{"success":true,"version":"v1","request":{"tool":"list_calculators","category":"photography"},"result":{"entity_type":"calculator_list","status":"completed","count":12,"calculators":[{"calculator_id":"depth-of-field","entity_type":"calculator","name":"Depth of Field Calculator","category":"photography","tool_name":"calculate_depth_of_field","description":"Computes the near and far limits of acceptable sharpness, the total depth of field and the hyperfocal distance from focal length, f-number, focus distance and the sensor's circle of confusion, using the standard thin-lens depth-of-field equations.","use_when":"You need to know how much of a scene is acceptably sharp for given camera settings, or how far sharpness extends in front of and behind the focused subject.","do_not_use_when":"You only need the focus distance that maximises depth of field (use hyperfocal-distance), or you shoot macro above about 0.2× magnification where lens extension and pupil magnification make the thin-lens 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length to its full-frame equivalent, or quantify how much smaller a sensor is than full frame.","do_not_use_when":"You need the actual angle of view in degrees (use field-of-view) or the depth of field at a focus distance (use depth-of-field).","required_inputs":[],"optional_inputs":["sensor","sensor_width_mm","sensor_height_mm","focal_length_mm","aperture_f"],"urls":{"html":"https://tttkmbb.com/photography/crop-factor","markdown":"https://tttkmbb.com/photography/crop-factor.md","schema":"https://tttkmbb.com/api/v1/calculators/crop-factor","api":"https://tttkmbb.com/api/v1/calculate/crop-factor"}},{"calculator_id":"exposure-value","entity_type":"calculator","name":"Exposure Value Calculator","category":"photography","tool_name":"calculate_exposure_value","description":"Computes the exposure value EV = log2(N²/t) of a camera setting, the ISO-100 normalised light value EV100, an illuminance estimate in lux (incident-meter calibration C = 250) and a description of the lighting the settings correspond to.","use_when":"You want to express aperture, shutter and ISO as a single exposure number, estimate how bright a scene is, or check settings against the Sunny 16 rule.","do_not_use_when":"You want to translate one setting into another with the same exposure (use equivalent-exposure) or to work out a long exposure with an ND filter (use nd-filter-exposure).","required_inputs":["aperture_f","shutter_seconds"],"optional_inputs":["iso"],"urls":{"html":"https://tttkmbb.com/photography/exposure-value","markdown":"https://tttkmbb.com/photography/exposure-value.md","schema":"https://tttkmbb.com/api/v1/calculators/exposure-value","api":"https://tttkmbb.com/api/v1/calculate/exposure-value"}},{"calculator_id":"equivalent-exposure","entity_type":"calculator","name":"Equivalent Exposure Calculator","category":"photography","tool_name":"calculate_equivalent_exposure","description":"Solves the shutter speed that keeps the exposure unchanged when the aperture and/or ISO are 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exposure-value).","required_inputs":["base_shutter_seconds"],"optional_inputs":["nd_stops","nd_factor"],"urls":{"html":"https://tttkmbb.com/photography/nd-filter-exposure","markdown":"https://tttkmbb.com/photography/nd-filter-exposure.md","schema":"https://tttkmbb.com/api/v1/calculators/nd-filter-exposure","api":"https://tttkmbb.com/api/v1/calculate/nd-filter-exposure"}},{"calculator_id":"megapixels-print-size","entity_type":"calculator","name":"Megapixels to Print Size Calculator","category":"photography","tool_name":"calculate_print_size_from_megapixels","description":"Computes the megapixel count and aspect ratio of an image from its pixel dimensions and the print size it yields at a chosen resolution in dots per inch, with a table for 150, 200, 240 and 300 dpi.","use_when":"You want to know how large a photo can be printed at a given quality, or how many megapixels a camera needs for a print size.","do_not_use_when":"You need a screen's pixel density (use screen-ppi) or the storage size of the image file (use image-file-size).","required_inputs":["width_px","height_px"],"optional_inputs":["dpi"],"urls":{"html":"https://tttkmbb.com/photography/megapixels-print-size","markdown":"https://tttkmbb.com/photography/megapixels-print-size.md","schema":"https://tttkmbb.com/api/v1/calculators/megapixels-print-size","api":"https://tttkmbb.com/api/v1/calculate/megapixels-print-size"}},{"calculator_id":"telescope-magnification","entity_type":"calculator","name":"Telescope Magnification Calculator","category":"photography","tool_name":"calculate_telescope_magnification","description":"Computes the magnification of a telescope and eyepiece combination (with optional Barlow), the exit pupil, true field of view, focal ratio, useful magnification range, Dawes and Rayleigh resolution limits and an estimated limiting magnitude.","use_when":"You are choosing an eyepiece or Barlow for a telescope and want to know the resulting power, field of view and whether the magnification is useful for the aperture.","do_not_use_when":"You need the angle of view of a camera lens (use field-of-view) or exposure settings for astrophotography.","required_inputs":["telescope_focal_length_mm","eyepiece_focal_length_mm","aperture_mm"],"optional_inputs":["barlow_factor","eyepiece_afov_degrees"],"urls":{"html":"https://tttkmbb.com/photography/telescope-magnification","markdown":"https://tttkmbb.com/photography/telescope-magnification.md","schema":"https://tttkmbb.com/api/v1/calculators/telescope-magnification","api":"https://tttkmbb.com/api/v1/calculate/telescope-magnification"}},{"calculator_id":"image-file-size","entity_type":"calculator","name":"Image File Size Calculator","category":"photography","tool_name":"estimate_image_file_size","description":"Estimates the storage size of an image from its pixel dimensions, bits per channel, number of channels and a compression ratio, and scales the result to a number of images, in decimal megabytes and gigabytes.","use_when":"You need 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needs from a per-frame file size.","use_when":"You are planning a time-lapse and need the intervalometer setting, how many shots it takes, or how much card space is required.","do_not_use_when":"You need the file size of a normal video (use video-file-size) or the size of individual photos (use image-file-size).","required_inputs":["event_duration_minutes","clip_duration_seconds"],"optional_inputs":["fps","file_size_per_frame_mb"],"urls":{"html":"https://tttkmbb.com/photography/time-lapse","markdown":"https://tttkmbb.com/photography/time-lapse.md","schema":"https://tttkmbb.com/api/v1/calculators/time-lapse","api":"https://tttkmbb.com/api/v1/calculate/time-lapse"}},{"calculator_id":"flash-guide-number","entity_type":"calculator","name":"Flash Guide Number Calculator","category":"photography","tool_name":"calculate_flash_exposure","description":"Scales a flash's guide number (quoted at ISO 100) to the working ISO with GN × √(ISO/100) and solves the guide-number equation GN = distance × f-number for the required aperture at a distance or the maximum flash range at an aperture.","use_when":"You are using a flash in manual mode and need the f-number for a subject distance, or the distance a flash can reach at a chosen aperture and ISO.","do_not_use_when":"The flash is in TTL/automatic mode, is bounced or heavily diffused (the guide number no longer applies), or you need ambient exposure settings (use exposure-value).","required_inputs":["guide_number_m"],"optional_inputs":["iso","distance_m","aperture_f"],"urls":{"html":"https://tttkmbb.com/photography/flash-guide-number","markdown":"https://tttkmbb.com/photography/flash-guide-number.md","schema":"https://tttkmbb.com/api/v1/calculators/flash-guide-number","api":"https://tttkmbb.com/api/v1/calculate/flash-guide-number"}}]},"timestamp":"2026-09-24T03:46:49Z","next_actions":[],"links":{"docs":"https://tttkmbb.com/calculators.md"}}