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Square Filter System Pro from K&F Concept

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Posted by Paul Crawford on Monday 31st January, 2022
Last updated on: 21 February 2023

Review of K&F Concept Square Filter System Pro

Disclaimer: Please note I was sent these filters by K&F Concept free of charge to test. I have not been paid for this review and it is an honest and unbiased review based on my experience using the product.

I was very impressed by the K&F Concept Magnetic filter system sent to me for review last year. They make changing filters quick and easy, but doesn’t get around the issue of having to get several different sizes of filters for all your different lenses.

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Square filter systems consist of a holder and various different sizes of adapters to allow you to use the same square filters on different size lenses.

K&F Concept have developed a new 7 in 1 Square filter system that incorporates a very clever CPL (Circular Polarising filter) into it’s design.

I have used Square filter systems before and was usually disappointed with the results, due mainly to light leak and having to remove the system to fit CPL filters so I was keen to see what K&F Concept had come up with.

1st Impressions

The filters arrived in very secure packaging, in a hard cardboard box, with a very nice case inside.

The case can be fitted with a strap or attached to your belt for quick access when out and about shooting images.

The case has separate compartments for each of the elements. Pulling on the orange tab pulls the filter compartments out for quick access.

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The CPL has it’s own compartment and the filter holder is at the front, together with the 4 adapters.

The system comes complete with adapters for 67mm, 72mm, 77mm and 82 mm. I am not sure of there are additional sizes available for this system.

My one criticism of the case would be the lack of a separate compartment for the adapters. They tend to rattle around the case when not in use.

The adapter fitted easily to the lens and the filter holder fitted to the adapter by pulling back the locking button and then screwing it to secure it. It felt secure and in no danger of slipping off.

Circular Polarising Filter

Adding the CPL is a really smooth operation – a very clever system! Simply pull back the CPL bin cover and slide in the filter.

It needs to be fitted the right way up… it is full proof as the bin will not close if the filter is not inserted correctly.

Once the CPL is in place, you adjust the polariser by turning the CPL dial wheel until you get the effect you require.

If you are not using a CPL filter, the filter bin closes tightly with no light leak.

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Neutral Density FIlters

The system sent to me contained three ND (Neutral Density) filters – ND8 (3 stops), ND64 (6 stops) and ND1000 (10 stops) filters. This will cover most situations ND filters are required. Other kits are available that include graduated ND filters.

They are 100 x 100 filters ( a common size within the square filter market ) except they have a protecting frame around them. The filters are Nano coated, making them waterproof and scratch resistant.

This helps to stop finger prints and smudges on the lens. However, if you have a collection of 100×100 filters, they will not fit on the holder without a frame.

Within the manual that comes with the system, there are instructions for fitting a frame. There are no instructions for removing a filter from a frame and I really didn’t want to risk trying this as I am not sure the frame would survive being pulled apart.

Perhaps K&F Concept are planning to offer empty frames for sale, although I can’t find anything on their website. I have several ND Grad filters from older 100×100 systems that I would love to use with this system.

The holder allows you to stack two filters at once and the filters fit very securely with no light leak.

Sliding the filters into the holder was very easy, the “tabs” on the frame help prevent you smudging the filter with fingerprints!

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To test the system, I headed up to the North Coast of Northern Ireland late one afternoon. I was shooting with my Fujifilm X-T3 fitted with the 16-55 f2.8 lens.

The light level was very low. Without any filters, the exposure was 1 second at f8 at ISO 200. Fitting the ND1000 filter, this reduced the exposure to 15 MINUTES at f8 at ISO 200. Halfway through the exposure, we had several cold water swimmers jump into the scene. With such a long exposure, they didn’t register! Here is the final image….

15 minutes at f8, ISO 200, Fujifilm X-T3 with 16-55mm lens at 50mm with ND1000

There was a little colour cast on the RAW file, although this was probably due to the very long exposure and changing light colour in the late afternoon (almost blue hour!)

There was no vignetting when using the holder at this focal length, so I quickly tested it with my 10 – 24 mm lens at 10mm

30 seconds at f8, ISO 200, Fujifilm X-T3 with 10-24mm lens at 10mm with ND8

With this wide angle lens, again, I could see no evidence of vignetting caused by the holder. Very impressive!

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I am really impressed with the quality of product from K&F Concept. This Square filter System Pro feels really well built (although the frames don’t feel reusable) and would like to see more sizes added to the adapter range.

The CPL system is really clever and easy to use. Many of the square filter systems involve you removing the adapter to fit the CPL so this system wins on that front!

This Square filter system has won industrial awards and it is easy to see why!

There was very little colour cast from the ND filters – nothing that a quick tweak in Lightroom Classic couldn’t fix anyway!

And no vignetting caused by the holder, even at 10mm (16mm full frame equivalent). K&F Concept claim it will not vignette down to 14mm on a full frame camera.

I currently use the magnetic filter system from K&F Concept, although I only have them for my 72mm filter diameter for my 10-24 lens.

This system gets over that issue and switching the holder between the different lens was super easy.

I can see this square filter system making a regular appearance in my kit bag!

You can buy this system direct from the K&F Concept website – Square Filter System Pro or on Amazon

Any Questions or Comments?

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Posted by Paul Crawford

Paul has been a full-time professional photographer since 1990. He is married to Patricia and the proud Dad to 2 fantastic sons. He photographs around 30 Weddings each year in Northern Ireland and is an experienced Photography Tutor running Photography Courses and Workshops. He is the founder of

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