters reading.

This is important as some scenes will fool the meter - eg if you have a scene dominated by white snow the camera will normally underexpose it (because its going for that grey perfect exposure) so you tell the camera to over-expose by a stop to get the shot you want and gather in the most light.

In Nikon cameras you can also use exposure compensation in the full manual mode where the photographer controls all three settings. In this mode it simply makes the 0 point on the meter scale biased to the same value as the exposure compensation. So you're still getting the exposure arrow to point that the 0 in the scale, but the 0 now has a positive or negative compensation value (so its just the same as pointing the needle at several stops over or under the 0 without exposure compensation)

 

[sashbar]

You can not possibly change the gain of a sensor. As I mentioned in another your thread, it has an inherent sensitivity. The gain is applied digitally after the A/D conversion and this is the function of the ISO, not exposure compensation.

Exposure compensation allows you to underexpose of overexpose compared to the camera metering by a certain controlled number/fraction of stops. It is needed because with many scenes camera is unable to expose correctly because of the way it measures the reflected light.

You really need to read some book about the exposure all this related stuff, it is impossible to explain everything on a forum.

 

[Alexr25]

Exposure compensation changes the the camera exposure meter reading so that it reports "correct exposure" when the true exposure is off by the amount of compensation setting.

 

[runnah]

Exposure comp is basically you calling your camera a liar.

The camera says: "I think this is they right exposure!"

But you say: "shut your lying mouth camera!!! I know what's best!!"

 

[snapsnap1973]

Thanks guys! I am doing a lot of reading as we speak on the subject(s).

 

[Bebulamar]

The exposure compensation control is one often misunderstood if one started using a camera with full auto. My brother who has a PhD in mathematics didn't understand how the exposure compensation worked either when he start using a camera some years ago.
The exposure compensation control has become the only control that actually control the exposure and so it has a prominent placement in newer camera design. Not only when one is shooting in one of the auto mode like P, S, or A that the exposure compensation is used. Nowaday, even in M mode the photographer simply chooses the aperture and shutter speed depending on the subject matter and not by the amount of light available. He/she then let the camera automatically set the ISO to get the right exposure. Often the meter is a bit wrong so the exposure compensation is the one control for the photographer to get the exposure right. It took me quite a while to figure out why this control is so important today while I have done photography for 40 years and yet haven't used such a control.

 

[Designer]

Dear "confused". If only I could read your user's manual, I might be able to answer your question.

 

[dennybeall]

You can control all or just part of the actions of the camera. If you chose to control them all in manual mode with manual ISO but know that your camera exposure meter will under or overexpose the shot based on your experience as a photographer then you can dial in a fudge factor (exposure compensation). If you chose to control speed or shutter only and know based on your experience as a photographer with that camera that the camera will under or over expose the shot then dial in a fudge factor.
It's just one more tool that is available to use for those that know how to use the tools in their toolbox.

 

[Overread]

Dear "confused". If only I could read your user's manual, I might be able to answer your question.

First and last warning before its time for a vacation.

There is no need to be rude in how you reply to people on the forums.

 

[The_Traveler]

Often the meter is a bit wrong so the exposure compensation is the one control for the photographer to get the exposure right.

hmmm, not so much, I think.

The camera uses the foal area you have chosen to read from - matrix, spot, full- screen, whatever- averages all the readings from all the pixels in that area and gives you back a reading that will make that average medium gray on the sensor. Whatever mode you are shooting in, when the meter needle is centered on the zero, that will give you a medium grey from the area chosen to be read for the exposure.

If you want to change the exposure, you use exposure compensation.

Example: Much of the scene is fairly light with a good range of dark and light, but you want to be absolutely certain that that the faces underneath the brims of the hat are exposed - use the ec to increase the exposure.

 

[SquarePeg]

It took me a while to figure this one out even after reading the manual and several online tutorials. Still not sure if I'm using it correctly so please let me know if I'm way off track.

I usually shoot in A or S mode depending on the situation (A mode 90% of the time since I don't shoot much action). After the first shot, I'll peek at the display and if it looks like I need more or less exposure, I'll use the + or - to make that happen without having to change my desired aperture. For example was taking photos of my daughter and her friends against a white backdrop at an outdoor party and they were a bit too dark. I think the white background was throwing off the metering so I used the + to get the exposure that I wanted. I suppose you could get the same effect using M mode and adjusting other controls but I like using A especially if the light is changing like at the end of the day.

 

[bratkinson]

Although your camera has a zillion settings possible, trying to learn photography from the user manual of a camera or examining all the buttons and learning their functions are like stepping into the cockpit of a Boeing 747 and trying to figure out from 'scratch' how to fly. Learning the basic controls and the basics of aerodynamics and how/why/what's it take to make an airplane fly need to be understood before ever entering the cockpit of a Cessna.

Not to appear rude to the OP, but based on some of the questions you've asked here, I'm thinking you need to brush up on basic photography before trying to fly a 747. Here's a really good start with lots of tutorials...
Cambridge in Colour - Photography Tutorials & Learning Community

 

[wfooshee]

Exposure in the camera is determined by the metering in any of the modes other than full manual. The camera decides, based on what light it measures, what Exposure Value to use to render then image.

Exposure compensation lets you dial a bias into that automatic decision made by the camera. There may be a reason you want the image a little bit darker, maybe the intended subject is under a bright spotlight and the rest of the picture is dark. "Correct" metering would have the subject washed out. Set the exposure compensation to -1 or -2 or -whatever-it-takes, and the metering system still figures the exposure for you, with the bias you've told it to use, so you can forget about compensating manually and just shoot.

Opposite direction for heavily backlit, you want to overexpose relative to being "correctly" metered.

The camera can't see, it can only measure. It's up to you to see.

 

[runnah]

I always heard that a camera meters by sending the live view back to the camera makers HQ where a team of experts calculate the proper exposure and then beam it back.

All quite advanced really.