Any professional photographer will tell you that one of the most important accessories they carry are their filters. A quick search online will bring up hundreds of results of different filters. With varying price ranges, they can be cheap for an entire set, or expensive for an individual filter. It can all seem overwhelming with so much to choose from. But often the first question that you need to answer is if you need a square filter or a screw-on round filter. So if you don’t know which is right for you, here’s a quick guide on the difference between the two.

What is the difference between the two?

Whilst it might seem complicated, the difference between the two filters is actually very simple. A screw-on filter is a piece of glass that screws onto your lens directly. Whereas the square filter, shaped either square or rectangle, would fit onto your lens using a filter holder. That is the difference between the two.

Keep in mind that the filter glass of either system will vary from manufacturer to manufacturer. You can get everything from plastic to coated glass. The better the quality of the glass the more expensive the filter will be. But when it comes to filters quality does matter.

What are the pros and cons of each?

The biggest difference between the two formats is that circular filters have to be purchased to fit a specific lens size. In other words, you need to buy one that is going to be the same size as the diameter of your lens. This means that if you decide one day to change cameras and lens sizes then you will need to buy new filters. The only other way to be able to match your filter to a new lens size would be to use an adapter.

On the other hand, square filters will fit onto a lens with an adapter that is purchased separately. Normally this would be in the form of a plastic or metal holder that the filter will slide into. This adapter will then attach to an adaptor and screwed onto the lens using a converter. So this means that if you one day decide to change lens sizes you will just need to replace the adapter that the holder fits onto. This means you can save yourself considerable money not having to replace every single filter or buying new adaptors.

Why should you choose circular screw-on filters?

Based on the above, it sounds like it’s a no-brainer that you should choose square filters. That’s not necessarily the case. Screw-on filters are also a valid option for any photographer. The main benefit of screw-on filters is that they are much easier to store and transport. Not to mention that they are generally harder to break. Naturally, a piece of glass is going to be more brittle than one which is surrounded by a frame.

Arguably the biggest advantage of using screw-on filters is price. They are generally cheaper than square filters. Also, you can now buy variable filters which cover a whole range of different stops. In other words, you can turn the filter and the mechanism inside can make the filter go From an ND2 to an ND16. This means that being able to cover a wide range of filters becomes far more affordable than buying individual ones.

So which one should you buy?

With both systems, you will be able to stack filters on top of each other. You can adjust the position by turning the filters. The one benefit that square or rectangular filters have is that you will have more glass area to play with. So it’s less likely you will get vignettes. So the real question to ask yourself is whether you are going to be changing your lenses any time soon and what your budget is? This will determine what is right for you.

In addition to this, it also depends on what it is that you are going to be photographing. For example, for landscape photography, you often have plenty of time and have your camera set up on a tripod. So square formats are the better choice. But if you are going to be photographing on the go and will be requiring different ND filters, then screw in filters will be easier to work with. Especially variable ones that cover a wide range of stops as it means you don’t have to change filters all the time. Ultimately the only person who can decide which is right for you is you.

Filters are an essential part of a photographer’s set of accessories. For anyone wanting to photograph outdoors filters will need to be used on more occasions than you can imagine. So it pays to make sure that you buy the right thing for you. Keep in mind that the quality of the glass does make a big difference to the quality of the image that you will end up with. So make sure you buy good quality filters. After all, why would you want to put a cheap piece of glass on the front of your expensive DSLR or mirrorless camera? Hopefully, this article will help you decide.

Photo credits: Kav Dadfar – All rights reserved. No usage without permission.