Many photographers make the mistake of thinking that optical filters, whether polarizing, ND or gradient, are not necessary. Far from it. Despite the constant advances in digital processing with the RAW format and retouching processes, it is very difficult to achieve the same results as with optical filters. And if you look at the equipment of professional landscape photographers, for example, you will see that they have a lot of filters. And they use them both individually and in combination to produce spectacular results. results.
For all those who love landscape photography, a good set of optical filters is essential for achieving outstanding results. Here we will not only introduce you to the most important filters, but also explain how to combine them to achieve even more beautiful pictures. And because times are hard for everyone, I have prepared a small buying guide for you so that you can complete your equipment gradually, without it being an unbearable effort.
Important things to consider when buying filters
Value for money
Photo enthusiasts sometimes have a limited budget, which is why it is important to always find the best filters at the best price. In other words, the price/quality ratio should fit your wallet and not the other way around. There is often a tendency to buy cheap filters that end up disappointing, so that you buy better ones later on, with all the extra expense that this entails. So it is better to save a little more and in the meantime look for information on filters with good value for money, so that you can invest in them when the time comes.
Versatility
You have to be smart and if you are going to buy filters, you have to look for the most useful and versatile of them. You can buy a filter holder, square filters and adapters for all your favourite lenses. If you buy circular filters, buy them for the largest diameter lens you have. Another thing to consider is the type of filter you will need, to avoid buying a filter that will soon gather dust after only a few uses. If you often photograph mountains, for example, a gradient filter is unlikely to be of much use. And if you buy several ND filters, don't think you can multiply their effects by combining lots of them. Two filters will be more than enough to produce the desired results. We'll come back to combining filters later in this article.
Batch or set filters
Once we have analysed the factors to be taken into account when buying filters, we will present here three recommendations according to your level and the fitters that I find most interesting. This is just my personal opinion, based also on my discussions with fellow photographers over the years. The sets are progressive, in other words, those of a higher level will include those of a lower level. This forms a kind of itinerary that will help you spread your investment over several years. This way you can progress, slowly but surely, and always using quality filters and not the cheap ones, for the sake of economy, as we have seen before.
Beginner's sets
There is no need to buy all the filters at once. This is an indicative order, so that you can buy the filters little by little and complete your equipment, if you start taking pictures.
A polarising filter
Regardless of the discipline you are interested in, every photographer should have a good polarising filter in their equipment. And for landscape photographers, it's even essential. It will help you bring out the sky, enhance the contrast with clouds and especially eliminate reflections on surfaces with water, such as lakes, rivers and other watery environments.
A variable ND filter
This filter is of great interest, but it must meet two criteria. The first is that the ND range should not be too wide, because if it is too wide, the filter system will leave dark cross-shaped marks that are unpleasant to the eye and difficult to remove. I therefore recommend a filter between ND2 and ND128, for example. There are some very good quality filters that go up to ND400 but they are often more expensive. Before you make your purchase, you should make sure that the filter in question does not produce this kind of cross-shaped mark. The second criterion is that it can be used at the same time as the polarising filter. Hence the interest in buying it in the same diameter as the latter.
An ND 10000 filter
For me, this is a special filter because I get spectacular results by extending the exposure time to more than 60 s. Very often you get very nice pictures with lower density levels, but once you freeze the water currents, make the passers-by disappear, etc., you can get really striking results.
Filter holder system
The filter holder system should be able to fit your cinema lenses, normally with rings of the diameter of the cine lens in question. It is best if the filter holder is no larger than 100 mm on a side, because if you opt for 150 mm filters, you will have to spend twice as much, at least. For this reason, it is better if your cine lenses can use this standard and not a larger filter holder system. At least two filters should be able to fit in it and also be able to be turned to adjust it to the needs of the moment. Finally, if it can be used with the polarising filter from the beginners' filter kit, even better.
Multiple ND filters
When you superimpose several ND filters, you must be able to calculate the total value of the light reduction of the whole. It is often a mistake to add up the density levels of the filters directly when in fact you have to multiply.
How do you calculate the light reduction with several ND filters?
Let's take a simple example. Suppose you have an ND8 filter and an ND16 filter and you place them in front of each other to extend the exposure time. The fatal mistake would be to add up 8 + 16 = 24 and assume that the density level would be that of an ND24 filter. The correct operation is to see how many stops of light the reduction is for each filter and not to mix the reduction stop values with the density value.
The ND8 filter reduces by 3 stops: 23=8 You have to multiply the exposure time by 8 to get the same result.
The ND16 filter reduced by 4 stops: 24=16 The exposure time must be multiplied by 16 to get the same result.
Now you have to add up the reduction stops of each filter: 3 stops of 4 stops = 7 stops. And seven stops is a density factor of 27=128. You have to multiply the exposure time by 128 to get the same result.
So the ND8 + ND16 filter tandem would be equivalent to an ND128 filter or what amounts to the same thing: 8 x 16. The process is very simple, provided, I insist, that you do not mix the stop values with the neutral density values.
Calculating light reduction with optical densities
Another issue to consider is the classification of filters graduated by their optical densities (0.3 - 0.9 - 1.2, etc.). In this case, things change, but we will still proceed in the same way, adding the light reduction stops of each lens on the darkest area, which is the one that gives the value to the filters in question. To do this, bear in mind that each decimal point of optical density corresponds to one third of a stop. You can therefore deduce that a filter with a density of 0.3 reduces the light by 1 stop (which would be equivalent to ND2, but let's not get too tangled up).
Let's take an example. You have two graduated filters of 0.9 and 1.5. What would be the total reduction of the set?
The 0.9 filter is equivalent to 3 stops: 0.9/0.3 = 3 The 1.5 filter is equivalent to 5 stops: 1.5/0.3 = 5 Now add up the stops without any problem: 3 stops + 5 stops = 8 stops, which is equivalent to a filter with an optical density of 8 stops x 0.3 = 2.4. You can deduce that you can directly add up the optical density values to calculate the total density.
Conclusion
All photo enthusiasts, as they progress, see that they need certain accessories. In this case, filters that allow you to improve your results. As amateur photographers, you cannot afford to buy all the products and filters, hence the interest in establishing a series of priorities and assessing your real needs according to your interests, knowledge, experience and of course, your budget.
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