Stacking square filters

[larry n.]

Is it possible to stack Lee polyester filters (of the 4x4 variety)? Do they need to spaced apart or is it better if they're right up against each

other?

[bob_sunley]

Space them, unless you have a filter holder that can hold a liquid of the exact same refractive index of the filter material. That is the only way to eliminate the air/"glass" interface between the filters. Even that won't eliminate the possibility of dust scratching the surfaces, but it will improve the light transmission of the filter stack and reduce and flare/diffraction caused by existing scratches on the filter surfaces.

[larry n.]

Thanks. I'm thinking specifically of ND filters. Say I need eight stops. Is it a good idea to combine two 4-stop filters?

[fwstutterheim]

I have successfully stacked 3 Lee ND Grads. I needed the whole lot: 0.3+0.6+0.9. I had them air spaced in a 4 slots filter

holder.<p>

 

<a href="http://www.stutterheim.nl/rolleigraphy/frames/belvedere1.html" target="_blank">Tuscany</a><p>Ferdi.

[fwstutterheim]

Norman, <p>

I was a bit quick answering your question. It is only now that I see your question is about polyester filters. I have used resin

filters. Sorry. <p>Ferdi.

[tim parkin]

Hmmm... I've stacked polyesters and have ended up with obious polarisation stress patterns

 

http://flickr.com/photos/timparkin/2592444220/

 

This was with a resin filter too... however?,.?