D. Exposure | Nikon D5100 guide

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:

• The D5100 measures the brightness in the current frame using the exposure metering method you have just set.
• It translates the measured brightness into a combination of aperture, exposure time and ISO-sensitivity − the exposure control.

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 c2 Auto off timers.

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 f2 Assign AE-L/AF-L button.

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 AE lock (hold). Then just press the AE-L/AF-L button briefly and the exposure remains locked until you press the button again. In the meantime, an AE-L indicator in the viewfinder indicates that the metered exposure is frozen.

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 On in the custom settings menu c1 Shutter release button AE-L.

Set exposure lock to other buttons | This is another option, you can switch it on in custom setting menu f1 Assign Fn button.

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 Metering:

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 Auto ISO sensitivity control.

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 f1 Assign Fn button.

The ISO sensitivity can be permanently on display in the viewfinder – if you switch the custom settings menu d2 ISO display to On.

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 ISO sensitivity settings. 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 D5100 uses the ISO sensitivity you set as long as the exposure time is shorter than the minimum shutter speed stored in the menu. The longest exposure time depends on the focal length when it is set to AUTO.
• If the exposure time would become longer, the D5100 automatically increases the ISO sensitivity up to the maximum sensitivity stored in the menu.
• Only when the maximum ISO value is reached does the D5100 allows longer exposure times.

The ISO automatic has two little pitfalls:

• If you are shooting with flash in low light, the auto ISO will still increase the ISO sensitivity, even though it may not be necessary due to the flash.
  
• The ISO sensitivity remains active when you use the manual exposure control, camera mode M. This can also be seen as an advantage − it turns the mode M, which is intended for manual exposure, into an automatic exposure control that adjusts the ISO sensitivity to a given aperture and exposure time.

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

• exposure time with the command dial and
• aperture with the command dial and the exposure compensation button. The aperture icon next to it is a little reminder for this.

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 b1 EV steps for exposure control.

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.