20th November 2003, 12:16 PM
LENS TECHNOLOGY by Klaus Schroiff (not me!)
Cut&Paste from Photozone:
Quality Lenses are pointless ...
... if you prefer print film, give it to a cheap lab and never enlarge beyond 10x15cm. Any lens will do the job in this case - even those miserable super-zooms.
Combing a high end camera with a cheap lens ...
... will _NOT_ increase the quality of your results. The camera is the box that holds the film, provides the exposure values and gives you a helping hand in regard to focusing BUT it is by no means capable to overcome the shortcomings of a bad lens. It seems to be a very popular approach by beginners to start with an overkill on the camera side at costs of lens quality. Admittedly cameras are sooo much cooler with all these bells and whistles but if you've limited resources you should rationalize that the investment into quality glass is more important than a fancy camera - finally most of today's base class cameras exceed the features that were present in professional cameras 20 years ago.
The Myth of the "Super-Zooms" ...
... is just a myth. There's a very simple rule-of-thumbs: the bigger the zoom range the worse is the lens. Till now I haven't seen a really good lens with a zoom ratio of more than 4 (28-200mm: 200/28=7.1!). Usually the results get -VERY SOFT- towards the long end and things don't get better just because a manufacturer calls his lens an "APO Aspherical RF macro" or so. Don't expect an acceptable performance for slides or bigger prints. Despite the marketing efforts of the manufacturers these lenses are convenient ONLY! So please be careful in regard to marketing statements that a 28-200mm or 28-300mm is capable to "produce superior results" ... it doesn't.
Ultra High-Speed Lenses often deliver ...
... superior results ... NOT! Most manufacturers offer ultra high-speed lenses such as a 28mm f/1.4, 50mm f/1.2, 85mm f/1.2 or even 200mm f/1.8 etc. Apart from beeing extremely expensive the lenses do not produce wonders in terms of optical quality at wide-open aperture. Usually there's a lack of contrast and sharpness especially towards the edges as well as hefty vignetting. For portraits the problem is not sooo significant because the subject itself -appears- to be sharp within the blurred fore- and background. Stopping-down to f/5.6 will cause a heavy increase of the optical performance but maybe just reach the level of "lower-speed" counterparts (e.g. 28mm f/1.4 vs 28mm f/2.8) - sometime they're even inferior here.
For the vast majority of applications like landscape, architecture these lenses don't make too much sense because you simply do not need such a large aperture lens.
High-speed ultra-wides can be useful for something like available light (hand-held) and photo journalists (e.g for in-room shots of a group of people). High-speed tele lenses are certainly interesting for several applications where a minimal depth-of-field is useful (like portraits).
Teleconverters on low-speed Lenses ...
... are not exactly a good idea. You've one of these fancy 75-300mm f/4-5.6 and want to get something which is a bit longer ? You think a teleconverter is a solution for this problem ? NO WAY! Sure, you'll be able to shoot a "picture" with this combo but the quality will be MISERABLE! Sharpness and contrast will suffer more than acceptable.
Furthermore you would loose AF. A 2x converter will cost you 2 f-stops, a 1.4x converter reduces the max. aperture by 1 f-stop (e.g. 75-300/f4-5-6 @ 300mm plus 2x converter = 600mm f/11.5, 75-300mm f/4-5.6 @ 300mm plus 1.4x converter = 420mm f/8). Usually the AF system of your camera will be able to focus with a f/5.6 lens but will stop to work reliable with anything slower.
Converter works reasonably well on good quality "fast" lenses with a large max. aperture such as f/2.8 or maybe f/4.
Sharp and cheap ...
... is possible! Just take a look at a lens which is considered to be absolutely boring by many beginners and very important by many professionals: the 50mm standard lens. Stopped-down to f/5.6-f/8 it is as sharp as it can get in the 35mm format and all for a bottom-end price (at least for a 50/f1.8 or so). As soon as you buy such a lens you should do one or two field trips with this lens alone. Apart from its amazing performance zoom users will discover a very interesting side-effect: a new sense for perspective. Just to make it clear - this lens is not suitable for the common P&Ser but it'll certainly help on the road to become a serious photographer!
Famous last words ....
Now I have pro glass and the results show no gain of quality !!!
Where was your tripod, monopod or at least the bean-bag ?
Did you use a hood ?
Shoot for slides instead of prints!
Go get a good book and imporve your technique!
20th November 2003, 12:30 PM