My 7-14 takes filters ... at the rear end

OK. So here's the "how to" post I promised.

First, a brief background for those who haven't followed prior threads on this and related subjects:

The reason I became interested in using filters with the Panasonic 7-14/4 was that a filter eventually turned out to be the solution to the problem with purple flare plaguing this lens when used on the E-M5 (and probably at least some other Olympus bodies as well). As shown here, a Kodak Wratten 2A pretty much eliminates the purple color, thus making the flare far less visible than it would otherwise be (and no worse than when the lens is used on a Panasonic body).

The reason why the problem is there with at least some Olympus bodies and not with Panasonic bodies is that a) the antireflective coatings on at least some of the lens elements of the 7-14 do not fully remove reflections close to the border between ultraviolet and violet and b) the on-sensor UV-filter on the E-M5, unlike that in most/all Panasonic bodies, does not eliminate these wavelengths. The Wratten 2A, which is effectively a strong UV filter, does eliminate them and thus solves the problem.

Now, one practical solution to the problem of using such a filter with the 7-14, and the one I tried first, is simply to attach a Wratten 2A gel filter to the rear baffle by means of double-sided tape. This works just fine in my experience, provided that the tape is thin so that the filter does not protrude too far to the rear and thus risks coming into contact with the area surrounding the sensor inside the body.

However, in the process of investigating various potential solutions, I discovered that one MFT lens, the Panasonic 8 mm fisheye, did have a holder for gel filters behind its rearmost element. Thanks to the measurements and images provided by Mjankor here I could establish that this holder would probably fit the 7-14 as well. This would of course be a neater solution and would additionally make it possible to use filters other than the 2A as well, e.g., an ND filter or an IR filter. For those interested, gel filters are available from (under Kodak's brand name). Edmund Opticseven offers polarizing filters in gel form but you would of course encounter certain difficulties in rotating the piece of gel for best effect.

After some further research, I found out that the part I would need, i.e., the filter holder itself, the baffle to which it is attached, and the three screws holding the two parts together, was available as a spare part with part number VXQ1911. Regrettably, the price if I were to order it from Panasonic's service outlet in Sweden would be pretty high (about 60 USD without shipping and 70 with). In the US, it is available from Cumberland Electronics as well as from the Panasonic Service and Technology Company for about USD 20. Shipping is only about USD 10 if you are in the US but to get it to me in Sweden would cost about 40 from the first source and about 100 from the second. Fortunately, Optical1 was kind enough to help out by buying the part for me and forwarding it to Sweden.¨

Now to the question of how to mount the baffle-holder assembly once you have it. You begin of course by removing the three screws holding the original baffle to the mount. Just make sure you have a screw-driver that really fit the screws so that you don't destroy them. In the image below, I have already removed them so that the baffle can simply be lifted off.

This is what the rear end of the lens looks like after removing the baffle. Note in particular the three little "wings" on the ring around the rearmost lens element. These are probably handles to be used for tightening and untightening that ring.

Here is the original baffle seen from the back. Note that is constructed so as to provide room for the three "wings" inside the baffle.

Now let's look at the baffle-holder assembly from the back. As you can see, it does not leave room for the three wings in the same way as the baffle originally designed for the 7-14. There is an inner ring, that protrudes half a mm or so (upwards in this picture) from the broader platform surrounding it. This means that the baffle-holder assembly will land on the "wings" surrounding the rearmost element rather than on the mount when you try to put it in place. Consequently, you would put considerable tension on the plastic if you were to tighten the screws.

To resolve this problem, you need to insert a shim of some kind between the mount and the baffle-holder assembly. Ordinary washers are unlikely to work well for this purpose since the risk that they would fall down into the innards of the lens when mounting or dismounting the baffle-holder assembly would be extremely high. So I looked for another solution.

I considered using tape but found the idea a bit messy, particularly since several layers would probably be needed. Eventually, it struck me that the kind of plastic used in certain product packages would probably fit the bill. The kind of package I have in mind is the one where there is a piece of printed cardboard at the back, the product inbetween, and clear plastic on top so that you can see the product itself as the package hangs on its hook in the shop.

I eventually thought that two layers of plastic might be needed. But since you effectively make the plastic a bit thicker around the holes for the screws when you make them (I used a pretty thick needle for that purpose) one turned out to provide enough cushioning that I dared to tighten the screws fully whereas two turned out to be a bit too much. Obviously, I tried to find the thickest plastic available from the packages I happened to have laying around. In the picture below, you can see what my home-made shim looks like when put in place.

Now all that is left is to put the baffle-holder assembly in place, reinsert the screws, and tighten them. For reasons spelled out above, the baffle-holder assembly will of course protrude slightly further backwards, into the camera body, than it is meant to. However, the discrepancy is small (about half a mm or so) and does not give rise to any problem when mounting the lens on either of my two bodies (E-M5 and G1).