RE: Trick for long exposures

2001-05-29 Thread Patrick White 


Ayash Kanto Mukherjee wrote:
 My procedure is like this. I make changes in the ISO setting
 of the camera
 and fool the lightmeter.
...
 Recently, Todd pointed out that some of the older bodies like K1000 or
 Canon AE1 are unable to measure the light using light meter
 for high speed
 films and low shutter speeds like 1/4 sec. If that is the
 situation, then
 the trick described above will be of no use to determine the
 duration of
 long exposures.

I've used the same procedure.  When the light meter in the K-1000 shut off
for lack of light, I punted and used spot meter mode of my PZ-1p body as a
light meter since it is more sensitive.  Without it, I would have had to
guess -- I probably would have picked the part of the scene I wanted to
meter from and then moved close enough to get a reading off only it to use
as a starting place.
One thing I learned to be careful about with my K-1000 (and maybe others
need to be as well?) is that down at the extreme end of the light meter
range, the metering gets severely non-linear.  When I'm close to that range,
I always check the reading by making a one-stop change.  If the needle
deflects more than I expect a one-stop change to do, then I can't trust
either reading.

hope that helps,
patbob ([EMAIL PROTECTED] [EMAIL PROTECTED])

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RE: Trick for long exposures

2001-05-29 Thread Ayash Kanto Mukherjee 

On Tue, 29 May 2001, Patrick White wrote:
   I've used the same procedure.  When the light meter in the K-1000 shut off
 for lack of light, I punted and used spot meter mode of my PZ-1p body as a
 light meter since it is more sensitive.  Without it, I would have had to
 guess -- I probably would have picked the part of the scene I wanted to
 meter from and then moved close enough to get a reading off only it to use
 as a starting place.
   One thing I learned to be careful about with my K-1000 (and maybe others
 need to be as well?) is that down at the extreme end of the light meter
 range, the metering gets severely non-linear.  When I'm close to that range,
 I always check the reading by making a one-stop change.  If the needle
 deflects more than I expect a one-stop change to do, then I can't trust
 either reading.
 
 hope that helps,
 patbob ([EMAIL PROTECTED] [EMAIL PROTECTED])

Hi!
Many thanks for suggestion. Yes, it helped me. I didn't know that the
lightmeter of K1000 also behaves nonlinearly under certain situation.

With kind regards,
Ayash Kanto.

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Re: Trick for long exposures

2001-05-27 Thread Peter Alling 

I guess you would have to go back to dead reckoning after a fashion.

First off  bw film does suffer from reciprocity failure.  According to 
Kodak tri-x requires
a 3 stop increase in exposure at an indicated exposure time of 100s and 
plus an increase
in development time.  You can find  data sheets for various emulsions in 
their respective
data guides.  At least the kodak data guides contain this information.  If 
you're using
bw film you can get acceptable exposures if you stop down the lens to 
about f8 for 35mm and
and bracket around a 1 minute exposure time. don't bother making small 
exposure
changes change by at least 2 stops and depend on the film latitude to help you
out.  Since you're using these long exposures you are probably taking 
photos of rather static
subjects so taking a series of 5 shots would be my recommendation.  True 
this doesn't exactly
give you a determination of proper exposure but you should get one or two 
negatives with an
acceptable range of contrast and detail.

At 11:59 PM 5/27/2001 +0530, Ayash Kanto wrote:

Hi all!

Recently, I started a thread on Long exposures and I got quite helpful,
creative replies from many of you. I shall like to thank once again to all
who contributed to that thread.

As a continuation of that thread, I have something new to discuss and that
is the trick for determination of long exposures.

My procedure is like this. I make changes in the ISO setting of the camera
and fool the lightmeter. Suppose, a film of 400 A.S.A. film is loaded in
the camera and the shutter dial allows a minimum shutter speed of 2
sec. If the lightmeter shows an underexposure with full aperture at 2 sec,
I change the film speed to 3200 A.S.A., an increase of 3 stops and suppose
the lightmeter shows correct exposure at 2 sec with maximum
aperture. Therefore, for 400 A.S.A. the correct exposure will be 16
sec. in principle. However, for colour films, reciprocity failure is a
significant factor to think about and therefore one should take care of
that. I don't know the situation for black and white films. Do black and
white films also suffer by reciprocity failure? If no, then f/4 at 16 sec
will give correct exposure with a 400 speed film.

Recently, Todd pointed out that some of the older bodies like K1000 or
Canon AE1 are unable to measure the light using light meter for high speed
films and low shutter speeds like 1/4 sec. If that is the situation, then
the trick described above will be of no use to determine the duration of
long exposures.

In that case, how shall I proceed to determine the duration of exposure?

Any comments, suggestions, explainations will be well appreciated.

With kind regards,
Ayash Kanto.

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