Multigrade Paper Negatives

Introduction

I shoot all my pinhole and Wollaston Landscape photos using multigrade MG (or variable contrast VC) enlarging paper instead of film. It can be easily loaded and developed in a darkroom with a red safelight. Also, buying a box of 100 8x10 resin coated paper sheets and cutting each down to four 4x5s brings the cost to about $0.10 a shot or a fraction of sheet film. By the way, they need to be about a millimetre smaller in both dimensions to fit into a standard sheet film holder. The biggest downside to paper is that it has an equivalent film ISO speed of only about six where film would be in the hundreds.

You used to be able to buy contrast graded paper and by using low to average (0 to 2) contrast values get very reasonable negatives. However, due to lack of demand and the high cost of graded paper, only MG is readily available today. Right out of the box these papers will work fine but the negatives tend to have too much contrast for me. This web page describes my analysis and solution to the problem along with an alternative developer.

Spectral Sensitivity

Multigrade paper is mostly sensitive to light between near ultraviolet and green. The spectrum for a typical MG is shown above. Because of the insensitivity to the red end of the spectrum, processing with a red safelight is possible. But there is more to this spectrum than meets the eye. The paper is made with three emulsions where each has a different sensitivity to green light but the same to blue. If you only exposed the paper to green light, it would have a lower sensitivity as demonstrated by the lower slope in the figure on the left. If you only exposed the paper to blue light it would be much higher.

Contrast Control

When MG paper is used as it was designed, color filters are inserted into the light path of the enlarger to shift the spectrum from more green to more blue depending on the desired contrast. White light from an enlarger should result in a near average (2) contrast. However, most enlargers use incandescent lamps and I doubt they produce all that much light in the shorter wavelength UV end of the spectrum. This becomes a problem for using these papers as film especially outdoors. The sun has plenty of ultraviolet light and so the blue sensitive emulsion wins out and the negative tends to have too high contrast.

Filters

Sadly, the only way to control the contrast is to filter the light. Yes, it detracts from the elegant simplicity of a pinhole camera, but it might be worth the effort if you are looking for better quality photos. Below I've plotted the sensitivity of MG paper (blue line) along with four candidate photographic filters. All of these filters cut blue light but leave the green. They may also cut the red colors, but that doesn't matter.

1. Yellow Hoya Y2, K2, Nikon Y48, Wratten #8, B+W 022 - Fairly common for B&W and color looks a lot like the 00 MG filter

2. Yellow-Green Hoya X0, Wratten #13, B+W 060 - Lighter and more yellow than X1 green

3. Green Hoya X1, Wratten #11, B+W 061 - Fairly common for B&W but dark enough to require two full stops of exposure compensation

4. Green Wratten #58 - Not very common and is normally used to extract green for RGB systems

New Spectral Sensitivity

The new spectral sensitivity is calculated by taking the product of the paper sensitivity and the filter spectrum. I've plotted these below along with the total transmission. A total transmission of 0.5 would mean that the filter removed one half of the initial sensitivity. In other words, halves the ISO rating from 6 to 3, requires a 1 stop increase in exposure, or doubles the exposure time. For pinhole photography, where only time is controlled, Y2 and X0 would double the exposure time, X1 would be times 4, and a 58 times 6. So, Y2 and X0 look like the best choice.

Is it worth it?

The increase in exposure time is long, but not a deal breaker if it really results in significant improvement. Below is a page from an old 1977 Kodak Professional Photoguide that shows eight steps in brightness along with an 18% gray card and some color bars. I photographed this page without and with a green X0 type filter. On the left is the typical higher contrast image where only about five of the eight steps are discernible. On the right, the lower contrast is evident with all eight steps visible. Naturally the contrast of the right image could be increased with a little post processing, but what was lost in the left image is gone forever.

Examples

Here are two portraits shot in the same way, but the one on the left is nearly pure black and white while the one using a X0 filter shows considerably more variability and shadow detail. Then there are two power plant photos taken with a pinhole camera. Without the filter the sky is blown out, but with a Y2 filter the clouds and smoke are seen along with better detail of the power plant.

Vitamin C Developer

I try to keep my photography simple, so I was intrigued by all the fuss over Caffenol film developer recipes on the web. It does work on paper, but naturally the coffee stains the negative and it smells really bad. So I tried to try to find a substitute for the instant coffee. I started by leaving all the coffee out. That means you just have a base solution of water, washing soda and vitamin C. Then I’d try different things to substitute for the phenols in the coffee and see what works best.

To my surprise, the base solution worked really well all by itself. In fact, everything I tried that was supposed to have phenols in them didn’t make any real difference. This led to more Googling and to find a guy named Roger Bunting and his post on Shutterbug about Vitamin C developer. Also, reading between the lines of some enlarging paper data sheets, I’ve concluded that most have some developing agent right in the emulsion of these papers.

Here are some quotes:

• KENTMERE VC Select - Although VC Select does contain a developing agent within the supercoated layer, it is insufficient for use with activation processing.

• Arista Ultra VC RC - While the paper does contain developing agent, activation/stabilization processing cannot be used.

• ARISTA ULTRA GRADED RC - Developing agents incorporated into the emulsion layer facilitate rapid machine processing and a shortening of development times in manual processing.

• Adorama Variable Contrast Resin Coated - While the paper does contain developing agent activation/stabilization processing cannot be used.

• Ilford Multigrade IV RC Deluxe - is NOT developer incorporated. (However, this emphatic statement is not made for the other papers they make)

So after conversing with Bunting and experimenting with different quantities of washing soda and vitamin C, I’ve come up with this basic recipe:

• 25g Arm and Hammer Washing Soda

• 8g Pure Vitamin C Powder

• 250g Distilled Water

The cost is incredibly low. A 3 lb box of Arm and Hammer Washing Soda is about $4 which is nearly a lifetime supply. A 1 lb (453g) container of Vitamin C Powder is $14 or $0.25 per batch. Everything is just room temperature and it only takes a couple minutes to mix. I try to keep development time to 60 seconds. If I see the negative is over exposed, I'll pull it early. or if it is under exposed, I might push it a few minutes. I get about 16 4x5s per batch.

I thought I’d side by side compare this to Dektol. Maybe that isn’t the most state of the art developer in the world, but it is what I have and I assume represents real store bought chemistry. Here are two photos taken with identical conditions, developed for the exact same length of time, scanned and digitally processed at the same time. The results seem to be identical; Dektol on the left and Vitamin C on the right.