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There have been some comments and questions in the RX10/etc threads about lens hoods and filters, pros and cons of using protective UV for example. Over the years I've done many tests and used hundreds of lens types, and also (probably) hundreds of filters though my best UVs have survived over 30 years. My worst UVs have lasted a day. I generally don't use any lens long-term, outside the studio, without a permanently fitted filter. Today you can buy filters such as Sigma DG (which in comparison tests I've done prove to be equal best with the very top level Hoya Pro 1 Digital or best B+W MC but at much lower cost). These now have nanocrystal type lens coating which is extremely hard and can be cleaned vigorously without destroying the coating, and also rejects water. I've bought several lenses recently which should have been perfect but with their relatively soft front element glass and fragile coating have been ruined by past owners cleaning them. The filter also protects against atmospheric film deposition - this is for example when you are in a Las Vegas casino, the last bastion of heavy smoking, or shooing in Beijing smog, or at a fire. Even in your own home you'll get this (try cleaning some paintwork after it's been around ten years, especially anywhere near your kitchen). Every time you overheat some oil or burn the toast, you send particles and oils into the air, and glass loves them. As my kitchen windows tell me... So, let this land on your filter and not on your lens front element. There is a myth that small marks and scratches on a lens don't show in the image and do not matter. This may be true if the lens is a 50mm f/1.4 or a 300mm f/2.8, but it certainly is not the case with standard and superzooms, and retrofocus wide-angles (rangefinder wides are less affected). With a typical 20mm wide angle or the 24mm end of a zoom, the surface of the front element can be softly resolved by f/8 and may show sharp details at f/16. Of course the same applies to a filter in front of the lens. But if you get a scratch or a chip (the worst type of damage even if it's a tiny sub-mm point) on the lens it is there for good. Solutions like filling the chip with permanent marker ink might be a way to repair a valuable lens sold to you damaged for a fraction of its mint value. That was the loss the previous owner accepted by not using a filter. You can do nothing about fisheyes, 14-24mm Nikkors, 12-24mm Sigmas, etc - except use them with great care and guard those vulnerable front elements. You also need to be really careful with the rear elements of RF and mirrorless wide angles. I received one with a fingerprint on it I didn't spot, ran some test shots and thought my sensor must have a fingerprint - help! No, it was the rear element, and that mark was 'projected' with surprisingly clarity. UV filters are a potential danger to all your shots, mostly because so many are very poor. Hoya's output is graded; even within the Hoya brand, there are levels of planar accuracy (the more you pay, the better the filter) and the sub-brands of Marumi (moderate good) and Kenko (cheap and cheerful) also have standard and superior ranges. New Chinese filter brands using Hoya glass also vary but it's really hard to find out what's good. I've tested many filters in the way which reveals their flaws - a standard to long focal length used at a medium aperture on a distant detailed target, on a day free from haze (or an indoor substitute). The worst filters show patches of blurring, even plain protectors and UVs can reverse all the resolution benefits you've paid for in that Zeiss manual focus special lens. Polarisers are actually the worst culprits and very few have good optical properties - they also deteriorate with age. Lens hoods - again I always use if possible. The modern petal lens hoods with cutaways are far more effective than old shorter 'round' ones but my favourites are full metal rectangular hoods I've found in vintage gear bins - a Konica one for 28mm, a Minolta for 35mm, clamp-on. I actually use the 35mm one on a 28mm lens without cut-off and it is 100% effective, there's no image area projected into the camera significantly outside the frame, and it is also black flock lined. Since having a filter fitted can only increase flare, no matter how well it is coated, I always use a hood when there is a filter fitted. It's also worth temporarily removing the filter, when conditions allow, for the best results - but never a good idea to do without your lens hood. On the RX10 (one of the cameras mentioned) the front element is very large and needs to be kept absolute pristine (the design of the lens means it can be brought slightly into focus). The lens shade is reversible, the lens allows a normal slimline filter without vignetting, and mine has a 62mm Sigma DG. The hood is taken off only for wide-angle flash shots with the built-in flash. On the RX100 I purchased the third-party filter adaptor kit with lens cap, which goes over the shutter-type cap (fragile) of the camera. Sony now has this as an official accessory, a rare example of them buying in an independent design. I can fit a filter, but for this camera I don't bother, as I always turn it off between shots and the lens is covered. I can also fit a lens hood but also don't as it defeats the pocketability. The arguments against fitting a filter are not very sound because you can always remove the filter as needed. I also always use lens caps, over the filter. I don't use a filter to protect the lens the way a cap does. I do use a cap to keep the filter perfectly clean. Recently, I shot a set of pix without realising my filter had been hit by sea spray and then dried, and the electronic viewfinder was not a clear enough viewing method to alert me. The pictures were degraded, not entirely ruined, except for some in backlight which were 'delete' fodder only. The filter was easily cleaned. That would not have been the case with a lens... Discuss :-)