{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"crop-factor"},"result":{"entity_type":"calculator","id":"crop-factor","calculator_id":"crop-factor","canonical_url":"https://tttkmbb.com/photography/crop-factor","name":"Crop Factor Calculator","title":"Crop Factor Calculator – Sensor Diagonal, Equivalent Focal Length and Aperture","category":"photography","category_name":"Photography & Optics","tool_name":"calculate_crop_factor","featured_mcp_tool":false,"description":"Computes a sensor's crop factor (43.27 mm full-frame diagonal ÷ sensor diagonal), its area relative to full frame, and the full-frame equivalent focal length and depth-of-field-equivalent aperture for a given lens.","use_when":"You want to compare lenses across sensor formats, convert a focal 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).","inputs":[{"name":"sensor","label":"Sensor format","type":"enum","required":false,"default":"full_frame","values":[{"value":"full_frame","label":"Full frame (36 × 24 mm)","aliases":["ff","35mm","full-frame"]},{"value":"aps_c","label":"APS-C (23.5 × 15.6 mm; Nikon, Sony, Fujifilm, Pentax)","aliases":["apsc","aps-c","crop"]},{"value":"aps_c_canon","label":"APS-C Canon (22.3 × 14.9 mm)","aliases":["canon_aps_c","canon"]},{"value":"micro_four_thirds","label":"Micro Four Thirds (17.3 × 13 mm)","aliases":["mft","m43","four_thirds"]},{"value":"one_inch","label":"1-inch type (13.2 × 8.8 mm)","aliases":["1_inch","1-inch","type_1"]},{"value":"medium_format_44x33","label":"Medium format 44 × 33 (43.8 × 32.9 mm)","aliases":["medium_format","gfx","44x33"]},{"value":"smartphone_1_over_2_3","label":"Smartphone 1/2.3-inch (6.17 × 4.55 mm)","aliases":["smartphone","phone","1/2.3"]}],"description":"Sensor format preset providing the sensor width and height.","example":"aps_c"},{"name":"sensor_width_mm","label":"Sensor width","type":"number","unit":"mm","required":false,"max":200,"exclusive_min":0,"description":"Optional sensor width in mm; overrides the sensor preset.","example":23.5},{"name":"sensor_height_mm","label":"Sensor height","type":"number","unit":"mm","required":false,"max":200,"exclusive_min":0,"description":"Optional sensor height in mm; overrides the sensor preset.","example":15.6},{"name":"focal_length_mm","label":"Focal length","type":"number","unit":"mm","required":false,"min":1,"max":5000,"description":"Optional actual focal length; returns its full-frame equivalent focal length.","example":35},{"name":"aperture_f","label":"Aperture (f-number)","type":"number","required":false,"min":0.5,"max":128,"description":"Optional f-number; returns the full-frame aperture giving the same depth of field.","example":2}],"outputs":[{"name":"crop_factor","label":"Crop factor","type":"number","decimals":3,"description":"Full-frame diagonal (43.27 mm) divided by the sensor diagonal."},{"name":"sensor_diagonal_mm","label":"Sensor diagonal","type":"number","unit":"mm","decimals":2,"description":"√(width² + height²)."},{"name":"sensor_area_mm2","label":"Sensor area","type":"number","unit":"mm²","decimals":1,"description":"width × height."},{"name":"area_ratio_to_full_frame","label":"Area relative to full frame","type":"number","decimals":3,"description":"Sensor area divided by the full-frame area of 864 mm²."},{"name":"light_gathering_stops_vs_full_frame","label":"Total light vs full frame","type":"number","unit":"stops","decimals":2,"description":"log2(area ratio): stops of total light the sensor collects relative to full frame at the same exposure settings (negative = less)."},{"name":"equivalent_focal_length_mm","label":"Equivalent focal length","type":"number","unit":"mm","decimals":1,"description":"focal_length_mm × crop factor: full-frame focal length with the same diagonal angle of view (only when focal_length_mm is given)."},{"name":"equivalent_aperture_f","label":"Equivalent aperture (depth of field)","type":"number","decimals":2,"description":"aperture_f × crop factor: full-frame f-number with the same depth of field and diffraction; exposure is unchanged (only when aperture_f is given)."}],"input_schema":{"type":"object","properties":{"sensor":{"description":"Sensor format preset providing the sensor width and height.","type":"string","enum":["full_frame","aps_c","aps_c_canon","micro_four_thirds","one_inch","medium_format_44x33","smartphone_1_over_2_3"],"default":"full_frame","examples":["aps_c"]},"sensor_width_mm":{"description":"Optional sensor width in mm; overrides the sensor preset. Unit: mm.","type":"number","maximum":200,"exclusiveMinimum":0,"examples":[23.5],"x-unit":"mm"},"sensor_height_mm":{"description":"Optional sensor height in mm; overrides the sensor preset. Unit: mm.","type":"number","maximum":200,"exclusiveMinimum":0,"examples":[15.6],"x-unit":"mm"},"focal_length_mm":{"description":"Optional actual focal length; returns its full-frame equivalent focal length. Unit: mm.","type":"number","minimum":1,"maximum":5000,"examples":[35],"x-unit":"mm"},"aperture_f":{"description":"Optional f-number; returns the full-frame aperture giving the same depth of field.","type":"number","minimum":0.5,"maximum":128,"examples":[2]}},"additionalProperties":false},"output_schema":{"type":"object","properties":{"crop_factor":{"description":"Full-frame diagonal (43.27 mm) divided by the sensor diagonal.","type":"number"},"sensor_diagonal_mm":{"description":"√(width² + height²). Unit: mm.","type":"number","x-unit":"mm"},"sensor_area_mm2":{"description":"width × height. Unit: mm².","type":"number","x-unit":"mm²"},"area_ratio_to_full_frame":{"description":"Sensor area divided by the full-frame area of 864 mm².","type":"number"},"light_gathering_stops_vs_full_frame":{"description":"log2(area ratio): stops of total light the sensor collects relative to full frame at the same exposure settings (negative = less). Unit: stops.","type":"number","x-unit":"stops"},"equivalent_focal_length_mm":{"description":"focal_length_mm × crop factor: full-frame focal length with the same diagonal angle of view (only when focal_length_mm is given). Unit: mm.","type":"number","x-unit":"mm"},"equivalent_aperture_f":{"description":"aperture_f × crop factor: full-frame f-number with the same depth of field and diffraction; exposure is unchanged (only when aperture_f is given).","type":"number"}}},"formula":"crop_factor = √(36² + 24²) / √(width² + height²); equivalent_focal_length_mm = focal_length_mm × crop_factor; equivalent_aperture_f = aperture_f × crop_factor; area_ratio = width × height / 864","method":"Diagonal-based crop factor as used by camera makers; sensors with a different aspect ratio (4:3 Micro Four Thirds) have a slightly different horizontal factor. Equivalent aperture describes depth of field and total light, not exposure.","sources":[{"name":"Wikipedia – Crop factor","url":"https://en.wikipedia.org/wiki/Crop_factor","type":"reference","retrieved_at":"2026-09-24"},{"name":"Cambridge in Colour – Digital camera sensor sizes","url":"https://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm","type":"reference","retrieved_at":"2026-09-24"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"APS-C 23.5 × 15.6 mm with a 35 mm f/2 lens","inputs":{"sensor":"aps_c","focal_length_mm":35,"aperture_f":2},"expected":{"crop_factor":1.534,"sensor_diagonal_mm":28.21,"equivalent_focal_length_mm":53.7,"equivalent_aperture_f":3.07,"area_ratio_to_full_frame":0.424},"url":"https://tttkmbb.com/api/v1/calculate/crop-factor?sensor=aps_c&focal_length_mm=35&aperture_f=2"},{"name":"Micro Four Thirds with a 25 mm lens","inputs":{"sensor":"micro_four_thirds","focal_length_mm":25},"expected":{"crop_factor":1.999,"sensor_diagonal_mm":21.64,"equivalent_focal_length_mm":50,"sensor_area_mm2":224.9},"url":"https://tttkmbb.com/api/v1/calculate/crop-factor?sensor=micro_four_thirds&focal_length_mm=25"}],"faq":[{"q":"Does a crop sensor change the lens' focal length?","a":"No. A 35 mm lens stays 35 mm; the smaller sensor records a central crop of the image, so the framing matches a 53.7 mm lens on full frame (35 × 1.534)."},{"q":"Why is there an 'equivalent aperture' if exposure does not change?","a":"f/2 gives the same exposure on any sensor. But for the same framing, a crop sensor at f/2 has the depth of field, diffraction and total light of f/3.1 on full frame; the equivalent aperture expresses that."}],"tags":["crop factor","equivalent focal length","sensor size","aps-c","micro four thirds","full frame"],"related":[{"calculator_id":"field-of-view","reason":"Actual angle of view for the lens on this sensor."},{"calculator_id":"depth-of-field","reason":"Depth of field with the sensor's circle of confusion."},{"calculator_id":"hyperfocal-distance","reason":"Hyperfocal distance for the same sensor and lens."}],"links":{"html":"https://tttkmbb.com/photography/crop-factor","markdown":"https://tttkmbb.com/photography/crop-factor.md","json":"https://tttkmbb.com/photography/crop-factor.json","api":"https://tttkmbb.com/api/v1/calculate/crop-factor","schema":"https://tttkmbb.com/api/v1/calculators/crop-factor","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T03:44:31Z","next_actions":[{"tool":"run_calculator","calculator_id":"crop-factor","reason":"Run Crop Factor Calculator with the inputs above."}],"links":{"markdown":"https://tttkmbb.com/photography/crop-factor.md"}}