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05-05-2011, 05:25 AM   #1
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Is a filter ever a good idea?

I've noticed that a lot of people say not to use a filter. Is there ever a time that using a filter is recommended? Don't they help with the glare from water etc.?

Thanks!

05-05-2011, 05:36 AM   #2
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UV/clear filters - Around salt water or in very dusty & windy conditions, yes. Salt water is very corrosive and sprays everywhere, not to mention the fact that is present in just the moisture in the air that you can't see. Same with the dust, except that it's more abrasive than corrosive. Otherwise, I don't use one. In fact, I've yet to purchase a 77mm clear filter for my 16-50/70-200.

Polarizers and NDs - As the lighting situation requires it, yes, absolutely. NDs will block light through either part or all of the frame, and polarizers will reduce glare, saturate colors, and act as a mild ND.
05-05-2011, 05:41 AM   #3
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QuoteOriginally posted by mom2mny Quote
I've noticed that a lot of people say not to use a filter. Is there ever a time that using a filter is recommended? Don't they help with the glare from water etc.?

Thanks!
Well, some filters are designed to purpose for achieving particular effects. For instance, various color filters will allow you to achieve different effects when doing B&W photography (though this can be emulated digitally now). Polarizing filters can allow you to cut through reflections on water/glass/etc. as well as deepen the color of the sky when facing in the right directions. Neutral density (ND) filters give you the ability to take long exposures even during the daytime (useful for keeping the shutter open long enough to achieve a fog-like appearance for moving water). Graduated ND filters help you to compress the dynamic range of a scene so that your camera's sensor can capture it all (the top of the filter will let less light in than the bottom half, so you would position it such that the sky has most of its light blocked, while the landscape below does not, for instance). Probably there are other effects filters of value that I don't know about, but these are the ones to come to mind.

To get more to the heart of your question, though, a lot of people say you shouldn't use filters because they degrade optical quality. Almost exclusively they are talking about UV or Skylight "filters", which do not enhance your images in any way despite dubious claims in their marketing. These are primarily marketed as protection devices, to create a barrier between the harshness of the world and the delicate front element of your lens. The value of their use is a highly divisive topic -- it is true they can degrade optical quality because you are adding an additional piece of glass that can diffract and reflect light... Your images may appear measurably less contrasty, less sharp, and may be more prone to exhibiting flare, depending on both the lens you're using and the filter. However, except with the very worst filters, these degradations of image quality are very hard to notice, though allegedly you can notice it with some severe pixel peeping no matter how nice your filter is.

If you are looking into getting a protective filter, the question is whether you are comfortable losing 2-3% of image quality off the top (potentially). Even if you do decide to use one, you're not obligated to use it all the time. There are plenty of places where it just makes good sense to protect the lens, even if you normally wouldn't bother -- on the beach, in high winds with particulate, around smoke or other acrid vapors, or anywhere else you might expect shit to fly through the air at your camera.
05-05-2011, 05:42 AM - 1 Like   #4
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QuoteOriginally posted by mom2mny Quote
I've noticed that a lot of people say not to use a filter. Is there ever a time that using a filter is recommended? Don't they help with the glare from water etc.?

Thanks!
Filters are a Highly debated topic,

I personally am all for using filters;
UV filters for day to day use, as it protects the lens and also reduces haze.
Polarizing filters are the ones that reduce reflections and make colours more vibrant, these are also near impossible to replicate with software (as far as I am aware).
Neutral density are block some of the light allowing longer exposures at higher apertures. eg to smooth out running water in bright situations.

There are heaps of different filters depending on what effects you trying to achieve.

On the other hand people believe that they reduce image quality to much. matter of personal taste.

Hope this helps clarify things a little.

Cheers

05-05-2011, 05:47 AM   #5
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The thought that a filter is never a good idea is based on the idea that you've got a big bucks, multicoated (or SMC) lens (read as fancy piece of glass) hanging on the pointy side of your camera now. Do you really want to put a cheap piecve of glass (read as filter) in front of it to shoot through?
A lot of people (me included) put a UV(O) filter on their lenses for protection. A lens hood is better protection for most situations (except for blowing sand or similar). One time to save money, I bought a UV(N) filter. I finally got an answer from a filter professional that the (N) designation means non optical glass and the (O) means optical glass. (I bought a new UV(O) immediately).
The reality is that any UV filter is meant to block excessive UV light which doesn't happen until you are way up in the atmosphere. If you're climbing Mount Everest, you need a UV(O), otherwise no.
There are other specialized filters that for the most part are made redundant by Digital Photography and processing.
There are several other filters that are still useful. A Polarizer's effects can not be duplicated in post processing (that I'm aware of). It is the filter that helps control the glare as you mentioned. Also a Neutral Density filter provides a useful function of cutting back on the amount of light hitting the lens to allow slower shutter speeds. I still like Graduated Neutral Density which allows you to darken a part of a picture (usually a too bright sky). This can be duplicated in post processing, but it is just more natural to do it when taking the photo.

So, to directly answer your question, it depends.

(boy, I'm long winded today).
05-05-2011, 09:09 AM   #6
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All the above are quite right. Physical filters have their places in digital photography:

* UV filter for extremely high elevations; otherwise, they mostly protect the finances of whomever sold you one.
* UV or Skylight filters for protection in harsh environments, although Skylights affect color balance slightly.

* Neutral density (ND) filters for longer exposures; strong ND's can effectively remove movement from photos.
* Polarizing (PL and CPL) filters to reduce glare and reflexions, add contrast to skies, and increase saturation.
* Close-up (CU) 'filters', +dioptre meniscus lenses for fast easy cheap close-up work and softening effects.
* Graduated ND and Split CU filters, to apply effects to just half the image; a GND makes better exposures of bright skies and darker foregrounds; a SCU effectively thickens DOF.

Other filters have more limited, specialized applications:

* IR-pass filters for blocking visible light and shooting in infrared
* Red (#25) filter to slightly increase detail when shooting B&W
* Light blue (80A, 81A) filter to emulate earliest B&W photo emulsions
* Yellow (K2) filter for nifty color effects with glaring neon lights at night

Virtually all other filter effects can be achieved digitally in-camera or in post-processing. Exceptions: optical adapters, such as corrected close-up, fisheye, wide, and tele screw-in / strap-on lenses. Also, spectrum-slicing filters are used in scientific and forensic work, to 'see' just narrow slices of the EMF spectrum of (in)visible light.

That's the overview. I should write a book.

Last edited by RioRico; 05-05-2011 at 09:15 AM.
05-05-2011, 09:25 AM   #7
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Some uses not mentioned so far: protection from dog noses and childrens fingers.

Some examples of filter usage, starting with getting a deep blue sky using a polarizer filter:



A Hoya R72 filter filters out visible light and lets in infra-red:



Hawaiian vacation boat tour, avoiding salt spray:

05-05-2011, 09:52 AM   #8
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QuoteOriginally posted by Just1MoreDave Quote
A Hoya R72 filter filters out visible light and lets in infra-red:
Is that photo just an R72 mounted on a standard DSLR or has the camera been adapted for IR?

05-05-2011, 09:59 AM   #9
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QuoteOriginally posted by Just1MoreDave Quote
Some uses not mentioned so far: protection from dog noses and childrens fingers.

Some examples of filter usage, starting with getting a deep blue sky using a polarizer filter:



A Hoya R72 filter filters out visible light and lets in infra-red:



Hawaiian vacation boat tour, avoiding salt spray:
May I ask is it possible not to use filter but get the same effect by PP?
05-05-2011, 11:10 AM - 1 Like   #10
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QuoteOriginally posted by calicojack Quote
Is that photo just an R72 mounted on a standard DSLR or has the camera been adapted for IR?
I used a regular unmodified K-7. The lens was the FA 35mm f2 at f8, ISO 100 and 15 seconds, on a tripod. My *ist DS is about 5 stops more sensitive to IR, but trickier to use.

QuoteOriginally posted by metalmania Quote
May I ask is it possible not to use filter but get the same effect by PP?
IR photos are a kind of gray area for that. My image is somewhat fake, because "colors" don't exist in infrared. It's aready a post-processing effect. Some software and cameras come with digital filters to mimic the effect. With some PP skill, you could get close. I've taken the same scene with the filter on and off but never tried to get them to look the same.
05-05-2011, 03:23 PM   #11
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QuoteOriginally posted by Chaos_Realm Quote
;
UV filters for day to day use, as it protects the lens and also reduces haze.
The former is indeed hotly debated - some saying the protection it provides is worth the degradation in IQ, some claiming not. But I haven't heard anyone but a filter salesman ever try to claim that a filter actually "reduces haze". Every comparison I've ever seen or heard of attempts to quantify how much *worse* a picture gets by using a UV filter, but I don't think anyone seriously believes any modern camera or lens would ever be *helped* by a UV filter. I think once upon a time, before modern lens coatings, and when dealing with films that were especially sensitive to UV light, there might have been an actual advantage to using one, but I don't think that's been true for a long time.
05-05-2011, 03:54 PM   #12
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QuoteOriginally posted by Marc Sabatella Quote
<snip> But I haven't heard anyone but a filter salesman ever try to claim that a filter actually "reduces haze". <snip>


I remember the "good old days" (God I must be getting old) when every lens used outside was sold with a "Skylight 1A" filter to reduce haze.
05-05-2011, 08:33 PM - 1 Like   #13
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QuoteOriginally posted by metalmania Quote
May I ask is it possible not to use filter but get the same effect by PP?
PP can remove spectral elements; it can't add them. That's why IR and UV imaging are very important in science and forensics, because they show stuff we can't see visibly. The IR and UV portions of the EM spectrum convey different information than the visible portions. Without an IR-pass filter, that info just doesn't reach the sensor, and it can't be added in PP. UV is filtered out by sensor materials, so is not recorded either.

[Edit - slight correction. An IR-pass filter blocks visible light that would otherwise swamp-out the much lower-level IR light, thus allowing the IR to be recorded.]

Polarization is similar. It changes the angles at which light hits the sensor, and reduces glare that would otherwise be recorded. AFAIK digital filters can't polarize, else they'd be offered as in-camera options. Again, it's a matter of what spectra hit the sensor and are recorded, and which aren't. What isn't recorded is lost, gone.

QuoteOriginally posted by calicojack Quote
I remember the "good old days" (God I must be getting old) when every lens used outside was sold with a "Skylight 1A" filter to reduce haze.
And that's because most film emulsions ARE sensitive to UV light, while almost all digital sensors are made with UV-blocking filters. [NOTE: Some full-spectrum sensors exist, with no filtration, for specialized uses.] Skylight / UV filters are film-era relics, unnecessary now.

Clear optical glass filters (multicoated, of course) *would* be useful with digicams for protection in extreme environments. Meanwhile, I keep my lenses away from prying noses, tongues, and digits of humans and canines.

Last edited by RioRico; 05-05-2011 at 08:40 PM.
05-06-2011, 12:32 AM   #14
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- And the debate goes on, and on...
Even some of the distinguished masters of color negative film do not use filters. Just look at the landscapes of Harry Cory Wright.
05-13-2011, 10:10 PM   #15
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Helpful information, thank you all!
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