How to Photograph a Painting With Your Phone

Light the painting evenly, with a light at about 45° on each side or under an overcast sky, hold the phone square to the canvas, and turn off the flash and any filter or style. A photo taken this way is close enough to the painting to compare with your reference and find the values that have drifted.

Light it evenly

• Outdoors, an overcast sky or open shade gives soft, even light. Direct sun throws a shadow off every ridge of paint and glints on anything wet or varnished.
• Indoors, use two matching lights, one on each side, the same distance from the painting and at about 45° to it. The cultural heritage imaging studio at Rochester Institute of Technology lights paintings this way for even illumination. Choose bulbs with a color rendering index (CRI) above 90, which US federal digitizing guidelines accept for museum and archive work.
• Check the light before you shoot. Archive imaging guidelines check it at the center and the four corners of the artwork. A quick version: prop a sheet of white foam board where the painting goes and photograph it. If one side comes out darker, move the lights until the board looks even.
• Turn off the flash. It sits beside the lens, so its reflection comes straight back into it. On an iPhone, tap the flash control and choose Off.

Get rid of glare

Glare is light bouncing off the paint like a mirror, and it leaves at the same angle it arrived. With the lights at 45° on either side, that reflection goes past the camera instead of into it. If wet oil paint or varnish still shines, move the lights farther out to the sides and look again. Thick impasto is harder: its ridges face every way, so some of them always catch the light.

The studio fix is cross-polarization: polarizing film over the lights and a polarizing filter over the lens, turned until the shine disappears. It removes most mirror-like reflection and leaves the color underneath almost untouched, but it only works if the polarized lights are the only light on the painting, so the room has to be dark.

Square the camera to the canvas

If the phone tilts toward one edge of the painting, that edge comes out bigger and the rectangle turns into a trapezoid. US federal digitizing guidelines call for the camera sensor, the lens and the artwork to be parallel, and suggest a spirit level or the level built into a phone to check.

• Hang the painting on a wall or stand it upright on the easel, and hold the phone level with its center. If the easel tilts the canvas back, tilt the phone back to match.
• On an iPhone, turn on Grid and Level in Settings > Camera. Line the grid up with the canvas until opposite edges look parallel.
• Fill most of the frame with the painting, but leave a little wall around it so all four corners are in the shot.

In Paintsight you straighten the photo of your painting before comparing it, which takes care of a slight tilt.

Exposure and color

• Exposure. Tap the painting to focus, then drag up or down beside the focus box to make the picture lighter or darker. Set it so the lightest passages still show their brushwork. Touch and hold the focus box until you see AE/AF Lock to keep the same settings for the next shots.
• No styles or filters. In Settings > Camera > Photographic Styles, choose Use Standard, and don't add a filter.
• HDR. The iPhone blends several exposures to bring out more detail in highlights and shadows, and uses it automatically. Apple's guide lists a switch only for iPhone 11 models, iPhone SE (2nd generation) and iPhone 12. Apple describes HDR as a help in high-contrast scenes; even light keeps your setup from being one.
• White balance. A white object takes on the color of the light it's in. Put a gray card or a sheet of plain white paper beside the painting for one shot. If it comes out tinted, drag a white balance eyedropper onto it, such as the one in Lightroom's Color panel, and the app sets the white balance from it.

Compare it with the reference

In Paintsight you photograph your painting, straighten it and compare it with the reference: overlaid, flicking between the two, or side by side, in any view. Each way shows something different:

• Flick between them in grayscale to check values. A shape that jumps lighter or darker as you flick has drifted from the reference. See value and color.
• Overlay them to check the drawing. Edges that don't line up show where a proportion or a placement slipped.
• Put them side by side in the value study at 3 to 5 values, to see whether the painting groups into the same big masses as the reference. See how many values a painting should have.

Set the lights up the same way each time, and mark where they stand with tape on the floor, so photos from different sessions compare fairly.

Sources

• Joel Witwer and Roy S. Berns, "Increasing the Versatility of Digitizations through Post-Camera Flat Fielding", Studio for Scientific Imaging and Archiving of Cultural Heritage, Rochester Institute of Technology. For two equal lights at 45°, the center-and-corners check, and a white board to show how light falls.
• Federal Agencies Digital Guidelines Initiative, Technical Guidelines for Digitizing Cultural Heritage Materials, 2016, "Lighting", "Accessories" and "Paintings and Other Two-Dimensional Art". For CRI above 90 and keeping camera and artwork parallel.
• Roberto Balzani and others, "Saving temporary exhibitions in virtual environments: the Digital Renaissance of Ulisse Aldrovandi", 2023, section on cross polarization.
• Apple, iPhone User Guide: Use camera tools (grid and level, focus and exposure, flash), Adjust HDR camera settings and Use Photographic Styles.
• UVic Libraries Digital Scholarship Commons, Smartphone Photography: White Balance, 2023.