Does the "CRI" have an effect on how the human eye receives light?
It can in certain cases, but we'd need to talk in specifics, not anything as general as your questions. CRI by itself is just a basic (doesn't get any more basic than a single number) indicator of how closely a type of light with a certain spectrum renders colors with respect to an ideal light source of the same color temperature. On its own, it tells us nothing about how bright objects will appear (apples & oranges, really)--it depends on the specific light source and specific object (CRI is incidental).
If you have a light with 300 lumens with a low CRI, and a light with 100 lumens with a very hi CRI, will it look the same?
In general, no, but perhaps in some extreme cases involving certain lights sources and certain objects it might. Then again, the same could be said if we left CRI out of it altogether.
A Hi CRI will be able to produce a high spectrum of color.
With white LEDs, for example, in practice high CRI usually means more relative output in the deep red and cyan ranges of the spectrum (sometimes just deep red), where most white LEDs are lacking. Sometimes it can have a noticeable effect on color rendering, all else being equal, and sometimes not so much, depending on the objects being viewed.
I was just wondering if it had any effect on the way the eye interprets the light in lumens.
In certain very specific cases, it can have a significant effect, but generally no in the case of white LEDs. Perhaps one of the more general cases, which I've mentioned here on a few occasions, is that greater cyan output can make high-CRI LEDs more effective per lumen under low-light conditions, since the "rod" receptors in our eyes are most sensitive to these wavelengths. That said, in practice few are going to care much about the difference between 0.1 lumens versus 0.2 lumens.
Only when throwing more light at long distances can CRI possibly make the kind of difference that you're describing, but it's really not CRI itself but rather the quirks of white LEDs and the human eye.
Ok, :0) I over exaggerated the 300vs100 lumens.
Well, it's still within the realm of possibility, depending on the specific case. It's just not going to be generally true for white LEDs in all usage scenarios, if that's what you have in mind.
But is there a margin where Hi and Low CRI over lap and you cannot tell a difference. Maybe with-in 50-100 lumens. Like 200-low CRI and 250-hi CRI lumens. Or
400-low CRI or 500-hi CRI lumens.
Generally speaking, CRI is just not related to output in lumens--it's about color rendering accuracy according to a certain standard, that's all. I can find specific cases and exceptions, but CRI per se, as mentioned earlier, would merely be incidental.
