page_title: John Wall (inventor)
hierarchical_section_title: John Wall (inventor)
caption_attribution_description: English: John Wall - retired design engineer Inventor of the Crayford focuser. ATM, optical research , painting, making things. Writing articles. Inventor of the Zerochromat retrofocally corrected refractor, discoverer of a new refractor concept, the Hypochromat.
context_page_description: John Wall was an English design engineer, amateur astronomer, amateur telescope maker and member of the British Astronomical Association. He lived in Coventry, England.
context_section_description: John Wall (26 June 1932 – 27 January 2018) was an English design engineer, amateur astronomer, amateur telescope maker and member of the British Astronomical Association. He lived in Coventry, England.
caption: John Wall
exif: {"Image ImageDescription": "", "Image Make": "NIKON", "Image Model": "E4300", "Image Orientation": "Horizontal (normal)", "Image XResolution": "300", "Image YResolution": "300", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "E4300v1.5", "Image DateTime": "2008:07:08 07:56:36", "Image YCbCrPositioning": "Co-sited", "Image ExifOffset": "284", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "300", "Thumbnail YResolution": "300", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "4084", "Thumbnail JPEGInterchangeFormatLength": "5129", "EXIF ExposureTime": "2/221", "EXIF FNumber": "9/2", "EXIF ExposureProgram": "Program Normal", "EXIF ISOSpeedRatings": "100", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2008:07:08 07:56:36", "EXIF DateTimeDigitized": "2008:07:08 07:56:36", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "1", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "3", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire, auto mode", "EXIF FocalLength": "39/2", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "2272", "EXIF ExifImageLength": "1704", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "1026", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "0", "EXIF FocalLengthIn35mmFilm": "92", "EXIF SceneCaptureType": "Standard", "EXIF GainControl": "None", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal", "EXIF SubjectDistanceRange": "0"}