| X-Ray | That part of the electromagnetic spectrum above ultraviolet in frequency (i.e. of shorter wavelength than UV, but not as short as Gamma rays). |
| Xenon | A gas in photographic flash tubes. |
| XD picture Card | Fuji and Olympus proprietary storage media. The name xDPicture Card was derived from eXtreme Digital and with a capacity for up to 8Gb of data. |
| X Sync | Electronic flash synchronization. |
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