Enlarging Lens

Overview

An enlarging lens is not a camera lens. It is optimised for a flat subject at a short distance, with even illumination across the whole field and no field curvature. A camera lens used as an enlarging lens will give you corners that never quite come sharp.

Focal length is chosen by format. 50 mm covers 35mm; 75–80 mm covers 6 × 6; 105 mm covers 6 × 9; 135–150 mm covers 4 × 5. Using a lens that is too short for the format costs you even illumination; using one that is too long just means a taller column.

The aperture matters more than the badge. Almost every enlarging lens is at its best two stops down from wide open, and almost none are diffraction-limited wide open. An f/2.8 lens used at f/8 will beat a much more expensive f/4 lens used at f/4.

What it does well

• Flat-field design keeps the whole print sharp at once
• Optimised for short working distances
• Multicoating controls flare from the enlarger light source
• Stepless aperture versions make f-stop printing arithmetic easier
• A better lens is usually the cheapest print-quality upgrade

Safety notes

Working notes

• Match focal length to format. A 50 mm lens on 6 × 6 will vignette no matter what you do.
• Work at f/8 or f/11 for critical work and f/5.6 when you need a short exposure.
• Clean the rear element as carefully as the front — it is closer to the paper and its faults are magnified.
• If the corners are soft at every aperture, check alignment before blaming the lens.

Compatible with