Tone-reproduction laboratory

Explore how subject range, flare, negative slope and paper range combine in an explicitly simplified model.

Subject range (stops)Flare as fraction of highlight illuminanceNegative straight-line slopePaper ISO range, from its published tablePaper maximum density, measured or published

Calculate

Enter your values and calculate. Read the assumptions below before using a result.

Method and assumptions

This is a qualitative educational model. It does not predict a particular film, paper or developer. Its numeric outputs are consequences of the stated simplifications; they must not replace measurement or a manufacturer’s processing data.

The first panel normalises the subject highlight to one and adds a constant flare fraction v. A subject range S stops has a shadow at 2⁻ˢ. The image range is therefore log₁₀[(1 + v)/(2⁻ˢ + v)]. With zero flare the result is S log₁₀2. Increasing flare compresses the lower end because the same added veil is a larger fraction of the shadow than of the highlight.

The second panel uses a straight negative response of the chosen slope. It omits the toe, shoulder and exposure placement, which a real negative requires. The third maps that range to a paper log-exposure interval equal to its entered ISO range divided by 100, then clips at the entered maximum density. The final panel composes those transformations. It shows available tonal-range use rather than a measured visual appearance or a calibrated display simulation.

Try zero flare, then 0.01, holding every other field fixed. Increase subject range and observe that the flare penalty grows. Next decrease the paper range and identify where the model clips. Explain which assumptions break first for a real negative. For a physical print, measure the dry result under a stated viewing condition and use the full discussion of toe placement, paper response and viewing light in the linked lesson.

Evidence and record

Read the teaching method and its sources. Keep your inputs, the displayed assumptions and the result together; a result detached from its conditions cannot be checked.