Wikipedia:Non-free content/Definition of "low resolution"

The Wikipedia Fair Use policy specifies the images must be of "low" or "web" resolution. It does not currently attempt to define this in any detail, however. This page is meant to give some guidelines for determining whether an image is sufficiently low-resolution to be within the policy, as well as the justification behind the policy.

In a nutshell

 * Unlicensed copyrighted images used under the "fair use" clause of copyright law should be low-resolution
 * Strictly speaking this means they should be of no larger size than that necessary to satisfy its informational purpose in the article
 * For most forms of media this means that they should probably not be bigger than 400 pixels wide or so; if the image cannot be displayed at full size on the image description page, it is probably too big
 * Images which need for some reason to be larger than this need a detailed justification given; otherwise they should be resized or deleted

Why does resolution matter?
Courts have held that the physical size of a reproducible image can constistute a factor in the "amount of the image used" consideration of whether an image is "fair use" or not, and have implied that in a digital medium pixel size can be considered analogous with physical size. There are two cases usually cited for associating image size with image use, though neither are easy to apply in a straightforward manner. Kelly v. Arriba Soft Corporation (2002) held that low-resolution thumbnails were non-infringing in the case of their automatic generation by a search engine (but a lot of the judgment was specific to automatically-generated images and to very low resolution thumbnails, much smaller than most images on Wikipedia). Image size in particular was relevant in that the derivative works did not plausibly infringe on the market of the copyright holder, and the use of the entire image was held neutrally since there would be no other way to convey the same information ("If the secondary user only copies as much as is necessary for his or her intended use, then this factor will not weigh against him or her."). The combination of these factors could be interpreted to mean the pixel size could be correlated with image use in the case of low resolutions, but it does not necessarily follow. (The case of Perfect 10 v. Google, Inc. (2006) held that thumbnail images could impinge upon markets of images of that size — cellphone background images.) In Bill Graham Archives v. Dorling Kindersley Limited (2006), though, the courts explicitly held that significantly reducing an image in size did affect its likelihood of being designated "fair use" favorably, citing Kelly v. Arriba Soft as a precedent in this respect: "...even though the copyrighted images are copied in their entirety, the visual impact of their artistic expression is significantly limited because of their reduced size. See Kelly, 336 F.3d at 821 (concluding that thumbnails are not a substitute for full-size images)". Additionally, it is practical to keep unlicensed images as low a resolution as is necessary for their use here in order to avoid unwanted attention and ire of copyright holders. Our goal is not to provide an archive of high-resolution copyrighted images, but to use such images sparingly when illustrating an encyclopedia — there is little justification for high- or print-resolution unlicensed images in almost all cases.

Defining "low resolution"
A general rule of thumb about image size is that the image resolution should be no higher than that necessary for the image to convey its information within the context of the Wikipedia article. In most cases anything which is not obviously too high a resolution is probably fine. Another approach to the rule of thumb is that if Wikipedia's software is forced to use a thumbnail of the image on the image description page, it is almost certainly an image of too high a resolution. One of the few possible exceptions would be if it were important that the user be able to read text in the image, which would not be legible at that resolution; in that case, the minumum legible resolution might be acceptable.

Examples
As a few examples, a scan of a magazine cover with a 400 px vertical height is probably large enough to read almost all of the text on the cover of any importance, as well as clearly see the image on the cover. A scanned CD cover should probably not need to have a vertical height larger than 300 px to accomplish this task. In both of these cases, the medium on which the scan is based exists in the non-digital world and has a much higher original resolution (around 300 px per inch, depending on the printing quality), and our scans would not be using much of the original material (and would not be possible to serve as a substitute for it).

In the case of screenshots from video games and computer applications (which are meant to be showing the game or application itself), though, because the original source image exists only digitally (and has a resolution of around 92 px per inch), resizing the image could cause the loss of important information contained in the screenshot, and would ultimately make the final image noticebly less useful for an encyclopedia. (Additionally, in video games there is a well-established culture of using screenshots for discussing and identifying games, potentially making it a less problematic legal category in any case.)

In cases where the low-resolution images would directly compete with an existing market for low-resolution images, extreme caution should be taken. One recent Circuit Court case held Google as infringing for its search engine making automatic thumbnails of images which could potentially be sold as cellphone background images. Though the exact extent of this ruling is not yet known (are all images potentially cellphone backgrounds?) in cases where direct overlap is known, invocation of the "fair use" policy should probably be avoided if possible.

Exceptions
If individual images must be used in a somewhat high resolution to convey their point, then a detailed explanation of why this is so must be on the image description page. In cases where only small parts of the image must be magnified to convey the point, these should be separately cropped from the image and displayed alongside a low-resolution image of the total work. (Conversely, images like magazine covers should not, in general, be cropped in any way which would make it unclear which magazine they came from.)

If there is no good rationale for having a high resolution "fair use" image, then the image should either be resized (tagging it with the fair use reduce template may facilitate this) or removed through the normal channels (i.e. Possibly unfree images).