All D5100 settings around exposure, i.e. everything that leads to a combination of aperture, exposure time and ISO and thus controls the image brightness, collected here on one page.
Same reminder about the camera mode as in other chapters: Only in P, S, A, M the D5100 allows you to use all available settings.
What | Two things happen when the exposure metering is started:
If you have set an exposure compensation, it contributes as a correction to the measured subject brightness.
Where & how | The exposure metering of the D5100 always starts when you tap the shutter button = press it carefully until you feel a slight resistance.
In Nikon's default settings, the exposure metering adjusts continuously when you change the frame, point the camera to a brighter or darker subject. It is kept unchanged only when you activate the exposure lock at the same time.
Switching off the exposure meter | The exposure metering switches off after 6 s of inactivity when you don't touch the shutter release button. You can set a longer time in the custom settings menu .
What | Exposure lock means that a metered exposure is retained while you change the frame, point the camera to lighter or darker areas.
Where & How | In Nikon's presets, you have to press the AE-L/AF-L button in addition to tapping the shutter to activate the exposure lock. And keep it pressed as long as you want to keep the exposure.
The viewfinder will show AE-L, for auto exposure lock.
Note: Nikon's presets also freeze the autofocus, i.e. the focused distance is preserved as well.
AE-L/AF-L button behaviour | You can change it in the custom settings menu
For example, you can make the button lock only the exposure without autofocus. Or if you find it inconvenient to press the shutter release and this button at the same time, you can select the menu item
Exposure lock with shutter release button | The D5100 can also activate the exposure lock immediately when you tap the shutter button. It then behaves like a simple point & shoot camera – metering the exposure when you tap the shutter release and holding it until you release the shutter and tap again. If you want to go for this, select
Set exposure lock to other buttons | This is another option, you can switch it on in custom setting menu
It is a matter of taste which you choose. These options give you the choice of using the AE-L/AF-L button for something else than exposure lock.
Where | You find the exposure metering method in the shooting information as :
Matrix metering = brightness measurement with 2016 sensors over the entire image area and evaluation with complex logic of the camera electronics.
Centre-weighted = measurement of brightness over the entire image area with higher weighting of the centre of the image (a circle with a diameter of approx. 50% of the image height)
Spot metering = metering of brightness exclusively in a small circle around the active autofocus sensor or the centre of the image. The diameter of the spot metering area is only about one tenth of the image width, unfortunately not marked in the viewfinder.
What | An exposure compensation makes a photo lighter or darker than the automatically measured exposure. You can apply it to any metering method as a manually selected correction.
Where | Exposure compensation can be selected by pressing the +/- key and simultaneously turning the rear control dial.
The +/- button is a shortcut, you can do the same in the shooting information if you prefer.
What | You can select the ISO sensitivity yourself and decide whether you want to let the D5100 have a say in it too with.
Where & How | The easiest way to find the ISO sensitivity is in the shooting information.
Alternatively there is also an entry in the shooting menu.
If you want to set it without taking your eye off the camera, the ISO setting can be assigned to the function key in the custom settings menu
The ISO sensitivity can be permanently on display in the viewfinder – if you switch the custom settings menu to .
Showing ISO sensitivity in the viewfinder is more useful than the counter for remaining pictures that you would normally see there. You don't lose it, it still appears in the shooting information on the monitor.
Auto ISO control | You can switch it on and off in the shooting menu . This menu also allows you to change the ISO sensitivity as you do it with the ISO button and/or the command dial. This is how the auto ISO control works:
The ISO automatic has two little pitfalls:
What | For each measured image brightness plus possible exposure compensation, a number of combinations of ISO, exposure time and aperture match, resulting in the same image brightness. Exposure control means selecting one of the possible combinations.
Where & How | Exposure control depends on the camera mode.
P, AUTO, SCENE, EFFECTS and = programmed automatic, the D5100 suggests aperture and exposure time, in the fully automatic modes AUTO, SCENE and also the ISO sensitivity.
In mode P, you can change the aperture / exposure time combination by turning the rear dial.
This is called program shift, and the camera mode display changes from P to P*.
If the aperture and exposure time do not change when you turn the rear dial, you have probably reached the maximum or minimum possible aperture for your lens.
S = Shutter priority, you select an exposure time with the command dial and the D5100 selects the appropriate aperture.
A = Aperture priority, you select an aperture with the command dial and the D5100 selects the appropriate exposure time.
M = Manual control , you select
Short and sweet, and really very special:
The step size for changing aperture, exposure, ISO is 1/3 light value steps in Nikon's default settings.
You can change this to 1/2 light value steps in the custom settings menu
Scale for exposure compensation and direction of rotation of the command dial | While setting an exposure compensation, a scale appears in the viewfinder at the bottom, with the usual order - 0 +, i.e. negative values on the left. To match this, turn the command wheel to the left for smaller values and to the right for larger values.
You can turn both around to adopt a behaviour that was a peculiarity of Nikon cameras for a few decades. The custom settings menu f3 Reverse dial rotation and f5 Reverse indicators would take care of that if you want it for some reason.