Reduce a reference to four or five values on a toned ground, the way an underpainting is laid in, and paint from that instead of the photograph.
Converting a photograph to greyscale keeps every value it had. A study throws almost all of them away and commits to four or five. That commitment is the entire exercise: it is the decision you would otherwise be making later, with a loaded brush and less patience.
Because the reduction happens before the painting rather than during it, you get to see whether the structure holds while it still costs nothing to change your mind.
Historical underpainting was rarely grey. Rembrandt worked over burnt umber, Caravaggio over a red-brown ground, and that warmth stays visible in the finished picture. A study laid over the same ground tells you what the painting will feel like, not merely how dark it will be.
The presets in the tool apply the ground and the value count together, so one tap gives you a five-value burnt umber study or a four-value red-brown one. Grisaille and a neutral grey are there when you do want the colder version.
Keep both open, but match the masses in the study first. Most of the drift in a painting comes from deciding values and drawing shapes at the same time; the study separates those two jobs.
Above about seven you have stopped deciding and started copying. Two is a notan and answers a different question. Four or five is the range where the study is still a plan.
A study you have to keep re-generating is a study you will stop consulting. Save it, and take the value scale alongside it so you know what each mass is in hex.
A small, fast painting that works out the light and dark of a subject before the real picture starts. It uses a handful of values and usually one colour, because its job is to settle the structure while changing your mind is still cheap.
A greyscale conversion keeps every value in the image. A study throws most of them away and commits to four or five, which is the decision you would otherwise be making with a loaded brush. The reduction is the study.
Because most historical underpainting was. Rembrandt worked over burnt umber, Caravaggio over a red-brown ground, and the warmth of that ground carries through the finished picture. The presets below apply the ground colour along with the value count, so the study looks like something you would actually paint.
Four or five for most subjects. Two is a notan and answers a different question. Above about seven you are copying rather than deciding, and the study stops doing the work it exists to do.
Paint from it rather than from the photograph. Download it, keep it beside the reference, and match the masses first. Most drift in a painting comes from working out values while also drawing, and the study separates the two.
No. The study is computed in your browser on your own device. The image never leaves your computer.