一个永恒的追求 - 纪念加拿大著名摄影人Michael Reichmann
Michael Reichmann at work
Michael Reichmann在中国可能没啥名气，但他在英文摄影圈是大名鼎鼎的，这部分是因为他1999年创办的摄影网 www.luminous-landscape.com。和现在大部分拍报纸和展板的技术派摄影网站不同，luminous-landscape主要是从摄影者实际操作方面来评测器材的。
Michael Reichmann本人从事摄影五十多年。作为记者、编辑和摄影教育家，他对影像圈的影响是众所公认的。我从2000年开始就是他的忠实读者。应该说，在风光和人文摄影方面，Michael Reichmann的很多摄影理念对我帮助良多。
2003年时候我翻译了他的一篇文章《Lens Sharpness - The Never-Ending Quest 》。今天稍加修改刷在这里，愿Michael 安息。
Lens Sharpness - The Never-Ending Quest
But How Sharp Is it Really!? One of the most common questions that I'm asked is, Is the ...lens sharper than the ... lens? A variation on this theme is... What do you think of the ... lens? Is it sharp? Or there's the more generic... Is a zoom lens as sharp as a prime lens?
That's enough! I'm about to answer your questions, (as well as a few that you didn't ask), and from here on, until the end of time, you need ask them no more. And, if anyone asks you these questions, you'll now know where to refer them. Right here.
够了！现在我就来回答你的这些问题（还包括其他你也许没问到的），从此直到地球的末日，你就再也不会问此类问题了。如果再有人问你，你知道该让他们上哪儿找答案 － 这里。
What's All This About Sharpness Anyhow? There are photographers who love to test and compare things. When they make prints or examine their slides under a loupe, they are not looking to see if they have properly captured a special location, light or subject. They are first and foremost concerned with technical quality rather than image quality.
Consequently they fret and fuss. They choose primes over zooms. They buy the most expensive brands of bodies and lenses. But then when they have them, what do they do? Do they settle down t pursue their photography? No, they fuss and fret some more, worrying that if only they had a sharper lens their photography would somehow improve. Sound familiar?
There isn't a photographer alive who doesn't care about how sharp his or her lenses are. It's one of the primary manias of anyone playing this game. We buy and sell different brands of cameras in search of the holy grail of sharpness.
Should I trade in my Nikon gear for Canon? Should I trade in my Canon outfit for Nikon glass? damn, maybe I should buy a Leica system. I hear Leica lenses are fantastic. But, how about Contax? Those Zeiss lenses have great reputations. But boy, are those lenses ever expensive. Are they worth it?
I know you've never had these thoughts, but you have heard from lots of other photographers who have. Go to any of the on-line discussion boards. You will find that talk about lens sharpness represents probably half the discussions — most of it filled with unsubstantiated opinions and mistruths.
After 40 years as a professional photographer as well as an ardent amateur, as a teacher and as a journalist, I've learned certain things about photography and photographic equipment, and specific to this topic — about lens sharpness, its importance as well as, frequently, its lack of importance.
Some Cosmic Truths
I'm now going to let you in on the great truths. The ones that all true cognoscenti know, but that are hidden from newcomers and the otherwise uninitiated. If you're really observant you may notice that this piece has some scattered evidence of the use of irony, (some would call it sarcasm.) Ignore the man behind the curtain. I stand behind every statement.
Finally, note before you enter the inner sanctum that I have occasionally used the word "Usually". That's because to be a universal truth, there must be an exception that makes it so. Otherwise, what would we have to argue about?
Prime Lenses are Sharper than Zooms Lenses (Usually)
The title says it all. There is no free lunch! If you want the utmost in sharpness, don't buy a zoom lens. But, if you want greater shooting versatility by all means do buy a zoom. You'd be a fool not to.
Why are primes sharper? A number of reasons. Zooms lenses by necessity have more elements than primes. This makes them more difficult to design, increases the risk of various forms of optical aberration, and can reduce contrast and increase flare.
Prime lenses usually have larger apertures than zooms, and the laws of optics say that all other things being equal (which they often aren't) a wider aperture lens will be sharper than one with a smaller aperture — the issue being diffraction effects.
Having made the case for prime lenses, let me say that three of the sharpest lenses I own, the Canon 70~200 f/2.8L IS zoom, Leica's M series 28-35-50mm Tri-Elmar, and the Pentax 67's 55~100mm f/4.5 zoom, are as good as any primes in their formats that I've ever used. As I said — "usually" sometimes defines the rule.
OK，这是定焦镜的一般规律，让我来说说我的三支锐度最高的镜头，它们是：佳能的70－200F2.8L IS变焦镜；莱卡M系列的三段式变焦镜头 Tri-Elmar 28-35-50mm；宾得67的55-100mm F4.5 变焦镜。这三支变焦镜比我用过的任何定焦镜都不差。这就是我前面为什么老是用“一般来说”这个词。
Camera Manufacturer's Lenses are Sharper than Third Party Lenses (Usually)
Camera manufacturers want you to buy their lenses. They don't want you to buy a lens from a third party. If you do they don't make as much money, and making money is why they're in business. Therefore they have to make some of their lenses as inexpensive as possible. But, professionals and other serious photographers want the finest lenses possible, which are expensive to make. What to do?
Most major brands therefore make two lens lines, sometimes so indicated (like Canon's "L" series glass), and sometimes just differentiated by price. This allows them to cater to both markets.
Third party lens makers usually aren't interested in selling camera bodies. They want to sell you lenses. And since most amateur photographers make their buying decision based pretty much on price alone, it isn't hard for these companies to figure out what to do to get this business.
If you want the finest lens of a given type, buy the manufacturer's top-line lens. If your priority is to save money, then buy the third party lens. No matter how hard you try and imagine it to be so, that $200 lens (including a free skylight filter) from Sigma, Tamron or their brethren just isn't going to be as sharp, free from flare and optical aberrations, well designed and sturdily constructed as a $900 optic from Canon, Nikon or one of the other majors.
Are there exceptions to this. Yes, maybe, sometimes. Some types of lenses are easier to design than others, so low-cost third-party lenses can be quite decent. But, this brings us to our next cosmic truth.
You Get What You Pay For
Test drive a BMW or a Lexus. Now test drive a Chevy or Nissan. Notice any differences? Of course you do. Compare the prices. Now you understand why better costs more.
What applies to cars applies to lenses as well. Quality costs money. When is "good enough", good enough? Only you can answer that. If you can afford a Mercedes, good for you. If a Leica prime lens is within your reach, go for it. But if you can't afford one don't delude yourself that a lens that costs 2-3 times as much as another isn't worth the money. It is. For those that can afford it! For those that can't — get over it, and live happily with what you can afford.
Please read my parable on coveting high-end equipment for further thoughts on this topic.
Good Technique Trumps Sharp Optics
Now for one of the biggest truths of all. You can fret all you want about how sharp a given lens may be, but if your photographic technique isn't first rate, having a lens capable of producing high resolution and high contrast is hardly worth a damn.
To get the best from any lens here are some things that you should be doing:
Use a solid tripod
For 95% of the landscape, nature and wildlife work that I do I use a tripod. Religiously. I own three; big, bigger and biggest. Just about the only time I hand-hold a camera is when I'm doing documentary-style street shooting. Hand-holding usually leads to inferior images, particularly in landscape and nature photography.
Use mirror lock-up and a cable release.
Vibration; any vibration, is a sharpness killer. Don't hand-hold a lens at a slow shutter speed and a wide aperture and then worry about whether the lenses sharp or not. What are you thinking of?
Whether it's Canon's IS or Nikon's VR, this is one of the greatest innovations in lens design of the last quarter century. It works, and it works damn well. for serious long lens work, even when working on a tripod, Canon's family of Image Stabilized "L" series lenses are worth their weight in gold (which partially explains their price).
不管是佳能的IS（image stabilization）还是尼康的VR（vibration reduction），都是近25年来镜头设计上最伟大的发明。它们确实真有用，而且是真TMD有用！当使用长焦镜头来进行严肃的摄影创作时，即使是使用三角架，佳能“L”系列IS镜头的图象稳定器之作用也珍贵如金，这也就是为什么它们都那么贵。
Use the lens' optimum aperture.
This is typically not with the lens wide open, and never when stopped all the way down. Only the finest lenses are as sharp wide-open as when closed down somewhat, and no lens is at its best when stopped down to f/22 or f/32, due to diffraction effects. Most lenses have their optimum aperture at 2-3 stops down from wide open.
Use fine-grain, high-resolution film
You want to be able to see what you've paid all that money for, don't you? Of course using such film means ISO speeds of under 100, which means that a tripod, cable release and mirror lock-up are a necessity when combined with the use of the lens' optimum aperture.
花了那么多钱，你一直想得到最佳解像度的图片，不是吗？当使用最佳光圈时，你还应该同时使用ISO100或者更低速的胶卷（如ISO50的 FUJI VELVIA － 译者注），相机的反光板锁定功能，三角架，以及快门线。
Your image processing technique and equipment must be as good as your photographic technique and your lenses. Whether in the chemical or the digital darkroom; whether using an enlarger or a computer, anything less than the finest tools and techniques will obviate whatever investment you've made i n fine lenses.
Can you honestly say that your prints match your hopes for a given image? It may not be your lens that's at fault. It may be what you're doing and the tools that you're using after the photograph was taken that's limiting your ultimate image quality.
If all of the above are not part of your everyday shooting technique then you're likely not getting the most from your expensive lenses. Only when you've given a lens every chance to show its best do you have the right to determine if its performing at its best.
Think about the variables standing between a scene in front of the camera and a print hanging on the wall. A large number of factors determine whether or not the print will be sharp.
The lens' resolution capabilities; The film's resolution capabilities; Camera and/or subject motion; Aperture used and consequent depth of field as well as use of optimum aperture.
Film flatness — is the pressure-plate doing its job properly? 胶卷平度－ 相机的压力盘（压住胶卷的那个小长方形盘）正常工作吗？（也就是胶卷是稳妥的否上好了－译者注）
Film thickness — are all layers in the film (color) bringing the image into focus？胶卷厚度 – 多层过厚的彩色胶卷是否影响准确了聚焦？
Film grain — sometimes grain makes images look sharper — sometimes the opposite! 胶卷颗粒－ 有时候颗粒使图片看起来更锐利，而有时候则正好相反！
Enlarger parallelism — many aren't, and sharpness suffers 放大机的平衡度－ 许多并不平， 所以也达不到最佳锐度；
Negative carrier precision and film flatness 底片输送机的精确度和胶卷的平度；
Enlarging lens quality and aperture used 放大机的镜头质量和所用光圈；
Resolution of the printing paper used 相纸的解像度；
Of course digital post-processing has its own issues, including... The film flatness capabilities of the scanner's carrier; The native resolution of the scanner chip and firmware; The Sharpening level applied in post-processing ; The native resolution of the printer; The resolution of the printing paper used.
For digital cameras many of the same issues as for film cameras apply, as well as those for digital image processing. See what I mean? The sharpness of a given lens is just one of a myriad of factors, and usually not the most important one, in determining if a print will look "sharp".
The Bottom Line
Are you ready for this? Here's the big one. The one big truth that I've learned about this subject after more than 40 years as a photographer, and which summarizes the points above.
"Most Lenses are Better Than Most Photographers"
Does this idea make you uncomfortable? Good. That's what it's meant to do. Think about it.
Yes, there is a difference between brands. There definitely is something special about many Leica lenses, and Zeiss lenses are generally superb. Top Nikon and Canon glass can be as good as it gets. On the other side of the coin, some Sigma-Tamron -Tokina lenses are indeed so much junk. Some though are pretty good.
All of these statements are based on personal experience. None though are universal truths. But it's my unquestionable experience that it is rare indeed that I ever see photographs taken by folks that fret about these issues that even come close to matching the capabilities of even the least pretentious of lenses.
This is why there are those folks that makes the claims that they do about some lenses or brands, or countries of origin, while there are others who say that they don't see the differences. This isn't a case of "the emperor's new clothes". It's often just a matter of experience and skill, each of which can be acquired if one has the will.
So, unless you are utilizing all of your photographic skills and know what to look for and how to achieve it, stop worrying so much about sharpness. Buy the lens that fits within your budget and that meets the needs of the type of shooting that you do. Most of all, stop worrying and just enjoy doing your photography.