PDA

View Full Version : Expose direct positive paper



henk@apug
05-01-2012, 09:49 AM
Hello,

I was just wondering : with direct positive paper, should one expose for the
highlights, as opposed to expose for the shadows with negatives ?

ic-racer
05-01-2012, 02:19 PM
Exposing for the shadows, in B&W negative photography, makes the thinest printable negative (least possible exposure), which is usually a good thing. Since you are not using the paper as an intermediate, the latitude is zero. Therefore it does not matter if you make the least possible exposure (exposing for the highlights) or greatest possible exposure (exposing for the shadows) ; the exposure would be the same.

Personally I'd expose for the highlights because determining the first light gray band when calibrating your system is easier for me than determining the first dark gray band in the black area. You will probably not be able to make the assumption that the first gray band (usable zone) on either side of middle is 4 stops away from your meters factory calibration (like one does in negative B&W film calibration). Maybe it is more like 3 stops with the Ilford paper.

Maybe even easier is to forgo the spot meter and use an average meter. Adjust it to give the best possible image of your usual subject matter and lighting conditions.

andrew.roos
05-01-2012, 03:05 PM
You have to expose for both the shadows and the highlights, as you would a print. The dynamic range of Ilford Harmon paper is less than 3 stops unless it is pre-flashed as per the directions on the data sheet. That should make for some interestnig exposure trade-offs. (I'll be trying this in about a month when I'm running a class on pinhole cameras at my daughter's school).

Joe VanCleave
06-13-2012, 03:36 PM
Yesterday the itch was strong enough such that it required satiating by exposing a number of Harman direct positives in my Speed Graphic, using a 150mm binocular lens improvised as a camera lens, stopped down to 20mm aperture. Lighting was indirect north daylight, absent any artificial illumination.

All images preflashed and developed in Ilford PQ Universal paper developer for 2 minutes at 1+15 dilution.

Hat: (1:00 minute exposure)
http://farm9.staticflickr.com/8155/7369679618_3dd90fc874_b.jpg (http://www.flickr.com/photos/31285363@N07/7369679618/)
Hat001a (http://www.flickr.com/photos/31285363@N07/7369679618/) by jvcabacus (http://www.flickr.com/people/31285363@N07/), on Flickr

Pig: (45 second exposure)
http://farm8.staticflickr.com/7102/7369679344_29d0890f4d_b.jpg (http://www.flickr.com/photos/31285363@N07/7369679344/)
Pig001a (http://www.flickr.com/photos/31285363@N07/7369679344/) by jvcabacus (http://www.flickr.com/people/31285363@N07/), on Flickr

Candle: (1:00 minute exposure)
http://farm9.staticflickr.com/8006/7369679416_4028279735_b.jpg (http://www.flickr.com/photos/31285363@N07/7369679416/)
Candle001 (http://www.flickr.com/photos/31285363@N07/7369679416/) by jvcabacus (http://www.flickr.com/people/31285363@N07/), on Flickr

henk@apug
06-14-2012, 01:51 AM
Waaw, nice images Joe !