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The point source illumination is a variation of the condenser enlarger and is constructed to eliminate as much light diffusion as possible before it reaches the negative.

Its light source is a very small, intensely focused, unfrosted clear lamp that is directed down onto the negative without diffusers.

Because the light rays pass down the chamber without bouncing around in the condenser head, the circle of light created is very narrow. The condensers read the single small filament as a single point of light rather than many hundreds of points as with the normal enlarger lamp with a frosted coating. The effect in the resultant print is that the grain appears sharper, and the transformation from light to dark at the edge of the shadow areas is more sudden.

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It is important there are no hot spots and the bulb needs to be positioned both vertically and horizontally inside the lamp hosing so that it is in the correct relationship to the negative and the enlarging lens, ensuring the most even lighting across the area that is to be printed.

Because the enlarging lens must be left wide open at full aperture during both the adjusting and printing to prevent vignetting at the edges of the negative, exposure control is only through variations of time or a variable transformer.