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how long is the exposure?!?!?!?!?!?



 
 
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  #1  
Old August 26th 06, 01:35 AM posted to rec.photo.darkroom
max
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Posts: 22
Default how long is the exposure?!?!?!?!?!?

HI, i was wondering about how long my exposure time should be for a
quaker oatmeal box pinhole camera. the hole is about 1/8 inches and i'm
using black and white paper. pleeez help me out
thanks

  #2  
Old August 26th 06, 02:08 AM posted to rec.photo.darkroom
Richard Knoppow
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Posts: 751
Default how long is the exposure?!?!?!?!?!?


"max" wrote in message
ups.com...
HI, i was wondering about how long my exposure time should
be for a
quaker oatmeal box pinhole camera. the hole is about 1/8
inches and i'm
using black and white paper. pleeez help me out
thanks

Since pin holes do not have a definite focal length the
equivalent f stop is calculated from the distance the hole
is from the image.
A 1/8th inch hole is too large. A more reasonable size
would be around 1/50th or 1/75th inch, very small.
You can get some information from Kodak at:
http://www.kodak.com/global/en/consu...leCanBox.shtml

The instructions there talk about Kodak Kodabromide paper
which has been discontinued. However, most variable contrast
paper has a somewhere from the same to about half the speed
when used without a filter.

Another good site is:
http://www.photo.net/learn/pinhole/pinhole
Which has the formulas for calculating the optimum size of
pinhole and its effective f stop.
The pinhole size is not at all critical. Also, while an
ideal pinhole should have no burrs around the edges the
difference in practice is slight so a pinhole made by
pushing a pin through some aluminum foil will work fine.

If you use an exposure meter the effective speed of
typical fast enlarging paper is around ISO-5.
You will, of course, get a negative, but you can contact
print to another sheet of paper to get a positive print.


--
---
Richard Knoppow
Los Angeles, CA, USA




  #3  
Old August 26th 06, 02:18 AM posted to rec.photo.darkroom
Greg \_\
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Posts: 464
Default how long is the exposure?!?!?!?!?!?

In article . com,
"max" wrote:

HI, i was wondering about how long my exposure time should be for a
quaker oatmeal box pinhole camera. the hole is about 1/8 inches and i'm
using black and white paper. pleeez help me out
thanks


1/60 of a second for the white side of the paper, and 1/2 second for the
Black side.
--
Reality-Is finding that perfect picture
and never looking back.

www.gregblankphoto.com
 




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