New Light Meter,,,can this be true,,,,
 

I just got a light meter,,it is in Lux,,but i have a conversion table. I have a south facing window in souther California,,,i measured this moring at 10am,,,it said at the window I have almost 5,000 fc,,,and about a foot back about 3,500 fc,,,,i was amazed there was this much light,,i even have a sheer curtain up....could this be right?

I guess i will have to add more shade,,,I wanted to keep my Dends and Catts in about 3,500fc...but I will have to move my Phals and paphs to the very back,,,,
Still cannot get over how much light,,,

If you've used the correct converstion factor, you are probably correct. South light can be intense.
Joann

This does sound about right.

This time of year, a southern exposure gets very strong light.
I haven't used a light meter - but have plants in a south window for the winter - catts, den bigibbum, tolus, ascda, neostylis - the den, tolus, ascda and neostylis definitely shows signs of receiving very high light. I do have a couple catts that burned in that window but others have been fine, so I guess it depends on the individual plant.

After winter soltice, the light intensity in south facing window will slowly diminish, so you may wish to recheck the light intensity in spring and summer. It will become stronger again in the fall.

thanks,,,,i will recheck later in winter,,,but going to get another sheer curtain,,,then in summer i can see what i need to keep or remove,,,going to put Phals and Paphs on lower level,,,,

If you have an east window that would be great for the Phals possiblly even the Paphs.

Hi like everyone has said it's very probably true!!
I actually 'double' my sheer curtains in the summer months in my S & W patio doors where alot of my orchids are. I also have catts & Vanda which I move from one to the other to give as much light as possible.
Unfortunately my east windows are alot smaller so I keep my House plants mostly on that side but double the curtains there too in summer.

What is the proper way to take a meter reading for plants? In photography, you meter on the object. Do you take your meter reading on your actual plants or on the area around the plants. Vast difference between the two, especially if you are metering on a white windowsill.

Rangiku, when I meter the light falling on my plants I try to put the meter parallel with the leaf and pointing at the light source. In photography you meter the object you're shooting b/c you're concerned with how much light is reflected from it to your camera. You can think of the leaf as the photographic sensor (or 'film' for anyone still using that stuff ;)), so you want to measure the amount of light emitted or reflected onto it.

Growing on windowsills with natural light is tricky. I get really bright sun in my W-SW windows for part of the day, but some things grow and bloom better under dimmer artificial lights b/c the lights provide more radiation each day at a more tolerable/useful rate for those plants. I can diminish the light coming in with screens, curtains, etc., but I can't easily add more hours of sunlight.

--Nat

Gnathaniels absolutely correct about photography measuring light reflected by the subject, whereas in growing we measure the light hitting the subject (the intensity of the source). One idea (using the camera analogy) that helped me understand window lighting better:
Imagine the orchid as a relatively wide angle lens pointing at the light.
When close to the window, the field of view of the lens is completely filled, and it is just like being outside. The intensity is pretty much the same as being outside (unless there is screening or the window is dirty).
Once you get far enough away that the field of view is not filled, the window acts like a point source and the intensity falls off with the square of the distance from the window.

Thanks for the explanation, Nat. I've been putting off getting lights, but it going to happen soon.

P.S. I still use film: black and white with a 4 X 5 camera shooting and developing using Ansel Adams Zone System. And, I print my own color film.

Try metering on your plants. You're going to notice a big difference in the readouts.

Think Incident Light Meter for a photographic term.

Frank

Exactly, Frank. Not reflective. Time to google the conversion to foot candles.

That's cool that you still use film! I used to love shooting and printing B+W but I've never tried printing color. I finally switched to digital a few years ago for convenience and it is nice in its way, but I miss a lot of the subtle qualities the film media brought to my photos...

I have a good friend who shoots mostly 4x5. He worked at a photo equipment store for a while so he was able to pick up a lot of gear for cheap. Definitely nice for some enormous blow-ups.

--Nat

That is a great explanation! Thanks. :waving

Off topic, but, in photography both reflective and incident light meter readings are used. Reflective is used for the most part when the sun is the light source; incident is used when studio lights are used.