Vibration Due To The Reversal Of The Mirror How To Solve
Vibrations, especially as you use a very long focal length lens, can be particularly harmful for the final photograph, whether these are due to human hand (no stand, press the shutter button or simple tremors of our hand) that the camera itself (the vibrations introduced by tilting the mirror, a tripod is not too stable). For this reason the suggestion prince is always to use a tripod and a repeater by shooting can cancel the vibrations related to our interaction with the camera.
As these two devices are able to solve most of the problems related to vibration, there is a further cause of vibrations which it does little reference or more, trivially, we forget: the tilting of the mirror.
The tilting of the mirror is a mechanical movement that leads to move the mirror from its position parallel to the sensor to a position perpendicular to the same, so as to allow the passage of light from the lens to the sensor itself http://smilesmultimedia.com. This movement is very fast (the “clack” that you feel when you take the picture) and the weight of the mirror generates micro vibrations that are by no means negligible, especially in very long shutter speeds.
The following series of photographs shows a series of tests carried out using the same target subject (a banknote) cameras with different times and different openings (working in shutter priority). The images on the left show the banknote photographed in standard mode (the mirror flips normally) while the images on the right show the banknote photographed with the mirror locked (open). As a matter of practicality, carrying only a detail of the pictures where you can see the difference.
As shown, the images on the left are more moves than those on the right and moved incremented increases as the shutter speed; camera shake due to the tilting of the mirror is very clear and shorter exposure times makes it illegible lines detail of the banknote.
The test course was carried out by placing the camera (Canon 5D Mark 2 equipped with a 70-200 F2.8L IS) on a tripod, was employed repeater by a shutter and in both cases (with or without mirror locked) we used the manual focus, set at the time of the first shot (with the mirror raised, remember, you have to focus manually before lifting the mirror).
Obviously, starting from f11, also suffer the images on the right of the moved but this is due to the diffraction phenomenon against which we can do little.