How to check the lens ?

How to check the lens ?

quality lenses usually vary greatly from model to model.In this digital cameras are more demanding of the characteristics of optics than to shoot on film.But sometimes it is extremely difficult to choose the appropriate instance, that he had no backing - the focus was sharp enough and without the blurry edges.Typically, budding photographers is not always afford to buy a new lens, there is an alternative - buying the lens in a thrift shop.But how to test the lens in such a case, and what to look for, especially when purchasing a new optical not?There are a number of characteristics which can be determined-good-quality optical instrument.

Appearance lens

Start scan lens it is necessary to external examination, which is especially important when buying a used lens / y.This is the most basic indicator, especially if you are thinking how to check the lens.The shop is required to ask the unit to take in hand, to better consider it.

  • presence of scuffs and scratches.If there are scratches, it means t
    hat the lens has ever worn on the camera lens at the terminals.The magnitude of these scratches can be, even indirectly, to judge the frequency of use of the lens.
  • Inspect the terminals.Even clean terminals still do not say anything without a scratch, becauselens could never be removed from the camera, especially if he's the one.So watch need the presence of scuffs and scratches on the zoom ring and the bayonet.
  • presence of traces of impact or fall.Determine need and whether the lens is dropped.To do this, check if there are marks on the housing falling, for example, metal parts dents, cracks, and other plastic parts. The drop leads to the fact that the optical elements are shifted, and this makes the lens defective.If you lightly shake the lens, the lens should not make clip-clopping sound.A number of models can be small metallic noise that normally produces auto-focus drive.
  • see if the lens handed in for repair.It is also a very important step on how to check when buying a lens.Becausescratches on the lens screw indicate that the lens is disassembled.Repair service is not terrible, but the optics were repaired by amateurs.Inspect the screws must also, if slots are torn and bent, it is characterized by unqualified repair.
  • necessary to examine for the presence of glass chips and scratches.If you hold the lens close to the desk lamp, you can close, the inside can see the dust, bubbles, villi, and so forth. To see it all the better, it is necessary to position the lens to the light at an angle to the lens formed a dark background.If the number of tiny bubbles and dust is small, it is considered acceptable.
  • presence of bubbles and scratches on the front of the lens will have virtually no impact on image quality, but it can have a psychological impact on you, especially when buying expensive optics.Scratches and bubbles that are on the back of the lens - it really is a poor indicator.It is necessary to remember that most of the proximity of the defects of the matrix increases the impact of these defects on the image quality.

Work

lens mechanism's second stage of the importance of how to check the lens before buying, is to check the electronics and lens mechanisms.

  • zoom and focus rings must rotate smoothly, without the characteristic scratches and jams, but at the same time, not too loose, lest it lose focus.Pull out the retractable portion of the lens until it stops, and gently shake it - play should be minimal.
  • If you send lens vertically up and down, respectively, the movable optical unit in the selected position does not move under the action of its gravity.In some models to prevent this have a special lock.
  • It is worth paying attention to the bayonet, asset the lens to be rigidly fixed to the camera, without strong backlash.
  • should also check the electronics work.Especially check the autofocus work in manual and automatic modes.
  • Check diaphragm work.To do this, see the depth of field using the preview button.
  • Check the flash operation, especially for lenses that report focus distance camera.The subject should be equally illuminated by the flash at any distance.
  • lens is best to check on the camera to which you plan to install it.BecauseSometimes the lens can not dock, and when you turn the camera will produce an error.

Now you know how to check the lens.This will allow you to get the best shot.Good luck!