06-27-2007 Council Agenda - Laserfiche WebLink

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PRELIMINARY DRAFT FOR REVIEW BY CITY OF MINNETONKA Further changes are anticipated following Signage Workshop **Preliminary Report is specific to City of Minnetonka issues and may not be sufficient to address concerns in other communities ** Table A -1 - Luminance Standards Ambient Approximate Minimum Maximum Light Light Luminance Luminance (lux) (nits) (nits) 40,000 Sunlight 12,400 62,000 10,000 Cloudy 12,400 - 4,000 Overcast 2,200 11,000 400 Sunrise /Sunset 600 3,000 40 Candlelight 250 1,250 less than 4 Moonlight 75 375 Source: NEVIA TS -4 (2005) Billboard Resolution Billboards require far less resolution than print advertisements. For example, Clear Channel's LED "Digital Outdoor Network" LED bulletin -size (14' x 48') billboards require dimensions of only 208 pixels high by 720 pixels wide. If this image were to be printed at 300 dots per inch (dpi), a typical print resolution, the entire image would be less than 1.7 square inches. Therefore, it is ideal to keep the message on these signs simple and clear because they do not currently allow resolutions similar to printed images. Dimming To maintain readability, the brightness of a sign must be adjusted to match ambient light conditions. If this is not done, the image will appear too bright and can even degrade the image quality through a phenomenon called "blooming." If the image blooms, the brightest areas of the image bleed over into darker parts and the image clarity is degraded. Dimming is typically controlled by a photocell, which measures the ambient light conditions and varies the light output of the sign based on preconfigured settings. As ambient light conditions darken, the photocell senses the decrease and lowers the light output of the sign. Some sign manufacturers do not incorporate photocells in their electronic signs. Electronic billboard dimming can also be controlled by scheduled dimming according to time of day or manual dimming. On- premise signs may use any of these methods, but most, if not all, off - premise standard size electronic billboards are auto dimmed by photocell. Some signs include user - defined dimming curve capability allowing total control over sign brightness and adjustability to accommodate local brightness ordinances.