Light meter phone app

[SueinNC]

Does anyone have suggestions on a light meter that runs on the android OS?

[Discus]

It's called a "camera" Cameras, by their very nature, require a good light meter.

Assuming you can view the requisite EXIM/EXIF data, taking a picture of a white piece of paper/card at 30cm away will let you work out the light intensity. (i.e. stick the piece of paper where you want to measure light intensity - at the height you want to measure it). Using the white card gets you a fairly standard, well understood amount of reflectance.

On my android phone, you click on the picture in Gallery to open it, click the Menu button, Click on Details, then find the ISO, shutter speed and aperture.

Here's a handy calculator for doing so, once you know the ISO, aperture and shutter speed.
Light Intensity Measurement

---------- Post added at 02:05 PM ---------- Previous post was at 01:46 PM ----------

If you want to work this out yourself,
digital camera as a light meter - Growing under Lights Forum - GardenWeb
gives the formula as:
6*F^2/(I*E)

where F = F stop (aperture)
I = Iso setting
E = Shutter Speed (exposure)

So, I just did this in my office, and under the dim lighting in here the result was ISO 80 f2.6 1/33

6 * 2.6*2.6 /(80*1/33) = 16.731 FC (wow, that is dim).

The bonus of this is if your camera uses ISO or other values the calculator at firstrays doesn't have, you can still work it out.

It should be possible to make a small app that scrapes this info out of files, but my programming skills go about as far as :
10 PRINT LOL
20 GOTO 10
or "hacking" other people's existing code to slightly tweak a thing!

---------- Post added at 02:11 PM ---------- Previous post was at 02:05 PM ----------

This app will give you lux, which IIRC, you divide by 11 to get footcandles. https://play.google.com/store/apps/d...htsensor&hl=en
That one costs money.
This one will give you footcandles, for free but seems quite poorly featured. My method above may require slightly more effort, but it will work and is free.
https://play.google.com/store/apps/d...ghtmeter&hl=en

[jeremyinsf]

I use BeeCam and also "Light Meter" (Borce Trajkovski). They report slightly different numbers so I take the average. They are both free. One of the ones listed above is a paid app, I haven't tried it.

[Discus]

I just tried some free apps -
Lux Meter by "not quite them" which seems to use the light/dark sensor on the front of my S3
I tried Light Meter by "boris trajkovski" which seems to use the same sensor
BeeCam also uses that sensor

The first two I easily found a way to change from Lux into Foot Candles in the settings, beecam, not so much.

Boris' light meter says 43 FC
Lux Meter 35/36 FC
and as noted earlier, the camera gave me half that (although there was shadowing from the phone on the paper which may explain that).
Seems quite variable.
Some of these have options that let you calibrate things.

It seems to me the camera light sensor will be rather more accurate than the "how light is it" sensor on the front, which is really only intended to adjust screen brightness, which may make the tedious calculation from the pictures worthwhile.

---------- Post added at 04:22 PM ---------- Previous post was at 04:20 PM ----------

All of them have ads, beecams are the most obtrusive.

[jeremyinsf]

I do agree with you Discus! I don't use it to get -actual- light... if I wanted that, I'd buy a real light meter. I use it for what I call 'perspective light metering' (that's my term haha) where I want to see the difference in the amount of light at different places in my grow area under the lights. Different shelves, the size of the plant (height of the leaves from the light) and things like that. I trust the app knows what is 'half', but don't take the FC reported to me as something to grow by.

[Discus]

I bought a light meter, and I don't trust it either. LOL.

I think it's kind of like watch syndrome, which goes something along the lines of "a man with one clock knows what time it is. A man with two clocks is never sure"...

I'm sure it's possible to calibrate these things fairly accurately, but I've never cared enough to look it up - after all, the difference between say cattleya light and phal light is massive, and something you'll be able to see even with quite rudimentary readings.

Of course, once you have a light reading, now you need to work out what will like it there... Orchids on a Balcony: New Gadget: Light Meter

[SueinNC]

I knew I could get some good answers on this board. It makes sense that the phone's camera is accurate. I had downloaded BeeCam, cant' beat the price but I was unsure about accuracy. A man with two clocks is never sure, love that quote. It applies to a lot of things. Thank you all so much for your input.