I want to go over 4 different visible symptoms of light burn and at the end of this video Ill show you how to determine how far you should place your lights from your plants.
Now light intensity is extremely important and there is perfect distance, but ultimately, I think having too much is worse than having too little because plants always grow out of it.
The first is the most obvious, the upper most leaves look shriveled and thinner and they fold inwards like a taco shell. They’ll feel dry and brittle and droop down similar to overwatered leaves. Also, not to be confused with nitrogen or sulfur deficiency, the leaves appear more yellow. Here you can see lighting at comfortable levels on the left and too much light on the right. Notice how it goes from green to yellow.
2. This is a curve ball and I know it’s not calcium issues. I only observe these spots on the higher leaves, even if the leaves look healthy otherwise. It appears like you dropped a speck of bleach onto the plant and it has absolutely no texture, Its just a discoloration and it isn’t beveled or embossed at all. At first I thought this may have been a reaction to water droplets which were accidentally spilled and caused the magnification of light so I tested the theory and this is not the case.
3. Extreme literal burn from leaves physically touching the light and burnt spots eventually start to brown. The burn will never recover but the leaves will survive and continue to grow
4. Looks similar to boron deficiency but it makes your leaves a lighter shade of green or yellow instead of brown. It looks like you scuffed the leaf and exposing a lighter shade of green under the scraped surface. The last photo is what a non light burned canopy looks like that was not subject to any forced light stress.
Hope this gives guidance to growers who may think they have some sort of over watering/under watering or deficiency issues. Best Lights (In my opinion and in order from best)