How to choose a lens

I decided to write the text of the choice of lenses that form the basis of the quality of the pictures . In the days of analogue photography was a simple affair . The camera was just a box that provides information shutter speeds . The image quality lens and decided to use the film. Currently, the case is a little complicated . With a digital camera imaging an essential element of the matrix is also used . Note, however, that modern SLR matrices are products of such high quality that it is the lens determines how many of them you can " squeeze " .
But I do not want to dwell on the multipliers , focal length , MTF charts etc. These issues are important , but there are several others who are often forgotten, and have a direct impact on the quality and convenience of taking pictures. Here are some tips I have reached on the basis of their own experience and my friends photographers :

    If you want to buy a lens with high optical performance , avoid zooms a large range , ie, those that cover its range of wide angle and telephoto . Physics and optics can not be deceived , and the greater the range offered by the zoom , the more design compromises to which it is decided .
    Personally, I am a fan of prime lenses ( not zooms ) , as they force a more thoughtful framing and are usually better in terms of optical performance . In the days of digital cameras, it should be aware of some issues :
        Older structures (especially wide angle lenses ) are not adapted to the requirements of the matrices used in digital cameras . Therefore, a great lens from the time of the analog can produce average results hooked to a digital body . This is because the array, have high demands on the angles of incidence of light rays on it , which passed through the lens. The analog camera that uses film, did not matter much what angle a ray of light falls on a silver halide molecule to be registered . Digital Matrix recalls, however compartments , separated by a high wall . If a ray of light falls on it vertically , but from the side , such a barrier may prevent its registration .
        When photographing various objects using prime lenses , then we are often przepinać (one wide , one telephoto). This, in turn, favors deposition of dust on the sensor .
        This all means that if the analog world still recommend " liners " that in the world of digital zoom ( but not too long) can provide better performance optical and ergonomic .

    Buy from zooms of " the one " for example, a wide-angle 17-35mm and a tele 70-200mm . As I wrote , zooms the 18 -200mm are always lower quality than their shorter counterparts . When you sow a particular type of photography Invest at least one bright prime lens (eg for a portrait 85mm/1.8 , 35mm/1.4 to reportage , 50mm/1.8 for general photography ) . An interesting type of lens is also a macro lens with a focal length of 90mm or 105mm , suitable according to the same both for shooting small objects as well as for a portrait.
    Look zooms possible bright ( f2.8 -4 ) , preferably at the same brightness ( f2.8 , f4.0 , if necessary ) . Brightness -zoom is not determined directly by its optical quality, but the utility values ​​. First of all , bright zooms significantly contribute to improving the system AF ( focus) . In addition, the old rule is that the lens is optically the best when it turn a blind about two stops from the maximum aperture offered by . Therefore, having a brightness of f2.8 zoom can enjoy a good quality of pictures around f5.6 aperture . As our objective is for example the maximum aperture telephoto position 5.6 , the best results are achieved in the area of ​​the aperture f8 or f11 . This aperture does not provide , however, such a nice background blur when shooting portraits ( so-called issue . Depth of field) . Constant brightness , in turn, is useful when working in manual mode , with flashes or studio , as if zooming does not change a picture's exposure .
    If you can , you choose lenses with built-in motor -type USM , HSM , SW (the name depends on the manufacturer) . This engine really improves the speed of focusing lens and comfortable working with him ( quieter ) .
    If you are reading lens tests pay no attention to focus only on what it offers. Look closely at the other optical parameters . From my own experience , I would highly suggest to pay attention to the vignetting (darkened corners of pictures that some lenses may no longer be visible only after stopping at three stops from maximum aperture ) and distortion (degree of deformation of the object in the picture , especially disruptive in wide-angle lenses ) . It often happens that the lens (especially cheap, added to the set of SLR ) has a pretty decent focus, but each image the sky and see the bright surface of the darkened corners and objects made ​​to look like a broad set deformed in a distorting mirror .
    Because it is difficult to fool the laws of optics , making it difficult to find a good wide-angle lens digital camera . Due to the smaller field of the image sensor , compared to the traditional box frame film to get a wide-angle field of view lens with a focal length of 28mm , the digital SLR lens we use about 18mm . These lenses are, however, always high distortion . If we want a little geometrically distorted images of wide-angle lenses (eg architecture ) it is worth investing in so-called reflex camera . full frame sensor (Full Frame) , but this type of body cheapest three times that of a typical digital SLR .
    Keep in mind that many dedicated lenses for digital SLR is designed to work with a smaller field imaging ( APS -C). Therefore, it can be used in analog SLR or a full-frame SLR (Full Frame) . It is difficult to predict the development of the market , but if in the future it is Full Frame format ( 24x36mm ) was standard ( as evidenced by the current high-end cameras already , such as the Canon 5D and Nikon D700 ) , or ever he wants to go back to traditional photography , the you may want to invest in lenses designed to work in " full frame " . I must admit , however, that it is a very long-term thinking and dedicated lenses can provide better performance than universal lenses while being cheaper and smaller.
    When it comes to choosing between the lens branded and independent manufacturer ( Sigma, Tamron and Tokina ) , it is difficult for unambiguous answer. Frequently we get what we pay for it . Dear nonproprietary lens , will be comparable with an expensive lens company . Cheap zooms (less than 1000 PLN ) almost always will have a significant optical aberrations . Once an argument in favor of the company's lens was better quality control . Unfortunately slip volatility of individual quality copies, there are even higher class brand lenses , but probably less frequently. Another issue is the compatibility of the lens of the body ( matter uploads of control signals ) . Unofficially, it is said that such as Canon deliberately limited compatibility with objects niefirmowymi body , which can cause such errors in focusing . While it may be just a rumor . The real problem in some lenses niefirmowych , and sometimes proprietary , but the phenomenon . Back and Front Focus . As for the cases in which , although the camera focuses on a particular point , the lens blades a few millimeters ( inches ) behind, or in front of him . Some companies such as Sigma , even offer a free adjustment of such a lens under warranty.
    Finally, I would only add that you should not blindly seek to purchase the best optical lens. It is important to be able to perform various photos and consciously choose the camera lens to the situation . Personally amuses me popular lenses 50mm/1.8 . Yes, they are cheap and good optically , but digital SLR hardly be regarded as a standard (ie, imaging lens of the human eye perspective ) because they have converted focal length of about 75mm , which is vague . Such a lens is difficult to perform dynamic staff reporter , or the portrait of a flattened perspective. Currently, the standard should rather be considered a bright lens 28, 30 or 35mm ( by the way, if anyone thinks that one standard lens is boring and restrictive , it is now, look at photos of Henri Cartier Bresson ) .