[Technosavant]

Well, the K100D with both the DA 18-55 and 50-200 lenses arrived today. I'm brand-spankin' new to the DSLR world, and I am rapidly realizing that what I had learned about equipment from my 35mm days is largely obsolete. While in the past, I would put a UV filter on just about every lens, I have seen things that indicate this is not necessary in the digital world (unless I just wanted the extra protection), since there is no film to fog.

So, I ask this: what filters, if any, are absolutely necessary? Not just very useful, but "beware pulling the lens cap off without one" necessary. I think a circular polarizer is likely in my future, but I have to make a trip to the local shops to pick up a smaller camera bag (the one I have is just far too large), and I just want to know if I need to grab anything else while I'm there.

I'm almost afraid to ask, because I don't really want to buy huge selections of filters, but neither do I want to hose anything right out of the gate. I did try to search, but basically only found the ongoing debate about using the UV filter solely for lens protection (looks to be good arguments on both sides there).

[Jonas B]

What filters can not be emulated in software?
Basically three: Graduaded and Neutral Grey, Polarizer and Star filter.

Star filters can be emulated to a degree (maybe better now than two years ago or so when I tried it) and it's very possible that you don't use them at all. That levaes us with the two other.

Graduated neutral grey is sometimes the only way to get a landscape, or buildings against the horizont without blowing the sky. The alternative is either to try to fix it from a raw file but it often leaves you with noise and less pleasing shadows, or make a composite from two different exposures. Works most often but still a graduated grey is the way to go in many situations. But, it isn't absolute necessary.

So, the sibling: A neutral grey is good to have when you need longer exposure times (waterfalls ?) or when ISO 100 or ISO 200 and 1/4000 is too much light for large aperture openings. A neutral grey is imho a good thing to have.

Finally, the polarizer. It is just necessary in situations where you need to avoid reflections. There is no way whatsoever in software to bring out what that was under the water surface, or to give that natural look of things where reflections are evil.

Something like that, others will chime in I'm sure.

For the UV protective thing... Well, I'm all for the UV-filters in 99% of all situations. I very much prefer to clean the UV-filter from salt spray compared to repeatedly clean the front lens element. I once tried to make it all clear to myself here:
Home Test: UV-filters - good or bad?: Pentax SLR Talk Forum: Digital Photography Review
I still have to get any sensible and thoughtful reply on that one telling me that the filters will ruin my life. Oh yes, we are all told from time to time that this will happen, but I say: check it with your lenses and find out.

regards,

[joele]

No filters are necessary... Some of us use protective (hopefully high end ones) filters on our more expensive lenses, others don't.. But nothing is really needed.. I use B+W MRC UV on my DA21, FA35, FA50 and F*300 as replacing them in Australia is darn near impossible at the moment (or at least rather expensive US import)...

A circ-pol is usefull to have mainly for cutting reflections.. ND filters can be usefull too, say if you want to really slow down the shutter speed a lot, for say a waterfall..

[Evolution]

I'll second B+W MRC UV filters. I've used them on my previous Canon and Minolta lenses with great results. They've never caused any degredation in image quality (as far as I can tell), and they are very easy to clean... just some water and dish soap. They're a bit pricier than some other filters, but why would you want to put some cheap piece of glass in front of a considerably more expensive lens?

[SpecialK]

Here's a link to a rather long thread that about covers all ranges of filter-use opinions.

Filter recommendation - Digital Camera Resource Page - Forums

I've asked this before and it has not been answered yet...

If we can get a single piece of optically flat and clear multicoated glass (i.e., a filter) with only a mounting ring as the other part for say $100, then why does a stabilized 18-200 lens with many elements all having been ground to precise curvatures and assembled into an optically sharp system with many moving parts such as diaphragm and barrel mechanism including some type of motorized focusing and stabilization system only cost 10 times as much?

Sounds like the lens is cheap by comparison :-0