Square vs Round camera filters
Camera filters are available in either round or square/rectangular designs. The round filters simply screw onto the front of your lens, while the square type need a holder and an adapter ring to attach them.
Which system you should choose depends on the type and number of filters you’re likely to use, and also the lenses you’ll want to use them with.
Round camera filters are ideal for using individually, and if all your lenses have the same filter thread size. Square filters are a better option when you plan on using more than one filter at a time, or if you own a range of lenses with different thread sizes.
The end use of a filter also has a bearing on your choice of filter system. For practically full-time lens protection, you can’t beat the convenience of a circular screw-in filter, whereas rectangular filters are more suited to specialist effects – graduated filters, for example – as you can slide the filter in its holder to position the effect precisely.
Save some money
Buying the whole system for square camera filters can be very expensive, but as a stopgap you could consider simply holding the filters in front of the lens.
You need steady hands and the camera locked off on a tripod for this technique to work, and it won’t be easy to hold the filter still for exposures of a second or more.
Another simple solution is to use a tiny amount of Blu-Tack to help keep the filter in position while you hold it.
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