GTom

It's not (just) for white balance setting although you can indeed set the WB using the grey part. Real-world underwater video LED lights, even the "high end" ones have a far from perfect spectrum that can't just be perfected by a WB setting. Ambient light is also a mixed bag as in real world water absorption is more than just "red-orange-yellow are gradually disappearing". Effectively, the PP software can use the defined color spots of the card to calibrate the entire image. Similarly to white balancing, besides white, other colors are "moved" to their right place, something along this line: https://www.youtube.com/watch?v=PYmhGkVShSI That's a valid point. I see Keldan is selling their colorchecker card, but it obviously works only if the card is near the actual target and as you mentioned, angle to the Sun isn't much different either. Cumbersome to arrange in a recreational dive.

So far I haven't done any color grading or any serious video post processing. I wonder do people use color calibration cards? Sounds like a straightforward way to get colors twisted by the usually non-ideal absorbance conditions. Something like this: https://www.amazon.co.uk/DGK-Color-Tools-DKK-Calibration/dp/B00AWT2QCE Are there underwater-friendly models or shall I keep it in a waterproof pouch?

Is there a general rule of thumb how much does the Color Temp increase by every feet/other unit of distance in clear blue tropical seawater? Asking because some video lights appear too yellow/orange at close range.

Meantime getting leakage/battery swelling news across the "Leton world"...

Couldn't agree more. Cheap manufacturers probably cater for the single light user. It's not all lost though, sticking to flat window lights instead of domed ones moderate those extreme wide beams.

Built in without quick replacement option is an absolute no-go. Imagine being out all day long on a zodiac, you defo won't mess with USB charging between dives. Quick battery swap both in the light and the gopro, that's it. Also, batteries usually have a limited lifespan. If you can't reliably disassemble the light and swap the cells, that's the end of it, the whole gadget goes in the bin.

That sounds interesting, don't get the "built in" but "21700" concept, would be interested to see a teardown video if this is somehow user-serviceable.

Just figured the big Leton's have built in battery. Big no-no for practical reasons, one of those planned obsolescence stories, LoL.

I think I can get the same for about half the price in the nitescuba NVS60. Apparently a tried and tested unit, not the average Aliexpress stuff.

Got my genuine gopro13 housing on the festive sales for £22 so I think I'll skip this one :)

Not exorbitant pricing indeed, slowly finding some real competitors around: second hand Sealife 4500 pro (about the £300 mark with old battery): top color (CRI96!) but proprietary battery, not huge lumen figure Nitescuba SEA60 (on sales now) or NVS60 - these are only CRI 90, yet probably the best of the "cheap" lights: I could get a pair for the price of the Sealife. Other great plus is that it uses standard batteries! Second hand weefine smartfocus 6000: I am finding VERY conflicting CRI's here though. This is an older model, manual says CRI 80 (no-go), seller says from whatever datasheet: CRI 96... Probably skipping that and look at the new 4000v2. Need to research other practical parameters like shutter-free dimming, reliability, weight etc as it seems I am looking northwards of £500 for a pair, definitely not a "don't like it, throw it in the bin" purchase.

Many thanks! Seems their Smartfocus 4000 model is getting close. Will investigate if I'd be significantly better with that compared to a Leton L15+CTO filter. Not cheap but at least not Keldan money...

Yeah, that's my problem too. SOME (but far from all...) "Aliexpress" lights do deliver near the lumen figures they claim, or at least "bright enough for the money". BUT they do that at 6500K that becomes like 10'000K with a subject distance of 0.5m and have literally a Mariana Trench in the middle of their color spectrum, around @480nm. After days of hunting I found CRI's very rarely quoted, and as with everything in life, I highly suspect that that's for a reason. I got another idea: get a pair of really bright but cheap lights and leave my snorkeling orange filter on, acting as a full CTO color temperature corrector. That'll likely affect CRI/R9/the overall SPECTRUM of the lightsource positively while sacrificing maybe 30% of the light intensity. Started a separate topic with a candidate (Leton L15): I am reluctant to shell out $600+ on lights that are still of questionable CRI, not to mention $4k on Keldans that do what everybody should do...

I have an opportunity to pick up a second hand Leton Power L15 light, pricing seems quite attractive for the claimed output. Does anybody have experience with this manufacturer? I am looking for high CRI lights for my gopro setup, this might be a useful start. Claimed CRI 90 needs to be valid though and thought about further improving that with a filter sacrificing maybe 2-3k Lumens. 4000k, CRI95+ video lights seem to be rainbow unicorn category at down to earth prices...

I'm also guessing you haven't seen many divers with wet wide lenses attached to their action cams in the wild either?