今天DPREVIEW上有个类似贴:
http://forums.dpreview.com/forums/readflat.asp?forum=1029&thread=26532891其中有不少很有意思的发言,我摘录几段供大家参考....
#1
Some people seem to advocate primes simply because they seem to imply that "better" photographers work "better" with primes. In fact, all my lenses are primes, and one of the big plusses of using a prime is that I don't have to think as much as when using a zoom. When using a prime, I need only consider framing, and DOF. When using a zoom, I need to also consider persepctive. Of course, I do have to consider perspective when choosing which prime to use, but I need only consider that one time, whereas when using a zoom I am inclined to think about it with every shot.
Some may argue that not having to think about perspective frees the mind to consider framing more carefully. I have to agree with this, at least for me. Others with more powerful brains may be able to consider both equally and simultaneously and put zooms to better use than I can.
However, while zooms allow more perspective control than primes, some primes allow more DOF control than zooms. Of course, as I'm normally shooting wide open because I love shallow DOF, in practice, I don't consider DOF directly -- I merely consider how to frame the shot to make the ultra shallow DOF effective.
Fast primes can also be used at a lower f-ratio and ISO to capture a scene with less noise, but at the expense of a more shallow DOF. If a more shallow DOF is preferable, bonus, if not, at least you have the option. In addition, many fast primes are smaller and lighter than the zooms in their range: the 24 / 1.4L, 35 / 1.4L, 50 / 1.2L, and 85 / 1.8 are all smaller and lighter than the 24-70 / 2.8L, and the 85 / 1.2L, 100 / 2, 135 / 2L, and 200 / 2.8L are all smaller and lighter than the 70-200 / 2.8L. Now, when we enter the realm of f/4 zooms, the primes are still smaller, but not lighter.
Anyway, I would not choose a prime over a zoom for reasons of IQ. The difference in IQ between modern zooms and modern primes at overlapping f-ratios (well, at least one stop down on the zoom) are largely insignificant.
Choose between primes and zooms on the basis of perspective/DOF control, size, and weight.
#2
I believe it’s a matter of personal choice and photographic philosophy. All photo gear should be seen as tools. If a prime is better to get the job done (shooting indoors without a flash) then fine. If the versatility of a zoom is better for traveling light and having a larger focal range at your disposal, then also fine.
The description “better”, I find hard to like. Ten photographers will define a “good” lens differently just as those ten will make different choices when describing which lens out of a selection is “best”. A friend of mine is a professional photographer. She learned the trait during a three-year apprenticeship and has now worked some two years for a German sports magazine. She still uses the kit lens with great success! Who is willing to rate that lens a “pro lens”? If I started a thread describing the kit lens or the 300D body as high quality professional hardware, I’d be swamped with replies suggesting I visit a shrink.
In “the past” (early 70s), when zooms first became available, their image quality was not accepted by professionals. And many, if not most, pros and experiences photographers lead a crusade against anything not prime, not 50mm as a “standard lens”. In short, anything unorthodox. Since then we’ve come a long way. We shoot color most of the time and b&w is for a minority. The majority of folks prefer to carry one zoom (or two at the max.) instead of four or more primes when vacationing. Many folks shoot indoors without flash – only the realm of specialists with expensive gear in the past.
In short, our gear has changed, the manner in which we shoot pictures has changed and photography has truly become a very affordable hobby. I’m suggesting that, though the laws of physics still hold true, we photographers should embrace change and adapt our technique accordingly. That also goes for primes versus zooms or what the “first lens” should be. Though I often find it difficult to follow our rapidly changing photographic world (and I do miss aperture rings and proper manual focus) myself, I’ve become accustomed to using zooms a great deal. And I feel that a beginner is not worse off by choosing a zoom kit lens to learn the ins and outs of his/her new hobby.
What’s more important is, that a person understand their gear and use it within its limits. A talented photographer will search for new and different approaches to the hobby by himself/herself. A lazy person will sit on a bench and shoot snapshots of a subject regardless of the lens fastened to the body. He/she will simply crop or adjust the image on the PC. Is that a “good” shot? Well, there are many shots which have won prizes where I would have immediately deleted the image or wonder why the photographer needed such expensive gear to take such a horrible shot! That brings me back to the beginning – whatever the photographer is pleased with, is “best” or “good” for him or her.
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#3
If I had an unlimited budget, perhaps I would mostly dapple in zooms, but I don't. I also have bought a Canon printer that will blow up images to 13 by 19. Do you know how many images I have blown up to that size? Zero, nadda, zip. Why: I'm not happy with the quality of any shots I have taken so far.
Now I don't blame the lens for everything, most of my great images which have not been so great due to technical problems like noise, not holding up to cropping, etc are results of my lack of experience. But I am conscious of wanting some quality images so that I can do a little cropping and not loose to much quality in the photo.
I divide my gear into two parts, and I mean this in relation to my DSLR: 1) the times when I used it as a point and shoot 2) when I am trying to create the best image I can.
Point and shoot shots are when I use my middling zooms in terms of quality, you know the Canon 28 - 135, etc. I use this to record events, friends and travel. But my other gear is for serious amateur work. So for example, I am using a Tamron 200 - 400 zoom which is soft at the 400 end. I'm not worried about speed of the lens, but I do want quality images. So I am seriously thinking of purchasing the "forgotten" Canon 400 f5.6 - no IS. This lens isn't fast, but it is excellent. I have found as most do that with longer zooms, most of the shots are taken at the longest focal length. So when I am shooting water fowl, I will have a quality lens I can depend on and know when I have a soft image, its something I've done wrong, not the camera, nor the lens (no I won't blame it on a "bad copy."
Now if you look at all the Canon 400's, you'll see there's a bit of choice all much more expensive than my wished for lens above. But the Canon 400 f5.6 will deliver the goods in terms of IQ.
I just purchased the old version of the Canon cheapy 50 f1.8. I bought the Canon f1.8 Mk l lens. I was using it just two nights ago and shot indoors without a flash in a well lit room. The images were great, and I know I wouldn't have captured them with my 28 - 135 lens, as the f stop is to slow for what I was doing. Speed is important with primes, but the bulk of shots taken by 'fast" lenses are usually one or two stops less than wide open.
Quality is what is important in a lens, then price, and lastly speed.
