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Flash - one more time



 
 
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  #1  
Old August 26th 06, 06:09 PM posted to rec.photo.equipment.large-format
j
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Posts: 77
Default 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  
Old August 27th 06, 02:14 AM posted to rec.photo.equipment.large-format
Greg \_\
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Posts: 464
Default 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  
Old August 31st 06, 04:48 PM posted to rec.photo.equipment.large-format
Dave
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Posts: 36
Default 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  
Old September 8th 06, 05:09 AM posted to rec.photo.equipment.large-format
Bandicoot
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Posts: 470
Default 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  
Old September 8th 06, 07:10 PM posted to rec.photo.equipment.large-format
Dave
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Posts: 36
Default 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  
Old September 9th 06, 01:20 AM posted to rec.photo.equipment.large-format
j
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Posts: 215
Default 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  
Old September 9th 06, 03:55 AM posted to rec.photo.equipment.large-format
Bandicoot
external usenet poster
 
Posts: 470
Default 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  
Old September 9th 06, 02:57 PM posted to rec.photo.equipment.large-format
j
external usenet poster
 
Posts: 215
Default 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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