Pre-Exposing slide film to control contrast?

[Bryan Lemasters]

While reading through Gevalia's recent thread on film options for a slot canyon trip http://www.largeformatphotography.in...t=slot+canyons a thought came drifting up from the deep, dark, cobweb-filled corners of my brain : What about flash or pre-exposing color slide films on large format? Are there any chrome shooters here that use pre-exposure (shooting an out-of-focus, evenly-lit gray card at 2 to 2 1/2 stops under to put down a little light on the film, then recomposing and shooting the subject) to bring up detail in shadows?

I had experimented briefly with this a few years ago with 35mm before I switched to a digital darkroom, but was a bit dissapointed with saturation, IIRC. With Photoshop, saturation would no longer be an issue.

While this process could be a bit awkward with large format in the field, one could easily do pre-exposure on a few sheets of film earlier in a more controlled environment - especially if using Quickloads - before heading into the field. Simply pre-expose the film at home, note it on the Quickload label area, then use those sheets as the need arises.

Any thoughts? Do Provia and Velvia respond well to this process?

Bryan

[Ed Pierce]

I've had success with this technique with 4x5 b&w film. I do it right there on the spot using any even toned object I have on hand, holding it near the lens and exposing it to zone II.

Of course with slide film you would have to consider color.

[Jiri Vasina]

I have not done that, but have read that it's possible. But the most important problem is introducing color cast in the image - even if your eyes tell you you're shooting neutral grey (white) surface, it might actually be tinted and get exaggerated by the film...

If I remember correctly, it can also be done as "post-exposure" (shooting the grey after the image is shot) - then you could do the flashing in a controlled studio conditions with color casts under control... But I'm not sure if I remember this correctly.

I think it's surely worth a try...

[GPS]

It is possible but it dilutes colors (you mix them with a white color).

[Darryl Baird]

In higher altitudes and deserts, where the light is harsh, I have overexposed (+1 is max) and had the processing lab pull the film, thus reducing contrast. Pre-flashing is harder and a bit more risky in chrome than negative film, in my experience.

[Greg Lockrey]

I was going to also say that with transparency film it's easier to overexpose just pull the development times of the first developer. Like Darryl said. Flashing is trickier due to color shifts especially in the light tone areas.

[Bryan Lemasters]

Ed, Jiri, GPS, Darryl and Greg, thanks for your responses. I occasionally do pull processing, also, but was curious as to whether pre-flashing might offer any advantages. I suppose it's use would be most advantagous when using roll film, where you might only want the added contrast control on selected shots.