Hello I need some help whit ND filters.
I wonder if you can give me some advise.

I want to use a 4x5 film rated ISO 100 and I wont to reduce the ISO factor under 1 ISO (minimum 1 ISO).

I want to shot 90 minutes (aprox.) minimum 1 hour. Off course will depend also of the light available (exteriors).
I know some people have use a 16x ND filter to get such long exposition.

I was looking for ND filters and I find the B+W ND filter series, they are the only one I find whit high factor.
Bud I get a little confuse whit the filter factor and the f-stop reduction.
which filter I should use? a B+W 106, 110, 113, 120?

This is the link of B+W
http://www.schneideroptics.com/filters/filters_for_still_photography/neutral_density/more_information/

I will really appreciate if you have some experience to share.

By the way, which holder system you recommend, certainly I will use other filters like Graduated ND, Polariser, B&W and temperature correction.
I shoot 4x5 and my first lens is a Rodenstock Sironar-N 210/5.6 MC if someone know what is the filter size for this lens I would really appreciate.

Thank you very much Salvador


<font size=-1>[ This Message was edited by: salva on 2003-10-13 18:47 ]</font>

You really need to check things like the reciprocity failure. Are you going to use a colour filter to? What F/stop are you looking at? Using F/16 and Agfa's claim of 3 stops lost with exposures longer then 10 seconds my back of the envelope math comes up with 10 stops of ND filter. On a sunny day. Stick an #8 filter on the lens then that drops to 9 stops. Go to F/22 then it goes to 8 stops. Obviously you're going to have to test. And test.

I got to ask why 90 minutes?

About the reciprocity failure and the test, I know I will have to make "few" test.
I will only use the ND Filter.
I will use f16 or 22.
Why 90 minutes? I wont to record the Time.
Who produce the filters you mentions?


Some one tell me that the filter size of the lens is:
M 67x0.75 filter.
The outside dimension for push-on
filter holders is 70mm.

Quote:

Why 90 minutes? I wont to record the Time. Who produce the filters you mentions?

If you use this much ND all you'll get is a picture of what is standing still for 90minutes. I guess it's a good way to take a picture of a crowded place and to remove the people but I doubt you really need 90 minutes.

Plenty of different people make ND filters. Ranging from Tiffen to the more expensive B+W. Personally I'd get a few filters instead of one really dark one. This way you can use what ever the weather requires. Plus it'll be easier to find future uses of the filters instead of one really dark ND filter.

Salvador, I've used the ND filters you mention and agree with other posters that you should combine several weaker filters to get the density you want. Also, for expense savings, if you can find them, gel filters are much cheaper than glass, and more suited to occasional use. I've got a number of them in the 3" size, adequate to cover that lens.

Thanks!!!
What it's the thickens of 3"x3" or 4"x4" B+N ND filter. Will fit a Lee holder? 2mm thick.