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# Online lens calculator - Calculating measurement errors caused by height variations

The use of an ordinary entocentric lens can easily cause measuring errors. As opposed to a telecentric lens, the field of view is dependent on the working distance. This is caused by the fixed opening angle of an entocentric lens.

Height deviation of test objects can therefore lead to measurement errors. Caution: The calculated error refers to the image corners! This error will be "0" in the middle of the image and will have its maximum in the image corners.

Note:Even when using the drop-down lists own values can be entered. Please use the first entry "user def."!

 Sensor size: User def. (mm) 1/4" 3.2 mm 1/3" 4.8 mm 1/2.5" 5.7 mm 1/2" 6.4 mm 1/1.8" 7.2 mm 2/3" 8.8mm 10.5 mm 1" 12.8 mm 1.2" 14.2 mm 15.3 mm 4/3 17.9 mm APS/C 23.7 mm KB 36.0 mm Line .5K 14µm Line 1K 10µm Line 1K 14µm Line 2K 10µm Line 2K 14µm Line 4K 7µm Line 4K 10µm Line 6K 7µm Line 8K 7µm Line 12K 5µm Sensor size in pixels: User def. (pixel) 240 px 320 px 480 px 512 px 640 px 800 px 1024 px 1280 px 1400 px 1600 px 2048 px 2452 px 3200 px 4096 px 4872 px 6144 px 8192 px 12288 px Focal length of lens: User def. (mm) 2.8 3.2 4.8 6 8 9 12 16 17 23 25 35 50 60 75 85 100 125 150 Working distance in mm: Variation of distance or variation of object height (+ / - mm): Calculated opening angle of lens: Calculated field of view: Length variation for total field of view in mm: Max. length variation for object at one side of image corner caused by height variance : (center of image=0...image corner=max)

Attention: For accurate measurements, it is essential to use telecentric lenses! Also geometric distortion is also substantially lower.

For further details on optical calculations, see chapter "Entocentric lenses" or chapter "Telecentric lenses".