I've just bought a 67mm Hoya circular polariser (Hoya 67mm Pro1 Digital Circular Polarising Filter) for my Canon lens (70-200), but the polariser is quite thin so the snap on lens cover doesn't stay on as well as it does without the polariser attached and dust somehow manages to get onto the lens with the cap on.
Does anyone know if you can buy a cap specifically for Hoya polarisers, or if you can buy a (67mm) screw-on lens cap anywhere?
To bobflannigon. I have a variety of Canon lenses, including the 70 - 200mm L series f2.8 IS lens and fortunately have not had the trouble that you have had. What I wonder is (and no doubt you have already done so) have you tried exchanging lens caps between other lenses of the same size? provided, of course that they are all Canon lenses. On my Canon 16 -35mm lens, I have a top-of-the range professional Hoya 82mmų circular polarising filter (like yours) which is even thinner so as to prevent vignetting at the widest angle setting, but the lens cap does stay in place. However, you will find that even when the lens cap does stay in place, there will always be an ingress of a certain amount of dust, because the lens cap is not an airtight fit. This dust is usually extremely fine and light and non abrasive and is easily removed with a soft lens brush and blower without doing any damage. The lens brush is something that you should always carry with you and use rather than a lens tissue or cloth. Because, of course, filters (like both you and I have) screw into the front ring of their respective lenses, the lenses themselves keep reasonably dust free, but even then, sometimes dust will find its way in. The lenses that I have bought for my Canon cameras are all L series, and these come with their own (in the case of the 70 - 200mm it's a sturdy zip-up case) soft cylindrical pouches with a rugged circular base at one end, and a draw string at the other. The benefit of these coverings is that they are such a good fit that they keep the lens caps in place, so possibly that is something you could try to get (or maybe try a resealable plastic bag of the type used for holding food in freezers). Also, I have seen lens caps made by an independent manufacturer which have an attachment to secure the cap to its lens, which has the advantage, of course that the cap is less likely to get lost. I have to admit, that I do have the bad habit of putting lens caps down somewhere and not being able to find them! One thing to beware of with lens cleaning cloths, is that they can become contaminated with abrasive dust so always use the brush first. Tissues have the advantage that they are disposable but again, brush first. There is a first class blower made by Giottos. Again, it pays to buy a good quality item because I have found in the past that some of the cheaper ones have the puffer part made of an ordinary rubber which perishes in time. Murphy's law states that this will always happen after it has not been used for a while, and the first time you are out on a shoot.........! Apple retail a "Macbook Cleaning Kit" called "KeepitClean". It is not cheap but is supplied in a generous 200ml size spray bottle (I think mine cost me around £12.00) is also antibacterial, which, of course will help to keep such things as organic moulds at bay and comes complete with a microfibre cloth. It is made primarily for Apple screens and casings and I have found it to be optically perfect and smear free. Again brush first, spray the liquid onto the cloth and apply to the filter that way. I have not checked on the Amazon sites, but there is of course the possibility of getting something suitable there. Do not spray the liquid directly onto the optical surface first. Regarding the lens caps that I mentioned earlier, I suggest that you try a Jessops store if you have one near you if you cannot find anything on Amazon or in the Amazon Marketplace. I'm sorry to have been a bit long-winded and if I can be of any help to you, my e-mail address is firstname.lastname@example.org, Cheers, David Hodder. (I just prefer to be called David). As an after thought, I have not checked very closely, but it could be possible that some lens caps I have seen fit over the outside of the lens/filter, just in the same way that a round tin lid fits on a cylindrical tin, and are made of a soft strong pliable material so that they are a snug fit and don't slip off or damage the lens.