Several of us including the OP.
What I'm saying is, comparing the Kessil to MH (original style, i havent seen the 700 in person) is that the Kessil puts out a seizure inducing amount of shimmer with heavy surface movement compared to MH.
Some other LEDs, like the Mitras, puts out a much more subtle and IMO, more natural looking shimmer.
Of course like anything else, this is just my opinion based on years of running all types of lighting and various fixtures. YMMV.
I gotcha, I think I can better explain what I was saying.
So shimmer is talked about like it's one thing, but it's not entirely. You have things like shimmer lines at the bottom of the tank which is what is being talked about here. With shimmer lines, yes the Kessils can totally be overwhelming at times -- but that can be mitigated with the diffusers, at least for the AP700. MH doesn't really have this problem since the reflectors create a huge area of light.
So, why is it that I tend to refer to a Kessil light as having more natural shimmer than even MH when it requires diffusion to be calmed down? Well, that comes down to another aspect of shimmer that is often overlooked: rays of light. The one thing that you get with Kessil more so than any other light I've personally seen (and I'm not claiming to have seen anywhere near close to them all) is the appearance of the rays of light breaking through the surface and shining down to the bottom of the tank. I believe generally they are referred to as "god rays". This is something that absolutely appears on real reefs that you don't get with most other lighting sources.
So while the Kessils absolutely do benefit from either diffusion or reducing surface agitation, that is somewhat offset by the fact that they offer this additional aspect of "shimmer" that even MH doesn't really provide. When I look into my tank I don't just notice the shimmer because of the ripples appearing on the surfaces inside the tank, but because of the dancing rays of light that you get as well. I found that once I added the diffusion lenses I got the benefit of reduced shimmer lines on the bottom while still keeping the appearance of sun rays coming through the water. I actually think the most natural look you can probably get is by using a small amount of T5s just to get cover along with an AP700 (without diffusers). That way the Ap700 drives the majority of the light and provides the shimmer and god rays, but the T5s help balance out some of the extreme dancing you get at the bottom of the tank. I haven't tried it yet though.
Anyway, that's where I was coming from. I now realize I've spent way too much time and energy thinking about this lol.
EDIT: I also want to add that I think people under estimate how extreme shimmer can be on a real reef. I don't know if you are a diver or not, but I've absolutely been in shallow reefs that have shimmer right up there with a Kessil light. It's just that, again, in a small box it tends feel amplified because you focus on it. Out in a real reef, you don't tend to focus on it as much because you're not staring at like 8sq feet of reef at a time lol.
