Using a 9... no 12 stop welding glass for ND:

I've been trying to get dialed in on the affect of a shade 10, welding glass as a ND filter. I metered it as -9 but the highlights barely showed up on the negative. I tried 12 stops on this one.

1. The sun was about 40 deg high, camera left. It was behind a tree but kept finding little holes to peek through during the 7 minutes of exposure. That accounts for the several spots of lens flare. I should've shaded the lens.

2. I actually got the exposure right. My aim was to put the shadow area under the awning in zone III. I metered the sky at about 3.5 stops above that so, with a 2 stop ND grad filter it should've worked. Wrong. This was a 7 minute exposure through my welding glass filter. The reciprocity failure is exponential so two stops would show up more like 5 stops (or more). I hadn't thought of that. I don't believe I'll be using NDG's with the 12 stop anymore.

How did you attach the filter to the lens? It looks like you had a light leak between the ND filter and the lens causing lots of flare.
If there is shadow detail in the negative you might be able to get a better print on a higher grade paper.

Quote:

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Originally Posted by ic-racer

How did you attach the filter to the lens? It looks like you had a light leak between the ND filter and the lens causing lots of flare.
If there is shadow detail in the negative you might be able to get a better print on a higher grade paper.

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I had a glass company cut it down to 4". It was too thick for my Lee kit but I removed the mounting rails and put them back with a couple of fiber washers from my computer tool kit for a little extra spacing. It slides in just like a Lee ND filter now.

Is welding glass very high quality glass?

Quote:

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Originally Posted by Kirk Gittings

Is welding glass very high quality glass?

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It's the highest quality $4 glass I've ever used ;-)

I would buy a Lee Big Stopper except they haven't been available for some time now.

This actually works better than most people think.
There is a big thread w/ 35mm use:
http://photography-on-the.net/forum/...d.php?t=767152