marknorton Posted February 12, 2007 Share #1  Posted February 12, 2007 Advertisement (gone after registration) The standard filter solution for the WATE involves a 67mm step up ring and filter and is that size to avoid vignetting in the worse case which is when the lens is set to 16mm and used with film. Vignetting depends on the diameter of the filter and how far in front of the lens entrance pupil it sits. Make the filter smaller or move the filter forwards and you increase the level of vignetting.  My interest has been in looking at whether an IR filter glass could be incorporated into a modified lens hood so that we wouldn't have to use the filter ring which, as other users have pointed out, gets in the way of the viewfinder and rangefinder.  Leica have thoughtfully published the position of the entrance pupil of the lens in relation to the apex of the front lens element. The position moves as you change focal length and the lens element itself moves, so I was interested in looking a where a smaller filter would have to be mounted to avoid vignetting. The attached spreadsheet shows my results, film on the left, M8 on the right.  Leica WATE Vignetting.pdf  The first columns show 16mm with film, worst case, and the use of the 67mm filter which yields a glass diameter of about 62mm. The front of the filter has to be within 10.5mm of the reference point I chose and at 16mm focal length, the front lens element is 4mm in front of the same reference point, meaning that the spacing between the front lens element and the back of the filter (assume a 2mm filter glass) is less than 5mm. A negative clearance would let you experience the feeling of the front lens element breaking through the filter.  Switch to the M8 and we can use a smaller filter but where does it have to be positioned? The aperture in the lens hood is 46mm diameter. If we were to use this size of filter glass fixed inside the hood, a 51mm nominal filter, it would need to be positioned so that the back of the filter is no more than 4.3mm in front of the front lens element when the lens is set to 16mm.  The neck of the current lens hood is about 4mm. If Leica were to produce a hood with an extra 10mm length in the neck, fix a 46mm filter glass at the front of it, we'd have a lens hood with built in filter which, subject to testing, would not vignette on the M8. Link to post Share on other sites More sharing options...
Advertisement Posted February 12, 2007 Posted February 12, 2007 Hi marknorton, Take a look here WATE Filter Vignetting. I'm sure you'll find what you were looking for!
Englander Posted February 12, 2007 Share #2 Â Posted February 12, 2007 Boy, I hope they are listening. Your ideas are a great resource. Â Joe Link to post Share on other sites More sharing options...
stephengilbert Posted February 12, 2007 Share #3  Posted February 12, 2007 Mark,  I've mentioned SK Grimes before. I've bought two of their filter adapters over the years, one just recently. They make them to fit over the outside of the lens, held on by an O-ring that fits around the adapter. These have both been custom made, designed to fit the lens and hold a filter of my choice, the most recent being a 67mm filter for a Schneider 35mm Digitar lens.  It seems to me that they could make a similar item that would screw into the front threads of the Tri-Elmar and would allow the filter size and distance from the lens to be chosen by you.  They are quite knowledgeable and helpful. The most recent adapter they made for me cost $95. It was a custom part, made of black anodized aluminum. Here's an image of the part in brass: SK Grimes - New type Slip-on Filter Adapter  I will probably speak to them whenever I get my lens.  Good luck,  Steve Link to post Share on other sites More sharing options...
marknorton Posted February 12, 2007 Author Share #4 Â Posted February 12, 2007 I've sent them an email explaining the requirement. Link to post Share on other sites More sharing options...
albertknappmd Posted February 13, 2007 Share #5 Â Posted February 13, 2007 keep me in hte loop as well... Tehy just made a polarizer filter adaptor for me... A better version of the FILTERVIew system which is crap... They initially amde it in brass but could not anodyze it (it turned grey) so they are remaking the adaptors in high grade aluminium which will be anodyzed correctly. Anything they make for WATE should be in high grade aluminium or it will not blend in. Link to post Share on other sites More sharing options...
marknorton Posted February 13, 2007 Author Share #6 Â Posted February 13, 2007 One other thing I've noticed is that around the base of the red screw thread is a very thin rubber o-ring and it's this which causes the thread to tighten as it approaches the stop position. Once there, it stops the hood coming loose. Â Look at the rim of the hood and you can see an indentation all the way round where the o-ring is seated when the hood tightens down onto the lens. Â Not necessarily a bad design IMHO, but I do question how long the o-ring is going to last if you switch between the hood and the filter carrier several times a day. Â It's crystal clear to me that Leica have not thought through the day-to-day practicalities of using this lens in a world where "IR" and "486" loom large in our collective conscience. Link to post Share on other sites More sharing options...
ChrisC Posted February 13, 2007 Share #7 Â Posted February 13, 2007 Advertisement (gone after registration) Mark - You've obviously handled the lens a lot, have you actually bitten the bullet and purchased one? Link to post Share on other sites More sharing options...
marknorton Posted February 13, 2007 Author Share #8 Â Posted February 13, 2007 Yes, Chris, I bought one using the 30% discount. I'm pleased with the image quality and the handling of the lens and as I posted before, it's barely bigger than a 50mm Summilux ASPH. Â Leica need to sort out the filter attachment and the one-size-fits-all lens coding; I haven't got to the bottom of the mounting problem I had but I routinely mount it now with the lens set to minimum focus at which point the focus cam is not engaged. Link to post Share on other sites More sharing options...
ChrisC Posted February 13, 2007 Share #9 Â Posted February 13, 2007 Yes, Chris, I bought one using the 30% discount. I'm pleased with the image quality....... Â Mark - Quite a leap of faith for you given the as yet unresolved problems, I'm really glad you're pleased with the image quality. I have been trying to find out how the Frankenfinder works; did you buy it? If so, is it a zoom finder? How good is it for assessing the field of view e.g. for 21 mm on M8? If not the Frankenfinder, did you opt for the 21/24/28 Leica finder? Your feed-back would be greatly valued. Â ......................Chris Link to post Share on other sites More sharing options...
albertknappmd Posted February 15, 2007 Share #10 Â Posted February 15, 2007 I would consider having Leica design the lens hood to accept a slightly larger filter as there is a good chance that the M9 will be full frame. If they are going to go to the effort of making the new accessory, they might asw well make it for a true FF. Furthermore, the FF filter will be most useful to film users who like to shoot with filters as well. Finally, having the filter attached to teh lenws shade would obviate teh problem of the dreaded O-ring on the red ring of the WATE. Link to post Share on other sites More sharing options...
marknorton Posted February 15, 2007 Author Share #11 Â Posted February 15, 2007 Chris - yes a bit of a leap of faith but I wanted to be able to use the lens now. The Frankenfinder - great name - is much better in the reality than in the expectation. Clear, bright and the spirit level is a good idea. There is some barrel distortion which they admit to in the manual to keep the finder small. Well, relatively. The normal 21-24-28 finder is an alternative - I have both - but I like being able to see around the image, even with a 16mm lens. The FF is NOT a zooming finder, it has click stop and you see one frame or the other. Â Albert, at the moment, the lens and the hood do not accept any filters and the filter ring is used to mount filters if you want to. As my spreadhseet suggests, there's little scope for reducing the filter size when used with FF. If they went down to 60mm, it would have to be positioned less than 2mm in front of the front lens element to work and real-world filters will differ in thickness and mount design. Â If the M9 is indeed FF and still requires IR filters, we'll be back to using the filter adapter. In the meantime, we have the M8, it requires filters most, if not all, the time and because of the crop factor, there's scope for using a smaller filter in the lens hood. Link to post Share on other sites More sharing options...
albertknappmd Posted February 15, 2007 Share #12 Â Posted February 15, 2007 I agree fully. Link to post Share on other sites More sharing options...
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