Converting verticals using your enlarger

Words and images Peter Bargh

Taking pictures of buildings is fraught with problems if you don't have the right gear. When you point your lens upwards you will see the walls of tall buildings start to slope inwards making the picture look like the Leaning Tower of Pisa from all angles.
This is because of perspective and while there are several methods of preventing this when taking a photo, there are times when you have no option other than take a shot and put up with the problem.
If you are a darkroom user you may not be aware that you can rectify such things using a few tricks with your enlarger.

1 Put the negative to be printed in the carrier and adjust the height to obtain the right magnification to fill the printing paper.

2 Notice if you raise the side of the easel that has the base of the building on it that it will become smaller the closer it goes to the lens. Adjust to the optimum height and the bottom of the building's walls will become as narrow as the top resulting in straight walls. Now this can be quite tricky to the naked eye as it's easy for nearby detail to help create optical elusions, making it more difficult to get them perfectly straight. A good tip here is to place a sheet of graph paper on the baseboard to help you get everything spot on. If you don't have such paper draw out a grid on a plain piece of paper or card.

3 Once you have adjusted the angle of the board you need something to prop it up. I use a film tub with Blu-Tac on top which can be moved further in to obtain a more acute angle. There is of course a limit to the angle using this method and then, less convenient but more appropriate is a stack of books taking out or adding as necessary.

4 Now you'll notice that only the part nearest the baseboard is sharp and the rest becomes progressively blurred the closer it is to the lens.  To improve this you can do a number of things. If your enlarger is a fancy one, such as a Meopta 6 or LPLC7700 it will have a tilting lens board. This can be adjusted so that all the image becomes sharp - a technique that involves the Scheimpflug principle.

To ensure you adjust to the correct angle you should draw an imaginary line across the lens plane, negative plane and printing paper plane. Each should meet at an imaginary point (see the diagram). When the points meet everything will be pin sharp on the paper. Many enlargers don't have this advantage so you have to rely on depth of field. Set the smallest aperture you can and to ensure that the whole area is optimised refocus mid way up the image.

5 Another problem you may encounter is exposure accuracy. Obviously the closer the print is to the light the darker that area will be compared with the base point. Make a test strip and if there's a big difference you will have to step the light reaching the print by gradually masking off using a sheet of card in the light path.