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View Full Version : Paper Negative timings - Help please.



bambooflyrod
01-05-2006, 12:40 PM
Can anyone help me please.

I've built a PH out of a 10"x7" box file. Depth/Focal length is 70mm. This acording to Pinhole Designer gives a pinhole of .37mm and an f stop of f189.

I intend using paper negs with the camera but I'm struggling to find where to obtain exposure timings.

I assume I rate the paper at asa6 but that's where I run out of info. I certainly don't mind experimenting etc, but did wonder if there is anywhere online with an exposure calculator.

I use Pinhole Designer a lot but the asa doesn't go low enough.

Any help would be appreciated.

Ian M

JoeVanCleave
01-05-2006, 04:15 PM
Ian; I usually run a series of calibration tests after finishing a new camera. Pour up your paper chemistry in the darkroom during the daytime, then go outside and do a series of tests.

A good starting time for f/190 is :30 seconds to 1:00 minute in bright daylight.

Once you find the optimal time in bright daylight, you can also do a test in cloudy daylight. I'd give cloudy daylight around 3:00-5:00 minutes as a starting time for your tests, with paper negatives.

Good luck, and post some images soon.

bambooflyrod
01-05-2006, 04:17 PM
Thanks Joe. As I said earlier, I'm not bothered about experimenting. That's all part of the fun, but I just needed some guidence and reassurance.

Many thanks. I'll let you know how it goes.

Ian M

JoeVanCleave
01-05-2006, 04:29 PM
One more thing I should mention is that my experience has shown that paper negatives, in the range of exposure they see with pinhole apertures, have a non-linear density response to exposure. Which is why light meters and other aides don't work well, as these are predicated on a linear response curve (that is, linear in a logarithmic sense).

Which is why I merely calibrate my cameras for two lighting conditions: bright sun and cloudy daylight, the two most likely scenarios within which I would be using my cameras.

If you have a particular special lighting circumstance, such as artificial lights for tabletop scenes, then you'd want to do a test series for that condition, as well.

Also, as others here know from my previous posts on the subject, I've taken to using graded paper for negatives. I find blue daylight activates the high-contrast emulsion of multigrade paper, making it even more difficult to get decent contrast that's printable.

bambooflyrod
01-05-2006, 04:47 PM
Thanks Joe. I appreciate the help.

I've loaded it up and will give it a shot tomorrow.

Ian M

steve irvine
01-05-2006, 05:48 PM
Ian,

The paper that I'm currently using in my cameras is Agfa Multicontrast B/W paper, Premium MCP 312 RC semi-matt.

As a guideline I'd suggest the following starting points. For bright sun on snow, sand or light coloured rocks, 45 seconds. For a sunny landscape of trees and grass 90 sec. - 2 min. For dull overcast days about 10 - 20 minutes. Interior photos with indirect light coming in a window 90 minutes to 3 hours.

As Joe mentions, the paper is very sensitive to the blue end of the spectrum and skies are usually totally washed out, even in short exposures. The paper is also designed to be insensitive to the red end of the spectrum (so that it won't be affected by darkroom safe lights) so it is difficult to get a good image if you try to illuminate the subject with an incandescent light. I see these light sensitivity qualities as characteristics rather than problems and try to use them to advantage when composing an image.

Hope this helps.

Steve

bambooflyrod
01-05-2006, 06:13 PM
Thanks very much Steve. I have jotted down what you and Joe have said and given half decent weather, I'll be out tomorrow somewhere. If I get a result, I should be able to post it tomorrw night.

Many thanks,

Ian M

taco
01-09-2006, 07:42 PM
Can anyone help me please.

I've built a PH out of a 10"x7" box file. Depth/Focal length is 70mm. This acording to Pinhole Designer gives a pinhole of .37mm and an f stop of f189.

I intend using paper negs with the camera but I'm struggling to find where to obtain exposure timings.

I assume I rate the paper at asa6 but that's where I run out of info. I certainly don't mind experimenting etc, but did wonder if there is anywhere online with an exposure calculator.

I use Pinhole Designer a lot but the asa doesn't go low enough.

Any help would be appreciated.

Ian M



I made a little chart based on Pinhole Designer and recalculated to 5 ASA (that's what I use for Ilford Multigrade IV, if it's 4 or 6 ASA is not so important) and it works more or less Attached files http://f295.f295.org/uploads/paper_8731.jpg (http://f295.f295.org/uploads/paper_8731.jpg)