[madison_wi_gal]

I had a pile of UV/polarizing/etc. filters for my old beloved ME Super (and Ricoh KR-5 before that), but in most cases are filters even necessary (for the average dSLR user) if you have a decent post processing app? If so, what are common use cases?

[bigdavephoto]

Generally speaking, no you do not need a filter on your lens.

But, depending on what you are shooting, filters come in handy. UV filters, no not really needed. Polarizers, yes, can come in handy on sunny days. ND filters, same thing. Can come in handy depending on subject and day.

[othar]

Polarizers are also usefull when you want to reduce reflections in windows or on water surfaces.

[35mmfilmfan]

You seem to have an enviable skill of asking controversial questions with an air of innocence - keep it up !! Many will say 'No, you need no filters, not even protective ones, as they will adversely affect the image', whilst others will take the opposing viewpoint 'Filters are cheaper to replace then lenses - filters at all times !' Circular polarisers and NDs are certainly worth using for the times they are needed, or various effects filters (though much of this can be done in PP), but UV filters are not considered necessary by many.

My own viewpoint is pretty much between the two camps - I tend to use UV or protective filters as a form of transparent screw-in lens cap, removing them in most situations, and leaving them attached in inclement weather - as rain on the lens will degrade the image in any case, I would rather have an inexpensive filter to wipe dry than the front element of a lens which may have cost me as much as £25.

For lens protection in other situations, a sturdy lens hood may well protect the lens against any damage in a situation where the lens could strike an unyielding surface, but I have been lucky enough not to test this theory myself. You may wish to perform tests to discover just how much image degradation occurs when using filters - if you do, please post the results.

[kypfer]

If you're in a particularly hostile environment … motorcycle scrambles, seaside/beach, just filthy weather, a piece of glass that can be wiped clean of dust, grit and spray without risking damage to the underlying lens can be at least reassuring, but only leave it on for as long as necessary
Other than that, ND, polarizing (and infra-red, if you're interested) are what I carry for use when needed for effect.
I've proved to my own satisfaction that some UV/Skylight filters do cause unwanted flaring/reflections on some lenses under some conditions.
For "protection", from impact and stray light, I invariably fit a lens hood, usually the dedicated bayonet-fit unit which lives reverse mounted on the lens when it's in the bag, but any hood that's not so long as to cause vignetting is better than none at all!

[rogerstg]

I had a pile of UV/polarizing/etc. filters for my old beloved ME Super (and Ricoh KR-5 before that), but in most cases are filters even necessary (for the average dSLR user) if you have a decent post processing app?

FWIW, a UV filter is not needed with digital because the sensor has a UV filter. The effects of a polarizer are difficult to impossible to duplicate in post, so a CPL is still a good idea.

Regarding protection: when dslrs came into widespread use, lots of "protection filters" were sold by camera sales staff to unsuspecting customers, which increased profit margins. They used the straw man fallacy that it's cheaper than replacing a lens. Regarding impact damage, tests have shown that filters are very fragile compared with the front lens element and does little to protect the lens from functional damage. The filter might protect the lens's filter threads from being dented, or the front element from being scratched. Dented threads are inexpensively fixed, and scratches are easily mitigated with black shoe polish. Ironically, the shards from the filter might cause scratches to the lens element that the impact object would not have. At worst, replacing a front element is still not close to the cost of replacing the lens. People incorrectly assume that if they've shattered a filter, it protected the lens from ruination.

Personally, I have a few protection filters for lenses I would use in circumstances outlined by kypfer, mainly for speed of cleaning while shooting in extreme conditions. The cost of outfitting all my lenses with high quality protection filters would exceed the cost of several lenses.

[madison_wi_gal]

You seem to have an enviable skill of asking controversial questions with an air of innocence - keep it up!!

Not intentional, or at least not conscious of that, but with the acquisition of the K3 III I decided I ought to get my ~money's worth and use it properly (whatever that means, and I'm sure there are a lot of different definitions of "proper"). I brought up the filter thing mostly due to getting the 40 XS for my eBay Bumblebee and wondering if I needed to go get an itty (27mm) filter for it, which led to "well, if I am buying a filter the THAT do I need to go get some others for the LBA collection"?

I am having a blast with taking new (and old) DNGs and running them through DxO and DCU and a few others I am trying (no Adobe), and realized that all the stuff that I used to do with some specialty filters (I had a complete set of Cokins for my ME Super) I could probably do in PP.

---------- Post added 05-24-22 at 17:59 ----------

Polarizers are also usefull when you want to reduce reflections in windows or on water surfaces.

Ahh, thanks! I forgot about that usage.

[kypfer]

Not intentional, or at least not conscious of that, but with the acquisition of the K3 III I decided I ought to get my ~money's worth and use it properly (whatever that means, and I'm sure there are a lot of different definitions of "proper"). I brought up the filter thing mostly due to getting the 40 XS for my eBay Bumblebee and wondering if I needed to go get an itty (27mm) filter for it

FWIW, I use an old 27mm screw-in filter holder with the glass removed on my 40mm XS, both as a short lens hood (paint the inside surface matt black) and for mechanical protection of the rather exposed front element … it has the advantage of taking the original lens cap, so it's fitted permanently, but only increases the thickness of the lens by about 5mm

[ramseybuckeye]

I also proved to myself the problems of a UV filter several years ago. I think the filter had a defect, but it was a good example of extra glass that was the opposite of constructive.

[clackers]

I own complete sets of polarizing and ND filters, but of course have slung any UV filters into the nearest bin.

A cap does a so much better job of protecting a lens from knocks and drops. It's what it was designed for.

[Paul the Sunman]

I also proved to myself the problems of a UV filter several years ago. I think the filter had a defect, but it was a good example of extra glass that was the opposite of constructive.

Same with me. I couldn't figure out why I was getting diagonal striations in the bokeh with my DA 55-300. It was driving me crazy. Eventually discovered it was a dodgy UV filter. I never use them any more.

[Wheatfield]

I had a pile of UV/polarizing/etc. filters for my old beloved ME Super (and Ricoh KR-5 before that), but in most cases are filters even necessary (for the average dSLR user) if you have a decent post processing app? If so, what are common use cases?

I don't use "protective" filters, but I also am not putting my gear into conditions where that sort of mechanical protection is needed. I was hired to do some promo shots in a steel mill one time. I was doing some of the shooting near the furnaces. I put protective filters on my lenses for that.
The only filters I use these days are neutral density and polarizers as they are about the only ones that can't be emulated in post processing.

[madison_wi_gal]

The only filters I use these days are neutral density and polarizers as they are about the only ones that can't be emulated in post processing.

OK, that was what I was getting at, thanks!

[mikesbike]

If a protective filter is to be used, it should be of top quality, being multi-coated as is your lens itself. This will minimize or eliminate any negative effects it might impose. I have taken numerous shots with a high-quality protective filter installed and not installed, shooting the exact same scene under the same lighting, and under varying sometimes challenging lighting conditions, and have not been able to detect negative effects from the filter. But I do believe there could be some conditions where the presence of the filter might possibly make an already negative aspect come out worse.

I sometimes use one on certain lenses, while rarely use one on others. Some of my fine lenses with which I never use such a filter I also never expose to conditions where such a filter might be needed. I use another lens instead, and with the filter. There are some potentially damaging conditions where I will always use one- like blowing sand on a windy day, for example. Not all of my lenses have a protective Pentax SP coating, but I do have high-quality protective filters having such coatings, and will employ them where such a need might exist. However, a multi or super multi-coated filter, and those also having SP style coatings, are not cheap!

[pres589]

I'd rather clean a UV filter than a lens front element. I use them on basically everything. I know I'm going against the grain on this and I don't care. I will say that mikebike's statement about buying really good filters is something I agree with.