Analyzing your image before correcting

Tonal analysis is the first step of any correction in Calibration Flow. You load an image, the app reads it, shows you how it's built tonally, and proposes a starting point to correct it. This starting point isn't necessarily the final version — it's designed to be close, so that you only have to adjust a little rather than rebuild everything by hand.

The idea behind the mechanism: a good correction begins with a good reading. If you correct by instinct without understanding the tonal distribution of your source image, you work blind. If you measure first — without applying judgment — and correct afterward knowing what you're changing, the result is more stable and more reproducible.

#What you see

You import an image, and the analysis screen appears. Three zones share the space:

The image itself, in the center. As you adjust the correction, the preview updates in real time — you see what you're making, not what you hope to make.

The histogram, alongside. It plots the distribution of the luminances of your image in the L* CIELAB space (the scale that matches human perception, not a raw technical RGB scale). You see where your pixels are — concentrated in the shadows, spread across the whole range, packed in the highlights.

The correction curve, superimposed on the histogram or displayed alongside depending on your display mode. At startup, this curve is a straight line (no correction). When you start adjusting the sliders, the curve deforms and you see exactly how each input tone is transformed into an output tone.

Below the image, three sliders: black point (what becomes your densest black), white point (your lightest white), midtone gamma (the curvature between the two). A Reset button puts everything back to zero if you want to start over.

The Smart Analyzer runs in the background as soon as you import and proposes a preset for these three sliders according to the detected intent of your image. You start from a reasonable starting point instead of a null correction.

#Why it matters

To reproduce a result. Three sliders with numeric values is three numbers you can note or save as a preset. You open an image three months later, you apply the same three values, you get exactly the same correction. By instinct with a brush, you'd never have that reproducibility.

To understand what you're doing. The histogram tells you where your pixels are before correction. The curve tells you what you're going to change. The preview tells you the result. The three pieces of information together turn correction from a blind act into a measurable one. You see live whether your adjustment is crushing your shadows or your highlights.

For calibrating alternative processes. Tonal analysis is the foundation the

.acv

.acv

#When you don't need it

For quality control of an already-processed image. If your source image came out of a full Lightroom workflow and only needs a final export, tonal analysis is one more useless step. Go straight to negative generation.

For batch processing where you trust a pre-calibrated curve. If you already have your cyanotype correction curve in a preset, you can reapply it to all the images of a series without going back through the individual tonal analysis of each one.

For abstract images where the standard distribution makes no sense. On a high-contrast photogram with only black and white, the bimodal histogram tells you little that's useful, and the three sliders lack material to adjust.

#Worth remembering

#The test

Load a well-exposed image into Calibration Flow. Run the analysis. Note the three values proposed by default (the Smart Analyzer has positioned you on a starting point). Now push the black point slider to the right — you should see the image darken, the histogram shift to the left, and the curve deform to show the new threshold. If you see none of these three changes, either the analysis didn't run, or the preview is frozen — reload the image.