Velvia reciprocity light failure

[Bob Haight]

I was shooting velvia on a 6 x 7 rollex back at small apertures of f32 or f45 ca lling for 1 sec exposure. I rated the film at 50 which probably would do better at 40. Nevertheless, exposures were dark at least 1 to 1.5 stops under. The mete ring seemed right and contrast not a problem. Could velvia have a light failure problem at one second requiring additional compensation exposure?

[QT Luong]

In my experience, Velvia needs double exposure time somewhere between 30s and 1min. There is no way Velvia would need it at 1s. Your metering was most likely off.

[Paul Schilliger]

It could be a defective meter, but your experience reminds me also of when I sta rted using that film. I soon realized that with Velvia it's better not to use incident light metering, especi ally if the scene is not evenly lit, but rather use reflective spot measurements. Determine a middle gray value (gras s, etc.) or better: use a simplified zone system measurement method, and rate the film as you say at 40 AS A. Reciprocity failure for Velvia is from 4 sec. +1/3 and 5 CC M, from 16 sec. +2/3 and 10 CC M.

In other terms, in seconds, measurement-compensated exposure time: 1-1, 4-5, 6-8 , 8-12, 10-16, 15-24, 20-40, 30-64, 45-100, (60-150, 90-250). Don't bother with magenta filtering unle ss you have no mean to apply color corrections in post production.

[Eric_2840]

Kerry Thalman wrote a nice article in View Camera magazine one or two issues ago that touched on this a little. You might check it out.

[John Burke]

I'd check this out: http://people.smu.edu/rmonagha/mf/reciprocity.html

He's got a reciprocity failure chart for Velvia, among other helpful items.

[Matt Brain]

Also remember to allow for bellows factor for anything inside infinity focus. It is often amazing how many quater stops you loose for even a little bit further than the lens focal length. I recommend the spreadsheet printout that you can tailor to your lens that is linked to off The Large Format Photography Homepage. http://www.ai.sri.com/~luong/photography/lf