ND calculations

[Hughjb]

Looking for some wisdom on this one.

I'm trying to come with the right amount of neutral density for a 1/2 hour exposure.

So far I have been able to get a 1 1/2 exposure with 3200 film rated at 1600 with an ND 6.0 filter and a 8 minutes exposure with a 3.0 filter and additional stacked filter at ISO 400.

The goal is 1/2 hour with ISO 400, any ideas?

Thanks

Hugo

 

[Nancy Gutrich]

Use a pinhole as aperture...

 

[Leon]

Hugo - b&w filters make a minus 10 stop filter and used to make a minus 13 stop one. you could get one of those and stack a few lighter ones to get where you want to be. Or you could get some Lee ND material and double/ quadruple etc that until you get the required light loss.

 

[percepts]

I'm sure there is a reason but you will have to explain it to me.
Why are you using the fastest film when you want the longest exposure.
Right tools for the job comes to mind. just get a slow film such as ISO 25 and you will lose another 6 stops. Or 4 stops with against your 400 speed film. Either way that you should put you where you want to be.

 

[Hughjb]

Thanks for all the responces.

Percepts, I'm experimenting with grain.

 

[Hughjb]

Nice Pics Leon!

 

[vet173]

I do beleive a wratten # 96 is a 10 stop ND.

 

[percepts]

Thanks for all the responces.

Percepts, I'm experimenting with grain.

try developing your film in print developer.

 

[Hughjb]

Humm!, can you be more specific. I just got my Jobo setup and will love to try that.

Thanks

 

[percepts]

you might try Ilford PQ Universal diluted 1:29 or something similar at similar dilution. i.e. 3 times normal dilution. You will have to experiment with film speed and times. Fuji Neopan 1600 is good for grain effects. expose it at around EI 640. No need of ND filters!

p.s. I'm assuming you want visible grain effects.

Another alternative is FX1 developer used with Neopan 1600. see http://www.jackspcs.com/fx1.htm

and if possible use a point source enlarger. A diffusion enlarger will lose much of the effect of grain.

 

[Helen B]

I do beleive a wratten # 96 is a 10 stop ND.

Just a small point: Wratten #96 filters are available in a range of densities from 0.1 (1/3 stop) to 4.0 (13 1/3 stops), including 3.0 (10 stops) - but they are all 'Wratten No. 96' filters. I suspect that if you want grain and a half-hour exposure you will have to use 'quite a lot' of ND.

Best,
Helen

 

[percepts]

another would be neopan 1600 exposed at EI 320 developed in rodinal 1+50 20degC for 5mins. Thats inversion tank so you will have to experiment for rotary processing times.

but again, point source light is best for grain effects.

 

[Hughjb]

Great info, thanks