The Objectives – Guide To Buying A Used Lens
Buy a lens used is not simple in most cases, in fact we find ourselves in front of the object with a long history, many shots but most wear such as to make void the performance. There remains always the problem of why someone gets rid of a target if there are cases of upgrading of systems from half frame in full frame in which it is necessary to rebuild kit or move from targets to non-stabilized optical stabilized (also cost 10 times more!), there are many cases where the seller wants to get rid of its objective because it is no longer happy. And this may be due to one thousand factors like a ring that resists scratches, dust, misalignment and so on.
And ‘good thing akusewa, when you buy a used, do a series of tests before the first seller to close the deal. At least if you want groped not to do business in those optics sold it!
The first control is the simplest one the appearance. Definitely a goal of living will microabrasions but these little importanto as not affecting the optical functions. Obviously, if in addition to micro-abrasions found broken, missing pieces or dents is the case of let it go.
The external lenses should be completely free of scratches and signs and if you look into the sun, must show an iridescent purplish patina (coating – anti-reflective coating) uniform. If there are white areas there is a problem.
Open and close several times the diaphragm and watch the goal. A diaphragm closed the hole should be as round as possible, without lamellae who can not shake like any other. A fully open aperture, you do not see mold, dull areas or water fogging inside the lens. The powder is instead normal, even in the new one you can observe.
Always on the diaphragm, check that the sliding of the slats is smooth and not jamming if he resists forget it. By the way, to change the aperture do not need a camera body, just use the lever that you find on the inside of the lens, as shown in the figure.
There must be no oxidation on the screws and electrical contacts, there must not be fat or oil near the gear, including two focus rings and zoom or aperture blades. The screws must be new, or rather never opened if even a screw shows signs of opening, it means that the target has been repaired, its value falls drastically. In addition of course to having possible problems as the formation of condensation.