Archived posting to the Leica Users Group, 2008/11/21
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I have asked Leica this question and didn't get an answer. I can offer the following evidence: 1. I took a 1974 version II 35/2 M lens that a friend had wrecked. I demolished it further. I cut the elements in half and took sections from it that I looked at by electron microscopy. It was multicoated on both surfaces of the front and back elements. I did not cut the other elements because the process is fairly time consuming and expensive. 2. Reflectance and absorption spectrometry tells me that the coatings on my type 1 f1 (58mm filter thread) Noctilux, my late 1980s 75 Summilux and my early 2000s 35/1.4 asph have different types of coating. This suggests that not only are Leica lenses multi-coated, but that Leica has upgraded their coating incrementally since they introduced it. What we can assume is that the optical performance and in particular the flare resistance that we see means that the front and back elements of Leica lenses made after about 1975 or so are multicoated. About the internal surfaces we can be less sure - manufacturers will single coat these wherever possible to save on manufacturing costs. One confounding fact is that multi-coating is easy to retro-fit, so I am assuming out 35/2 was multicoated when made, not later on. This all makes sense - we would see vastly more flare if these lenses were not multi-coated on at least the front surfaces. But I think how many times has the type of coating changed? and on what lenses and to which surfaces is multicoating applied? are interesting questions that can tell us a lot about why our lenses behave as they do. I have long suspected single coating of internal elements for being at least partly responsible for the flare problems I've had with a succession of six-element 50mm Summicron Ms. >If not? By now I'd have scored/scratched the surfaces of many a Leica lens >while cleaning with my under shorts as the cleaning cloth! :-) This isn't a good benchmark, unfortunately - until recent very hard coatings were available, many types of optical glass were harder than multicoating. >Multi-coating protects lenses from being scratched? How wonderful! (If >only it were true.) Modern hard multicoating (with a lot of flouride in the coating layer) does protect lenses from being scratched, quite effectively. The coatings on modern Leica lenses are a couple of orders of magnitude more scratch resistant than the glass that they typically cover. >If the green and magenta reflections are any indication Unfortunately this is no indication; it indicates that coating is present, but not if it is multi- or single-coated. The reflections are too influenced by the elements below in an assembled lens to draw many conclusions from them. You need to examine the elements individually and even then you can't draw too many conclusions. >I would consider the presence of the green and magenta reflections pretty >good evidence of multi-coating, in fact, proof. Unfortunately not - Nikon multi-coating fairly reliably reflects green, but the Leica 35/2 which we examined, which was definitely multicoated, showed no coloured reflections. >Guys get real!! Who the hell cares about this stuff and knowing it or not >knowing. Does it make for a better photograph? Multicoating has made more of a practical difference for 35mm photography than almost any technical advance in the last 50 years. The flare resistance we see today, to which tonality, resolution are linked, providing the flexibility to which you have become accostomed, are all derived from good multi-coating. Ted, the photo of yours in the FOMII book could not have been taken without coating. All you would have got was a frame washed out by flare. Single coating helped us, but multicoating, in some ways, made small format photography what it is. Even if you don't care about it, multicoating is helping you wherever it is present. If Leica won't tell you and you really want to know, you can send your lenses to me for a definitive answer derived from destruction testing ;-) Marty Gallery: http://gallery.leica-users.org/v/freakscene -- Be Yourself @ mail.com! Choose From 200+ Email Addresses Get a Free Account at www.mail.com