Square Filters vs. Screw-on Round Filters

If you’ve ever researched camera filters, you might have been overwhelmed by the array of different types to choose from. As your skill progresses, so do your qualifications for the perfect filter for your photography. This makes choosing the perfect filter even harder! At the pro level, you're faced with a dizzying choice of filter types. And even after you're figured out what you need, there's still the nagging question of square filters vs. circular filters.

So what's the difference? 

It’s actually pretty simple. A square filter is shaped like a rectangle or square, while a circular filter is – you guessed it – shaped like a circle. However, the main difference between the two is in the way they attach to the end of your camera’s lens.

Square and rectangular filters are made from glass or resin, and are attached to the end of your lens by a lens holder, which must be separately bought. These filters can accommodate multiple camera systems. And of course, multiple types of filters, most commonly neutral density and graduated neutral density, can be bought in a square format.

There are quite a few advantages to using square filters, mainly that you don’t need to change your filters as you swap out your lenses. Instead, you just need to adjust your filter holder to fit your lens diameter. Normally, different adapters can be bought that correspond to different lens diameters, which attach to the lens before the holder itself. These adapters are cheap, and don’t get in the way of another major advantage of square filters: you can stack multiple filters in front of each other. This is a huge benefit when you've got 3 or 4 lenses out in the field: you don't need to buy different sized filters for each of them. 

Most filter holders allow you to stack filters on top of each other, which lets you experiment with combining them. For example, you could use a neutral density and graduated neutral density filter together, or use multiple filter of the same kind to amplify the effect. Normally, this can be done without vignetting the image – the surface of the filter usually goes beyond the edge of the lens.

However, this makes square filters much larger than circular filters, and in some cases, more fragile as well. They also require quite a bit more care – when you’re moving your camera from location to location, you’ll need to detach and reattach the filter holder rather than keeping the filter screwed on to the end of your lens.

Circular filters, on the other hand, are a totally separate category. They’re also called screw-on filters, because unlike a square filter (which uses a filter holder), circular filters simply screw onto the end of your lens. Like square filters, these are also available in many sizes and types, including neutral density (graduated and otherwise), polarizers, and UV filters. The size of the filter is dependent of the size of your lens.

Several features make the circular filter a good choice to consider, mainly, they’re much easier to set up than square filters – you just screw the filter on the lens and you’re free to move around with having to detach and reattach. Like the square filter, you can also stack circular filters. Because they’re able to screw onto the lens, they can also be screwed onto each other. They’re also smaller and easier to store away when not in use, and due to the metal rim around the edge of the filter, they can act as a sort of last-ditch drop protection for your lens.

On the other hand, the most drawback to the circular filter is fairly obvious: you need to match the size of the filter with the size of your lens, so you need multiple filters for multiple lenses. This problem can be partially solved by using an adapter to adjust this, in which case you’d buy a filter that fits your largest lens, then use a step adapter to fit the smaller lenses. In addition to this, leaving your filter on your lens for too long could lead to the filter sticking, particularly if it’s cold outside. And stacking is limited: adding more than a couple of filters can cause vignetting.

But when it all comes down to it, buying a square or circular filter really depends on your intent. Whatever filter you end up going for should reflect your subject, as well as your personal style. As we’ve seen above, there are many advantages and disadvantages to using square and circular filters, and this is just one of the many factors to consider when choosing the right filter for your needs.

What sort of camera system are you using? Cokin Filter has the perfect holder for your newest filters!