What Size Font Is Visible From 3 Feet

(Enlarged delineation of visual angle)

Full general notes

The Font Size Computer is designed to make it easier to identify inclusive font sizes in compliance with the German DIN 1450 standard on legibility. Depending on the relevance of compliance with specific standards, further examination based on all the criteria of DIN 1450 and possibly on other standards may exist necessary.

A summary of information on this topic can exist found in the chapter on font sizes (in High german) and more detailed information is available in DIN 1450 (in German language).

The recommendations on font sizes in DIN 1450 are based on usually sharp vision of at least 70 % (visual vigil ≥ 0.7). Font sizes can exist multiplied by a cistron appropriate for the visual acuity of people whose vision is less sharp to provide them with an adequate font size. Font size cannot however be enlarged arbitrarily because of the limits set by the reader'south field of vision, cavalcade widths, formats and technical reading aids. Factors ranging from 1.4 (visual acuity ≥ 0.five) up to a maximum of 1.75 (visual acuity ≥ 0.4) have been shown to be practicable. Using these factors, font size can be multiplied for texts that are specially designed for readers with visual impairments. The standard font sizes recommended in DIN 1450 are sufficient for all other applications.

The background to the calculation

The calculation of font size as prescribed in DIN 1450 is based on 10-heights. Font size (here x-height) is mostly set depending on the viewer'southward distance from it. The shorter a viewer's distance from a text is, the smaller its font can be and vice-versa. DIN 1450 bases its recommendations for 10-heights that function independent of the viewer's distance on the visual angle.

Zwischen der Shilouette eines Frauenkopfes und einem kleinen a ist ein gleichschenkliges Dreieck aufgespannt, dessen Scheitelpunkt im Auge des Frauenkopfes sitzt. Der Winkel zwischen den beiden gleichschenkligesn Seiten ist als Winkel Alpha markiert.

The visual angle is the angle at which a viewed object is perceived. Minimum x-height values for the 3 types of text in DIN 1450, reading text, consultation text and signalling text, are expressed through the visual angle in the unit of arc minutes. For more data see as well the Wikipedia articles on athwart bore and visual vigil.

Based on the minimum values stipulated in DIN 1450 for the prescribed visual bending α, the x-height G tin can be adamant, taking the viewer's distance D into account, through a adding using an isosceles triangle.

M = ii D \times \tan (\frac{α}{ii})

DIN 1450 also makes it possible to take the viewer'southward sharpness of vision (visual vigil) and adaptive luminance (or more than simply 'lighting') of the signifier into account in the calculation past including these two aspects every bit the Luminance/Visual Acuity-Correction factor 1000_LV in the adding every bit follows:

One thousand = 2 D \times \tan (\frac{α \times {Yard}_{Fifty 5}}{2})

The Luminance/Visual acuity Correction cistron Chiliad_LV can be derived from Table A.1 in DIN 1450 as follows:

K_{L 5} = \frac{L f_{51}}{V}

Lf_V1 corresponds with the Luminance Correction factor shown in cavalcade 1 for a visual vigil of 1. V represents the viewer's visual acuity.

In almost every computer program you lot can adjust font size (actually trunk height) only not x-meridian. To calculate font size from the calculated 10-height, the x-height-font size ratio Thou_South of the font to exist used must be known. This can vary from font to font and vary greatly in some cases. Information technology can be identified past measuring the x-summit of a known font size to determine the ratio between the x-height M and font size S:

{Grand}_{S} = \frac{M}{South}

If no individually determined value is entered in the prescribed field, the Font Size Estimator assumes an 10-height-font size ratio of 0.47 as standard. This tin can be obtained from DIN 1450. The specification of recommended font size in points is in this case but a rough value. In contrast, the calculation of x-height in millimetres is always exact.

Special features of calculating font sizes for screens

Some special features apply to calculating font sizes for screen display (see also Digital Media). Here the device's virtual resolution must be specified in pixels per inch (ppi) in an actress field.