What are the advantages of Nikon AIS vs. AF-D lenses?
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Bronze Member Username: JackkesslerPost Number: 11 Registered: Jun-05 | There are instances where Nikon's AIS lenses have rouughly the same specification as their AF-D lenses. The Nikon 35 mm manual focus AIS lens is f/2 and so is the 35 mm AF-D autofocus lens. Yet the manual focus lens costs a third more than the autofocus lens. What does one get for the extra money? Are there tests showing the AIS lenses are sharper or contrastier or better in some other way? |
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Gold Member Username: Project6Post Number: 4338 Registered: Dec-03 | Hi Jack, Have you come to any conclusions? |
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Bronze Member Username: JackkesslerPost Number: 17 Registered: Jun-05 | I have come to some conclusions. As so often the answer to my question is that I was asking the wrong question. First I was confused by the fact that the scientific measure of the sharpness and contrast of a lens is the MTF test and resulting graph. It is more than a little complicated to understand what each line on the graph signifies. Then one has to learn to put the results in context so that one is making valid comparisons. For instance a faster lens often looks worse than a slower lens because one set of measurements is taken with the lens wide open. Wide open is usually the worst aperture for sharpness. An f/1.4 lens might be sharper or less sharp at f/2 than the f/2 lens you're comparing it to, but the MTF graph won't show you which. Second, long lenses always do better (and in fact are better) than short lenses because the difference in angle between the edge of the image and the center is less. So all the problems of flare, distortion, and problems of focus are less. So one cannot reasonably compare lenses of different lengths. Then there is the problem of so many reviewers disagreeing with the measured results. At first I assumed this meant they were subjective pompous windbags who were just wrong. Then I realized that it is not so simple. If all the reviewers say that automobile A gets better gas mileage than automobile B but the objective tests say otherwise, the reviewers are wrong and one gets automobile B because one wants the best mileage. But if all the reviewers say that the pictures produced by lens A appear sharper and more contrasty than lens B, does it matter that lens B does better on an objective test? What one wants is the subjective result, that people, including you, see the pictures as sharper, not the objective one of whether they actually are or not. So one cannot rely on the MTF graphs alone, though they are an excellent place to start. One must also read reviews and examine images oneself. Some other conclusions I came to were damaging to the conventional wisdom I have received. Judging by The MTF graphs alone (which I have already said one should not do) I learned - primes are still usually significantly sharper and more contrasty than zooms. - the big two, Nikon and Canon, make the sharpest lenses. A few of the smaller companies (Leica, Minolta, Pentax) make a number of lenses that tested well too. - even the big two have quite a few substandard lenses in their product lines, so even brand name is not an automatic guarantee of quality. Even Leica sells some that didn't test well. - The aftermarket lenses I saw tested (Sigma, Tamron, Vivitar, and so on) tested consistently and substantially lower than the brand name lenses. A few of these were genuinely terrible lenses. I have also learned that the most important feature of lens performance is the tripod it is standing on, and the fact that it is stepped down, for most lenses, to f/8. Given a choice, use the longest lens that will take the picture you want, or the longest zoom setting. On a tripod at f/8 it is a rare lens that is so bad that which lens one uses will make much difference. As to the specifics of Nikon AIS vs. AF-D lenses, the Nikon engineers have in some cases used the same lens configuration but updated the electronics, such that the newer lens tests the same as the old one. In other cases, the newer lens tests a little better than the old one. Finally, it appears to me, that Nikon's manual focus lenses are generally very fast, large, heavy very expensive prime lenses with a durability usually associated with tank warfare. Their autofocus lenses are engineered to be small, light, less expensive, and have features like silent wave and vibration reduction. They are often zooms. In a word, manual focus AIS lenses are for professional photographers. Autofocus lenses are for everyone else. In this context "pro" does not mean "better". It means that one line is useful for people who are willing to carry around 70 pounds of lenses and two or three bodies, all running into tens of thousands of dollars. Nobody would do that unless they were doing it for a living, not for pleasure. For someone who wants a convenient versatile quiet lens on one body, there are VR autofocus zoom lenses. Unless you are prepared to have a long row of primes with you at all times, the manual lenses' extra stop of speed is not worth the trouble nor the expense. As between manual primes and autofocus primes of the same length and aperture, it appears to me that the manual lenses are heavier, more durable, have better quality mechanical parts, and of course are more expensive. The glass appears to be the same. Which makes sense. Why would Nikon pay to engineer the same optical system twice? For tens of thousands of shots, get the autofocus. For hundreds of thousands of shots, you need the heavier lens. My guess is that keeping the professional lenses manual focus is related to the lenses being fast. In plentiful light the aperture will be small and the depth of field large so the risk of focus errors is small for both systems. In dim light at full aperture, Nikon assumes, probably correctly, that no autofocus system will be as good as the human eye, especially the eye of a professional photographer. It also avoids the autofocus pre-flash which can be unacceptable in some situations (shooting politicians, celebrities, other forms of wildlife). By having manual only, not even switchable like the prosumer lenses, Nikon assures the user that she will not come to rely on an autofocus that will not be good enough some of the time. Again, the palpable inconvenience of using manual focus even in daylight, only makes sense if one is doing it for a living. It is an unjustifiable pain in the rump for anyone else. A good site for MTF test results is http://www.photodo.com/nav/prodindex.html |
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Gold Member Username: Project6Post Number: 4349 Registered: Dec-03 | Very nice findings Jack and well put! So, what will be your next lens purchase? |
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Bronze Member Username: JackkesslerPost Number: 18 Registered: Jun-05 | What I have seen in galleries an on line has made me think I want to learn black and white photography. I toyed with the idea of getting a Canon point & shoot. No DSLR shoots in monochrome and no Nikon point & shoots do. Only Canon P&S. Then I learned from Tiffen techsupport that their Sepia #2 filter will produce almost monotone images on a color sensor. The D70 menu provides places to reduce color saturation and increase contrast, so I am going to fiddle with those variables after the filter arrives to see how close I can get to sepia and white images. (S&W? Isn't that canned vegetables?) I also expect to buy a Nikon 18-200mm VR lens as soon as they become available, supposedly in December, if it gets decent reviews. I travel a lot so I want a wide range zoom like that. Also VR-II is supposed to be a full stop faster than VR so the new lens will be fast indeed. That may or may not help enough if it is crummy wide open though, so I will have to wait and see. Nevertheless it is ironic that with Nikon's long list of lenses running into many thousands of dollars each, among their best and most useful lens is the 50mm f/1.8D lens which can be had mail order for $90 plus shipping. I am trying to use it more and the zooms less. It is not quite as fast as the VR lens but it is so much sharper wide open than the VR zoom is wide open at 50mm, that even my uncritical eye can tell the difference. Also, without a wide aperture lens I am never going to learn how to use aperture and bokeh. If the sepia filter experiment works as well as I hope, I may start pricing the Nikkor 105mm f/1.8 or the Nikkor 135mm f/2. But I have to learn to use the 50mm first. By the way, I keep seeing people saying that they changed their minds about such and such a lens and they sold it and got something else. Where are they selling them? Ebay maybe? There doesn't seem to be much in the way of used lenses for sale there, so it seems it must be somewhere else. Any ideas where to look? |
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Bronze Member Username: JackkesslerPost Number: 19 Registered: Jun-05 | And thanks for the compliments, Berny. It feels great for a newby to be appreciated by someone who knows what's what. |
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Gold Member Username: Project6Post Number: 4382 Registered: Dec-03 | Jack, Please let me know about the Tiffen filter eperiment. I am very interested in knowing how well it works on digital sensors. Personally I like changing my images to monotone/duotone by using Photoshop. Your options are varied and you can play with the different channels and come up with a picture all your own. Check this: http://www.earthboundlight.com/phototips/more-black-and-white-photoshop.html As for used camera equipment, check. http://www.keh.com/hmpg/index.cfm I try to stay away from ebay when it comes to main photo equipment such as lenses. You have to be able to check used lenses personally and see if there is gunk in the blades or mold, etc. If you are going to buy lenses online, go with a reputable seller specially on used lenses. I am also interested in the 18-200mm VR, a light VR lens with a decent reach and light weight is always a plus. I do love the 50mm 1.8, it is so useful and versatile and tack sharp. They manage to keep so cheap because it is simple to manufacture in relative terms as opposed to the longer or wide angle lenses. |