technical: Making a test strip

Making a test strip

To make a test print, set up the enlarger as you would for a print. See Making a b & w print. Set the aperture of the enlarger lens to about f.8.

Instead of placing a whole sheet of photographic paper in the masking frame, cut a strip of paper and place this in the masking frame across the middle of the picture, or where there is a good range of light and dark tones. This should be done under safe lighting and with the enlarger off.

Set the timer to 5 seconds, and hold a piece of card over the image so that the light is masked off from most of the strip of paper. Expose about one quarter of the strip for 5 seconds.

Move the card along allowing light to expose about half of the strip. Expose for a further 5 seconds. Do not allow the photographic paper to move.

Repeat this until the entire test strip has been exposed in 5 second intervals, then process the test strip.

When making a contact sheet, a test strip can be made by following the same procedure, using a strip of paper in the contact printer instead of a whole sheet.

test strip showing 5,10,15 and 20 second exposures

Assess the test strip and choose the best exposure to gauge the exposure time for your photograph. If the whole strip is too light, open up the lens by one stop and repeat the process, if it is too dark, stop down by one stop and repeat.

If your whole film was shot under similar lighting conditions the exposure time should be similar for each print and it can be assessed visually. You will be able to tell this from your contact sheet.

If your next negative is lighter and thinner than the one tested, it will look dark on the contact sheet. Give it less time because, as it is thin, it will allow more light to pass through onto the paper.

If a negative is darker and denser than the one tested, it will look light on the contact sheet. It will need more time, as the light will take longer to expose the paper.

Contrast can be assessed from a test strip - if it looks murky and grey, use a higher contrast filter; if there is too much light and dark and not enough grey, use a lower grade filter. Changing filters changes exposure, so a new test strip will have to be made. This applies to variable contrast paper, if you are using graded papers, and you want to change contrast level you will need several boxes of paper. See Photographic paper.