Topic: Neutral Density filters.

[eddie]

Help please,  I need some advice on using Neutral density filters.  Can i combine two ND8 filters  3 stops each to double the effect or must I buy a ND 1.8 for 6 stops.  Am I correct in assuming that i could use a red or orange filter along with the ND filter.  Would a polariser be of any benefit .   I appreciate i have to deal with a reciprocity calculation for the film at very slow speeds.  Working in Mono. Thanks in advance.

[Ailsa]

Hi Eddie

I regularly combine my 0.6 and 0.9 ND filters to extend the exposure by five stops. I use a Lee Filters system, so each filter just slots into the holder, and away I go. I've never combined this with a red or orange filter, but certainly there'd be nothing stopping you doing so. As for polarisers, I haven't used one myself with black & white, but I've seen some interesting results by others where, for example, using it turns water to a complete inky black.

As for reciprocity failure, I'm no technician, but I tend just to double the exposure to compensate. e.g. 'straight' reading is 1/4sec at f/8, to take account of the five stops it increases to eight seconds at f/8, therefore I expose at 16 seconds at f/8 to allow for reciprocity failure. It seems to work for me! Although I do bracket, too.

Hope this helps. Just for your interest I've attached an example where I used just this technique. If I remember rightly, the exposure was around one minute.



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[eddie]

Ailsa, exactly the type of image and mood I am after, lovely example,  and the exposure looks spot on.  Many thanks for the information.   

[Francois]

Reciprocity information is always listed on the film information leaflet... Look at the manufacturer's site since it changes from film to film.

[db]

No problems with stacking filters, although the absolute purists would recommend using the least individual items to get the effect you want. The optical qualities of some filters are not great, so the more surfaces the light passes through before it gets to your uber corrected ED multi coated lens, the more opportunity for distortion and dispersion effects.

[mcostolo]

Fewer filters also reduces the possibility of vignetting.  But yes, you can certainly stack ND filters.

[MarkBurley]

I regularly mix ND filters behind a polariser (in a Lee filter set-up) But I have found some newton rings when combining an orange filter behind as well, so I tend not to throw these in as well any more. As last time I was miffed at the rings appearing throughout several rolls of film.

I guess that I used a gelatine filter instead of glass, so it could be that I should invest in some glass filters instead.

Reciprocity failure has not been an issue for me, but varying exposure rates has led to an awfull lot of bracketing!

Mark

[eddie]

Thanks for advice everyone.  Tried one out last weekend, in the mist, pleased with results. Best results were with Fuji Acros, no adjustments needed for  reciprocity failure, some poor results from Ilford Pan  50asa as I forgot to adjust for reciprocity failure.  Experiments will continue . Sample below.

   

[Skorj]

I would be pleased too!

[This-is-damion]

indeed, looks great, water has come out very well indeed

[Ailsa]

Lovely composition and excellent use of the long exposure/ND filter technique. Look forward to seeing more!

[LT]

very nice Eddie

[eddie]

Thanks all, will have a go at printing on or two this evening.

[MarkBurley]

Good image Eddie - It looks to me that you got the gist...

Nice shot and composition too.

Mark

[outofcontxt]

Excellent stuff, indeed. I'm regularly pushing the envelope with combining red and ND filters with the slowest film possible so I can shoot wide open and still get a really shallow DOF and, possibly some movement in daylight. Works for me.