Reciprocity Test with ND1000 Filter

[giganova]

Hi all --

I could use some help with reciprocity: next week I'll travel to the ocean for a few weeks to go on vacation. While there, I thought I'll take some pictures of seascapes with my 4x5 camera on FP-4 with long exposures, keeping Hiroshi Sugimoto's "Seascape" images in mind.

Before I hit the road I did some reciprocity tests. All images were taken with my 4x5 on Ilford FP4 on a sunny day. I scanned the "Sunny 16" negative (no filter) first and kept the scanner's exposure setting while scanning the other negatives. The screenshots are from the un-corrected FITS files in Photoshop.

Left, top: "Sunny 16" image.
Left, bottom: same but with a red filter and compensating for +2 stops. Worked. Looks a bit dark, but that could easily be corrected in Photoshop by tweaking the levels a bit.

Middle row: ND1000 filter (10 stops) with -1EV and +1EV bracketing, taking Ilford's reciprocity correction into account. Worked out.

Right row: ND1000 filter + Red filter with -1EV and +1EV bracketing, taking Ilford's reciprocity correction into account. The images are too dark, even if I correct for 12 stops and reciprocity, and have a very high contrast, much more than you would expect from the red filter alone. According to Ilford's reciprocity table, this should have been a 60-sec exposure (ND1000+Red = 12 stops). The bottom right is 80 sec, maybe 2-min would have been better? The contrast is extremely high, much more than you'd see from one of the filters alone (ND1000 or Red). Is this the combined effect of a ND1000 plus a Red filter?

What's your typical exposure time for ND1000 filters?

Thanks,
Stefan

Ilford FP-4 Reciprocity Test by Stefan Immler, on Flickr