I am researching square/rectangular ND/ND grad filters and holders. I don't own any yet. I am wondering:

1) Are all filter holders' slots - into which you slide square/rectangular filters - and all square/rectangular filters themselves - a standard "thickness"? Ie. will any filter work with any filter holder?

2) If not, how do I know which filters will fit with which holders, or am I limited to buying filters and holders from the same manufacturer?

Thanks for your help!


3 Answers 3


There are various filter thicknesses. Most square filter holders are modular and can be disassembled/assembled using various pieces to allow for filters with different thicknesses.

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Most 100mm square/rectangular filters are in the 2-3 mm range and many filter holders can accommodate anything from 2mm to 3mm thickness without needing any changes.


I only have experience with formatt hitech, so, cannot say for certain...

But, the holder uses a u-shaped piece in the slot to compress the filter, like a spring. This action is what keeps the filter in the holder. The u shape would have been designed for FH's filters, but visually, I can tell you that it nearly goes all the way across the filter channel.

What this means is, force would still be applied to a thinner filter, allowing it to be held in. What won't work is attempting to use a filter thicker than what the slot was designed for - but I've never seen a filter that thick. They all seem to be in the 2-4mm range.


The most problematic part of choosing rectangular ND/Polarizer filters lies more on the size of the filters (not their width, most, if not all, filters conform to Lee standard width by having foam pads in the edges to allow a tight fit in the holder).

  • But if you choose filters smaller than your future wide lenses, you’ll end having to purchase a new set.

  • Or on the other hand, if you go for the bigger sizes the price of the filters, holder and adapters will increase exponentially, and you
    don’t end buying that beautiful 14 mm f:1.4, you wasted the extra you paid for them.

Yes, you can buy knockoff filter holders, but good quality filters don’t come cheap, and if they fall from the holder for whatever reason you will be regret the day you bought that cheap holder for the rest of your live.

There are few major brands (like Lee, Nsi and Hitech) that make high quality filters compatible with the gold standard, the Lee system. Others, less known, also make accessories and filters compatible with the Lee system.

The most renowned brand in the industry, and the one to which everyone compares, its Lee. They got an extremely good web page that I think it will help you decide what are your current needs and allow to predict your future necessities, and show the options that will cover each.

I believe that it’ll be helpful even if you decide to go for any other brand.


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