The Catadioptric For Basic Photography
Infiltration of moisture (but also dust) make them practically useless and even the temperature can be a hazard hot and cold dilate and constrict (slightly) the mirror resulting final effect change.
The third problem that the catadioptric have is linked to the total lack of electronics. Exposure control at all (missing the diaphragm!) but no autofocus http://bdmaster.net, so you can always and only shoot in the manual. Not recommended for those who are beginners with photography.
The fourth problem is the opening in the primary mirror through which the light reaches the sensor its size and its shape (circular) mean that all the lights out of focus they become transformed into many small bright donuts in the final sprint ( here the original) because the projection of the secondary mirror on the primary.
Another limitation of the retroreflecting is related to the depth of field always for the lack of a diaphragm is not manageable for which we should get used to the depth of field Messac available from the objective itself. The advantage disadvantage of this light is blurred which is able to provide. Remarkable, as you can see from the picture below
As for the focus, in addition to confirming the fact that it will be totally manual, it ranges from about 4.5 meters to infinity. Given the focal length of these objects, the thing that upsets obviously not being after all a telephoto (except that photographed with a 800mm something less than 4 meters is somewhat strange).
Another issue of the catadioptric, borrowed from the super telephoto, is the way we react to our movements move even just a few millimeters to frame means something else, so they are to be used more and objectives with a tripod, even being out of the stabilizer Service (no optics and that on the camera body, if any, can not balance). An alternative is to shoot in black and white, maybe a little increasing the ISO This allows you to reduce the shutter speed and a hand-clear photo is definitely easier to accomplish.
Apart from the advantages and disadvantages (the photo quality is not comparable course at a telephoto lens from thousands of Euros, but it is certainly acceptable, especially when compared to the price), the results that can be achieved with such an object is of great effect to photograph distant subjects and grasp all the details is not a trivial matter.
Here are two photographs taken with a powerful tele Tamron SP 350mm f 5.6 and the Nikon 1000mm f 11. The difference is stabiliante (here the source of the photos)