Lenna or Lena is the name given to a standard test image widely used in the field of image processing since 1973. It is a picture of Lena Söderberg, shot by photographer Dwight Hooker, cropped from the centerfold of the November 1972 issue of Playboy magazine.
The spelling "Lenna" comes from the anglicisation used in the original Playboy article.
Before Lenna, the first use of a Playboy magazine image to illustrate image processing algorithms was in 1961. Lawrence G. Roberts used two cropped 6-bit grayscale facsimile scanned images from Playboy's July 1960 issue featuring Playmate Teddi Smith (born Delilah Henry), with attribution, in his MIT master's thesis on image dithering.
Intended for high resolution color image processing study, the Lenna picture's history was described in the May 2001 newsletter of the IEEE Professional Communication Society, in an article by Jamie Hutchinson:
Alexander Sawchuk estimates that it was in June or July of 1973 when he, then an assistant professor of electrical engineering at the University of Southern California Signal and Image Processing Institute (SIPI), along with a graduate student and the SIPI lab manager, was hurriedly searching the lab for a good image to scan for a colleague's conference paper. They got tired of their stock of usual test images, dull stuff dating back to television standards work in the early 1960s. They wanted something glossy to ensure good output dynamic range, and they wanted a human face. Just then, somebody happened to walk in with a recent issue of Playboy.
The engineers tore away the top third of the centerfold so they could wrap it around the drum of their Muirhead wirephoto scanner, which they had outfitted with analog-to-digital converters (one each for the red, green, and blue channels) and a Hewlett Packard 2100 minicomputer. The Muirhead had a fixed resolution of 100 lines per inch and the engineers wanted a 512×512 image, so they limited the scan to the top 5.12 inches of the picture, effectively cropping it at the subject's shoulders.
This scan became one of the most used images in computer history. In a 1999 issue of IEEE Transactions on Image Processing "Lena" was used in three separate articles, and the picture continued to appear in scientific journals throughout the beginning of the 21st century. Lenna is so widely accepted in the image processing community that Söderberg was a guest at the 50th annual Conference of the Society for Imaging Science and Technology (IS&T) in 1997. The use of the photo in electronic imaging has been described as "clearly one of the most important events in [its] history". In 2015, Lena Söderberg was also guest of honor at the banquet of IEEE ICIP 2015. After delivering a speech, she chaired the best paper award ceremony.
To explain Lenna's popularity, David C. Munson, editor-in-chief of IEEE Transactions on Image Processing, noted that it was a good test image because of its detail, flat regions, shading, and texture. However, he also noted that its popularity was largely because an image of an attractive woman appealed to the males in a male-dominated field.
While Playboy often cracks down on illegal uses of its material and did initially send out notices to research publications and journals that used the image, over time it has decided to overlook the wide use of Lena. Eileen Kent, VP of new media at Playboy said, "We decided we should exploit this, because it is a phenomenon."
The use of the image has produced controversy because Playboy is "seen (by some) as being degrading to women,"  and the Lenna photo has been pointed to as an example of sexism in the sciences, reinforcing gender stereotypes.
In a 1999 essay on reasons for the male predominance in computer science, applied mathematician Dianne P. O'Leary wrote:
Suggestive pictures used in lectures on image processing ... convey the message that the lecturer caters to the males only. For example, it is amazing that the "Lena" pin-up image is still used as an example in courses and published as a test image in journals today.
The use of the test image at the magnet school Thomas Jefferson High School for Science and Technology in Fairfax County, Virginia provoked a guest editorial by a senior in The Washington Post in 2015 about its detrimental impact on aspiring female students in computer science.
- "Playboy centrefold photo shrunk to width of human hair". BBC News Online. 14 August 2012. Retrieved 15 August 2012.
- Roberts, Lawrence G (1961). "Picture Coding Using Pseudo-Random Noise". MIT.
- Hutchison, Jamie (May–June 2001). "Culture, Communication, and an Information Age Madonna" (PDF). IEEE Professional Communication Society Newsletter (archive). 45 (3).
- "The Search for Lena: Discovering one Playmate's role in the history of the Internet". Newsdesk. Playboy Enterprises, Inc. 1997. Archived from the original on July 4, 1997. Retrieved December 20, 2012.
- O'Leary, Dianne P (June 25, 1999). "But the instructor's attitude can't make the female student fail, can it?". Accessibility of Computer Science: A Reflection for Faculty Members. University of Maryland - Department of Computer Science. Retrieved October 26, 2013. (References list.)
- Rosenberg, Chuck (November 3, 2001). "The Lenna Story: Imaging Experts Meet Lenna in Person". CMU.edu.
- Zax, David (16 August 2012). "A Playboy Model and Nanoscale Printing". MIT Technology Review. Retrieved 24 September 2013.
- The International Conference on Image Processing (ICIP). "Banquet". Retrieved 11 March 2016.
- "_DSC2510". Flickr - Photo Sharing!. Retrieved 11 March 2016.
- Munson, David C, Jr (January 1996). "A Note on Lena". IEEE Transactions on Image Processing (Archive). 5 (1).
- Thompson, Brian J. (January 1992). "Editorial". SPIE Journal of Optical Engineering (Archive). 31 (1).
- Brown, Janelle (May 20, 1997). "Playmate Meets Geeks Who Made Her a Net Star". Wired News.
- Needell, Deanna; Ward, Rachel (February 29, 2012). "Stable image reconstruction using total variation minimization". arXiv: [cs.CV].
- Carron, Igor (March 9, 2012). "I can't believe it's not Lena". Nuit Blanche. blogspot.com.
- "Every Picture Tells A Story". Claremont McKenna. May 2, 2013.
- "Playboy and Fabio Helped Invent the Internet, Research Papers Reveal". dailymail.co.uk. May 12, 2015.
- Zug, Maddie (24 April 2015). "A centerfold does not belong in the classroom". Washington Post. Retrieved 7 July 2015.
- "Lenna 97: A Complete Story of Lenna". Dr. Lai Man P web pages. City University of Hong Kong. 28 July 1997. Archived from the original on 2012-12-04. Retrieved 24 September 2013.
- "Playboy Newsdesk - Lena". Web.archive.org. 1997-07-04. Retrieved 2016-11-03.
- Gonzalez, Rafael C.; Richard E. Woods. Digital Image Processing (2nd ed.). ISBN 0-201-18075-8. — image used numerous times in chapter 6
- Mayer, Gregory (2009). "the waterloo image repository". uwaterloo.ca. Retrieved 2013-12-31.
- "The USC-SIPI Image Database". Viterbi School of Engineering. 1981. Retrieved 2013-12-31.