Best Ways To Get Sharp Images: 06 Mirror lock-up
When you press the shutter release down fully on a DSLR, the mirror that allows you to see the scene in the viewfinder lifts just before the shutter opens.
It’s the mirror flipping up and hitting it’s stop and then flapping down after the exposure that makes up most of the noise that you hear when you take an image, shutters usually move quite quietly.
This mirror movement can create significant blur-inducing vibration of the camera, so for the ultimate in camera steadiness use your camera’s mirror-lock-up facility.
This lifts the mirror with the first press of the (remote) shutter release, while a second press made after any vibrations have died down fires the shutter.
This is becoming increasingly important for getting the absolute best from high-pixel count cameras like the Nikon D800.
Once the mirror has been locked, up the viewfinder of your DSLR will be black, so you need to compose the image and focus on the subject before you press the shutter release for the first time.
Because they don’t have a mirror, compact system cameras don’t suffer from mirror-slap and naturally they have no mirror lock-up mode.
Best Ways To Get Sharp Images: 07 Diffraction
One of the first things that most people learn about photography is that using a small aperture creates more depth of field so more of the image is sharp. This is true, but at very small apertures the impact of a phenomenon called diffraction becomes apparent.
Diffraction is the bending of light rays as they pass over the edge of the aperture. The smaller the aperture, the greater the proportion of light rays being bent.
Bent light rays don’t focus at the right point (on the sensor) and this means that this part of the image will not be sharp. The greater the proportion of unfocused light, the softer the image will be.
Even though the depth of field gets more extensive as the aperture is closed down to a very small size, the sharpest part of the image is not as sharp as it is in an image taken at a moderate aperture setting.
You can find your lens’s optimum aperture by shooting an object with lots of detail at every available aperture with the focus set to the same point.
Then examine each image at 100% on screen and find the image in which the focus point is sharpest. You will notice that the image focal point gets sharper as the the aperture is closed down from maximum before it starts to get softer again.
In many cases a mid-range aperture of f/8, f/11 or even f/16 produces appreciably better images.
Once you have discovered your lens’ optimum aperture, use this wherever possible and focus carefully to make maximum use of the depth of field available. The hyperfocal distance focusing technique can help with this.
If you need more of the image to be sharp then you could try focus stacking. This technique involves shooting two or more images taken at the optimum aperture, but with different focus points. These images can then be combined to create a single image that is sharp throughout. See here for more about focus stacking.