...that is the question I'm frequently asked during workshops and tuition sessions, and it came up in discussion on Facebook the other day - "Do you use protective filters?"
An example of a good filter, the Hoya Pro1 Digital UV.
It's the one main area that I'm in disagreement with most camera shops, who will generally advise a customer to buy a UV, Skylight or protective filter to protect the lens they've just chosen. The theory goes that if you're going to damage anything, it's better to scratch or break a relatively cheap filter, than your expensive lens. However, I think there's a better way to protect your lens, which serves another valuable service, and has no chance of reducing image quality. Use a Lens Hood.
Why not use a filter? Well, for a start, the lenses themselves, including the coatings on the glass, are tougher than you might think, and even if they do get scratched, it's unlikely to have any noticeable effect on your images, although you may be a tad upset. To see how tough some lenses are, just have a look at this video...
Now imagine there had been a filter on that lens.
The second reason for not using a filter, or at least any old filter, is the potentially detrimental affect it may have on your photos. Luckily, LensTip.com have tested various UV filters to see how good they are, looking at flare, light transmission and vignetting. The worst filter loses you around 10% of the light coming into your lens, completely ruins any contrast that may have been there, and has very uneven transmission too.
The best filter 'only' loses 3% of the light, and has no obvious flare or vignetting. This is what you'd go for (hopefully) if you insist on using a filter for protection. I'd still only use this in hostile environments such as the beach (lots of sand blowing about). I'd still use the lens hood too.
It's sometimes argued that if you've only got a cheap 'kit' lens, then there's no point spending a fortune on a filter, so just a cheap one will do, but from the above, we can see how much that could degrade the image quality of what is probably already a fairly mediocre lens. I say forego the filter, and splash out £50 or so on a secondhand kit lens if the need arises, which it probably won't.
Now, camera shops may be a bit miffed at me saying you shouldn't automatically buy a filter - these extras all help with profits, and I wouldn't want to dent them. But note that I'm saying you should definitely use a lens hood, and these days it's rare for one to be included with kit lenses (Pentax are usually an exception to this, apart from their very budget DAL lenses), so instead of saying "...and now you need a filter...", they could say "I can thoroughly recommend getting a lens hood, not only does it shade the front of the lens reducing flare and giving better contrast, but it also protects the front of your lens from knocks and scrapes. Now, do you go to the beach often...?"
Agree? Disagree? Let me know!