About reading the specification of commercial lights... (Chihiros WRGB2 45 Standard vs Slim)

[SirBuce]

Hi folks!

There are many websites/guides (like 2hrAquarist, Tropica etc) out there about the lighting for our plants and there are many commercial products out there for us to choose from nowadays -
the 'usual' way of choosing a product is that you look at the 'lumen' numbers and divide that number with the size of your tank e.g. 1800lumen/55L tank = 32.7lumen per liter (good enough for easy/medium plants).

But then how does one really justify the price point of these products, seemingly many of them simply outlined the very basic spec/info like 'suitable for X length tank' and 'Y lumens?
And do we just trust these magical 'lumen numbers' outlined by the company (that it is near impossible for common consumers to validate)?

So ya more or less a rant post that I made in the (very very likely) the best info thread on lighting of the hobby on the entire internet -
now that I have Chihiros WRGB2 45 both standard and slim versions on my hands, I will share my (simple) test results by using Photone app.

TLDR: Chihiros is quite smart to come out with the Slim range - I believe they are hitting the sweet spot in the market for the price per performance ratio, particularly for the nano tanks. The coverage/spread of these Slim version lights can be tricky depend on the tank size and plants layout - after all, the Slims are trying to mimic the performance of the Standard versions (sufficient PAR at substrate level) with ~30% less LEDs, and the Slims are performing rather well.

Results (PAR unit in umol/m2/s) of

• 41cm or 10cm distance from light at different positions of a 28*38.5cm surface with setting at R/G/B: 100%
• 

• The results of 41cm (substrate level) make sense as we see almost the same performance from WRGB2 45 Standard vs Slim. The design is rather smart as there are 3 lines of LEDs in the Standard vs 2 lines of LEDs in the Slim but they managed to show such performance for the Slim.
• The results of 10cm surprised me a bit but it also makes sense since in the end of day Slim has nearly 30% less LEDs than the Standard. This also makes sense to me now seeing how those studios hanging the lights at certain distance above their tanks.
• Notably, the cable side of the lights have ~3cm sticker/area without LEDs, which could explain the odd/lower reading at the top left corner.

Remark: I am pretty sure now the Chihiros WRGB2 Slim versions are the king for the nano tanks (smaller than 60 or 90 long), especially for the non dutch style setup.
I certainly don't mind for a Standard version when there is a discount (say like only 50euro more than the Slim version).

Spoiler: Test method (for those who want more details..)

(Seriously simple) Test method:

1. I grabbed the Ikea coffee desk and a M&S chocolate box (lucky to have both of them in the room lmao), collected the PAR values by using Photone app with my phone front camera.
2. I simply want to see how well the light performs at X distance especially at the 4 corners + center point:
3. 
4. The surface of the box to the light is 43cm, and I used a 30cm ruler (~31cm long) for the closer distance tests; the phone body/thickness is like 2cm. See attachment pictures for reference.
5. Tested with Chihiros WRGB2 45 (Standard/Non-slim) with acrylic brackets (10.5cm from the light to the tank surface), and 45 Slim version with default metal brackets (8cm from the light to the tank surface). M&S chocolate box is 28*38.5cm.
6. Somehow Slim results are a bit wonky so I did n=10; standard version around n=5.
7. Notably for the Slim I tried R:120%, G:80%, B:120%, the results were not significant vs 100% on R/G/B so I didn't bother to record them.