NIkon FX DSLR Mirror Up Mode

The Nikon FX cameras come with a new shutter release mode, called the “Mirror Up” or MUP mode. I have been playing around with this mode for a little while, and I wanted to share some of my experiences with this.

The mirror sits in front of the DSLR sensor allowing the photographer to compose a scene with the viewfinder of the camera.

When you press the shutter, the following things happen is a sequence:

1. The mirror flips up.

2. The physical front curtain shutter starts to open, allowing the light to reach the sensor.

3. The sensor captures the image based on the time duration of capture specified by the exposure time.

4. The rear curtain shutter closes.

If you are shooting high resolution images with slow shutter speeds with your camera on a tripod, vibrations from #1 and #2 may be visible in your image, affecting the sharpness of the image.

MUP mode allows the camera to wait for the mirror to be completely up before an image is captured. In other words, this mode forces the user to press the shutter once to flip the mirror, and press the shutter again to open the front shutter, thus eliminating any vibrations which may have resulted from flipping the mirror up.

Now, readers may ask that how is this different from exposure delay mode, which exists in most modern DSLRs. Typically, DSLRs provide an exposure delay with a maximum delay of 3s. The photographer may want to control the exact instant when the image should be captured, and MUP mode provides that. Now pressing the shutter when the image is intended to be captured will cause vibrations as well, and I would strongly recommend using a remote trigger.

So in a mirror up mode, the following sequence of events happen since the shutter is first pressed:

1. The mirror flips up.

2. The user waits for a specific amount of time and presses the shutter again.

3. The physical front curtain shutter starts to open, allowing the light to reach the sensor.

4. The sensor captures the image based on the time duration of capture specified by the exposure time.

5. The rear curtain shutter closes.

So this takes care of the vibrations introduced by #1.

Now what about the vibrations introduced when the front shutter starts to open? Well, Nikon provides another setting, which works only in MUP mode. This is the “Electronic Front Curtain Shutter”. When enabled, an electronic front curtain shutter is used to reduce the blur caused by the physical shutter movement.

Here are the sequence of events with Electronic Front Curtain Shutter after the user has clicked the shutter button:

1. The mirror flips up.

2. The user waits for a specific amount of time and presses the shutter again.

3. The physical front curtain shutter starts to open, allowing the light to reach the sensor.

4. Any image captured by the sensor immediately after the front curtain shutter is opened is discarded.

5. The sensor captures the image based on the time duration of capture specified by the exposure time.

6. The rear curtain shutter closes.

So by using Mirror Up and electronic front curtain shutter, ideally you should be able to capture super sharp images when shooting in slow shutter speeds on a tripod. As you don't control the time duration for #4 above, I would recommend using a remote trigger to reduce the effects of any vibration.

Nikon FX DSLR Mirror Up Mode