“Thames Sunset” shot with a 10 stop ND filter allowing to exposure for 40 seconds with the Sun within the frame.
Using Neutral Density filters can make a dramatic change to your photos. The photo above is a 40-second exposure, which only is possible with something to stop down the light. The Sun is within the frame and had I shot without the filter, the shutter speed would have been 1/25 seconds. I shot this at ISO 100 and f/8. I could have gone to ISO 50 and to F/22, and changed the shutter speed to maybe around a 1/4 or a 1/2 seconds, but not 40 seconds.
ND filters are pretty expensive stuff, and I have ended up spending a fortune on them, not only because I have a fairly complete set, but also because I have made some mistakes. Expensive mistakes, that is. In this buying guide, I will try guide you not to make the same mistakes.
There are two kinds of filters, primarily. There are screw-on filters, and there are filters you put in a filter holder. The filter holder is screwed on as well.
I don’t recommend the screw-on ND filters. Though it may seem like a good simple choice at first, it is less flexible. When you have more than one filter, you may start combining filters. A 2 stop plus a 3 stop makes a 5 stop filter. And you might also start using ND gradient filters and soon you might end up wanting to use 2 or three filters at the same time.
- The gradient filters do not come in screw-on for obvious reasons because you can’t place the horizon.
- If you want to combine screw-on filters, you will have to screw them together. I did that with a fairly expensive polarizer filter and a 10-stop filter. And they got stuck together, and I wasn’t able to remove them from each other again. $350 down the drain. I do not screw filter together anymore.
How about flexible filters? There are some brands that make screw-on flexible ND filters. The first ND filter I bought was such one. It went from 1 stop to 8 stops, which sounded just perfect. It was more expensive than one Lee Big Stopper filter, but it was more flexible too. It looked like a good choice.
The only problem with the flexible filter was, that it only worked as supposed for 28+mm and I wanted to use it on wide angle lenses. 28mm isn’t very wide. When used with a shorter focal length the stopping of the light got uneven which made this filter completely unuseful. Another $300 went down the drain.
What do I recommend to buy?
At this point, I had learned my lessons on filters and lost $650, and I went for a no compromise solution. Lessons are sometimes expensive to learn. I bought a Lee filter holder for 100mm / 4″ filters, and an adapter for my 77mm sized lenses, which fits most lenses I have.
B&H: Formatt Hitech 100 x 100mm ProStop 1.8 IRND Filter (6 stop filter – explanation for the 1.8 further down in the article).
This is a solution just over $300. Still a lot of money, but it’s worth every dime!
And why these? The adapters ring come in a variety of sizes, and you will be able to find one that matches your favourite lens, and reuse your 100mm filters without any problem.
There is also a 150mm system, to use on big lenses like the Nikon 14-24mm. At the time of buying my Lee filters, I was still on Canon and only had 77mm sized lenses. When I moved to Nikon to get the 14-24mm lens, I chose to buy the Nikon 16-35mm lens too, to shoot my filtered shots. That was an expensive solution, but the 14-24mm is so great and so wide, and I didn’t want to be without it. That was THE reason for switching to Nikon.
Anyway – I can live without the 150mm system.
The Lee Big Stopper was in back order, and I was told somewhere between 6-12 months delivery (oh God!). So I had to buy what I could get, which was a 2 stop Lee ND filter (and a set of ND soft gradient filters).
While the 2-stop ND filter is nice to have, it is not the one I would choose, should I choose just one filter. 2 stops is just not enough most of the time. If I were only to pick one filter, it would be a 6 stop filter (or Little Stopper as it is also called).
I would choose a 6 stop ND filter if I was only to have one filter
Why this one? 6 stops is quite a lot. 1/25 becomes 2.6 seconds. Enough to make a change to your photo, but not enough, in a sunset or sunrise situation like the example above shows, but you also have some flexibility from your camera. Let’s look at an example:
The EXIF information for a shot like above without the filter would be: ISO 100, 1/25 sec, f/8.
Simply by adjusting the camera, I can change the exposure too. If I change the f-stop from f/8 to f/22 I will change it by 3 stops (see #1 and #2 in the table below), making the exposure time approx 8 seconds. And then I can change the ISO from 100 to 50, which will double the exposure time again, and that makes it around 16 seconds, and that is a good start to get more smooth water. If you do a -2, 0, +2 bracket, chances are, that the water will not be blown out, and you can use that water. And that +2 exposure (#3 in the table below) will be a 64-second exposure. Now we are really getting somewhere!
If I shoot my shots bracketed with a filter attached, I just do it manually, with a cable release. It doesn’t have to be exact to work.
This table shows how calculate your way around the camera settings. The shutter speed and the f/stop’s are related. Any of these columns represents the same exposure.
|f/stop||Shutter Speeds in Seconds without the filter|
|f/22||8||4||2||1 (#3)||1/2||1/4 (#2)||1/8||1/15||1/30|
The highlighted reds are close enough to our example, just without the filter attached.
I would also be able to lower the shutter speed by changing the f-stop in the opposite direction to f/4 and increasing the ISO to, let’s say ISO 400. Then I would have moved the exposure 4 stops faster. I have a span of 8 stops, just by changing settings on the camera.
There are a few compromises. Images tend to be slightly less sharp at f/22 and maybe also at f/4, depending on the lens. Nothing serious, which I can’t get recover in the post-processing.
At ISO 400 there will be a little more noise, but no big problem.
The biggest problem can be the change of Depth of Field by going to f/4.
What brand to choose?
I have Hitech Formatt IRND and I have Lee Filters for my 100mm system. These are among the very best, and the price comes with them. But you do get what you pay for. I have seen cheap Cokin filters in use, and the photos simply couldn’t be used for anything serious. And putting two filters on top of each other, just made it go from bad to worse.
I can only recommend the most expensive and best filters, simply because the others are not good enough.
Why is 1.8 the same as 6 stops?
In my world only calculating in stops makes sense. That’s how you think as a photographer, but for some reason the filters are primarily given in another scale, having 0.3 pr. stop. A 0.6 filter is then a 2 stop filter, and 1.8 becomes a 6 stop filter.
Another number system used is ND64 for the 6 stop filter. This system is easier to understand. That’s the number you have to multiply you exposure time with, and that’s why 1 second (#3 in the table above) becomes 64 seconds in my example above.
Tips on shooting long exposure photos
I have another article on how to use ND filters for shooting long exposures. You can read it here.