If you're only intending to shoot B&W I've heard that sheets of welding glass make good 10 stop ND's... and as cheap as chips!
Paul
ND filters for long exposures
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Paul Mitchell
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Re: ND filters for long exposures
When people ask what equipment I use - I tell them my eyes.
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Re: ND filters for long exposures
Thanks for all this advice, it has given me plenty the think about. I'm going to try with the polariser initially, which will give me an indication of how many stops I need (i.e. how much more light reduction over the two stops it offers) and I'll then pursue some of this links. Thanks again.
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Charles Twist
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Re: ND filters for long exposures
For your testing, you can also take the aperture right down to f/64 or f/90 depending on your shutter.
Regards,
Charles
Regards,
Charles
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Emmanuel Bigler
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Re: ND filters for long exposures
Hello from France
Coming late to this discussion, today a LF friend of mine has told me that he has succumbed to the appeal of so-called VARIOGRAU filter recently introduced by Heliopan.
I prefer not to mention the price here (outch!), but I'm interested technically to see and understand how the device actually works. From the mnufacturer's specs the optical density varies from 0.3 to 1.8, 1.8 means 64x, 6 f-stops.
My first guess was that it is simply a good old pair of polarisers that you cross together in order to get a variable absorption factor by varying the relative angle between the two filters. This already existed on the market, and you could make it yourself by stacking 2 polarising filters, but I had doubts about the colour neutrality of the system, since many crossed polarisers I'm aware of, leave a very unpleasant blueish cast at high absorption ratios.
Well, those only shooting B&W will not care, but another problem with crossed polarisers is to precisely know the filter absorption factor at high densities: when the polarisers are almost crossed, the factor changes very abruptly within a few degrees of rotation, making an estimation of the proper (long) exposure time erratic.
For this new & expensive Heliopan device, I know from my personnal experience that Heliopan polarising filters are extremely neutral. But I do not even know if polarising filters are used in the VARIOGRAU !!
So: wait and see, and as soon as I can, I'll report here.
Coming late to this discussion, today a LF friend of mine has told me that he has succumbed to the appeal of so-called VARIOGRAU filter recently introduced by Heliopan.
I prefer not to mention the price here (outch!), but I'm interested technically to see and understand how the device actually works. From the mnufacturer's specs the optical density varies from 0.3 to 1.8, 1.8 means 64x, 6 f-stops.
My first guess was that it is simply a good old pair of polarisers that you cross together in order to get a variable absorption factor by varying the relative angle between the two filters. This already existed on the market, and you could make it yourself by stacking 2 polarising filters, but I had doubts about the colour neutrality of the system, since many crossed polarisers I'm aware of, leave a very unpleasant blueish cast at high absorption ratios.
Well, those only shooting B&W will not care, but another problem with crossed polarisers is to precisely know the filter absorption factor at high densities: when the polarisers are almost crossed, the factor changes very abruptly within a few degrees of rotation, making an estimation of the proper (long) exposure time erratic.
For this new & expensive Heliopan device, I know from my personnal experience that Heliopan polarising filters are extremely neutral. But I do not even know if polarising filters are used in the VARIOGRAU !!
So: wait and see, and as soon as I can, I'll report here.