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Gear Discussions, General Stuff, Tech Talk, Theory n Technique

A Little Bit About Lens Filters


A Little Bit About Lens Filters

I’ve been wanting to do a quick post on lens filters for a while now, and this looks like the morning I finally get down to it. I’ll try to keep it brief!

Ok, first of all, what is a filter? No, it’s not like the ones on Instagram. Well, not exactly. A lens filter, quite simply, is a piece of glass that attaches to the front of your lens, and…well, it filters the light that passes through it. Different filters have different purposes, and are used to get various effects and looks to your shot. Filters of some sort are a very important part of a photographer’s kit, and although I find them most useful when shooting landscapes, read through this post and the various filters I will try to describe here, and you might realize their usefulness for any other sort of photography you might be into

From Left to Right: Circular Polarizer, Neutral Density, Graduated Neutral Density, and a filter attached to a DSLR Lens

From Left to Right: Circular Polarizer, Neutral Density, Graduated Neutral Density, and a filter attached to a DSLR Lens

Before I start on the filters that show visible effects in your photograph, let me talk about what I think is the most common type of filter that people buy these days: the Clear/UV/Protective filter. The Clear protective filter is one that does absolutely nothing to your shot. It doesn’t filter anything. What this filter does is simple: it protects the front element of your lens. The filter is a piece of glass in front of your lens, right? So if you happen to bump your lens into something, it’s your $50 filter that gets scratched or cracked – and not your $1000 lens – makes sense? Yeah

Back in the days of film photography, UV filters were used, as UV rays affect film. These filters cut down the UV rays that enter the lens, and thereby avoids this problem. Digital cameras have UV and IR filters built into the body, in front of the sensor, and are therefore not affected by UV rays; however, UV filters are still used on digital cameras, with the same purpose as the Clear protective filter…which is why you find Clear and UV filters both being sold for pretty much the same purpose today…as protective filters

IMPORTANT: When buying filters, do NOT buy cheap filters! When you spend big bucks for a beautiful new lens, it’s that high quality glass that you’re paying for. It’s that glass that gets you that fantastic image quality. What do you think will happen once you stick a cheap, $5 filter in front of that glass? Yeah. If you’re buying filters, don’t be cheap. Get some good ones. B+W is a brand I personally recommend – awesome stuff. If you’re buying, please don’t forget to come back here and use these links below to make your purchase!

B+W Filters on Amazon

B+W Filters on B&H Photo

(Make sure you buy the correct size of filter to fit your lens!)

Alright, now I will finally get down to the filters themselves, and what they do. Before I start, let me tell you that this isn’t going to be a complete breakdown of every single type of filter there is. This is just me going through a few basic types of filters – the common types that I think any photographer should know about, and know how to use –  and what they do. Again, I find all of these filters most useful when shooting landscapes and outdoors stuff, but adapt it to your work in any way that you can. The first three that I’m going through are extremely useful, while the other two are a bit less useful in the digital age, but are nice to use too. Here we go

The Polarizer (CPL)

It’s pretty much a fact that the circular polarizer (CPL) is the single most useful filter you can buy. It is for me, at least. Particularly in landscapes. The difference between photographs taken with and without a CPL can be astonishing, especially if you haven’t used one before. Have a look at the sample shots below and see for yourself

What does a polarizer do to your image? Well, the biggest thing it does is it cuts down on reflections. Reflections off glass, off water, off anything that…well, that reflects! Reflections are nice, in some cases, sure – but most often they end up as annoying spots of glare that cause distraction. The polarizer does away with all that

The sun reflecting off the water (left) makes it quite unpleasant to look at. With the polarizer on (right), all that glare is gone and it just looks better!

The sun reflecting off the water (left) makes it quite unpleasant to look at. With the polarizer on (right), all that glare is gone and it just looks better! Image from Wikipedia (Photographer Unknown)

But no, that’s not it. Reflections also cause subjects – flowers, leaves, anything really – to look rather underwhelming in terms of color and contrast. Images taken outdoors in bright sunlight can sometimes look a bit flat and boring because of this. The polarizer fixes that too. By cutting down on reflections, colors pop out and look really nice and saturated, contrast improves, and things start to look much better overall…just like they did to your own eye as you captured the shot. This is, for me, the best part of the CPL

Not the best photograph, I guess, but a great example to show how a polarizer helps bring out color in a shot by reducing reflection. With polarizer on the left, if you need to be told!

Not the best photograph, I guess, but a great example to show how a polarizer helps bring out color in a shot by reducing reflection. The shot on the left is with the polarizer, if you need to be told! Image by JJ Harrison

Lastly, the CPL has a wonderful effect on sky. Blue skies immediately become deeper, richer, and just more pleasant to look at. Even flat, white cloudy sky can look better with a CPL on. I love this part of the CPL too!

See how the sky looks richer, deeper - and the entire photograph on the right (with the CPL on) looks so much better!

See how the sky looks richer, deeper – and the entire photograph on the right (with the CPL on) looks so much better! Image by Piccolo Namek

So yeah – a CPL enhances the scene by increasing contrast, and saturation. It cuts down on unwanted reflection. And it makes sky look better. Put this in a landscape situation, and compare With and Without versions, and you’d realize how wonderful this filter really is. But the real importance of this filter comes when you realize that unlike some of the other filters that I will go through in a moment, which have effects that can be replicated in Photoshop to some extent, getting the polarizer effect while post processing is very difficult, and impossible to me. That’s why I recommend you get a good CPL as the first filter for your kit

The Neutral Density (ND) Filter

A neutral density filter does to your lens what a pair of sunglasses does to your eyes. It cuts down on the amount of light that passes through it. Simple, right? It is! The cool part is that it cuts down on light in a controlled manner i.e. a particular filter will cut down light by an exact number of ‘stops’. They come in varying degrees of intensity, and depending on the strength or intensity of the filter, the amount of light that enters your camera is reduced, thereby allowing opportunities that you previously didn’t have

You might wonder why anyone would want to cut down on light. Most often, you’re trying to gain more light to expose the image properly, right? Well, imagine this situation: you’re shooting outdoors, in bright sunlight. Your camera’s fastest shutter speed is 1/2000 sec. Your lens opens up to f1.8, and you want to shoot with your aperture wide open, to get this really shallow depth of field. Unfortunately, with all this available light, opening up the lens to f1.8 results in a totally overexposed image, as your shutter speed of 1/2000 is just not fast enough. In this situation, maybe your shutter speed needs to be about two stops faster…maybe around 1/8000 sec? At least 1/4000. But you can’t get that. What do you do? Pop in a 2-stop or 3-stop ND filter! This reduces the light by 2 or 3 stops, thereby allowing you to get a correct exposure with a shutter speed of 1/1000 or 1/2000 sec, with the aperture at f1.8! Perfect

You can also use an ND filter to capture long exposure photographs in broad daylight. A common example of a long exposure daylight shot is when you shoot a scene with flowing water, such as a waterfall. A long exposure usually gives this water a beautiful, misty, soft look that is quite unlike anything you can get with a fast shutter speed. However, in bright sunlight (or even in cloudy conditions), achieving a long exposure of a few seconds is impossible, as there is just too much light, even if you stop down to f16 or f22. What do you do? Pop in an ND filter again! In this case, you might want to get a stronger ND filter – maybe a 4-stop one, or even stronger – but attach it to your lens, and you’d get a nice, long exposure of a few seconds long, with an aperture of f11 or f16

I’m sure you’ve seen this sort of shot before. Right? Well, you can be 100% sure that an ND filter was used in these cases. There’s just no other way. Beautiful, isn’t it?

I’m sure you’ve seen this sort of shot before. Right? Well, you can be 100% sure that an ND filter was used in these cases. There’s just no other way. Beautiful, isn’t it? Image by Jojo Nicdao

A long exposure in daylight does not necessarily have to be of flowing water, of course – it’s just a nice example – you can use it for any case where you’d require a long exposure and when you feel there’s too much natural light to get what you want without overexposing things

Ok, the polarizer effect cannot be achieved in Photoshop. How about the ND effect? Not easily, no. In the first example, shooting outdoors in bright sunlight, you could shoot in RAW, and fix the completely overexposed image in Photoshop, and end up with a useable, or even a really good result. But long exposures? Nope, that cannot be done. You need an ND filter for that. Looking at things this way, I guess the ND filter should be second on your list! 

The Graduated Neutral Density (GND) Filter

A GND filter is very similar to the ND filter (as the name sounds!) but is probably a bit more suited to general landscape photography. As the ND filter does, the GND reduces light that enters through the lens, but it does so for only one half of the frame. See the image of the filter itself – compare it with the ND filter, which is entirely dark – see how it is dark on top but clear on the bottom? That’s how the GND filter works. It is basically half a filter!

This works great for landscapes – the common type of landscape – where there is a significant amount of land as well as sky in the scene. Metering this sort of scene accurately is always a challenge, because of the high dynamic range in the scene i.e. the difference in luminance between the sky and the land is always high. You usually end up with a shot where the sky is accurately exposed, but with underexposed land, or vice versa, where the land looks great but the sky overexposed. You can recover this to some extent (or to a great extent if you shoot RAW) when post processing, but what do you do to get it right in-camera? Yeah, you guessed it: use a GND filter

Attach the filter, adjust it so that the darkened half covers the sky and the clear half covers the land, and shoot. As the dark part of the filter cuts down on the extra light that the sky emits, the camera’s meter sees the sky and land as pretty much the same in terms of brightness, and exposes the shot where everything looks very nicely exposed. Easy. And works just like it sounds!

First shot on the left (no GND): exposed for the land, resulting in overexposed, flat sky. Second shot (with GND filter): again, exposed for the land, but with the extra light cut down from the sky, the sky is exposed beautifully too, resulting in a much more pleasant look overall!

First shot on the left (no GND): exposed for the land, resulting in overexposed, flat sky. Second shot (with GND filter): again, exposed for the land, but with the extra light cut down from the sky, the sky is exposed beautifully too, resulting in a much more pleasant look overall!

GND filters, like ND filters, come in different intensities – 1-stop, 2-stop etc. – but unlike when picking an ND filter for a particular scene, you need to pick the correct GND filter for the shot, or else risk your exposure looking rather weird. Why? If you pick a GND that is too strong for the scene, you will get a result where the sky looks like it’s late evening, while the land looks like its bright mid-morning. Unnatural, right? Yeah. And pick a GND that’s too weak and you probably wouldn’t see a difference. Yeah, you need to pick the right GND for the job. Here’s how:

  • Set your camera to spot meter
  • Point your camera directly upwards, and meter just the sky. Nothing else. Note the exposure
  • Point your camera downwards, and meter only the land. Note that exposure
  • Compare the two exposures, and note the difference
  • Convert that difference into ‘stops’
  • Use a GND filter of an intensity as close as possible to that number of stops

For example, you meter the sky. The metered exposure is: 1/2000, f8, ISO 400

Next, you meter the land. The metered exposure is: 1/1000, f8, ISO 400

As the ISO and aperture have remained the same, the difference in exposure is the between the shutter speeds of 1/2000 and 1/1000. Quite simple, here: double the shutter speed means a difference of one stop. Therefore the difference in exposure between the sky and land is one stop. Easy, right? Pick a 1-stop GND filter and shoot!

If you don’t have the exact GND filter, use the closest one you have i.e. if the difference between land and sky is 3 stops, and you have a 2-stop or 4-stop GND filter, either one will be fine. But I think you get the idea that you will need a small selection of GND filters, and not just one. Maybe a set of 3 – 1-stop, 2-stop and 4-stop, for example – would be nice

GND filters give you the potential to take some stunning shots – especially in scenes with high dynamic range, such as landscapes – but note that it only works when there is a clear, straight definition between the bright and not-so-bright parts i.e. a flat horizon that separates the land from sky. If this definition is not flat and straight – maybe a backlit mountain, with patches of sky on either side and on top too – this wouldn’t work as well. In this case, try taking multiple exposures and merge them using the HDR technique – read my HDR post on how to do that!

The GND effect can be replicated on Photoshop. Lightroom has a very useful GND tool, which does the same thing. Read my post on Post Processing using Lightroom for more on that. It’s great to do it in-camera, without having to rely on Photoshop, so I recommend you get a set of GND filters if you can – however, know that it’s very possible to recreate this effect on your computer

The Warming and Cooling Filters

Warming and cooling filters used to be a crucial part of a landscape photographer’s kit, but due to the ease of which Photoshop does the same job, these filters are losing popularity, and are seemingly getting hard to even find. They do a pretty simple job: they adjust the color temperature of the photograph

If you’re not sure what color temperature and white balance and all that is, read up HERE and HERE. If you do, let’s continue

Ok, I guess it’s not that hard to figure out now, yes? Yeah, a warming filter ‘warms’ the color temperature. It makes things warmer. It gives things a mild yellow cast. A cooling filter does the opposite. It cools the color temperature, giving the image a slight blue tinge. Not sounding too useful yet?

Well, wait till you’re out shooting landscapes, and find yourself in a place you’re not going to be visiting again for a while, but in unfavorable lighting conditions. The light is cloudy, it’s flat, it’s white, the temperature too cool, and you’re just not able to get what you’re going for. You know what to do now, right? POP IN A FILTER! Yeah, attach a warming filter, and although it might not completely fix the poor lighting conditions, it will definitely help things. The flat white/blue light will get a lovely yellow tinge to it, making everything look warm and…happy! That sort of thing. If you feel things are too warm, or you simply want to go for a cold, dramatic look, try a cooling filter instead. Warming filters work well in portraiture too, and can really improve skin tone

These were very important back in the film era – people still carry them around even with digital cameras – but seeing that fixing color temperature is one of the easiest things to do in Photoshop, people rarely use them today. However, getting it right in-camera is always best, so if you can find some, and you can afford it, go for it!

See how the light seems to have a beautiful, warm, yellow glow? That's the warming filter at work

See how the light seems to have a beautiful, warm, yellow glow? That’s the warming filter at work. Image by Erica Wheelan

And here, the dramatic, cold look of a cooling filter

And here, the dramatic, cold look of a cooling filter. Image by Detlef Reichardt

 

NOTE: Do not confuse warming and cooling filters with color filters. Color filters are brightly colored pieces of glass that give strong color casts to your images, and come in all sorts of shades – green, red, blue, etc. Warming/cooling filters are pale yellow/pale blue filters that give this subtle cast that keeps things natural. Make sure you get the right filter! 

Important Tips on Lens Filters

    • I said it earlier, and I repeat it now: DO NOT BUY CHEAP FILTERS. You’re after an effect with filters, sure – but that does not mean you want to compromise sharpness and other aspects of image quality that your awesome lens can produce, right? Don’t spoil your expensive lens with a cheap filter. Get a good one. Remember B+W! Hoya, Kenko, Tiffen, and Marumi are other good brands. Canon and Nikon make pretty good ones too
    • Avoid stacking filters unless you really need to. Stacking filters (using more than one filter at a time) can be used to good effect i.e. using a polarizer and a warming filter can be very nice in certain situations, but unless you’re going for that specific effect, avoid stacking filters. Any additional piece of glass in front of your lens, even of the highest quality, will degrade your image quality a little bit. Adding more filters will degrade it even more. Your lens will be more prone to lens flare too. So unless you really need to, don’t stack filters. And unless you really need a filter for the effect, don’t use a filter at all. Remove them all once you’re done
    • And that brings me to my last tip. Don’t use a protective filter. Don’t get me wrong, I used a B+W Clear filter for most of my work, and I never noticed any problems with image quality. But it’s just not necessary. When I first started out, I gave in to the salespeople and others who advised me to get a protective filter for my new lens. Lately, after getting a lot of advice from far more qualified people…professionals and experts…I’ve switched to just using a lens hood instead. A lens hood protects the lens too, and unlike a filter, it actually prevents lens flare. And it does not affect image quality one bit. They usually come free with most lenses – so you save a bit too. Yeah, use a lens hood instead of a protective filter

Yes, that’s it for this post! I hope I made some sense here! To summarize, I find filters most beneficial when shooting landscapes, but there’s always the instance when I’d use one for other purposes too, and I’m sure you might as well. Now that you know what the basic filters do (maybe you already did!), you can use ‘em for whatever you want. Use them only when you need to, and remove them when you don’t

If I were starting out now, knowing what I do now, I’d skip the protective filter – and if my lens has no lens hood (my old kit lens never came with one!) I’d spend my money on one of those

Then, for my first filter, I’d get a circular polarizer! Like I mentioned earlier, you just cannot replicate the effect of the CPL in Photoshop, and the effect it has on landscapes is pretty stunning, so I’d definitely make the CPL my first filter

Next up, I’d get either a GND or an ND. It depends on what you want, when choosing between these. The ND filter and its long exposure effect is harder to recreate using Photoshop, sure…but if you don’t think you’d want to, why bother? Get a set of GND filters instead! I’d probably start out with an ND, and get a set of GND filters later on. But that’s just me

Lastly, if I managed to save up enough (!) I’d get a warming and cooling filter. They’re not super useful any more, but I always feel it’s best to get it all perfect right at the moment you click the shutter, so why not?

My Affiliate Links: 

B+W Filters on Amazon

B+W Filters on B&H Photo

Alright, I’m done for today. If you have any questions, please ask away! heshan@pixelogist.me – and of course, please leave a comment! Let me know what filters you’ve used before, and also if you use many filters outside of landscape photography. Anything, really…leave a comment! I’ll get back to you soon. As usual, if I managed to convince you to get yourself a few filters, using my affiliate links will be a wonderful thing to do! Alright then…until next time

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By Heshan Jayakody
All content is my own except where noted
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Discussion

21 Responses to “A Little Bit About Lens Filters”

  1. Fantastic post!! Very useful for beginners, I must say. I’ve been using these filters a lot in landscapes, like you mention…but outside of landscapes? Hmm. I have use warm filters for outdoors portraiture, but a long time back. Apart from this, I cannot say I have used a filter for other kind of work, really! And I agree 100% with using a lens hood instead of a protective filter!

    Posted by Steven | January 19, 2013, 09:27
    • Thanks Steven! Thanks for sharing your thoughts on the topic! For landscapes, then…what filters do you own and use regularly?

      Posted by pixelogist | January 19, 2013, 09:56
      • Hmm.. I own a couple of graduated NDs, a CPL – all Hoya/Kenko – and lately i’ve been into IR so i got myself a B+W IR filter. I also have a Hoya 2-stop ND filter

        Posted by Steven | January 20, 2013, 07:29
      • That’s a nice set. Pretty similar to what I have 🙂

        Posted by pixelogist | January 20, 2013, 10:38
  2. Great article! I totally agree about these filters being the most useful. An IR filter could be used in landscape work, but that’s a whole new thing, and not general landscape photography, isn’t it? I haven’t used warm/cool filters, but I’ve used the rest, and they really help get the right shot. I’d be lost without them. And yeah, you guessed it, I shoot landscapes 95% of the time

    Posted by Martin | February 3, 2013, 09:50
    • IR work is indeed a whole new thing! I’d try to cover it sometime, but I really don’t have much experience with IR photography myself, I’m afraid. But yeah, landscapes in general really can be improved by using the right filter!

      Posted by pixelogist | February 3, 2013, 18:16
  3. Another good post! I currently don’t have any filters, apart from a protective filter, but I’m considering replacing that with a hood now 🙂 And I really want a CPL now!!

    Posted by Anna | February 3, 2013, 15:16
    • Cheers! Yes, I’d definitely remove the protective filter (unless it’s a really good one, like a B+W), and get a lens hood instead. Even if your clear filter is a really good one, I’d use a lens hood instead, but that’s just me. A CPL – if you’re into landscapes, yes.. get one!

      Posted by pixelogist | February 3, 2013, 18:44
  4. I use a B+W CPL and the day I bought my first one, it changed my photography life! Yes, I use it mainly for landscapes, of course, but what it does for a landscape photograph can be stunning!

    Posted by Jenkins | February 3, 2013, 17:56
  5. Cool post, pixelogist 🙂 I definitely agree with the CPL part, it is the most useful filter, and is impossible to replicate on Photoshop. However, I’m kinda old-school, and although i haven’t used warm/cool filters, I’d love to get some in my collection, and avoid using Photoshop to recreate the effect

    Posted by George | March 7, 2013, 07:48
    • Thanks, George. I like old-school too, but even if I want to, I find it very hard to locate a store selling these filters. They’re really hard to find, I guess no one uses them any more. If you do find some, let me know!

      Posted by pixelogist | March 7, 2013, 12:43
  6. excellent post, very informative- thanks so much for sharing!!

    Posted by Martin | March 9, 2013, 14:58
  7. Good stuff, man. I’ve just got a CPL (a few weeks ago) and it’s changed my photographs dramatically. Landscapes never looked so good

    Posted by Yardley | June 24, 2013, 07:07
  8. Super helpful, this was. Haha. Learned a lot. Thanks. I’m just getting my feet wet in the whole photography thing with my first camera ‘system’ and now I want more! Haha

    Posted by Gillian | July 5, 2013, 07:22
    • Cheers, Gillian 🙂 Always glad to hear these posts helped someone! Get a CPL, and maybe an ND! And then try to avoid getting trapped in the buying frenzy that often comes with this hobby/profession!

      Posted by pixelogist | July 5, 2013, 16:21
  9. Great tips, thank you for sharing. I am still new in photography so it was of huge use.

    Posted by Steve Gold | August 22, 2013, 12:49

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