Photo Filters: Black & White, Sepia and Invert

Photo Filters: a quick guide

Which filter should I use?

Black and white is the most useful of the three. It removes distracting colors, hides mixed lighting (for example orange indoor bulbs next to blue daylight from a window) and puts the attention on faces, shapes and texture. It also makes printed copies look the same on any printer, because no color has to be matched.

Sepia gives a photo the warm brown look of prints from the late 1800s and early 1900s. Use it for portraits, family history projects, invitations and old buildings, or to make a set of photos from different phones look like they belong together.

Invert turns every color into its opposite. It is less of an artistic effect and more of a practical one: it turns scanned black-and-white film negatives into positives, makes a dark screenshot printable without using a lot of ink, and creates striking poster-style images.

How the black and white conversion works

A good black and white photo is not a simple average of red, green and blue. Our eyes see green as much brighter than blue, so this tool uses the Rec. 709 luminance weights that are also used for HD video: about 72% of each gray comes from green, 21% from red and 7% from blue. A blue sky stays a darker gray, and green leaves and skin tones keep their natural brightness.

The result uses all 256 shades of gray, not only pure black and pure white pixels. If you need a crisp two-tone document (for example a signed form), the Images to PDF tool has a separate black and white mode that turns paper white and ink black.

Photos with strong light and shadow look best in black and white. If a photo looks flat and gray afterwards, run it through Auto Fix Photo first to stretch its contrast, then apply the filter.

How the sepia tone is made

The sepia filter uses the classic sepia color matrix. Every new red, green and blue value is a weighted mix of the original three, with red getting the most and blue the least. That turns the whole photo into one warm hue: shadows become dark brown, mid-tones turn golden and highlights become a soft cream.

Because the mix brightens the red channel, very bright areas such as a white shirt or the sky can reach full brightness and lose a little detail. If that happens, darken the photo slightly before applying sepia, or choose black and white instead.

What inverting does

Inverting replaces each color channel with its opposite (255 minus the value). Black becomes white, red becomes cyan, green becomes magenta and blue becomes yellow. Transparent areas are left alone, so a logo on a transparent PNG stays a logo with a transparent background.

Black-and-white film negatives invert very well. Color negatives also carry an orange mask from the film itself, so after inverting the colors look blue or green; correct them with Auto Fix Photo afterwards. Inverting a PNG twice gives back the original pixels exactly. A JPG is compressed again each time it is saved, so it can change very slightly.

Tips for the best results

Start from the largest original you have. Filters change only the colors, never the size, so a small, compressed photo stays small. To make the result smaller afterwards for email or an upload form, use Compress Image or Compress to KB.

Do not use these filters on photos for official documents. Passport, visa and DV Lottery photos must be in color, and a black and white or sepia photo is a common reason for a rejected application.