10 stop ND filter? What happened?

[Hugo Zhang]

I bought a screw-on 10 stop ND filter to use with a 150mm ssxl lens and I exposed 4 sheets of 7x17 HP5 sheets last weekend. I rated the film at 200 and metered the scene, rocks and ocean in the sunlit afternoon, through the filter and I came out of my darkroom two days ago with 4 blank sheets. I mean, nothing at all! No light hitting the film at all for the entire 2 minutes at f/45.

Anybody have experience with these 10 stoppers? Maybe I will try to use it with my WP camera first and double the exposing time. I hate to waste large sheets of film.

[Robert A. Zeichner]

based on the "Sunny-16" rule, at an ISO of 200 and at an aperture of f45, a typical exposure should have been 4 seconds at f 45. Sounds like something other than the filter assuming the filter was truly a 10 stop ND.

[Aled Hughes]

Reciprocity??

[Policar]

I think your exposure was much too short. I may be wrong, but a four second exposure with no filter would translate into a 68-minute exposure with a 10-stop filter (4 seconds * 2^10 / 60 sec/min = 68.3 minutes). Taking reciprocity error into account this might be more like two or four hours (or way more) for a proper exposure.

I think a 10 stop ND might be a little extreme for use on ULF.

[GPS]

Well, what else did you expect? 10 stops is 10 stops, Policar is right. 10 ND I used when photographing the passing of Venus in front of the Sun, with 800 mm lens and a solar filter - directly into the Sun. Then only the exposure was of a few seconds, if even at some f16... (it was optical density 5, Black polymer, Thousand Oaks solar filter, 1/1000th of 1% light reduction - 0.001%)

[Jack Dahlgren]

I bought a screw-on 10 stop ND filter to use with a 150mm ssxl lens and I exposed 4 sheets of 7x17 HP5 sheets last weekend. I rated the film at 200 and metered the scene, rocks and ocean in the sunlit afternoon, through the filter and I came out of my darkroom two days ago with 4 blank sheets. I mean, nothing at all! No light hitting the film at all for the entire 2 minutes at f/45.

Anybody have experience with these 10 stoppers? Maybe I will try to use it with my WP camera first and double the exposing time. I hate to waste large sheets of film.

Sounds like your metering through the filter was not a good idea. I don't think many meters perform well at low light levels, and a small light leak could throw off the results.

I'd meter the scene then apply the ten stops of compensation. THEN figure out reciprocity.

[Bruce Watson]

Sounds like your metering through the filter was not a good idea. I don't think many meters perform well at low light levels, and a small light leak could throw off the results.

I'd meter the scene then apply the ten stops of compensation. THEN figure out reciprocity.

+1.

[brianam]

+1 to Bruce & Jack. I frequently use Rollei IR film, rated at ISO 6 in bright sun, and tack on a 6 or 10-stop ND (over an R72). Exposures in broad daylight are 4 or 8 minutes. -ish. Maybe up to half-hour depending on aperture. (Disclaimer: this is on 120 rollfilm in Mamiya 7. Haven't used the Rollei in 4x5 sheets yet.)

So yeah, I would think you should have registered something with 2 mins. f/45 and 200 ISO. In fact it might have even been over-exposed. (or, slightly under after maybe 1-2 stops reciprocity and bellows factor.)

[BetterSense]

I'd meter the scene then apply the ten stops of compensation. THEN figure out reciprocity.

+billionty

Many light meters use silicon elements that are IR sensitive and most likely, even a 10-stop ND filter will pass IR. I know ND Lee lighting gels are completely transparent to IR, because I use them as IR filters for IR photography.

EDIT: If it were me using the 10-stop ND, I wouldn't be using a light meter at all, and I would have given 10 seconds to 1 minute of exposure with TMAX 400. If your sheets were totally blank, it I would look into something besides exposure.

[Nathan Potter]

Hugo, it doesn't make sense. You should have been alright from what you describe, except for what might be serious reciprocity failure.

120 sec. - f/45 - ASA200

By the rough sunny 16 rule that's:

1/8 sec - f/45 - ASA 200 without the 10 stop ND.

Or by sunny 16 (1/ASA):

1/125 sec - f/16 - ASA 200.

Need to estimate reciprocity failure and possibly some gross error?

Nate Potter, Austin TX.