Traditional silver halide darkroom enlarger black and white printing: photographic paper contrast grade, test strip exposure, and dodging and burning

1. The two optical cores of the enlarger: Condenser vs. Astigmatism cold light source (Diffusion)

• Concentrator enlarger (such as Beseler 23C / LPL 7700): Use two thick plano-convex condenser lenses to direct light parallel to the film. Due to the "Callier Effect", direct light is scattered when it penetrates the silver salt particles of the film. The printed photos have great contrast and the particles are extremely hard and clear, but scratches and dust on the film will also be magnified a hundred times.
• Astigmatism Cold Light Source Amplifier: The light is diffusely reflected in the frosted reflective chamber and then emitted. The light is soft, it can effectively smooth out the slight scratches on the film, and the mid-tone gray scales transition smoothly. It is the mainstream of modern advanced portrait art giclee and fine darkroom.

2. Working principle of Multigrade RC/FB filter

Modern darkrooms use multi-contrast photographic papers (such as ILFORD Multigrade RC Resin Paper or FB Cotton Barium Paper). Photo paper is coated with two layers of emulsions with different photosensitive properties: one layer is sensitive to blue-violet light (high-contrast layer), and the other layer is sensitive to yellow-green light (low-contrast layer):

• No. 00 to No. 1.5 filter (yellow filter): absorbs blue light, transmits yellow light, and outputs extremely low contrast, which can pull out the rigid black-and-white transition into a dense middle gray.
• Filter No. 2 to No. 2.5: Neutral contrast standard, suitable for most films that are developed and exposed normally.
• Filter No. 4 to No. 5 (magenta-red-purple filter): Completely cut off green light, stimulate high-contrast emulsion, and achieve clear black and white, making gray and dull waste films instantly full of hard-core dramatic tension.

3. Practical Combat of Test Strip and Dodge & Burn

1. Step Strip Determination of Baseline Time: Cut a narrow strip of 2×5 inch photo paper and place it in the most contrasting area of the image (containing both highlights and shadows). Use black cardboard to cover, and move the exposure in 5 steps in steps of 2 seconds (to obtain exposure strips of 2s, 4s, 6s, 8s, and 10s). Put in the developer and develop for 1 minute, then look under the red light and choose the best number of seconds (for example, 6 seconds) when the black is deep and the bright texture is clear.
2. Local dimming occlusion (Dodging): In the 6-second basic exposure of the entire photo, use a small piece of oval black cardboard stuck to the top of a thin wire, and keep shaking it slightly about 10 cm above the dark area of ​​the portrait's face (shaking can soften the edge shadows and avoid hard edges) for 2 seconds. The face is actually exposed to light for only 4 seconds, and dark details are elegantly brightened.
3. Partial Light Burning: After the entire exposure is completed, take a piece of large black cardboard and dig a small 2 cm round hole in the middle. Aim at the sky clouds that are originally easily overexposed and fill in the light for 4 seconds, pressing the white cloud layer in the highlight into the photo paper.

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