Filters - What are they good for?

Filters

We photographers must be an argumentative lot, here again we have another aspect of photography that people will debate endlessly with such passion. This could be great of course if it led to a coherent position as debate is never a bad thing. The problem is, for people starting out they see wildly varying opinions added to what a salesperson has told them at their local retailer and have either no idea what they should be doing or are following the advice of some random forum poster or a salesperson, without knowing the reason why they’ve added another optical layer to their lens.

Filters can be very useful indeed, in fact I’d go as far as say there are a few that almost every photographer should have available to them. There are some basic assumptions we can make in photography. We are trying to illustrate a scene or tell a story with our images. To do that, we are creatively using either available or added light, colour and of course we should always be thinking when we look through our viewfinders what do we want in the scene and what should we remove/alter before taking the shot. Filters are nothing more, or less than tools to help us shape the image.

I’ll start the (very short) list of filters I believe are useful by talking about one I believe is a total waste of time & money. UV or skylight filters have gained an almost bewildering popularity in the last few years, which is ironic as it is with modern photographic equipment that their use has become redundant. I know this is probably quite contrary to what you’ve read on forums if you visit them, but please look into this some more before deciding to purchase them. Once upon a time, film was relatively sensitive to UV light and was enough of a concern that it could cause a haziness in your shots. Back then, it made perfect sense to pull out a UV filter as it was fitting in with one of our photographic assumptions of removing an unwanted element from our image. Truth be told though, film has been resistant to this effect for years now and even if it wasn’t, how many of us are evening using film these days. I pull out my F100 once in a blue moon, and even then I wouldn’t use a UV filter as it is not necessary. You never want to add another layer of glass unless there is a good reason. This is especially true if you’ve spent a lot of money to buy excellent glass that Nikon or whomever spent a great deal of time and R&D budget on getting the optical qualities just right. Even assuming you use the very best filters, you are still adding another layer and whilst most filters are multi-coated these days they can introduce flare and loss of resolution and contract. The other reason you’ll hear people say they use UV filters is for protection. I do understand why you may be tempted as it costs a lot of money for good quality lenses. This though is the exact reason why you shouldn’t use them, its not a good idea to spend £1000 on a lens to get Nikon’s expertise and then add another layer of optical glass, if Nikon had thought it a good idea to have that layer, they would have added it themselves. I work with my equipment so I can hardly be accused of babying it, yet scratches on the top of the lens is not something I have had to deal with. Even if there was a small scratch on your expensive lens, it would more than likely not show up in the image unless you are shooting at an extremely small aperture with a wide angle lens. Photographic retail stores want you to buy that UV filter to get an easy mark-up, its not doing you any good in this day and age.

Now, on to a filter that is very useful, the circular polarizer. For those of you that don’t know, there are other polarizer filters called Linear Polarizers but since you will be using an auto-focus camera, you will need a circular polarizer. These are immensely useful as they remove unwanted reflections and this can be very helpful when shooting water, through glass, or you have a beautiful blue sky you want to darken. They can be helpful though with many different images as they will often improve contrast and enhance washed out colours. The trick is learning how to use them effectively which can be frustrating for people that haven’t ever tried. The basic rule is that you’ll get the most effect when the filter (and thus lens of course) is at 90 degree’s to the light source, sun. You will be able to see the effect in the viewfinder so its just a matter or practice.

The next filter that I couldn’t be without is a graduated Neutral Density (or ND) filter. ND filters come in both full and graduated varieties and both can be helpful, but I find the graduated to be of most use. To put it at it’s most basic, a ND filter cuts down the amount of light that is reaching the sensor. Lets say you are shooting water and want a slow shutter speed, but its a very bright day and you do not want to close the aperture down any further, a ND filter will be very helpful here. Likewise, a graduated ND filter will help you if you have a bright sky and you want to include it in the shot, but there is too much dynamic range to hold in the image with the foreground subject and sky. Something that I see people doing sometimes is buying screw on ND filters, this is a mistake. Obviously the start of the graduation is fixed if using a screw on ND filter. I use graduation (or split as you’ll also see them called) from Lee with a Cokin P holder, but there are others available too.

Now there are many other filters I have, but in all honesty they rarely if ever get used these days. One of my favorite types filters in the past were 81A & 81B warming filters. These were useful when I was shooting film because they would give the image a warm glow which could be used to great effect if shooting at the beach for instance, but now that we are using digital camera’s their use has been usurped by our ability to control white balance so easily on the body. On my D300 for instance, the white balance range is between 2500K and 10,000K. The closer you get to 10,000K the warmer the image so you can achieve the same effect by learning how to use the WB setting on your camera. I will digress here just for a moment as its a very good idea to learn how to control the WB using the kelvin setting in your camera for many reasons. Digital camera’s have made incredible strides over the last few years, but even today the one area where they are still easily fooled is WB. They are normally very good at setting the WB when outside, but inside its a whole different ball-game as the American’s say due to all the light-bulbs in your house giving off a separate k setting, add that to the light streaming in through the window and you’ve given your camera an awful lot to deal with. There are always presets of course and quite often using one of them over the automatic setting will help a great deal, so long as you know what type of light bulbs are being used and the corresponding camera symbol. Light-bulbs will generally give off a k setting between 2500k to 5000k depending on if they are incandescent (closer to 2500-3000k), fluorescent (around 3000-4500k) etc. Apart from fixing the WB to match the lighting in the scene, it can be used for creative effect and this is where having direct control will pay off the most.

To wrap up our brief filter discussion, I would give this piece of long acquired experience, good filters cost a good amount of money. Don’t spend £1200 on a new 70-200mm VR lens and stick a £30 filter on the front of it, you’ve just zapped a lot of the excellent performance the lens is capable of. Personally, apart from the Lee ND grad’s mentioned above, my filters are always from B+W in Germany. They have been manufacturing filters for quite some time and know a thing or two about them. They only use top quality optical glass and just as importantly, the fittings are made very well so the filters smoothly attach to the lens. Like everything else to do with photography, filters really require spending a little time getting to know what you need and want. Listen to some people and you’ll end up with 15 different filters in 10 different sizes for your 4 different lenses, not one of which is helping you or the performance of your expensive equipment. You more than likely will not need many filters, clearly a portrait photographer is not likely to need the same variety as somebody who specializes in landscapes. Do your research and make sure that when you choose to add another layer onto the end of your lens, it is there for a good reason and that it is changing the scene in a way you desire.