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#1
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Flash - one more time
Been ill and forgetful. Forgive the stupid question.
Using flashbulbs. Say I know the outcome for one bulb, and need four more stops. How many flashes do I have to make? 15? |
#2
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Flash - one more time
In article ,
"j" wrote: Been ill and forgetful. Forgive the stupid question. Using flashbulbs. Say I know the outcome for one bulb, and need four more stops. How many flashes do I have to make? 15? 15 or 16 soundz right. -- Reality-Is finding that perfect picture and never looking back. www.gregblankphoto.com |
#3
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Flash - one more time
Greg "_" wrote:
In article , "j" wrote: Been ill and forgetful. Forgive the stupid question. Using flashbulbs. Say I know the outcome for one bulb, and need four more stops. How many flashes do I have to make? 15? 15 or 16 soundz right. Just as Greg has said, 16 is the correct answer. To add: 1 stop - 2 pops 2 stops - 4 pops 3 stops - 8 pops 4 stops - 16 pops 5 stops - 32 pops etc. Benn there, done that. Hope this helps, Dave |
#4
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Flash - one more time
"Dave" wrote in message
... Greg "_" wrote: In article , "j" wrote: Been ill and forgetful. Forgive the stupid question. Using flashbulbs. Say I know the outcome for one bulb, and need four more stops. How many flashes do I have to make? 15? 15 or 16 soundz right. Just as Greg has said, 16 is the correct answer. To add: 1 stop - 2 pops 2 stops - 4 pops 3 stops - 8 pops 4 stops - 16 pops 5 stops - 32 pops etc. Except that the intermittency effect means that after a while more pops really don't add as much exposure as they 'should' - a special case of reciprocity effect, but somewhat more severe. This means I find the sequence can be closer to 2 - 5 - 12 - 30 or worse. Run a test with electronic flash (so as not to waste a load of expensive bulbs) and you'll find the correct sequence for your particular film choice. Peter |
#5
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Flash - one more time
Bandicoot wrote:
"Dave" wrote in message ... Greg "_" wrote: In article , "j" wrote: Been ill and forgetful. Forgive the stupid question. Using flashbulbs. Say I know the outcome for one bulb, and need four more stops. How many flashes do I have to make? 15? 15 or 16 soundz right. Just as Greg has said, 16 is the correct answer. To add: 1 stop - 2 pops 2 stops - 4 pops 3 stops - 8 pops 4 stops - 16 pops 5 stops - 32 pops etc. Except that the intermittency effect means that after a while more pops really don't add as much exposure as they 'should' - a special case of reciprocity effect, but somewhat more severe. This means I find the sequence can be closer to 2 - 5 - 12 - 30 or worse. Run a test with electronic flash (so as not to waste a load of expensive bulbs) and you'll find the correct sequence for your particular film choice. Peter I bow to Peter's superior experience. I've only done this a couple of times and it was quite a while ago. My answer while correct in theory may not hold up in actual practice. It did work for me, but if memory serves, (doesn't always these days) I only needed to add a couple of stops. Dave |
#6
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Flash - one more time
Bandicoot" "insert_handle_here wrote:
2 stops - 4 pops 3 stops - 8 pops 4 stops - 16 pops 5 stops - 32 pops etc. Except that the intermittency effect means that after a while more pops You missed the reply, Bandicoot. My bulbs are all Edison base. You know, that filthy, unwashed Victorian era American Edison. Anywho, it's sooooo easy to build dirt-cheap flashes for Edison bulbs. They all go off at once. |
#7
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Flash - one more time
"Dave" wrote in message
... Bandicoot wrote: "Dave" wrote in message ... Greg "_" wrote: In article , "j" wrote: Been ill and forgetful. Forgive the stupid question. Using flashbulbs. Say I know the outcome for one bulb, and need four more stops. How many flashes do I have to make? 15? 15 or 16 soundz right. Just as Greg has said, 16 is the correct answer. To add: 1 stop - 2 pops 2 stops - 4 pops 3 stops - 8 pops 4 stops - 16 pops 5 stops - 32 pops etc. Except that the intermittency effect means that after a while more pops really don't add as much exposure as they 'should' - a special case of reciprocity effect, but somewhat more severe. This means I find the sequence can be closer to 2 - 5 - 12 - 30 or worse. Run a test with electronic flash (so as not to waste a load of expensive bulbs) and you'll find the correct sequence for your particular film choice. Peter I bow to Peter's superior experience. I've only done this a couple of times and it was quite a while ago. My answer while correct in theory may not hold up in actual practice. It did work for me, but if memory serves, (doesn't always these days) I only needed to add a couple of stops. It also varies a fair bit from film to film, and if you were using negative film any resulting under-exposure may not have been noticeable at all in any case. Going for four stops on Velvia I definitely notice the effect though. Peter |
#8
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Flash - one more time
Speaking of intermittency (attributes lost, sorry)
[...] Run a test with electronic flash (so as not to waste a load of expensive bulbs) [...] Incorrect! The period of exposure is significant. An electronic flash delivers a much shorter period of exposure. The difference is profound. |
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