Newbie question-light meters

[etex]

Hi everyone! I received a Hydrofarm Digital Light Meter as a Christmas present.The results I received are puzzling. For each plant stand I measured light with the wand in front of a plants leaves in direct sunlight and a leaf out of direct sunlight in the same stand.For example:Sunroom peaked at 7960(sun)/1200(not sun),lowest reading 4010/270. I would think the radient light would not allow this much difference in the same stand. The back does not look like it is deep shade and is a foot deep front to back.Does this mean I need to rotate plants here back to front? Do these readings sound right? Any tips?? I use this stand for my catts and they do well here,but not at the readings of 270! Thanks for any input as I am quite confused about the reading range. Thanks! Diane

[trdyl]

Now that is a great Christmas present!

Actually those readings sound about right. The sun's angle, cloud cover, tree branches, window supports, wall paint all affects the amount of light available at any given time.

I grow in windows my south facing windows with out any shading varies from 200 to 9000ftc depending all of the above. I inserted a light curtain between the window and plants so that the maximum is sitting at 5000ftc.

I would be careful with your Catts at near 8000ftc. They can easily sunburn at those levels. Rotating the plants will not hurt. I would not do it constantly but every day, two, or three should work fine. The more light they get the better. Of course there is a point that too much is too much. If the leaves feel warm you need to either increase air flow or decrease the amount of light.

[King_of_orchid_growing:)]

I take it the readings are in footcandles?

Or are they lumens?

[etex]

Sorry- yes, the readings are in footcandles.
Ted- Thanks for your input. Will be careful and watch for sunburn!

[Ray]

Interestingly enough (OK - to me, anyway) is the fact that plants seem to perceive the glazing (window or greenhouse) as the "source" of the light.

We're all aware of the inverse-square drop-off of light intensity from a point source - twice the distance has 1/4 the intensity, or 3x the distance, 1/9th the intensity - but if we considered the sun the source, rather than the window, it would seem logical that 93-million miles versus 93-million miles plus one foot would not be a significant difference.