Archived posting to the Leica Users Group, 2007/11/13
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]from Erwin Puts _http://www.imx.nl/photo/faq/_ (http://www.imx.nl/photo/faq/) I hope this helps, G. Medina...(Hexar is listed under Leica).... regards, bob cole Konica Hexar and register I am currently using the Hexar RF for several reasons. To test the new Hexanon 2/35mm, to check on Hexar body - Leica lens compatibility and get a feeling for the Hexar system. To start with the body: the specs are well known, so I can jump to the more philosophical topics. The body appears to be a very high engineering quality, has a very solid feeling and is really easy to use. The electronic shutter-motordrive unit is a sealed box and can not be separated. It is the same as used in the Contax G/2 series. As an aside: if Leica were to use this unit, the manual advance lever would have to go. The viewfinder is slightly lower in contrast than the Leica and the Hexar rangefinder patch has a distinct yellow tint, that will lower contrast and makes it more difficult to focus at objects at 10 meter or more distance. While the body has almost identical dimensions to the Leica, the look and feel is distinctly different. The rounded body contours of the Leica and the clean top cover make it look more elegant, compared to the squarish and somewhat boxy character of the Hexar. In use the Hexar is quite simple and its controls are well laid out and generally useful to the photographer. The exposure compensation feature is nice, but with the leica a simple half click stop of the aperture ring will do the job as fast and easy. Biggest drawback of the hexar is the small time delay between pressing the shutterknob and the actual firing of the shutter. This delay and the instant of wait and thus insecurity is most annoying and you can not use the Leica technique of prefocusing and fire when the object is sharp in the finderpatch. When you close your eyes and pick up the Leica and the Hexar several times, the difference in feeling and haptics emerges. When you hold the Leica, your thumb slides behind the advance lever and your finger lays on the shutter release button, which is sharp as a trigger. This simple and intuitive act signifies to the brain a state of alert attention and you fall into the mood of a hunter or an active sportsperson anticipating the moves of the other players. When holding the Hexar, both hands hold the body and wen your finger touches the release button, there is no trigger effect. The finger just rests there and you do not get any feedback from the body. So you switch almost automatically into a more passive state of mind and allow the camera to work for you. That is easy to do as the automatic functions of the camera (exposure, film transport, motorwinder) are so well executed that you start to rely on them and even transfer control to them. In fact you are starting to become an operator of the camera, adjusting the wheels and not the driver who forces the camera to do as he wants it to act. The transfer of controls to the camera and the mood of becoming more passive in the photographic act is in my view the fine distinction between the Hexar and the Leica. Photographing the same objects with a leica and a Hexar in quick succession underscores this difference: with the Leica the work is harder (more to think and act), but your act blends in with the subject and you are part of it. With the Hexar your work is easier, but the remoteness of the controls acts as a filter between the object and yourself. Let me say, that you become a bit lazier when using the hexar and that shows in the pictures. Technically there is nothing wrong with the Hexar pictures, well exposed, sharply focused etc. The Hexar then is for photographers who avoid technicalities and want good imagery with a minimum of technical and manual control and who feel that the visual involvement with the object has to be separated, even detached from the tool they use. In this sense the Hexar is close to the Contax G. The family resemblance goes a step farther. My test of the Hexanon 2/35 indicates that Hexanon imagery is in character very close to the Zeiss philosphy of correction. The Hexanon is an 8 element lens (with the now familiar negatively curved front lens, pioneered by Leica and quickly adopted by Konica and Voigtlander). The Summicron has 7 elements, but has one aspherical surface, and one such a surface equals two spherical surfaces). At full aperture the lens exhibits a medium contrast (less than the leica lens), has visible flare in the bright areas and small detail rendition. The performance on axis till an image height of 6mm (image circle of 12 mm diameter) is excellent with a very good definition of very small detail. In the outer zones the image quality drops significantly and now we see small detail with quite blurred edges. Astigmatism is very well controlled, but there is some curvature of field. The lateral chromatic error is quite large, and may add in the bokeh preservation. The corners are very weak. At 2.8 the flare is gone and the image crispens a bit, the central disk of excellent quality now extends to a image height of 8 mm, with the corners still bad and the outer zones hardly improving. At 4 we find an overall improvement, but the chromatic error still softens the edges of very small and tiny detail. At this aperture the quality is comparable to the Leica, that shows better reduction of the chromatic error and thus a crisper and cleaner image. If resolution figures were relevant, I had to note that the Konica has the edge here. But these are bench mark figures (large scale projection test) and in actual photography the small advantage would be lost. This sideline indicates that differences in resolution of 10 line pairs/mm are not indicative of superior image quality. Optimum aperture is at 8, and after that contrast and resolution drop due to diffraction effects. Close up performance at 1 meter is identical to the tested distance which is at 100 times the focal length. The inevitable question of course is how this Hexar lens compares to the last non aspherical Summicron. In my view the Hexanon is the better lens overall. But you cannot use the Hexanon lens on a Leica body: a collimator check showed that the Hexanon lens has a focus plane that differs from the Leica lens by 0.09mm. Is that important? The discussion on the Lug about the Hexar body/Leica lens compatibility dismissed small differenes in the area of less that half a mm as irrelevant, because some uses could not detect any difference when comparing different lens/body combinations. The truth is this: a did a test on the bench and focussed carefully on maximum image quality. Then I used a micrometer to defocus by 0.03mm (which is quite small). In the image the loss of contrast was very evident, but resolution at least at the lower frequencies (around 40 lp/mm) did not suffer. What did suffer was the edge sharpness. If you were to do your own testing and looking at the negatives with an 8-times magnifier, you would not se any drop in resolution (beyond the detection capability of the eye at that magnification). But at a larger magnification you begin to see it quite clearly. Now the continuing saga of the Hexar/Leica lens compatibility. First a few remarks: You can not measure the actual distance from bayonet flange to pressure plate by using the pressure plate itself as a reference. The slightest and unnoted pressure from the instrument itself on the pressure plate will give errors and the pressure plate itself is hardly ever a plane itself. So additional errors. The only way to do it is to remove the pressure plate and insert a device that is calibrated to be at the same distance where the pressure plate ideally has to be. To start from here. The distance from the bayonet flange to the pressure plate or more accurate the top of the outer film guide rails ( pressure plate rails) in the Leica M is 27.95mm. This distance is also (but wrongly referred to as register. But this distance and measurement is used to check if the guide rails and the bayonet flange are parallel to each other and have the correct distance. The second important measure is the distance from the film rail (the innermost film guide rails) to the bayonet flange. In the Leica this is 27.75mm. The film gate then has a distance of 0.2mm. In every Leica book I know of there is a reference to the filmplane/flange of 27.80mm. What is this. Rogliatti, Roger Hicks, Collectors Checklist, Hasbrouck you name them, all refer to flange to film plane distance or flange to film register. Now in German the word is "Auflagemass". This can be correctly translated as "flange focal length" or "flange focal distance". But this measurement is done for the lens itself on a collimator where the lens is adjusted such that the distance from the lens bayonet flange to the true optical focal plane (focal point) is indeed exact 27.80mm. First lesson: NEVER believe what is written about Leica in books that are focussed on history or collecting: these persons are no engineers. In every other book, check, double check, triple check to make sure the person knows what he talking about. To sum up: we have an optical measurement done on the lens to adjust the flange focal distance and that distance should be 27.80mm. We have a mechanical measurement on the Leica body, which is the distance from bayonet flange and the pressure plate rails which is 27.95mm. The film gate is 0.2mm. If we now use a film with a total thickness (emulsion plus base) of 0.13mm (APX25 as example) the thickness of the film will not fit into the film gate. There is some play and therefore the film will curl and curve inwardly (away from the lens). By using a focal distance of 27.80mm, Leica will ensure that the film when bowed a little, still will be correctly aligned in relation to the focal plane. It is intriguing to note that thick colour neg films of about 0.27mm will fill the film gate completely and the pressure plate will press the film to a plane position, instead of the curved position with thin film emulsions. Theoretically a thick film would have a better flatness than a thin film. Of course more research is needed, but these investigations do show that the information in the public domain is at best scanty or at worst misleading. Now for the Konica Hexar. Here I have only one official fact: that is the bayonet flange to the pressure plate rails of 28.00mm. But I do not have official info about the flange distance to the film rails (or film gate distance). Nor about the lens flange focal length. My own measurements on one Hexar body and lens showed that the film gate had a thickness of .24mm and the lens a flange focal length distance of 27.71. On the basis of these measurements the flange to film rail distance is 27.76mm. These results are however no reliable enough to draw firm conclusions. What I do know from discussions with konica people is that their tolerances are wider than with leica and are choosen such that the best fit of Hexar body to hexar lenses is assured. The many inconclusive reports about problems or the lack of problems with fitting a leica lens on a Hexar body is partly to be explained by these tolerances and partly by the unreliability of the reports themselves. The Konica people at the factory told me that the Hexar is designed for use with the Hexanon lenses and t hat all dimensions inside the Hexar are based on that fact. If a hexar user fits a leica lens and he has problems, than it is caused by these different dimensions and/or the chain of tolerances add up unfavorably. If he has no problems: than he is plain lucky as the tolerances are such that they are close to what is expected for leica bodies and/or his demands are such that they are below the visibility threshold for the mismatch to show up. This is not the end of the story. People would expect quick solutions and fast answers and move on to the next topic. That is living in the fast and superficial lane of user group discussions. Serious research takes time and experience and dedication: scarce resources in a hasty world. ************************************** See what's new at http://www.aol.com