A Hood Solution for the 40mm Summicron-C


THE 40mm Summicron-C f/2, designed for the Leica CL, is  an excellent performer. It represents an efficient compromise between the 50mm and 35mm focal lengths, and is a true bargain, on the used market costing about a third to half the price of Summicrons in other focal lengths. For M-series cameras, the indexing lug on the lens mount can be filed down to bring up the 35mm viewfinder framelines, which in practice correspond well to the lens's actual field of view. The modification does not inhibit the CL's native 40mm frameline projection. Although Leica's official line on M-series mounting of this lens has been that focusing errors may occur due to its graduated rangefinder cam, I have not found this to be a problem in use, and the lens produces some of my sharpest slides.

One problem with the lens, however, is its hood. Originally the lenses came with dedicated folding rubber hoods, but now after about 25 years most have disintegrated; and their folding design has always made them less effective at protecting the lens from knocks than rigid hoods. I am told that Leica still has replacement hoods available (for about $50); however, the new hood still brings with it the old design flaws.  Some third parties sell metal hoods as alternatives, but be aware that many mount by cross-threading, as the 40-Summicron's 39mm thread does not have a standard pitch.

Another solution  involves filing down a Leica retaining ring (Leica part # 11251, available for about $10 from places like B&H, Pacific Rim Camera, and KEH), and fitting the current Leica rectangular hood for the 35mm f/2 Summicron (Leica part # 12526, about $63 new. Leica's round vented hood #12504 will also work: see the last paragraph below). Small grooves can be filed into the reduced ring that correspond to the spring-loaded clips on the 12526 hood, thus making it possible for the hood to clip on quite securely. With this setup, the lens is very well protected from stray light, and does not vignette even at its smallest apertures. The hood barely intrudes into the finder's field of view, even less than the original rubber hood. It also remains relatively compact and looks fabulous, without any evidence of bodge-jobbery, and no damage to the lens.

And now the standard warning: if you decide to try this yourself, do so at your own risk. Unless you're a total klutz, your lens won't be hurt, but the ring and/or hood might get botched if you proceed uncautiously. The process is actually quite simple, but I'll go into detail in case this is not the kind of work you are used to.


Below are some photos of how the key component, ring 11251, is adapted:


The filed-down ring, screwed tightly in place. The ring has a thread which matches that of the lens. Note the two grooves scored into the ring to accept the spring-loaded clips of the hood; there are two more on the opposite side. The ring must be filed down so that the hood fits snugly (but is not forced). Once the ring is the right size, use a black marker to cover up the shiny aluminum, and then fit the hood, pushing the mounting tabs in to keep the spring-loaded clips retracted. Once you have found the correct point of alignment for the hood, release the tabs and rotate the hood a little from side to side. This will leave marks on the ring which you can use as guides for filing the grooves. The grooves do not need to be deep, just recessed enough for the tabs to take hold. These grooves will keep the hood on, but will not hinder it from rotating; the snugness of your main filing job is what will do that.



The 11251 ring before and after filing. You don't need to file off very much--just a little bit more than is needed to get rid of any trace of the knurled grip and numbering. File only the side of the ring, not the front. Don't file the ring while it's on the lens! I would recommend using a hand-file rather than a Dremel, so things don't get instantly out of control. Keep rotating the ring as you file, using the remaining depth of the knurling as your guide to consistency. Once the knurling is gone, paint the circumference with a black marker and then keep filing evenly around the ring to remove the marker. Make sure also to keep your file level (or vertical, depending on your technique) so that the ring does not taper back-to front or vice-versa. Reapply marker as needed, and keep trying the ring in the hood to see how close you're getting. Be patient and methodical. The ring is properly fitted when you can slide it in while twisting the hood a little to help; don't force anything.  When you're done, use 600 wet-and-dry sandpaper to remove the heavier filing marks. The ring should slide all the way in until it butts up evenly with the interior retaining bevel; the filed-down surface will then no longer be visible (see next photo).



The filed 11251 ring  inserted into the back of the hood. Note the aligning tabs near my finger and thumb. These are designed to fix the hood in proper alignment on the 35mm f/2 ASPH Summicron, but for the 40mm they are vestigial. You can, however, use the white index line on either as a rough guide to lining up the hood with the centerline of the lens. Whichever tab ends up being on the bottom (your choice) will need to be sanded down slightly to clear the aperture ring and make sure the hood remains aligned parallel to the film plane.

One problem which emerges from this fitting is that the aperture ring can become slightly hard to grasp, as the hood's rear rim stands up higher. I addressed this problem by affixing a portion of a toothed rubber belt from an old flatbed scanner to the rear bevel of the aperture ring. First I glued the belt to a strip of thin leather using rubber contact cement, and then glued the leather to the lens using a water-soluble paper glue-stick; works like a charm, doesn't damage the finish, and looks like it always belonged there (see third photo above).


Using the #12504 Hood Instead

A rectangular hood is the optimum shape for shading a rectangular image, but a problem with the 12526 hood remains the fitting of filters. There is room for a filter to be placed inside the front of the 11251 ring, but there is no thread. For what it's worth, the12526 hood is supplied with a dedicated rectangular cap to keep out dust and light. If, however, you elect to use the now-discontinued hood #12504, originally designed for earlier versions of the 35mm f/1.4 Summilux and 35mm f/2 Summicron,  you can use a Series 7 filter, which mounts inside the hood. The vented part of the hood unscrews to reveal a retaining ring for the filter. Used hoods appear on eBay with some frequency.

Here are a couple of pictures of the same lens fitted with the 12504 (the green reflection in the first picture is from the filter):



All photos copyright Stephen H. A. Shepherd.  Return to my Photography Page.