That is very true. The Viparspectra is a well known light and I like that the ballast isn't mounted on top. After sleeping on it, I believe I'll go with the ks5000. I just read a lot of reviews that the light isn't that bright and it's Viparspectras first bar led, so I shy'd away. I'm still going to look at the RDJ some more (btw they have a map and it's better than the KS), then I'll pull the trigger on one in a bit
The KS500 has a better PPFD map than the RDJ. And it's got a (slightly) better spectrum than the RDJ. We have PPFD values from an independent third party reviewer. RDJ is unknown.
The RDJ has the hot spot in the middle.
If their values are accurate, the light will give you a 32" square of usable light with 1400 going to 1300± and then collapsing. You can't run at 1400µmol so you have to drop the dimmer to ⅔ power to get to about 900. That gives you an area that has 800-900µmol, which is nice, but nothing usable for 8" strip on the edges. At 100% power, PPFD values are below the 600µmol threshold. If you drop that to 66% power, you can light seedlings. That's it. You get, at most,
7 square feet of usable PAR from the RDJ.
Look at the KS5000 PPFD map. It gives you ≈ 1kmol across a pretty good sized area and has good values from the front to the back and, even at the right and left sides, it's > 600µmol. You get
16 square feet of usable PAR from the KS5000, based on Vipar's site and by test results from a reliable third party reviewer.
Note that CfC does two sets of PPFD maps, one for PAR and one for ePar. ePAR is a broader range of light, incorporating far red which has a demonstrated benefit for cell expansion. The RDJ light does have a nice spectrum but zero far red. That's one way they can save on R&D and production costs.
Dollars to doughnuts, they're hiding the ball on PPFD because they're using non-standard grid sizes. That's not a mistake - the only time I've seen PPFD maps that don't use 6" squares is in off-brand lights. Check the cocoforcannabis site ("CFC") and they're following industry practice of 6" squares.
Final point - RDJ is not in the grow light business. They're in the light business and sell some grow lights. Vipar is an established company. This is very clear to my eye when I look at their site and, for RDJ, their page on Amazon. Their site is…I wouldn't call it shoddy but it's not professional. It's…cheap. On the Amazon page, their language is not…professional. They're not using industry standard terms and they have spelling mistakes. That tells me a lot about who they are - they don't put the time into their public face. I simply have no confidence in their products because there's nothing that indicates quality. Flip that around and I couldn't make the argument to favor their product or them as a company. The Vipar light has been reviewed and gotten good recommendations by a well known third party and Vipar's business is making, selling, and supporting LED grow lights. One is not like the other and, for my $$, I'd pick the Vipar over the RDJ without a second thought.
I've got no dog in this fight - my grow lights are Growcraft form ChilLED and I spent >$500 a light for very specific reasons. Vipar is a lot closer to ChilLED than RDJ.
There's just nothing about the RDJ light that makes me think it's worth buying when compared to the Vipar, especially since it gives you usable light on less than half the area that the KS5000 does.
