Exposure compensation. How to use the camera sensors

[Catalina]

I understand that exposure compensation is a way to make the pictures brighter or darker. The camera Nikon D 40 has a way to do this.

Positive compensation is needed when the main subject is darker than the background, for example when you are taking pictures in back light

Negative compensation is when the main subject is brighter than the background.

This is the theory but I don't understand enough as to put in in practice as Grahame pointed to me.

Does any one have a way in which I can practice and obtain better results in my photography, any advise Other than practice, practice, practice.

The manual in English says in the page 47: exposure compensation can also be adjusted pressing a button close to the shutter and rotating the commanding dial until the desired value is shown, but how I know which is the desired value?

Cordially,

Catalina

[Shadowman]

Catalina,

Your portrait shots are a good place to start, especially if they are backlit. Use a scenic background such as a cityscape or landscape, I suggest different backgrounds just to add to the challenge.
1. Set your camera to aperture priority, use f/8 and ISO 200 as a starting point.
2. Take a test shot and see what settings the camera chose for a good exposure. Write down the shutter speed and judge the image for midtones, shadows, and highlights, foreground middle ground, and background.

If everything balances out then you don't need to apply exposure compensation. If however, your model is not well exposed or the background is blown out, then you can consider applying exposure compensation. If you do plan to make adjustments and are happy with the aperture chosen, switch the camera to manual mode and then experiment with exposure compensation, adjusting depending on what you want to compensate for within the image.

[DanK]

In terms of exposure, exposure compensation is no different from the other ways you can alter exposure: changing aperture, changing shutter speed, or changing ISO. In fact, all your camera is doing when you use exposure compensation is changing one of those three. Which one depends on how you have set the camera.

So, the real issue is not exposure compensation as such. Rather it is getting a feeling for how much of a difference an increase or decrease of one stop makes. I would suggest something somewhat different from John's suggestion, although with the same underlying principle:

--find a scene with a lot of tonal variation (light to dark)
--set the camera to manual mode, so you will know exactly what is changing.
--meter, and take a shot just as the camera says to do it.
--now take 2 more, in each case increasing exposure by one stop. You can do this with any of the settings.
--now go back to the original setting, and take two more, decreasing by one stop in each case. This will give you a total of 5 shots with an exposure range of 5 stops.
--look at these carefully on the computer, looking especially at the extremes of light and dark.

Do this a bunch of times, with different scenes, and you will begin to get a feel for it. Later you can decide HOW to make those changes.

[Stagecoach]

Hello Catalina,

Perhaps we need to do a recap firstly on some observations and recommendations covered previously.

A number of your photos posted to date have shown that 'Exposure Compensation' has been used in both the 'P' Programmed Auto mode and the 'M' Manual mode and some of the values used appear excessive for the scene photographed. The reasons for this are still unknown and you have not confirmed that you were aware that you were using 'Exposure Compensation'.

The cameras exposure metering system looks at a scene and determines what 'it' considers is the right balance for an exposure. Most of the time it's pretty accurate but in certain situations such as a subject that is backlit it will not give the results 'you' want so in this situation we 'compensate' or 'bias' the decision the camera meter has made. This is called 'Exposure Compensation' and by biasing the camera reading we can make the image lighter or darker.

The D40 has two methods of entering an 'Exposure Compensation' value (eg +2EV) as follow which can cause confusion;

a) 'EC' (exposure compensation) can be entered by using the 'Menu' system for 'P', 'A', 'S' and 'M' modes.

b) 'EC' can also be entered by using the '+/- button and command dial' for 'P', 'A', and 'S' modes only. If the camera is in 'M' Manual mode using the '+/- button and command dial' will only change the 'Aperture' it does not compensate/bias what the camera has considered the correct exposure.

If you are in Manual mode you will see the meter in the viewfinder and the cameras exposure metering system considers exposure is correct when the pointer/indicator is in the centre of the + to - horizontal scale. You can alter this indicator position to the + or - side by changing either Aperture, Speed or ISO.

If you enter 'Exposure Compensation' through the 'Menu' system whilst in Manual mode it offsets/biases the exposure meter so if you were to enter -2EV exposure compensation and adjust either Aperture or Shutter speed to centre the meter indicator the exposure will be -2EV and hence darker than what the camera considered ideal.

Personally I would suggest the following to familiarise yourself with what Exposure compensation does;

a) Ensure you do not already have any EC entered into the camera by either the Menu system or the +/- and command dial method. The 'Two button reset' I have explained will reset any EC to 0.0.

b) Select 'P' Programmed Auto mode and take a picture of something around you that is reasonably lit outside and remember what was central to the scene.

c) Staying in P mode enter an Exposure Compensation of -2EV using the +/- button and command dial wheel and take exactly the same picture.

d) Staying in P mode enter an Exposure Compensation of +2EV using the +/- button and command dial wheel and take exactly the same picture.

e) Compare these three pictures on the LCD screen and you should see one dark, one ok and one too bright. This demonstrates how you have overridden what the camera metering system assumed correct.

If you do not get these results post the images here so that we can diagnose the problems.

As for knowing exactly how much exposure compensation is needed this can be determined by;

1) Viewing the result on the camera LCD or computer
2) Viewing the camera Histogram (next lesson)
3) Experience

These tests can be easily undertaken simply by sitting in a chair outside, the subject/scene is unimportant.

One thing you must remember Catalina is that once you have taken a picture using Exposure Compensation you MUST reset it to zero (0.0EV) before taking further pictures of different scenes otherwise they will be affected also.

Grahame

[Stagecoach]

Hello Catalina,

Here is an example of the affect of using the Exposure Compensation function to alter what the camera metering has assumed the right exposure for an image. My camera was set in 'P' Programmed Auto mode in Matrix Metering.

No 1 : No Exposure Compensation
The camera metering system has made a reasonable job of the exposure. On the Histogram top right, the peak to the right stops at the very edge of the right side and there is very slight overexposure.


No 2 : +1EV Exposure Compensation
The increased exposure caused by the +1EV has caused a too bright image and the histogram can be seen climbing up the right hand edge. The image is overexposed and too bright.


No 3 : -1EV Exposure Compensation
The decreased exposure caused by the -1EV has caused a darker image and it can be seen that the histogram is now clear of the right hand edge.


So these are the changes in darkness/brightness of this image with just alterations of +1 or -1 EV.

Now, which one is right? It very much depends upon which one you prefer and what part of the image you consider most important. Personally, for this scene I believe a slightly lighter version of No 3 would be ideal so I would have adjusted to -0.3EV or -0.7EV

Grahame

[tclune]

Some years back, I read and profited from a short article on the Luminous Landscape site explaining a simplified version of the zone system. You may also find it worth a read.

[rpcrowe]

Most cameras have Auto Exposure Bracketing (AEB) which will provide three shots (more on some cameras) that are separated by one of more stops in exposure.

Shooting three shots with AEB selected will provide one shot at a minus exposure, one shot as the meter reads and one shot at a plus exposure. The amount of plus and minus compensation is predicated on how many stops of compensation you have selected.

Using AEB will give you a graphic indication of which scenes should have a plus compensation, which scenes need a minus compensation and which scenes are O.K. when exposed as the meter reads. You should after a while get fairly proficient in determining how to use exposure compensation.

A general rule of thumb is that very dark subjects. like a black cat in a coal bin, need a minus exposure compensation while very light subjects, like a snow scene, need a plus exposure compensation.
The above is true because the camera's meter is designed to allow the camera to record everything as a mid-gray (about 18% gray). It will try to make the black cat look gray and your snow scene will look gray unless you have selected a minus or plus exposure compensation...
The amount of exposure compensation needed, if any, will often be predicated on how your camera meter is set up to read the light. As an example, when set up for spot metering, the camera will often give a different exposure reading that when it is set up for Evaluative metering (Canon Term: I think that Nikon calls this Matrix Metering).

When working with back-lit subjects, especially subjects fairly close to the camera, fill flash will often be a better choice than exposure compensation. My camera just about always wears a flash when I am out shooting...

[Catalina]

I printed all those instructions and put them into my manual, when I have the possibility I will do all those exercices.
Thanks for everything.
Thank you Grahame, Dan K, Richard and John (shadowman)
It will take time until I learn exposure compensation, but it will be a valuable skill.
When I will do the exercises I will post them here or in another forum (nature & architecture) (people & pets)
Cordially,
Catalina