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Saturday, June 8

Getting to grips with Paper Negatives

Not too bad at all considering the tonal range in this scene. This was a four
minute exposure through a yellow filter. Please ignore the fingerprints, spots
and marks on this image and the others: I had dirty fingers after mixing
chemicals and was pretty sloppy in my approach.

This has been an enjoyable couple of days. Paper negatives strip photography right back to the basics. The learning curve seemed steep at first but when you get into it, it's a fairly simple process. Not that I've even scratched much off the surface, let alone begun to master it, but I feel I know enough to be able to go out into a landscape and expose a few sheets of paper without making an idiot of myself.

As I said in my previous post on the subject, the big problem is coping with the high contrast that the process generates.* It seems to be a combination of the paper's sensitivity to blue light and its restricted tonal range. Once I learned how to deal with that, then things got a little easier.

An eight minute exposure through the yellow filter. Compare this one
with an eight minute exposure and no filter below.

Without the yellow filter (and even allowing for what is a stop more exposure),
the blue light has a tendency to swamp the image

The use of a yellow filter - the same type you would use with film to darken a blue sky - helps to overcome the high blue sensitivity of the paper. You can see the difference it makes in some of the scans on this post. When I was doing a few tests, I opened up a stop to make up for the light loss caused by the K2 filter but I think a half a stop is all I'd need to allow.

Quite an improvement on the same scene in my first post about paper
negatives and largely down to the filter.

A one second exposure at f11 with the filter in place.

The same exposure and no filter.

The other technique to control contrast is to pre-flash the paper. This can be done in two ways: either a brief exposure to light can be given to the paper when it is out of the camera or a pre-exposure can be made when in camera through an opal diffuser.

In my first attempt at paper negatives, I played around with the pre-exposure option. Basically you take a meter reading of the scene through the diffuser, close down three or four stops depending on whether you want a zone one or zone two pre-exposure and make an exposure at that setting with the diffuser held in front of the lens. The actual photograph is then double-exposed onto the same piece of paper. 

"The Key". I've been toying with the idea of shooting some
out-of-focus images of people because I love the way light
bends round a backlit body to create an abstract version of
a person. This was was shot at f8 on the Speed Graphic
through an old 127mm Ektar lens but f5.6 would have
been better. This was a two minute exposure with pre-flash
and a yellow filter. The bokeh is lovely.

The sophisticated set-up for the above shot.
A cardboard box "tripod" and a filter held in
place by electrical tape. The camera is just out-
side Freya's bedroom (my old darkroom) which
I'm about to repaint.

Paper, like film, has some inertia to photons, requiring a certain level of exposure before anything starts to record on the emulsion. The pre-exposure is designed to overcome this inertia so that any light that subsequently falls on the paper actually does record as a tone. This isn't so much a problem with the highlights which get plenty of light but it can be for dark shadows where there's little light to overcome the inertia. Pre-exposure, where paper is concerned, has the effect of expanding the range of tones that are capable of being recorded. It also means that a little less exposure can be given for the same shadow detail which helps to prevent the highlights from overcooking. First time round, I gave a zone one pre-exposure but I didn't feel that was enough.

So for my second attempt, I resorted to the pre-flash. The paper was placed under the enlarger with the lens stopped well down, the head as far up as it would go and no neg in the carrier. I did a test strip to find how much exposure had to be given to raise the paper's sensitivity to the threshold level where inertia is overcome. Part of the test strip was covered to stop light hitting it so that I'd know what unexposed paper should look like when trying to decide the minimum exposure needed.

You can see the first test strip above. There are seven grey tones visible above the white strip. All of these tones had gone beyond the threshold and would have resulted in the paper being fogged rather than pre-flashed.

This was the second test strip with reduced exposure times. You should be able to see three grey tones at the left hand side of the strip. The tone just before them was the same white as the unexposed paper so that was the threshold exposure time. All of the paper negatives I exposed were given this minimum exposure before going into their dark slides.

Having had a bash, roughly figured out what's going on and being reasonably confident of what I'm doing, I'll now think about going outside with the Speed Graphic and doing some "reconnaissance" for the WWII project. It's all good practise in getting used to the camera and will stand me in good stead when the time comes to start shooting some expensive sheet film.

* Jan on The Online Darkroom Flickr group suggested using film developer instead of print developer to reduce contrast. He says it works very well but I've yet to have a go.


Nasir Hamid said...

Thanks for this info. I've tried pre-flashing in the past but never managed to master it. Does it matter what grade you use? How long was your final exposure?


Hi Nasir,
My understanding is that the grade does make a difference but I haven't done any testing of my own. Maybe someone else can comment? The final pre-flash was seven seconds at f11 with the enlarger at the top of the column.

morris1800 said...

Admire your approach and patience Bruce look forward to see you posting the results from in the field. I am an admirer of Andrew Sanderson's work in this area who takes advantage of the properties of shooting paper here's a link to his site. In his book he uses pencil applied to back of paper for dodge/burn when producing positives.


Thanks for the link to Andrew. Andrew reads The Online Darkroom and I'm hopeful that he'll reveal some of his tricks for us.

morris1800 said...

That would be great Bruce, Andrew is an excellent photographer with great darkroom skills who as explored many techniques a winning combination for sure.

Jen Nifer said...

Thanks for this informative post, Bruce. I've yet to try flashing paper, but it obviously helps with contrast. I also need to get a yellow filter. My Crown Graphic is begging for me to pick her up again...