Thank you for this tip. I think that grids and barn doors on my stripboxes might make them even better suited for the white rooms I so often shoot in. As for using them on standard light banks (shaped more like squares and less like strips), this approach is counter-intuitive for me (you can read why, below) but I will experiment with it if I can afford to buy or borrow banks and grids and barn doors of that kind.
Although it seems counter-intuitive to me I will try that approach. Thank you for recommending it.
You're welcome; if this turns out to work for you, then the credit should go not to me but to others who have recommended it to me (like someone I quote below, and whose explanation might make this approach seem less counter-intuitive).
I have found that a member of another forum is especially helpful and convincing on this topic (he documents large and small flat art all day long for a museum in a high-end studio--at the museum--designed and equipped specifically for this task):http://www.dpreview.com/forums/post/42063556
Veteran Member • Posts: 3,188
Lighting-Strip Boxes for 2D work
In reply to pilgrimage6
17, Jul 19, 2012
"One other thing that came up in the conversation was the use of softboxes. Using 2meter x 2 meter softboxes can be problematic when reproducing paintings. I prefer to use strip softboxes. We have 12" x 50" (30.5 x 127cm) Westcott softboxes. The reason I like using the strips is ideally when lighting paintings and other 2D works, you want the lights at 45 degrees. The problem with having a very wide softbox (like a 2m x 2m) the problem is the center of the soft box may be at 45 degrees, but depending on how close they are to the painting, the one side of the soft box might be [at] 30 and the other side might be [at] 60. If you had a smaller work of art and got the softboxes very close, the one edge might be [at] 90 and the other might be [at] 180. The reason you want 45 degrees is to reduce the amount of specular highlights (as the saying goes "angle in = angle out"). As the angle gets closer to 90 degrees (directly where the camera is) the amount of reflection coming back is greatly increased so you get a lot more specular highlights. Now if your light source is closer to 180 degree you end up with the problem that you get more raking light and the edges will be noticeably brighter than the center."
"Ok[:] so you want a small light right at 45 degrees... well[,] not quite[:] a pin-point light will cause harsh shadows on any texture or impasto, [so] you want a broader source. Also if you have 2 pin point lights right level with the camera at 45 degrees[, then] the top and bottom of the object will be darker than the center. So if we use vertical strips it makes the light a little softer and keeps the illumination more even from top to bottom, but it doesn't create the extra specular highlights that a square light source would cause."
"Also it's possible to get rolls of 12" or 18" polarizing material which you can use to make frames to go infront of the strip boxes. This will help if you need to cross polarize.-- ~K"
I (Mark) quote K here not only because he can explain it better than I can but also because he's one of the people I mention above who seem to be especially good at doing this kind of work, and who knows better than I do what he's talking about. Though I have found so far that his advice on strip boxes for this application seems to hold true.