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Enabling better global research outcomes in soil, plant & environmental monitoring.


OptoLeaf is a film for measuring accumulated solar radiation and accumulated photon quantity.

OptoLeaf measures cumulative solar radiation based upon colour fade degree. OptoLeaf film enables measurement in places where a conventional pyranometer cannot measure, or would be too expensive for large scale multipoint measurement.

  • Small, light, tape/film based measurement.
  • Works anywhere (even under water).
  • Ideal for multipoint measurement.
  • Low cost-per-piece, required lengths cut from a roll.

Portable absorbance measurement instruments (RYO-470 & RYO-470M) are available to conveniently and accurately measure OptoLeaf film.

OptoLeaf is a film to measure the integrated amount of solar radiation and integrated amount of light quanta. The colouring matter of the film is faded by solar radiation, and the colour fade rate is converted to the integrated amount of solar radiation and integrated amount of light quanta with use of a calibration curve.

OptoLeaf enables measurements that have been difficult with a conventional pyranometer.

OptoLeaf is a file, which means small and light, and therefore, it can be placed anywhere. Because OptoLeaf can be prepared in large number by cutting it, it is suited for measuring in many places at the same time. There are three types of OptoLeaf available, which have different fading speeds and fading periods, you can choose OptoLeaf depending on your measurement environment or measurement period.

D-Meter RYO-470M

A portable absorbance measurement instrument dedicated to OptoLeaf. Absorbance (D) of OptoLeaf can be easily measured anytime, anywhere.
The dedicated tool is designed for convenience and efficiency in measuring many OptoLeaf pieces. It is compact, light, and easy to carry. The degree of exposure can be immediately checked on the site where OptoLeaf is pasted.

Measurement Period

Product No. (Colour/period) Summer/Fair weather Summer/cloudy weather
Winter/fair weather
Winter/fair weather
R-3D (Red – 3 days) 1 to 2 days 2 to 5 days 4 to 8 days
Y-1W (Yellow – 1 week) 3 to 7 days 5 to 14 days 1 to 3 weeks
O-1D (Orange – 1 day) 0.5 to 1 day 1 to 2 days 2 to 4 days

Fade Rate Formula

Product No. Max. Absorbance Wavelength Fading Rate Formula (Fading Rate %)
R-3D 521nm log10(D/D0 x 100)
Y-1W 468nm D/D0 x 100
O-1D 492nm D/D0 x 100 (Range 30-90%)

D = absorbance at the beginning (before exposure)
D0 = absorbance after exposure

OptoLeaf Measuring Instruments

RYO-470M RYO-470
Dimensions: 76W x 135H x 27D (mm) 90W x 135H x 35D (mm)
Weight: 209g (incl. batteries) 250g (incl. batteries)
Batteries: 2x AA 2x AA
Memory: 990 data sets (1 to 99 data sets of 10 blocks) None
Data Output: Data can be transferred to PC, application software to convert to Excel N/A