Solarmeter Model 5.7 has the most sensitivity for eyewear testing. It is 0-1999 µW/cm². Most sunglasses will transmit about 30-200 µW/cm² of UV depending on how thick the plastic lenses are. Tinting also has very little effect on UV transmission.

The noon summer sun emits about 5000 µW/cm² however, so, you can’t point the 5.7 meter at the sun without it going over range. If you need a direct sun reading you would also need a Model 5.0, which would read about 5.0 mW/cm². There are 1000 µW in a mW. So, 5.0 x 1000 = the 5000 mentioned above.

For example, if 50 transmitted through glasses out of 5000 from sun, then 50/5000 = 0.01 or 1% transmission. Hence 99% blocking. That process (2 meters) would give you the most accurate significant digits. An example not using round numbers is: 58/4700 = 0.0121 or 1.21% Hence 98.79% blocking.

A compromise sensitivity version would be Model 5.0SF mentioned on the 5.0 webpage. It reads in W/m². So, full sun would read 50.0 W/m² and through glasses say 0.5 W/m². Therefore, you could calculate percent transmission, hence blocking with only one meter. But, you lose some accuracy (significant digits) because the 0.5 W/m² could be anywhere from 45 to 54 µW/cm².

You can order a 5.7 and 5.0 online at www.solarmeter.com