The pre flash compensation...

[marciofs]

I tried pre flash the paper to shoot with a pinhole camera. I follow the instructions given by Ilford on how to pre flash. But I forgot to think of the compensation when shooting, because if the paper was pre exposed the exposition time when taking a photograph will be shorter isn't it?

But how to know how long short will be the exposition time when shooting?

Because I forgot about it all my shots were over exposed.

 

[Rich Ullsmith]

Preflashing paper for phole stuff, I really think you are going to have to experiment. Keep all your variables consistent, take notes.

 

[marciofs]

This is bad :/

 

[Doremus Scudder]

I tried pre flash the paper to shoot with a pinhole camera. I follow the instructions given by Ilford on how to pre flash. But I forgot to think of the compensation when shooting, because if the paper was pre exposed the exposition time when taking a photograph will be shorter isn't it?

But how to know how long short will be the exposition time when shooting?

Because I forgot about it all my shots were over exposed.

Marco,

If you just pre-flash to raise the exposure threshold of the paper and get more shadow detail in your paper negative, the exposure should not change that much from what you are used to. Many of us pre-flash film for the same purpose, and the enhancement of shadow detail only happens in the lowest Zones (i.e., the least dense areas of the negative). Mid-tones and high values should be unaffected for all practical reasons.

If your paper negatives were all overexposed, then you exposed too long or flashed way too much. Have you done a test to determine the exposure threshold of the paper you are using?

If you do, and flash just below that, then things should not be bad

Best,

Doremus

 

[marciofs]

I did the test but maybe I picked the wrong option (3sec pre flash exposure). I will pre flash 1sec and see if it works better.

Thank you.

 

[MattKing]

If your film/paper holder has a darkslide, you can experiment with a number of different amounts of pre-flash on the same sheet. Essentially you use the same procedure as when doing a test print in the darkroom.

Reduce the intensity of your light source and do several one second pre-flashes - move the darkslide 2.0 cm after each one. The cumulative amount of pre-flash on each section will be different. Then expose the entire sheet in your camera as calculated.

Afterwards, pick the section that worked best. If it was the one with three one second exposures, you need to remember that in order to duplicate the result, you need to use three one second exposures - not one three second exposure.

 

[marciofs]

This is what I did Matt. But I choose the wrong section...

I am actually thinking on doing this text but before develop the paper I load it into the camera and take a picture. Then I develop.
Like this I can see which one is the best time exposition pre-flash.

 

[RalphLambrecht]

i preflash with a yellow filter or adiffuserat the same exposure settings as the image forming exposure.