avail lumens (optional)
Available Lumens per Square Foot.
This is a new field as of May 2001, it is comprised of a lumen value and a qualifier suffix stating how the lumens were determined. What makes this optional data different from the rest is that it will appear in every entry whether or not the contributor supplied the lumen data.
While it is greatly appreciated when optional information is offered in a YOR contribution, for security reasons it's never been a requirement for someone to disclose information that could be used to determine the actual size of his indoor garden or the total electric power needed to operate it. For all intents and purposes each garden is just one square foot in size. Regardless, YOR contributors often offer much more detail than required for an entry. Where it relates to light, this detail is most often in the form of the actual wattage of the lamps being used. Even more detail can come in the form of the manufacturers lumens specifications for the lamps, or a light measurement taken by the grower with a meter. In the YOR's new Available Lumens field, the qualifier following the lumens figure will point to one of the above as being the source for the lumen information. If no information but the required watts/sq ft is offered, the lumen value will be estimated at the time the entry is placed in the YOR.
A review of all pre-existing YOR contributions was conducted to determine the lumen value for their entries, future contributions will be handled according to the level of optional detail supplied by the contributor. Either you can supply lumen/sq ft info yourself or it will be calculated at the time the entry is placed into the YOR, from whatever info you made available, and the appropriate qualifier character attached to it. The most accurate data is supplied by the grower, so if at all possible it would be best to at least look up the lumen output of YOUR bulb(s) at the manufacturers web site.
Below are the four qualifiers and a description of how each is used to determine lumens.
(M)easured - Measured with a light meter, usually in foot-candles (fc), 1fc=1lumen. Readings are taken at the flowering growth, from each square foot, then averaged over the total sq ft of canopy area by the contributor.
(E)stimated - This is used when only the watts/sq ft and light type(s) are known. Lumens are estimated using the Avg LPW figures found in the LPW Table then, depending on the nature of the lighting type(s), are applied to a standard formula which makes assumptions about the lighting.
(D)erived - This is used when the bulb(s) wattage(s) is offered by the contributor, but Specs or Measured lumens are not known. Lumens are derived from the LPW Table using the LPW value found under the known bulb wattage, or the bulb with the closest watt rating. The LPW figure is then applied to the contributors w/sq ft.
(S)pecifications - The manufacturer's actual initial lumen output specifications for the particular bulb(s) is known by the contributor and averaged over the total canopy area.
A lower case qualifier may appear in an entry that contains the Sequential lighting character (an exclamation ! point). This indicates a "weighted" lumen value. It was calculated using the number of flowering days for each light (when both are known), thus accounting for the lumen differences from each light over the total flowering period. The formula is: (light1 lumens x days use) + (light2 lumens x days use), total lumens are then divided by the total days.