Mastering Exposure and Contrast in Darkroom Printing - Test Strip techniques

Mastering Exposure and Contrast in Darkroom Printing - Linear Test Strip


At the enlarger


I start with Grade 2 (even contrast) for the test strip using Ilford multigrade filters under the lens.
After placing your negative in the enlarger's carrier and adjusting focus with your focus finder, you're not ready to print yet.

In order to spare photographic paper, you will need to make test strips. I usually cut my photographic paper into thirds, place it on the part of the image I want to check for highlights and expose it incrementally:
* Expose the entire sheet for the first 5 seconds.
* Without moving the paper, cover the first 2 centimeters and expose the uncovered section for another 5 seconds.
* Repeat the process by covering an additional 2 centimeters each time and exposing the new section for 5 seconds.

Note : As different papers (resin-coated, fiber-based) react differently to constrast and exposure, always make test strips with the specific type of paper you want to print.

Developing the print


Develop the test strip by immersing it sequentially in the developer, stop bath, and fixer. Always carry out this process under a safelight (e.g., red). For this chemical process, I use Dev It Darkroom Timer, I set a development time, a stop bath time and fixing time. This app emits red light to protect photographic paper.

The Dev Tray


I use Ilford Multigrade paper developer 1:9 (dilute 1 portion of dev concentrate in 9 portions of water) in a tray that is placed on Kaiser Fototechnik Developing Tray Warmer, which helps me keep the dev temperature constant (20°C).

Once the image starts to appear in the developing tray, I take a look at the clock (identify 15 seconds, for example) and multiply that time by 10 to get the whole dev time : 150 seconds, i.e. 2m30s.

I tilt the tray during the whole process. Every 30 seconds, I flip the photo paper and then flip it back right away.

The Stop Bath Tray


When the timer bell rings, I put the picture in the stop bath for 1 minute (water + a cap of acetic acid). Manipulate acetic acid carefully and store it away from children's reach because it is very corrosive.

The Fixer Tray


When the timer bell rings, I drop the picture in the fixing tray : I use Ilford Rapid Fixer 1:4 (1 dose of fixer concentrate with 4 doses of water). At 20°C, fixing time is about 1-2 minutes. In winter, my bath should be around 15°C, I use the fixing bath for up to 3 minutes. As for the developing process, I tilt the tray regularly and flip the picture every 30 seconds.

Test Strip Analysis - Expose for highlights, develop for shadows


"Expose for highlights, develop for shadows" is often associated with Ansel Adams, the famous American photographer known for his black-and-white landscape images.

This principle to achieve well-balanced prints requires that your highlights retain detail without blowing out, while shadows hold enough depth to create a dynamic tonal range.

The analysis of your test strip should be done under normal lighting conditions, otherwise, the safelight will not let you identify the exposure steps you used.

Analyzing a test strip requires you to first look for expected highlights, i.e. highlights of your liking that often present as areas like clouds or light reflections that should appear bright but retain subtle texture. Once you've found the time for these "correct" highlights according to your eye (or your artistic intention), you then look for shadows that are correctly exposed.
* EXAMPLE #1 : if highlights and shadows appear on the same part of the test strip : grade 2 is a good fit
* EXAMPLE #2 : if highlights come first and shadows appear later, you will have to make another test with a higher grade. You will then need to repeat the test strip operation since changing grades affects exposure times
* EXAMPLE #3 : if shadows come first and highlights appear later, you will have to make another test with a lower grade. You will then need to repeat the test strip operation since changing grades affects exposure times

Example #1 - Well-Balanced Highlights and Shadows - Grade 2 Confirmation


In this first example, the test strip obtained with Grade 2 (even contrast) shows that highlights and shadows progress rather evenly across the 7 steps of the test strip. Looking at the test strip from right to left, the highlights appear optimal between steps 4 and 5. The final print used Grade 2 at 11 seconds..

If you look at the test strip more closely, your eye may be attracted by the dark pine tree in the middle. You would be misled to think the shadows are optimal at step 3. With highlights appearing between step 4 or 5, you would impose a low filter Grade 1 for example to the overall picture because of the pine tree. In this case, only the pine tree would be printed as desired, while the rest of the image would lose its tonal balance. Considering the general tone of the picture, this pine tree appears as an exceptionally dark element. Treat the pine tree separately rather than using it to define contrast. For the print below, Grade 2 at a total exposure of 11 seconds was used, including 2 seconds of dodging (see my previous article) applied to the pine tree. Dodging will make the tree less prominent, it will remain a dark element stressing the tower's height but stays "in tone".






Test print #1
Test strip #1


Tower - Avignon
Final print #1 - Tower and city walls - Avignon
13x18cm - f/8 - Grade 2 - 11 seconds - 2 seconds dodge pine tree


Example #2 - Highlights Come First - A Higher Grade Is Required


In my second example (below on the left), highlights appear in the second step of my test strip. Shadows only arrive in the third step. This means a higher contrast will help them to appear at the same exposure time. The test was done with Grade 2. I tested Grade 2.5 (below on the right) where highlights appear not too dense and shadows show details on step 4, gaining some contrast with this slightly higher grade. I printed the negative with Grade 2.5 at 11.7 seconds. No dodging, no burning required. Easy peasy!

Test print #2 - Grade 2
Test strip #1 - Grade 2


Test print #2 - Grade 2.5
Test strip #2 - Grade 2.5


Here is the final print :
Final print #2
Final print #2 - Penitents Noirs Chapel - Avignon
13x18cm - f/8 - Grade 2.5 - 11.7 seconds


Example #3 - What If The Brightest Part of the Image Keeps Pure White?



On the last example, the sky plays a role in the image. It adds depth, realism, and should be somewhat textured which can appear as a light gray to add tonal quality to the picture. If it stays pure white, the picture being printed with white borders, the viewer won't see where the picture ends and the border starts.

A negative that shows edge markings correctly printed (clear and legible number) could be correctly developed. When highlights are faint, with no density, underexposure could be at work : The brightest parts of the scene didn't receive enough light. In that case, shadows would appear first in my test strip and highlights would hardly show. The test strip shows a faint light gray appearing on step 6 with shadows appearing around step 4.

The theory would suggest using a low grade filter (0 or 00, for example), but this would also affect the shadows and overal dullness of the print. In that case, I prefer to switch to split grade printing :
* Grade 4 (rather high contrast for shadows) : 9.20 sec
* Grade 1 (rather low contrast for midtones) : 6 sec
* burning sky with grade 00 (very low contrast that mainly affects highlights) : 13 sec

Note that in the photo below, I left the print white borders to be able to identify the difference between the pure white of the border and the light gray of the sky.

City Walls - Avignon
Final print #3 - City Walls - Avignon
13x18cm - f/8 - Grade 4 : 9.2 seconds - Grade 1 : 6 seconds - extra burn sky Grade 00 : 13 seconds
Test print #3
Test strip #3


Let's Recapitulate


Analyze your test strip under normal lighting conditions. Your test strip ranges from the very dim exposure (5 sec) to the most contrasted (20 seconds, for example). If the 5 seconds exposure is already too dark, you will have to change your lens' aperture and close the diaphragm. If no part of the test strip shows enough shadows, you will do the opposite or expose for longer. Keep in mind the ideal position in aperture for your lens should be around 2 stops from wide open.

However, linear test strips—with exposure increments of 5, 10, 15, and 20 seconds—don't provide a balanced progression of tonal representation. Photographic paper responds logarithmically to light, meaning the density difference between shorter exposures (5 and 10 seconds) is far more noticeable than that between longer exposures (15 and 20 seconds) with a linear test strip.

For a more accurate tonal progression, consider using an F-stop test strip. My previous article explains how F-stops work. They are to be found on your lens : the quantity of lignt is doubled when you go from f/11 to f/8, as well as when you shoot at a shutter speed of 1/60 (instead of 1/125).

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