From gnu.mat.uc.pt!news.rccn.net!scsing.switch.ch!swsbe6.switch.ch!swidir.switch.ch!in2p3.fr!univ-lyon1.fr!pasteur.fr!jussieu.fr!math.ohio-state.edu!uwm.edu!cs.utexas.edu!swrinde!tank.news.pipex.net!pipex!dispatch.news.demon.net!demon!mail2news.demon.co.uk!matrixlk.demon.co.uk Wed Mar 6 16:21:45 1996 Path: gnu.mat.uc.pt!news.rccn.net!scsing.switch.ch!swsbe6.switch.ch!swidir.switch.ch!in2p3.fr!univ-lyon1.fr!pasteur.fr!jussieu.fr!math.ohio-state.edu!uwm.edu!cs.utexas.edu!swrinde!tank.news.pipex.net!pipex!dispatch.news.demon.net!demon!mail2news.demon.co.uk!matrixlk.demon.co.uk From: Peter Headland Newsgroups: rec.photo.equipment.35mm Subject: Contax AF article analysed Date: Sat, 02 Mar 96 14:47:25 GMT Organization: Matrix Link Ltd Lines: 240 Message-ID: <825778045snz@matrixlk.demon.co.uk> Reply-To: Peter_Headland@matrixlk.demon.co.uk X-NNTP-Posting-Host: matrixlk.demon.co.uk X-Newsreader: Demon Internet Simple News v1.29 X-Mail2News-Path: matrixlk.demon.co.uk Let's examine Contax's hype a little: > ... It doesn't look like auto focus is going to wither away. I.e. "We hoped this would go away, but it didn't so now we have to do something". > Plastic has a lower coefficient of expansion than metal, The use of the term "plastic" as if were a single material with a single set of properties is the first sign of the technical illiteracy of the author. > leading to a conclusion that it may be a better basis for lens > construction. The problem is that while metal will return to > its original starting point before a temperature change, > plastic may not. This phenomena is known as warpage. Name me one modern camera which uses plastics which warp at any temperature which would not destroy other components in the camera. This is just crude FUD (Fear, Uncertainty and Doubt - as pioneered by IBM). > No materials will slide against each other as > easily and as well as aluminum against brass. What utter and total nonsense. What about phosphor bronze? What about oil- impregnated sintered metals. What about PTFE or even appropriate grades of nylon? Unlubricated, aluminium against brass will bind and seize very rapidly. In the presence of moisture rapid electro-chemical corrosion will take place. > For plastic to achieve this > unimpeded flow over the focusing track it must be a very loose > fit. More nonsense. The compliance of materials such as nylon enables interference fits to move smoothly. Harder materials such as the fabulous aluminium/brass combination require a physical gap which must be filled with a lubricant. > The silky smooth focusing movement of a CARL ZEISS lens will > last for at least 30 years with no visible change in the > resistance to movement (back-lash) in the focusing system. Now it gets worse! "Back-lash" refers to the dead zone in a gear or screw mechanism where turning one component does not immediately affect the other due to the small gap required between the moving parts (see above). It is noticeable when reversing the direction of motion. The only relation between back-lash and resistance to movement is that reducing back-lash tends to increase resistance. > Lenses, such as AF lenses found currently in competitive > systems, have virtually no back-lash for two reasons. Cheap AF lenses have *lots* of back-lash. It's their biggest failing. It's that nasty slack feeling you get when you're trying to fine-adjust focus. The author is completely reversing the likely effect of back-lash. > Another feature of competitive AF designed lenses is the very > small manual focusing ring incorporated almost as an after- > thought. All AF lenses which compete on price with CARL ZEISS (sic) lenses have wide focussing rings. Canon's shorter USM "L" ones also have low back-lash. Canon's EF telephotos have zero backlash, as they do not use a gear train at all. > This small ring is not an after-thought though, it is > a consequence of that small motor used to drive the lens to > focus. The smaller the driven mass, the faster it will move. Not true. The two main reasons are: 1. To reduce the chances of physical obstruction of the focus ring stalling the focus motor. 2. To make the lens physically smaller. The mass of the focus ring is insignificant compared to the load imposed by driving the focussing elements. > Along with these cost savings measures, optical > quality has suffered. No evidence is offered in support of this claim, it's just trotted in on the back of the (valid) comments about reduced production costs. In fact, modern cheap lenses are generally a great deal better optically than their price equivalents of a few years ago. Contax is just taking a cheap shot here, the more so since they sell no lenses in the price bracket to which their comments refer. > You cannot find a photographer today who > does not believe that the older manual focus lenses were > optically superior to today's plastic marvels. Take a look at an old metal-bodied manual-focus 70-210 zoom. Now check out a modern plastic-bodied AF equivalent. You'll find 9 times out of 10 that the modern lens is a mile ahead of what was available ten years ago. "You cannot find..."? Complete fantasy! You can find dozens! I'm one, to start with. > CARL ZEISS would not sanction changing their lenses in any way > to accommodate auto focus. I think they're saying they can't afford to re-tool so extensively. > ... focus by moving the film plane. There are no > compromises in focus quality by achieving focus in this way. Rubbish! 35mm lenses (including those from CARL ZEISS) are corrected for a specific film-plane position. Forming the image at another position will inevitably increase aberrations. This doesn't matter so much in large format cameras where the magnification for reproduction is so much lower and the lenses are designed for that type of focussing. > main benefit of a system of this type is that lens quality is > unchanged. There is no loss of optical quality what-so-ever > due to the auto focusing procedure. See above. > The second new technology is the Ultra Sonic Motor (USM). Funny, I thought Canon invented those years ago... So long ago, in fact, that the patents appear to have expired and hence Nikon and Contax are suddenly starting to use the technology. > The Automatic Back Focusing system on the AX can > move from minimum focusing distance to infinity or back in less > than 450 ms. Unfortunately, minimum focussing distance on longer lenses will *not* be that which you can achieve by manual focus. To get close focus with a telephoto, you'll have to pre-focus manually to very near to the required point and the the AF will do the rest. > This is a very quick indeed. But no better than other manufacturers have done for years. > The time required > to achieve an intermediate focusing distance is minute. Ditto. > Additionally, since the film is moving and not the rotation of > the lens, we can focus long or short focal length lenses over > the same time period. This is a lie. For very long lenses manual focus will be required. For shorter lenses, the shorter the focal length the less the distance the "inner camera" assembly will have to move so the faster focussing will be. > The AX offers auto focusing precision > beyond any other camera in the 35mm arena That remains to be seen. > without compromising > the manual focusing system one iota. Another lie. If the "inner camera" is not in the fully-forward position, it will be impossible to focus at infinity manually. At the very least you'll have to wait nearly half a second for it to move into place. Existing AF cameras with full-time manual focus don't have this problem. > CONTAX has applied for more than 100 patents now pending on the > AX. When CONTAX innovates look out! Look out for a torrent of bull-sh*t. >AUTO FOCUSING SENSORS > > The AF sensors in the AX are deep in the bottom of the camera > body. These sensors in conjunction with the USM and ceramic > technology produce the finest implementation of auto focus in > the world. That remains to be seen, but it seems *extremely* unlikely, given how many years Canon, Minolta, Nikon, etc. have been refining this technology. > This film position will effectively add a 10mm > extension tube into the optical system automatically when the > lens is focused to its nearest focusing distance. This makes very little difference for lenses over 100mm. > When the AF Button is > disengaged the camera immediately returns to a manual CONTAX. That lie again! If the AF positioned to a close focus point, you either have to wait half a second for the inner camera to move forwards, or you won't be able to achieve infinity focus. >THREE CENTRAL PROCESSING UNITS (CPU) > > The CONTAX AX utilizes three CPUs to control all of the > camera's functions. This is a more sophisticated computer > system than any other camera system in the world. Another lie, according to some *old* Canon and Minolta brochures I have. > The amount of ROM memory available in the AX is > 56k, the amount of ROM necessary to go to the moon with Apollo > 7 was 64k. We are becoming very sophisticated, indeed. Ho, ho, ho. This is just fatuous. > Coreless motors are > used to advance and rewind the film. This type of motor > provides quiet, fast operation. Translation: the gear train is as noisy as ever. > The weight of > the AX body is 1080 grams (38.09 oz.) while the RTS III is 1150 > grams (40.56 oz.). Given that the AX is substantially bulkier than the RTS III (oh, they forgot to mention that, didn't they?), plus it has the complex inner/outer camera construction, just how did they get the weight down? The only answer can be by reducing the thickness of the chassis and hence weakening the camera. I also wonder just how good an idea a ceramic guide-rail is given the brittleness of ceramic materials - this may well not be an issue but I'd be interested to know whether that rail could be shattered by a hard knock to the camera body. > A new generation data back is available for the AX. This Data > Back prints between the frames, as do other recent data backs > from CONTAX, or the D-8 will reserve the first two frames of > film, advancing past them to start photography on frame three. > Then upon rewind, the AX will download all of the exposure > information used to create the images on the roll onto frames > one and two. The D-8 can imprint the information next to each > frame, on frames one and two, or the unit may be turned off. Now *that* is brilliant. This is a first-class system that we Canon users can only dream of. I think even Nikon's best back can't do the trick with the "reference frames", which would be essential to those of us who shoot transparencies and don't care to cut and mount them ourselves. Bravo Contax! -- Peter Headland - Matrix Link Limited - Stoke-on-Trent, UK From gnu.mat.uc.pt!news.rccn.net!scsing.switch.ch!swidir.switch.ch!in2p3.fr!oleane!plug.news.pipex.net!pipex!weld.news.pipex.net!pipex!tank.news.pipex.net!pipex!newsfeed.internetmci.com!news.ac.net!news.cais.net!nntp.uio.no!nntp.uib.no!nntp-bergen.UNINETT.no!nntp-trd.UNINETT.no!news.uit.no!news Wed Mar 6 16:22:42 1996 Path: gnu.mat.uc.pt!news.rccn.net!scsing.switch.ch!swidir.switch.ch!in2p3.fr!oleane!plug.news.pipex.net!pipex!weld.news.pipex.net!pipex!tank.news.pipex.net!pipex!newsfeed.internetmci.com!news.ac.net!news.cais.net!nntp.uio.no!nntp.uib.no!nntp-bergen.UNINETT.no!nntp-trd.UNINETT.no!news.uit.no!news From: Paal Jensen Newsgroups: rec.photo.equipment.35mm Subject: Re: Contax AF article analysed Date: 2 Mar 1996 19:50:08 GMT Organization: University of Tromsų Lines: 176 Message-ID: <4ha8pg$m0b@news.uit.no> References: <825778045snz@matrixlk.demon.co.uk> NNTP-Posting-Host: melange.ibg.uit.no Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 1.1N (Windows; I; 16bit) Peter Headland wrote: >> Plastic has a lower coefficient of expansion than metal, > >The use of the term "plastic" as if were a single material with a single set of >properties is the first sign of the technical illiteracy of the author. Yes, just as using "metal" as a single material with a single set of properties. Lets stick to the point; plastic in the camera industry is exclusively used because it is cheap. Arguments of space-age plastic compounds is just as irrelevant as bashing metal cause lead is a soft material; they don't use it. >> leading to a conclusion that it may be a better basis for lens >> construction. The problem is that while metal will return to >> its original starting point before a temperature change, >> plastic may not. This phenomena is known as warpage. > >Name me one modern camera which uses plastics which warp at any temperature >which would not destroy other components in the camera. This is just crude FUD >(Fear, Uncertainty and Doubt - as pioneered by IBM). > >> No materials will slide against each other as >> easily and as well as aluminum against brass. > >What utter and total nonsense. What about phosphor bronze? What about oil- >impregnated sintered metals. What about PTFE or even appropriate grades of >nylon? Unlubricated, aluminium against brass will bind and seize very >rapidly. In the presence of moisture rapid electro-chemical corrosion will >take place. > >> For plastic to achieve this >> unimpeded flow over the focusing track it must be a very loose >> fit. > >More nonsense. The compliance of materials such as nylon enables interference >fits to move smoothly. Harder materials such as the fabulous aluminium/brass >combination require a physical gap which must be filled with a lubricant. > Well, modern AF lenses ARE wobbly and use low grade plastic. Older manual focus lenses are tight and focus smootly and last forever. Ask people in the camera repair business. Off the record, one representative from one of the two largest slr manufacturer told me that their cameras and lenses, regardless of price, was not built to last. This was true for the other volume manufacturers as well. I have no problem believing this. > >All AF lenses which compete on price with CARL ZEISS (sic) lenses have wide >focussing rings. Canon's shorter USM "L" ones also have low back-lash. >Canon's EF telephotos have zero backlash, as they do not use a gear train at >all. > All of them have a horrible focusing feel >> This small ring is not an after-thought though, it is >> a consequence of that small motor used to drive the lens to >> focus. The smaller the driven mass, the faster it will move. > >Not true. The two main reasons are: > >1. To reduce the chances of physical obstruction of the focus ring stalling > the focus motor. True >2. To make the lens physically smaller. No. 95% of all AF lenses would be no bigger with larger focusing rings. Cost cutting is the true answer. >The mass of the focus ring is insignificant compared to the load imposed by >driving the focussing elements. Not true. Although the focusing elements/system is surrounded by low-grade plastic in order to reduce strain on the focusing motor, the focusing ring also play a part in this system. By reducing the weight of the whole focusing system, small focusing rings and low grade plastic (NOT magnesium) is used in order for eg Canon to use the weakest (and cheapest) focusing motor possible and thereby increase profit. >> Along with these cost savings measures, optical >> quality has suffered. > >No evidence is offered in support of this claim, it's just trotted in on the >back of the (valid) comments about reduced production costs. In fact, modern >cheap lenses are generally a great deal better optically than their price >equivalents of a few years ago. Contax is just taking a cheap shot here, the >more so since they sell no lenses in the price bracket to which their comments >refer. > >> You cannot find a photographer today who >> does not believe that the older manual focus lenses were >> optically superior to today's plastic marvels. > True, except for Canon owners. Since Canon have made it impossible to use older MF focus design on AF bodies, not a single Canon owner will admit that MF lenses is better mechanically. Most Nikon and pentax owners that use both MF and AF lenses have no problem with the above statement. >Take a look at an old metal-bodied manual-focus 70-210 zoom. Now check out a >modern plastic-bodied AF equivalent. You'll find 9 times out of 10 that the >modern lens is a mile ahead of what was available ten years ago. "You cannot >find..."? Complete fantasy! You can find dozens! I'm one, to start with. This is not my experience. Most volume AF zooms from most volume manufactures are not very good; they are crap both opically and mechanically. The big recent progress in optical design is a myth; Computer assisted lens construction is nothing new; it have existed for at least 30 years. Paal From gnu.mat.uc.pt!gnu3.mat.uc.pt!not-for-mail Wed Mar 6 16:22:48 1996 Path: gnu.mat.uc.pt!gnu3.mat.uc.pt!not-for-mail From: rps@gnu3.mat.uc.pt (Rui Pedro Mendes Salgueiro) Newsgroups: rec.photo.equipment.35mm Subject: Re: Contax AF article analysed Date: 3 Mar 1996 17:23:42 +0100 Organization: Dep. de Matematica da Univ. de Coimbra Lines: 40 Message-ID: <4hch2e$csi@gnu3.mat.uc.pt> References: <825778045snz@matrixlk.demon.co.uk> Reply-To: rps@mat.uc.pt NNTP-Posting-Host: gnu3.mat.uc.pt X-Newsreader: TIN [version 1.2 PL2] Peter Headland (Peter_Headland@matrixlk.demon.co.uk) wrote: > Let's examine Contax's hype a little: > > ... focus by moving the film plane. There are no > > compromises in focus quality by achieving focus in this way. > Rubbish! 35mm lenses (including those from CARL ZEISS) are corrected for a > specific film-plane position. Forming the image at another position will > inevitably increase aberrations. I think this depends on the type of lens. I just checked my 50mm f/1.4 (Pentax) and it appears that the whole of the lens move with focusing. So in this case focusing the lens normally is exactly the same as moving the film plane. There are other lenses in which focus is achieved by moving inside groups of lens (internal focusing) (usually longer lenses) and for those lenses your objection is valid. I also read in these groups that zoom lenses don't work well with extension tubes. (It is no longer possible to zoom and keep focus ?) Although Zeiss makes only 3 or 4 zoom lenses, and so this problem is not so serious for them as it would be for other makers, it is still a problem. > > The second new technology is the Ultra Sonic Motor (USM). > Funny, I thought Canon invented those years ago... So long ago, in fact, > that the patents appear to have expired and hence Nikon and Contax are > suddenly starting to use the technology. No, it wasn't Canon. I read in some magazine that Nikon has licensed the technlogy from the same people from which Canon licensed some years ago. Maybe it was Kyocera ? -- http://www.mat.uc.pt/~rps/photos/ an ex-tiffoso until the end of 1997 .pt is Portugal| `Whom the gods love die young'-Menander (342-292 BC) Europe | Villeneuve 50-82, Toivonen 56-86, Senna 60-94 From gnu.mat.uc.pt!news.rccn.net!scsing.switch.ch!swidir.switch.ch!in2p3.fr!oleane!tank.news.pipex.net!pipex!dispatch.news.demon.net!demon!mail2news.demon.co.uk!matrixlk.demon.co.uk Fri Mar 8 13:19:55 1996 Path: gnu.mat.uc.pt!news.rccn.net!scsing.switch.ch!swidir.switch.ch!in2p3.fr!oleane!tank.news.pipex.net!pipex!dispatch.news.demon.net!demon!mail2news.demon.co.uk!matrixlk.demon.co.uk From: Peter Headland Newsgroups: rec.photo.equipment.35mm Subject: Contax AX - more info Date: Thu, 07 Mar 96 10:50:40 GMT Organization: Matrix Link Ltd Lines: 29 Message-ID: <826195840snz@matrixlk.demon.co.uk> Reply-To: Peter_Headland@matrixlk.demon.co.uk X-NNTP-Posting-Host: matrixlk.demon.co.uk X-Newsreader: Demon Internet Simple News v1.29 X-Mail2News-Path: disperse.demon.co.uk!post.demon.co.uk!matrixlk.demon.co.uk I've now seen a photo of the new AX body. Man is it *ugly*! I've also seen an extract of a pre-release manual for this odd creation. This confirms that: o AF is not recommended with lenses with "floating" elements (due, as I stated in an earlier posting, to image quality loss). o Zooming a zoom lens will lose focus. I've also realised that: o If you brush against your lens while carrying your camera and thus move the lens away from infinity, the AF mechanism will not be able to focus at infinity. o If you want to adjust the focus achieved by AF manually, you will only be able to do so to a nearer point, since the lens is already at its maximum (infinity) far point. o When returning from AF to full-range manual focus, the image will jump out of focus, due to the need to return the inner body to its maximum forward position so that manual infinity focus is attainable. And all this for just a tad under $3,000. Must be the bargain of a lifetime! -- Peter Headland - Matrix Link Limited - Stoke-on-Trent, UK From rps Fri Mar 8 13:50:17 1996 Subject: Re: Contax AX - more info To: Peter_Headland@matrixlk.demon.co.uk Date: Fri, 8 Mar 96 13:50:17 MET In-Reply-To: <40566@matrixlk.demon.co.uk>; from "Peter Headland - Matrix Link" at Mar 8, 96 9:55 am X-Mailer: ELM [version 2.3 PL0] Status: OR > The one I saw was in the UK magazine "Amateur Photographer". I'm not > aware of one on the net, sorry. I suppose it is this week issue ? It usually takes one or two weeks to arrive here. > > Do they make a lot of internal focusing lenses ? > I would guess all the ones >= 100mm, but I don't have a list. Of > course, the ones >= 100mm can't do full-range AF anyway. About the full range AF: That is not necessarily a bad point. I may be mistaken, but I think some long lenses from Canon/Nikon have focus range limiters, to reduce the hunting time. I know that this is the case for most macro lenses (at least 100mm and longer). If the range AF is reasonably large, this might be even an advantage: I think the maximum movement of the film plane is 10mm. Considering a 200 mm lens (manual setting at infinity) this gives a minimum focusing of: 1/d + 1/(200+10) = 1/200 <=> 1/d = 1/200 - 1/210 <=> 1/d = (210 - 200) / (200 * 210) <=> d = 42000 / 10 = 4200 mm = 4.2 m for f = 300 mm, d = 9.3 m for f = 400 mm, d = 16.4 m Hmm, it doesn't look very convincing to me, although the range with a 200mm would be enough for the kind of sport pictures I usually take (rally, see my homepage for examples). with a 50mm, d = 3000/10 = 0.3 m This is ok (in fact the usual value for a 50 mm is 0.45 m) in general d = f * (f + 10) / 10 > > http://www.mat.uc.pt/~rps/photos/ an ex-tiffoso until the end of 1997 > What about Irvine? Schumacher contract ensures that he won't get a chance. > > .pt is Portugal| `Whom the gods love die young'-Menander (342-292 BC) > > Europe | Villeneuve 50-82, Toivonen 56-86, Senna 60-94 > Nice .sig! Thanks. rps