Understanding Contrast Control in the Darkroom
Film photography and darkroom printing are actually on the rise. The processes aren't nearly as popular as they were before the 1990s, and never will be again, but for the last five years the market has seen increases. There are dozens of tutorials about processing film, but we're going to look at more advanced topic crucial to printing in the darkroom.
For the purposes of this tutorial, we'll be talking about black and white printing in the darkroom. Color printing requires different techniques and equipment. I'll be referring to some basic equipment in this article, including an enlarger.
An enlarger holds the negative in place and projects light through it and then through a lens. The image from the negative is projected on to a baseboard where you'll place photosensitive paper. This is the basis of all traditional printing.
When printing in black and white, there are really only a few things you need to control. First is the focus of the image. You'll use a grain scope and the focusing knobs on your enlarger for that task.
Next, you'll need to control the brightness of your final print. You do this using a timer. Enlarger lenses have apertures that also affect how much light is hitting the paper, however, it's best to stop down to achieve a sharp image and leave it (f/11 is good for most setups).
The timer is used to make exposures in seconds. Depending on the amount of enlargement and the density of your negative, you may have a ten second exposure or exposures that last several minutes. It may seem counterintuitive, but the longer you exposure the paper to light, the darker your print will be.
The final thing you must control in the darkroom is contrast, and that's what we'll be talking about today.
Contrast is the amount of separation between the bright tones in an image and the dark tones in an image. High contrast images have white tones and black tones and few grey tones in between. Low contrast images have a lot of different grey tones, but no true whites or true blacks.
If an image has too much contrast is will look like a bad photocopy. If an image doesn't have enough contrast it will appear muddy and is often described as being "flat."
Exposure (both in-camera and during the printing process) also plays a role in contrast. If you have too many black or white tones in an image, it might be an exposure problem and not a contrast problem.
Proper contrast in a black and white image usually means that the very brightest part of the image is white, and that the very darkest part of the image is black. If you're familiar with histograms, adjusting your image with a "levels" adjustment like the image below would achieve this.
Unlike, a levels adjustment, contrast controls in the darkroom affect both the highlights and shadows at the same time. There's no easy way to adjust them independently.
Another way of thinking about contrast is to consider it as clipping tones. The more contrast you add the more things you're turning black or white. Increasing a step in contrast would turn the things that are very dark grey and very light grey into black and white. Taken to the extreme, the highest possibly contrast in an image would turn all the tones either pure black or pure white.
In the darkroom, it's a bit more trial and error than a levels adjustment, but this gives you an idea of what you're trying to achieve. However, the tools used to achieve contrast adjustment are about as different from a histogram as photography is to painting.
Contrast Control with Graded Papers
There are generally three ways to control contrast in the darkroom. These are individual methods, so you'll pick one and go with that. They aren't used together. The first of these methods is to use graded papers.
There are many different types of photosensitive papers with different finishes or different materials, but they all fall into two main categories: graded or variable contrast. Graded papers are typically used in sets. So if you like heavy weight glossy paper from Ilford, you'll buy several boxes of that paper in different grades.
Graded papers come in range from one to five. Papers with a grade of one produce the lowest contrast. Papers with a grade of five produce the highest contrast.
Using graded paper is easy. If you're print is flat, step up a grade and try again. If your print has too much contrast, simply step down a grade.
Contrast Control with Variable Contrast Paper
I mentioned earlier than there are two main types of paper, and variable contrast is the second type. VC paper, as it's called, allows you to produce a variety of contrasts using the same paper. You do this buy changing the color of the light you project onto the paper. By adding magenta to the light, you increase the contrast.
While you can technically decrease the contrast with yellow filters, this is rarely done because VC paper is relatively low contrast when no magenta is used. However, yellow filtering does have another use we'll discuss in a minute.
There are two ways to filter the light coming out of your enlarger. You can use a filter set, or you can use a color enlarger which will have graduated filters for cyan, magenta and yellow.
The problem with filters is that they affect exposure. As you increase the density of the magenta filter to get more contrast, it absorbs more light. You then have to compensate by increase your exposure time. However, filter makers have come up with a way around that.
Using Filter Sets
You can buy filter sets new or used, and they are made by a variety of companies. Ilford and Kodak are probably the two most common ones. They typically come in steps similar to graded papers, one to five with one producing the least contrast. Many come with half steps as well, so you can fine tune the contrast more than you could with graded papers.
If your print is flat, you move up to a higher number (adding more magenta to the light) and you'll get a print with higher contrast.
The awesome thing about these filter sets is that they don't affect your exposure time very much. By mixing yellow and magenta light, they are able to keep the density of the filter constant. So jumping from one to another won't affect your exposure time. It's brilliant.
Of course, there are exceptions, but they really try to make it easy. My Ilford filters use the same exposure for steps one through three, but if you jump to 4 or 5, you have to double the exposure. Pretty easy right?
Using a Color Enlarger
Using a color enlarger gives you the most control over your contrast. Color enlargers will have a knob that allows you to change the magenta filtering is very small increments. The issue with doing this is that it will affect your exposure.
Being that the enlarger also has a yellow filter, you could attempt to reproduce the affect that filter sets have to keep your exposure the same. However, this is very tedious as every enlarger is different and a huge amount of testing is required before you could do it with any confidence.
Graded Versus Variable Contrast Paper
When you start printing, one of your first decisions needs to be how you plan to control contrast. For the beginner, the big advantage of graded paper is that it's easy to use. It doesn't require you to buy any filters and switching between grades will not affect your exposure time.
The downside is that most photographers will have to stock several different grades of paper, which could be expensive or at the very least inconvenient. Graded papers are also a little less common than VC papers, so you won't have as wide a selection of finishes and weights.
Using variable contrast paper is a little more complicated, but you get finer contrast control. Some fine art photographers would say that they not as high quality as graded papers because with a lot of experience graded papers can be manipulated so that highlights and the shadows can be adjusted in slightly different manners.
Other Development Factors that Affect Contrast
The first thing people do when they get a bad print is start shifting their contrast. Usually, a flat or overly contrasty print is caused by using the wrong paper grade or the wrong magenta filter. However, there are many other factors that can play a role in how contrasty your prints look.
The lens you make your photographs with can change the contrast on the negative, which will affect how you have to print the image. Most lenses made in the past 50 years have nice coatings and produce a good amount of contrast. If you're using lenses made before this period, or very low quality lenses, you may find that your negatives have a lack of contrast.
The quality of your film exposure and development will have a huge affect on the contrast. Usually, flaws can be compensated for in the darkroom, but sometimes the film is just too far gone.
Underexposure produced "thin" negatives with low density. When looking at the negative, the image my be difficult to see. This will result in low contrast prints. You'll want to use a high grade paper or high number filter to attempt to correct this.
Overexposed negatives are sometimes described as "bulletproof." They will appear very dark to the naked eye, and sometimes even feel a bit thick. These negatives will usually (but not always) produce high contrast prints. Hopefully, you'll have a low grade paper or yellow filter to help with this.
The last thing that will affect the contrast of your film is how you agitate it during processing. Agitating it too much will result in large grain and high contrast. Agitating too little will result in thin negatives and flat prints. There's no quick answer for agitation problems. Follow the instructions on your set of chemicals exactly, gain experience and then start adjusting your agitation routines.
The type of paper you use can also affect the contrast. How a VC paper reacts to a given amount of magenta will differ from brand to brand? Graded papers will also vary depending on the brand.
Contrast can also change due to the finish of the paper. Glossy papers tend to have the highest contrast. This is because the tend of have the most reflectivity from the white areas of the image. Meanwhile, matte finishes tend to produce a slightly lower contrast.
Your enlarger lens behaves a lot like your camera lens. Really cheap or very old enlarger lenses may produce less contrast than modern, expensive ones. That being said, sharpness is a bigger concern for enlarger lenses.
I've never seen an enlarger lens that was so lacking in the contrast department that it could be used. I have however used lenses that didn't have enough sharpness to produce anything larger than a 4x6 inch print.
Contrast is Fundamental
When you begin to understand that a photograph doesn't just get dispensed from your camera, contrast is really the first thing you need to tackle.
Whether you're working in the digital darkroom or a real one, it's an essential step. There are dozens of tutorials online showing you how to develop film or use an enlarger, but with this information about contrast under your belt, you'll really be able to take the next step in your darkroom journey.
Are you still using a darkroom? What tips do you have for understanding contrast? Leave a comment below!