Undersize apeture versus exposure time

[dickbromberg]

I am pretty new to pinhole photography and I need some advice.
I am almost finished putting the camera together.
The length from the pinhole to the film plane is 45 mm I expect to shoot Kodak tmax 100 film. The frame size will be 24 mm high and anything from 24 mm to about 50 mm wide. I included a removable mask so I can shoot wider than normal images.

I used a pinhole calculator ( http://www.mrpinhole.com/calcpinh.php ) and came up with a pinhole size of .283 mm and an f stop of 159 and an exposure time of a half second.

Now that seems to be a problem because how can I reliably expose the film with a manual shutter of a half second.

So I went back to the pinhole calculator and plugged in a couple of other pinhole sizes without changing any of the other parameters and found that if I reduce the pinhole diameter by about ten percent (down to .255 mm) then the exposure time goes up to 1.22 seconds. Using a manually operated shutter I’m sure I can approximate 1.22 seconds more accurately than one half of a second.

So the question comes down to the following:
Should I use an undersized pinhole diameter and a better approximation of the exposure time or should I use the correct pinhole diameter and a poorer approximation of the exposure time???

I understand that I could insert a neutral density filter inside the camera to extend the exposure time but I’d like to avoid that if possible.

Thanks for any suggestions.

Dick Bromberg

 

[RobertP]

What if you rated the 100 at half the box speed and developed accordingly? Or go to a 50 asa film? But I use an old studio shutter and I can get shutter speeds at 1/2 sec very consistantly. Same with a Packard shutter. I've seen guys use the lens cap and get pretty consistant at 1/2 sec. 1/2 sec is still pretty slow.

 

[dickbromberg]

What if you rated the 100 at half the box speed and developed accordingly? Or go to a 50 asa film? But I use an old studio shutter and I can get shutter speeds at 1/2 sec very consistantly. Same with a Packard shutter. I've seen guys use the lens cap and get pretty consistant at 1/2 sec. 1/2 sec is still pretty slow.

I am not familiar with this process. The pinhole calculator shows an exposure time of about two seconds for asa 50 film. That would be fine, but how do I adjust the developing time to accomodate this? Do I just cut the developing time in half??

 

[RobertP]

Dick, Yes you would reduce the development time. By how much depends of a few variables, such as developer type, temp, technique...ect...ect. Your best bet would be to shoot a few sheets and test. You will dial it in eventually. Just develope a consistent work flow. Processing the film coming out of a pinhole camera is no different than shooting the same film in any other camera and processing. Also if the problem you are having in achieving 1/2 sec exposure or even a 1 second exposure is because you are trying to use a stop watch to time your exposures then I suggest you put the stop watch away and try just counting. Something along the line of..one one thousand. You'll find it much easier and with a little practice you can get extremely accurate. Also don't forget to account for film reciprocity which will increase your exposure times also.