Long exposures on Velvia 50 after dark

[Brian Vuillemenot]

I just got some 4x5s back from a recent trip to the Bisti Badlands. I made one exposure about thirty minutes after sunset- 3minutes @ f22 on RVP. It was, literally as well as figuratively, a "shot in the dark". When I got the film back, I was surprized that it was my favorite one- the lack of shadows and ultra-low contrast give a surreal effect, very appropriate for the Bisti. Also, I didn't notice the sickly green glow I've seen on Velvia when exposed for 20 or 30 seconds! Does anyone have any experience with exposing RVP for multiple minutes- does the green color shift go down with longer exposures? Thanks!

[QT Luong]

In my experience, the longer the exposure time, the more green /brown cast you'd get with Velvia. I think in your case, the warmth of the light (typical in clear atmosphere up to 30min after sunset) might have neutralized that cast.

[Geoffrey Swenson]

I went as far as 30 minutes on Velvia with no ill effects. Of course some filtration might be needed after the sun goes down so a color meter or experience could help.

Sickly green in my experience happens during several hour exposures, for example with star trails.

[Brian Kennedy]

The only time I've noticed a Velvia 50 "green cast" was with exposures of 15-20 minutes or longer, and then it was mild. When I was in Italy last fall, I made lots of 5 minute nighttime exposures with V50, and they turned out great with no green cast at all. I'd bet your previous 20"-30" exposures were green for some other reason.

[Kirk Keyes]

Perhaps your were seeing a lack of artifical lights in the direction you were shooting. There's not a lot of population , centered or otherwise, to the west of the Bisti Badlands.

Maybe the green shows up more when shooting in areas that have higher backgrounds of artificail light? Mercury vapor lights are common for use as security lights and they have bright emission lines at 5460 nm (bright green), 4360 nm (blue), and a pair near 5790 nm (yellow). See the chart at - looking near the bottom of - http://members.misty.com/don/spectra.gif

We all know how Velvia 50 intensifies greens - so perhaps these emission lines found in artificail mercury vapor lights may be contributing to the green shift seen in some shots?

Kirk

[Mark_3632]

Kirk

To the west of the Bisti is the Chuska Mountain range. A very sparsely populated area. DO you mean east toward Farmington or southeast toward Gallup? Just curious.

[Kirk Keyes]

Mark,

I'm suggesting that looking west (into the Navajo Nation) will have less artificial lights illuminating the sky - so less green light scattering back to the camera. I've been to nearby Chaco Canyon and the skies there some of the darkest in the country (according to the park rangers there), but you can still see some light from Farmington and even Albuquerque.

So perhaps pointing the camera west (which could be warm from the sunset) and a lack of green-rich artificial lighting nearby might contributed to the good looking photos mentioned above.

Just a theory.

Kirk