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Value Analysis
How to use the Value Checker
- Upload a reference image — drag and drop or click the upload zone to select a JPG, PNG, or WebP file from your device.
- See the greyscale view — the tool converts your image to greyscale using standard luminance weights, giving you a pure value read with no colour influence.
- Adjust contrast — use the contrast slider to push the tonal range wider or compress it. Higher contrast helps you see the separation between light and shadow more clearly.
- Read the value scale — the five swatches below the canvas show the adjusted tones for Shadow, Dark, Mid-tone, Light, and Highlight. Use these to plan your painting's value structure.
- Download — save the greyscale version as a PNG to use as a reference while painting.
Value — the lightness or darkness of a colour — is the single most important element of a convincing painting. Most beginners focus on colour first, but experienced painters know that if your values are correct, a painting reads well even when the colours are off. The Value Checker strips away colour so you can judge your tonal structure honestly.
Using a value scale
A value scale is a strip of tones running from pure white to pure black in even steps. Nine steps is the traditional art-school standard, though five is enough for most practical work. Its purpose is to give you fixed reference points: instead of asking whether a shadow is “a bit darker,” you ask whether it is a 4 or a 6 — a question you can actually answer.
The classic studio technique is to make a physical scale on card, punch a small hole through the centre of each step, and hold it against your subject. Look through the hole: whichever step visually disappears against what you are seeing is the value you want. Isolating the tone this way defeats your brain's habit of correcting for context, which is the single biggest cause of value errors.
The greyscale conversion above does the digital equivalent for a whole image at once. Compare the two panels and note where your assumptions were wrong — most people consistently paint shadows too light and mid-tones too uniform. For a fuller explanation of the underlying idea, read what value means in art, or see five practical ways to check your values before you paint.
Value Checker FAQ
What is a value scale in art?
A value scale is an evenly stepped strip running from white to black, usually in five or nine steps. Artists use it as a measuring stick: you compare an area of your subject against the scale to identify its value precisely rather than guessing.
Why do my shadows always come out too light?
Because your visual system corrects for context — it tells you what an object is rather than how bright it appears. Most beginners also avoid committing to dark. Find the darkest note in your reference, put it down at full strength early, and judge everything else against it.
Is my image uploaded to a server?
No. Everything happens in your browser. Your image is never sent anywhere — it's read locally using the browser's built-in Canvas API and cleared when you close the tab.
What's the difference between greyscale and value?
Greyscale converts each pixel to a single brightness level using luminance weights (more weight on green, less on blue). This matches how the human eye perceives brightness, so it's an accurate representation of the visual value in your image.
Why does increasing contrast help?
Many reference photos have a compressed tonal range — especially photos taken in soft, even light. Boosting contrast spreads the mid-tones apart so you can more easily distinguish your shadow shapes from your light shapes. It's the same reason painters squint at their reference.
How do I use the downloaded greyscale image?
Keep it open in a second window alongside your colour reference. Glance at the greyscale version while painting to check that your values are reading correctly — especially when mixing colours that look different but share the same brightness.