The term Photo is short for photograph which is a picture taken with a camera. It differs from other forms of graphics in its scope and implementation.
Photographs were popular as early as the 1850s. They used a box camera that captured the image on a single glass plate of film in black and white which was then developed in a lab and and transferred to photo paper. By the 1890s rolls of film were in use. In the 1930s color images were gaining in popularity. Cameras using film are now pretty rare with most cameras taking digital images.
While a photo refers to the image making process, a picture can be a photo, a painting, or a drawing of a distinct object. A picture may also refer to forming an image in your mind.
 Use in eBooks
- illustrations or figures inside the books
- cover images.
- scanners, used to digitize images and OCR for text.
- a substitute for other book objects such as a table.
These will be expanded.
The most common format for digital photos is Jpeg but it is a lossy format so there are times when other formats are better to preserve the image.
- For ePub use only JPG, PNG and GIF are supported.
- For AZW and MOBI the PNG images will be converted to JPG or GIF images by the conversion software KindleGen.
- PDF has the widest support for images JPG, PNG, GIF, JXR, JPEG2000, TIF are all supported.
Descriptions of the formats:
- JPG - This generally produces the smallest file. This is the most popular image format in eBook readers and eBooks themselves. There are techniques that can be used to reduce the image file size by making the image less detailed.
- PNG - This is a lossless format but can be complicated. Some readers may not support this format at all or may only support 8 bit mode.
- GIF - A lossless format. This is great for graphic drawings but can also support photos with up to 256 colors. It is generally supported by eBook readers.
- JXR - A high compression photo with HDR support. Can be used in PDF files.
- HEIF - A recent format that supports both Wide color and Deep Color HDR. While this format is great for preserving the source image it is not supported by eBook readers.
 Photo sizes
16:9 ratio used for 4" x 7" landscape pictures popularized by the APS, Advanced Photo System, cameras using 24mm film.
- 1280 x 720 HD or WXGA720 .9MP
- 1920 x 1080 Full HD 2MP
- 3840 x 2160 UHD 8.3MP
- 4320 x 2432 16:9 10.5MP
3:2 ratio used for 4" x 6" landscape DSLR's use this ratio since it matches cameras using 35mm film.
- 1536 x 1024 1.6MP
- 2400 x 1600 3.8MP
- 2464 x 1632 4MP
- 2592 x 1728 4.5MP
- 3008 x 2000 6MP
- 3872 x 2592 10MP
- 4290 x 2800 12MP
- 4320 x 2880 12.4MP
- 4920 x 3264 16MP
- 5380 x 3620 19.5MP - typical 35mm scanned image.
- 6000 x 4000 24MP est.
- 7360 x 4912 36MP
4:3 ratio used for portrait 5" x 7", 8" x 10", 11" x 14" by cropping the image. Matches VGA
- 1400 x 1050 1.5MP SXGA+
- 2048 x 1536 3.1MP QuadXGA
- 2592 x 1944 5MP
- 3264 x 2448 8MP
- 4032 x 3024 12.2MP (iPhone 7 and later)
- 4320 x 3240 14MP
Compare with Nomenclature.