PBS Forum

Quote from: Arnold on April 12, 2025, 12:26:31 PMI've read that you can use the light meter in a good camera to measure light source using a grey card.

Have you seen or heard of this?

I tested this, because I used to do a talk on artificial light for orchids and it's one of those questions that always comes up. I had a couple of pretty expensive DSLR cameras around, and thanks to a friend not all from the same maker, and I couldn't find any good correlation to either my lux/footcandle or much more expensive PAR light meters.

I didn't reach the level of scientific rigor required to definitively say there's not a way with some particular camera and lens and reflective surface and technique, but I tried a grey card and several types of white surfaces, at different angles from  the camera lens pointed as directly down at the measured surface as possible without casting shadows to a rather shallow angle, and with several different light sources and a couple of lenses. The meters have diffusers and can be pointed directly at the light sources, but pointing the cameras directly at the light sources gave wildly variable numbers depending on the exact angle, and was very much not recommended for at least one (e.g., the sun) so the cameras were always seeing reflected light.

A side note - one thing I tried that surprised me by working, and rather well, was an app for my phone to measure color temperature. I tested it against several LED sources of "known" color temperature, and in every case the phone app was close enough. It's handy for photography.

Steve

Almost half of April is done, and we actuly had the very first rain this month - well 2.1mm. Anyway, time for a first wrap up - the month started with the crazy blue of Corydalis fumariifolia

- not a bad start indeed. Staying with blue, I'm actually not sure if this Anemone blanda

Height:	10-20 cm (3.9-7.9 inch)
Flower Colors:	white, pink, purple, blue
Flower Season:	early spring to mid spring

isn't virused - is there a virus making flowers double their size? Also, the species seeds around quite a bit for me, so hybrid vigor?
Definitely a hybrid is Muscari azureum x pallens, EX09_533 from Antoine's donation. To finish the blues: Mandragora, one of those things I'm still surprised they are hardy, and Bellevalia trifoliata

, the latter one is a current picture, like all that are to follow.

Staying with Hyacinths, the next is a Hyacinthus orientalis cultivar - sold as "Gloria mundi" from 1767. I'm always skeptical with "rediscovered" historic cultivars, but it is definitively an interesting variant. Follow-up in the "White and fuzzy" category is Sanguinaria canadensis

. Last one from the open garden is Bongardia chrysogonum

.

Lets close with some  things that have their pots finally out: Tropaeolum tricolor

and Tropaeolum brachyceras

madly intertwined, as always and, last but not least: my Pleiones flower again - seems last summer wasn't as bad for them as the one before - despite being warmer on average, they seem to have suffered less as the maximum temperature was 35°C and not 38°C as the summer before. As the cat dropped my pleiones a few times, I'm not sure about the cultivars. The one in the back seems to be "Glacier peak", the pink one should be Pleione limprichtii

Height:	0-10 cm (0-3.9 inch)
Flower Colors:	pink
Flower Season:	mid spring

. The ones in front? unsure. Simply formosana alba?

Babiana melanops that I got from the Fall BX.

Ixia Paniculata

Boophone Disticha - with current M. Polystachya working on blooming year 'round.

Gladiolus Carneus

2023 BX 

Vegetative growth is stimulated most by light in the yellow-orange-red, which is why HPS/SON/Lucalox was the lighting used commercially until LEDs came along. Inter-nodal distance (how "leggy" a plant is), is controlled by blue light, and rather little is needed, although quite a bit more than is emitted by SON, which emits very little.

The plants look very congested, if the garden is very new to you, I would just feed the plants very heavily this year with something that includes trace elements, seperating/breaking-up clumps if you like (although I would not), but see what you get next year.

Most of what I see could be fungus/rust and nutritional effects.

Your question is not easy to answer. The leaves do indeed look suspicious for a virus infection but I am not sure. Did you use a lens to search for thrips or other critters which might be causing damage to the leaves?
You do not state where your garden is, could it be a borderline climate for Amaryllis belladonna? Or did they suffer from intermediate drought?If the clumps are decades old and were neglected in the past there might also be some nutrient deficiency causing the symptoms. I grow many Amaryllis belladonna in different places of my garden and some, on poorer soil show the same symptoms. All were purchased from the same source. On the other hand it is well known that virus infection can be masked by fertilizing.
Depending on how attached you are towards these massive clumps a laboratory test could be considered, no idea how much it would cost. Personally I would find it easier but still painful to get rid of the Iris but removing all the belladonnas would be heartbreaking......
Not sure if my answer is really helpful.....

Thanks CG100

I think we know that my light levels here in the NE USA are low compared to the natural setting of my SA plants.

It's made a great deal of a difference adding a 8 foot strip of a LED fixture over the plant area  with some red diodes included.

It's worked so far.