The three Capture One tools - Exposure Evaluation, Levels, and Histograms show different values. Why does it happen?
The Exposure Evaluation, Levels, and Histogram tools show different values because they show the data while in different parts of the image pipeline.
Exposure Evaluation. The Exposure Evaluation tool shows the actual RAW data information as shot in camera together with the selected Film Curve and the White balance/Tint. The Exposure Evaluation histogram is modified only when a crop is applied or a Film Curve is changed or if White balance/Tint changes. No other adjustments will be reflected in the tool.
Levels. The Levels tool takes more adjustments into account. Adding exposure, contrast, saturation, brightness, HDR, vignetting, and clarity settings to the Levels histogram. However, it excludes itself from the displayed values. This enables the user to adjust the brightness from the darkest to the brightest pixels and adjusting the mid-tones or inverting the image. The RGB Channel modes also enables to correct for color shifts between the channels.
Histogram. The Histogram tool reflects what you see in the preview including all adjustments such as Curves, Color Edits, ICC profiles, etc. It shows the histogram based on all the adjustments applied on top of the RAW data and shows all the changes you have made.