Lighting still life
cgrady
several professionals.
You are photographing a still life with a small flash system. Your
flash meter tells you that for a proper exposure you need to use f 4.0.
However, for proper depth of field you need to shoot with your lens at
f 11. How many times do you need to flash for f 11 ? When this
question first came up half the pros asked got it wrong. I want to see
what some have to say before I post the correct answer. You might not
believe it.
Clint H.
js
"cgrady" <cgra...@yahoo.com> wrote in message
news:1145891371....@y43g2000cwc.googlegroups.com...
>I was in camera sales for 21 years and have a question that has stumped
> several professionals.
>
> You are photographing a still life with a small flash system. Your
> flash meter tells you that for a proper exposure you need to use f 4.0.
> However, for proper depth of field you need to shoot with your lens at
> f 11. How many times do you need to flash for f 11 ?
Six
rafe b
I know little-to-nothing about flash but I'll take a stab.
The delta is three f-stops so the ratio is 2^3 = 8.
So my guess is 8x.
rafe b
www.terrapinphoto.com
Draco
but remembering the square inverse
law, 8 pops should do it.
Draco
Getting even isn't good enough.
Tom Ferguson
flash units have a short enough time period to invoke reciprocity
trouble. Meaning 9 to 12 might be needed. Polaroid is often used to
check this, but Polaroid's reciprocity doesn't equal film's. In reality
you should shoot a few sheets then develop the first, and see if the
others need a push/pull.
In article <1145896096.9...@j33g2000cwa.googlegroups.com>,
Jean-David Beyer
> In theory 8 pops, 3 stops from F/4 to F/11 (1x2x2x2). In reality, many
> flash units have a short enough time period to invoke reciprocity
> trouble. Meaning 9 to 12 might be needed. Polaroid is often used to
> check this, but Polaroid's reciprocity doesn't equal film's. In reality
> you should shoot a few sheets then develop the first, and see if the
> others need a push/pull.
>
enough, 8 should do it. Assuming the subject does not move (or wilt in the
case of one of Edward Weston's cabbage leaves), and the camera does not
move, and you do not jiggle the camera recocking the shutter (if you need
to). There are different intermittancy effects, and I think the one where
the time between exposures is too long would be the most important unless
the flash pulse is very short. My flash units put out about 1/300 second
which is long compared to some. But I would not have the patience to use
more than about 2 pops.
--
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David Nebenzahl
> ... and you do not jiggle the camera recocking the shutter (if you need
> to).
That would certainly queer the whole deal, unless you're some kind of LF
Houdini. And why would you need to recock the shutter? (I'm assuming
using "T" here.)
--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.
- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"
Jean-David Beyer
> Jean-David Beyer spake thus:
>
>> ... and you do not jiggle the camera recocking the shutter (if you need
>> to).
>
> That would certainly queer the whole deal, unless you're some kind of LF
> Houdini. And why would you need to recock the shutter? (I'm assuming
> using "T" here.)
>
>
shutter again.
In my case, using T is not too good because the ambient light would expose
the film if the lens is left open too long.
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David Nebenzahl
> David Nebenzahl wrote:
>
>>Jean-David Beyer spake thus:
>>
>>>... and you do not jiggle the camera recocking the shutter (if you need
>>>to).
>>
>>That would certainly queer the whole deal, unless you're some kind of LF
>>Houdini. And why would you need to recock the shutter? (I'm assuming
>>using "T" here.)
>
> Just because the easiest way to trigger my flash units is to release the
> shutter again.
>
> In my case, using T is not too good because the ambient light would expose
> the film if the lens is left open too long.
In that case, I'd suggest getting a solenoid, like the ones from
Crown/Speed Graphics. (Mine, on my Crown Graphic, works like a charm
using 4.5 volts from batteries.)
David Nebenzahl
> In that case, I'd suggest getting a solenoid, like the ones from
> Crown/Speed Graphics. (Mine, on my Crown Graphic, works like a charm
> using 4.5 volts from batteries.)
Nevermind; that wouldn't do much good to *cock* the shutter, would it?
(unless you had one big honking solenoid). Duh.
Bandicoot
Well, assuming everything else is such that I want to 'go with' the metered
exposure, and there are no other corrections for bellows draw or whatever:
From f4 to f11 is three stops. Double the light needed for each stop,
therefore I need eight pops of the flash. BUT, most film suffers from
intermitency at least as badly as it does from reciprocity failure, which
menas that I actually need more than eight - experience suggests that with
Velvia, for example, it would take about eleven pops.
Is that even close to the answer you expected?
Peter
Dean Van Praotl
Eight pops ought to do the job, but an extra pop
would certainly do no harm.
cgrady
worked for a couple months figuring out this problem. It came out from
a problem that one of our local photographers was having. Try this on
for size.
Most people think of the f stops as a fraction. Each f stop is 1/2 the
light of the previous stop. I did for several years because I was self
taught. I had to learn piecemeal by reading every article and book I
could get my hands on (Try Kodak's book, "The Art of Seeing." One of
the best I ever read)
f 4 = 1 flash
f 5.6 = 2 flashes
f 8.0 = 4 flashes
f 11 = 8 flashes
Total 15 flashes
I know I will get arguments, but we did try this one out. Also, I have
a couple ideas to improve portraits and flash photography. Just ask
they are both interesting ideas.
Clint H.
rafe b
> f 4 = 1 flash
> f 5.6 = 2 flashes
> f 8.0 = 4 flashes
> f 11 = 8 flashes
>
> Total 15 flashes
I don't buy it.
By what logic should these four values be added together?
Sorry, but the logic of adding these four values completely
escapes me.
rafe b
www.terrapinphoto.com
Tom Ferguson
reciprocity with intermitency in my explaination........ opps.....
In article <gmgr42hknrc8u9k65...@4ax.com>, Dean Van
Nicholas O. Lindan
> f 4 = 1 flash
> f 5.6 = 2 flashes
> f 8.0 = 4 flashes
> f 11 = 8 flashes
>
> Total 15 flashes
This isn't argument: I am quite sure
the above is flat wrong.
WRT to confirming experiment:
With reciprocity failure from short flash times
you may need 10-12 flashes instead of the 8
the mathematics predicts. The difference
between 8, 12 and the fictional 15
is 1/2 a stop. The slight overexposure
may appear pleasing on B&W or CN film and
be of no consequence.
The method above will always result in a ~+1
stop error.
Lets turn the above on its head and do it
in the sun:
f 16 = What the meter read = 1 unit of light
11 = + 1 stop = 2 units
8 = + 2 stops = 4 units
5.6 = + 3 stops = 8 units
At f5.6 the exposure is +3 stops over f16 => 8x the
light. If we add 1 + 2 + 4 + 8 = 15x the light and
we get the wrong answer!
--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics, Photonics, Informatics.
Remove blanks to reply: n o lindan at ix . netcom . com
f-Stop enlarging timers: http://www.nolindan.com/da/fstop/
Cheesehead
light source.
One must subtract the time & other light quantity to arrive at the
answer.
It's not just simple math.
If more time allows other light sources to expose the flim, then one
should
subtract from the flash count or flash output accordingly.
Collin
KC8TKA
Richard Knoppow
Strictly on the basis of light transmission its 8 times,
however, in practice the intermittancy effect will require
more and will depend on the film used. In general
intermittancy effect is related to reciprocity failure so
films with relatively little reciprocity failure will have
less intermittancy effect. For some films you might have to
double the number of pops.
--
---
Richard Knoppow
Los Angeles, CA, USA
dick...@ix.netcom.com
Bogdan Karasek
Hi,
David Nebenzahl wrote:
> Jean-David Beyer spake thus:
>
>> David Nebenzahl wrote:
>>
>>> Jean-David Beyer spake thus:
>>>
>> In my case, using T is not too good because the ambient light would
>> expose
>> the film if the lens is left open too long.
>
>
> In that case, I'd suggest getting a solenoid, like the ones from
> Crown/Speed Graphics. (Mine, on my Crown Graphic, works like a charm
> using 4.5 volts from batteries.)
I never could get information on what made the solenoids different in
the use of flash. In high school, in 1960-64, did the school paper
(basketball games, football) and the year book with a Crown with 4x5
sheet film and holders and an Electronic Flash, looked like a potato
masher. Didn't need a solenoid. What makes it different?
Regards, Bogdan
>
>
--
__________________________________________________________________
Bogdan Karasek
Montréal, Québec e-mail: bkar...@videotron.ca
Canada
"Wovon man nicht sprechen kann, darüber muss man schweigen"
"What we cannot speak about we must pass over in silence"
Ludwig Wittgenstein
________________________________________________________________
Nicholas O. Lindan
"Bogdan Karasek" <bkar...@videotron.ca> wrote
> I never could get information on what made the solenoids different in the
> use of flash.
A way to add synchronization to lenses that didn't have flash synch.
You press a button on the flash gun, current goes to the the solenoid
and trips the shutter and current goes to the flash bulb to set it off.
The delay in the flash bulb and in the solenoid is
such that the flash is at full power when the shutter is wide open.
It is Rube Goldberg retro-fit idea. If you take the solenoid
off then you have two holes in the lensboard, so the solenoid is
left on. They survived to preserve compatability with older
flash guns.
Solenoids could be purchased as after-market accessories.
> In high school, in 1960-64, did the school paper (basketball games,
> football) and the year book with a Crown with 4x5 sheet film and holders
> and an Electronic Flash, looked like a potato masher. Didn't need a
> solenoid. What makes it different?
The shutter had flash X-flash synch. I have a 1953 Ektar on a Speed
with an X-sych terminal and a solenoid.
wilt
times.
--wilt
at @the-wire.dotcom Lloyd Erlick
<cgra...@yahoo.com> wrote:
>I have
>a couple ideas to improve portraits and flash photography. Just ask
>they are both interesting ideas.
>Clint H.
May 8, 2006, from Lloyd Erlick,
I'm always interested in anything that might
improve my portraits, so please continue.
I'm afraid I know little about flash
photography, and I almost never use flash
myself, but others will be interested.
Thanks.
regards,
--le
________________________________
Lloyd Erlick Portraits, Toronto.
website: www.heylloyd.com
telephone: 416-686-0326
email: port...@heylloyd.com
________________________________
--