Photo Tips Podcast - Choosing Square or Circular ND Filters - Photo Tips
Specialty filters often come in two shapes, Square and Circular. And neutral density filters are no different. Everyone is familiar with circular filters, because most of us have circular protective filters on our cameras. Circular filters just screw onto the front of our lenses where as square filters require a filter holder which connects to a speed ring that screws onto the front of your lens – like a circular filter.
Circular filters are generally cheaper than square filters because square filters are much larger and you have to pay for the holder and speed rings as well, but unless all your lenses are the same size you will need a circular filter for each size lens you have. Or you can buy a filter for the largest diameter lens you have and then purchase step down rings which will allow you to attach the same filter to a lens with a smaller diameter. This insures that you will have full coverage without any vignetting.
As I just mentioned, to use a square filter you will need two additional parts aside from the filter itself. You will need a device which will hold the filter and then a speed ring that will attach the holder to your lens. These are usually sold together. The benefit of this system is that you can have a ring on each of your different size lenses and then you just move the holder with the filter attached very quickly from one lens to the next rather than having to unscrew and screw the filter each time. Although every filter manufacturer makes their own holder, you do not have to buy the holder from the same manufacturer as the filter. This is because the filter sizes are universally 100 or 150 millimeters, you just have to make sure that you have the right holder for the size filter that you purchased. Filter holders can vary greatly in construction, quality and price. So you’ll have to choose what’s best for you.
If you plan on doing a lot of long exposure photography with ND filters, I would recommend investing in square filters. I didn’t think that I would be using these filters as often as I do, so I purchased circular filters and now I think that was a huge mistake because I’m spend too much time screwing and unscrewing filters. If I had square filters, I could just swap them out fairly quickly and move them from lens to the next without much hassle. And on any shoot I have ever completed with an ND filter I've had to change my lenses multiple times. And unfortunatley my lenses are not the same size. If I had square filters then I could just move them from lens to lens without any hassle.
There is another benefit to square filters. If you plan on using graduated filters at all, square is the way to go! Because with a square filter you can push the filter up and own to coincide with your horizon line. You cannot do this with circular filters.