Many years ago I sent up my old Pentax 6x7 on a sturdy tripod, locked the shutter open and shot the entire fireworks display on a single exposure. When there was little fireworks activity, I would carefully place the lens cap on, then take it back off when the show started up again. The problems I faced with this was that on this particular year, the fireworks were very consistent with where they "bloomed" and I did get some color wash out. I did, however, get excellent detail in a bridge in the foreground. The film used (yea, it is that old) was Fujichrome 100. The 6x7 makes a 2.25x2.75 inch image and the Fujichrome provided nice crisp detail. The image ended up making it into one of the Oregon Coast magazines as the center fold. I would think that using a black card would be similar to what I did. The longer exposure will provide more detail in the surrounding areas that in my opinion provides more interest to the image. Obviously, one would need a sturdy tripod and just have to be careful not to move the camera when blocking the lens with the black card.
TV, 2000 Dodge RAM 2500 Quad cab short bed, Cummins 5.9, Edge Comp, Gauges.
5ver, 2011 Palamino Sabre 31 RETS.