Tuesday, June 14, 2011

Output relativity

I was on my way home, heading toward Cambria along 46, when I noticed the beautiful view out over a sea of clouds, illuminated by a bright moon. I stopped at a vista to take some photos. While maneuvering my camera and changing settings, I was mostly using fairly low amounts of light to maintain adaptation, but I did a little light painting too. At one point, I became interested in the output of the high CRI Clicky, because I was noticing that it was just a little bit dimmer than I expected and wanted at the distance I was trying to use it. This is a common problem for me actually, and a strange one. I have this Clicky set to 25lm at its primary level because its max is only 100 and four times the output is required to achieve a perceived doubling. The problem is that, for some strange reason, 25lm always looks just a little dim to me, whether on this Clicky or another, with or without diffuser, inside or out, with adapted eyes or hardly at all. What I'm describing here is, I believe, impossible; it's not how eyes and perceptions work, but it's what I've consistently found for some time now. Anyway, I was looking at the output, noting how it was just ever so slightly, nigglingly dimmer than I wanted, so I started adjusting it back and forth between 25lm and 35lm, to once again confirm for myself that there was some kind of barrier between good and not so good at these outputs. I ended up deciding to just go ahead and set the level to 35lm instead, giving up on my attempt at technically correct spacing. After making the change, I switched levels on the light to compare, to see how the new setting worked with the others, and I got a bit of a surprise. I hadn't been on the primary level. I just thought I was because my eyes were so much more adapted than normal that I assumed the moderately bright level I was seeing had to be my 25lm primary. I had actually been going back and forth between 3.1lm, where I have the secondary set, and 4.4lm. I'd completely believed I was comparing 25 and 35.

Another thing I found interesting was that 4.4lm was, until quite recently, my standard setting on that secondary level. I chose it years ago because it looked right to me, then changed it down one recently for reasons not based on its appearance to my eyes. What this mixup demonstrated to me, beyond just the obvious relativity of output perception, was that my eyes consistently find ~4lm preferable to ~3lm, just the same way that they prefer 35lm to 25lm, and that if I let my eyes choose the settings instead of my head, I am likely to end up with results that are surprisingly consistent over time and in varying circumstances. I do not understand this. I don't understand why my eyes would have preferred levels that are so specific and fixed, but they seem to. Incidentally, when I got my first HDS light, five years ago, I noticed that 0.33lm just struck me as an unusually "nice" level. Perhaps it's another one of these lumen "sweet spots" that I react positively to. I haven't used 0.33 very much because I generally prefer to trade it for something much lower instead, but whenever I return to it I'm still struck by that same reaction, that it's just a really good level. Very strange.

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