Confusing about bright filtered light

[ArronOB]

Agree with Tmoney - invest some time in learning how to measure light intensity and then you will never be in doubt going forward.

There are various apps for a phone or tablet, you can use old photography light meters, or Google up less sophisticated methods like putting your hand between the light source and a white card and checking the sharpness of the shadow thrown.

Although not scientifically accurate, these methods should be adequate for optimising growing locations.

[Ray]

As far as light through a window is concerned, the window (or any glazing, for that matter) should be thought-of as being the light source, as the light does not actually pass through it, but is absorbed and reradiated.

In my greenhouse in PA, that is how vandas could thrive up near the ceiling, while phals did so on the benches 6’ below. If the sun, itself, is the source of the light in the structure, “93-million miles” and “93-million miles + 6 feet” is no different, so the phals should have fried.