Our local camera club has a once a year Christmas banquet. What better place, I thought, to try my hand at a banquet photo. The lighting would be the major challenge and I decided to use flashbulbs. A typical flash bulb has a guide number of 320 against a powerful electronic flash having a guide number of 100. However, that is deceptive as the camera mount flash has an angle of illumination of about 50 degrees and the bulb flash has an angle of 120 degrees. Ad to that that a guide number of 320 is not three times 100 but three squared or 9 times. This is because of the inverse square law which says that it takes 9 times as much light when you are three times as far away. So when you figure the area of a 120 degree coverage compared to a 50 degree coverage and then say you can be three times as far away you get to the fact that a single flash bulb is about 16 times as powerful as a good shoe mount or handle mount electronic flash.
To light the whole room, I ended up using 7 flash bulbs spaced at about 15 feet from each other. I had wanted to get some lights to the other side of the room but the slave flash I had wouldn't trigger with a flash bulb. Flash bulbs are still manufactured in Ireland but are very expensive. Most of the ones that I used represented horded stock from garage and estate sales purchases where I probably averaged 15 cents apiece. However, on Ebay they bring about $1 each now-a-days. So all in all with tests shots, set up shots etc, I burned about $100 worth of flash bulbs.
http://www.flashbulbs.com/index.shtml
In order to be sure I got something and to minimize the use of flash bulbs, I rigged up two cameras. One a 4x5 to use Polaroid type 55 positive negative film. (Developed with Ansel Adams as a consultant) and an 8x10 using TriX pan film. I set it up so that I triggered the 8x10 camera with a cable release, the flash contacts on the 8x10 shutter triggered both the flash bulbs and a solenoid which triggered the shutter on the 4x5 camera. So every time I tripped the shutter, I got an 8x10 negative, a 4x5 negative and a 4x5 print. (Pretty cool eh!)
This is a picture of me with the camera club president in front of the two cameras. I mounted the cameras as high as I could so that people in the front wouldn't block out people in the back.
As it turned out, it was lucky that I used two cameras because I didn't get anything at all worth keeping from the 8x10. This was because the shutter was off by about 1 F stop. Normally this wouldn't have been a problem and old shutters are usually slow. However, this shutter when set at 1/25 of a second was more like 1/50th. This meant that I lost quite a bit of the burn time of the flash and even by push processing the TriX I was still way underexposed.
However I learned a great deal and was as successful as I was do to a goodly amount of information and advice I got off the internet.
http://largeformatphotography.info/lfforum/topic/499876.html
My goal was to get a photo so sharp you could see freckles on people's faces and one that would stand an enlargement up to about 4x5 feet. I wanted to do it with nothing that wasn't available in 1940. I didn't use anything invented after 1940 but as far as getting something that could be enlarged to 4x5 feet, I missed that by a mile, but I learned enough that I expect to get it right next year.
Banquet
photo lessons learned
Things done right;
Triggering second camera with solenoid.
Using Polaroid Type 55.
Rubber maid containers of sodium sulfate and water (for the type 55)
Getting a high angle.
Dual camera mounting plate.
Focusing targets and stands
Stabilizing tripod to column.
Back up battery charger for enough current to trigger bulbs and solenoid.
Using flashlights to focus on.
Using TriX for 8x10
Using flashbulbs for enough light.
Making test negatives before people showed up to test development times.
Things done wrong:
Not enough flash lights to focus on. (A large format ground glass can be very dark so people use flash light filaments to focus on.)
Not allowing enough time to set up.
Not stabilizing flash stanchions
Not controlling flash cords
No light on the other side of room
Not getting far enough back to minimize difference in size of people.
Not using bigger tripod and getting in center of room so side table wasn’t blocked by columns.
Not using yellow filter with single element.
Not checking shutter speed (Main shutter was more like 1/50th than 1/25 which was critical because lose of burn time for bulbs cause a several stop underexposure.)
Not using a gray card to measure flash output. (had one but ran out of time)
Not cleaning contacts in flash fixtures
Not putting a gray scale in test negative shots (had one but ran out of time)
...