It's strange, I see this question come up on a fairly regular basis, but I don't think anyone has ever posted any example photos. So I'll give it a whirl here.
First, I needed something to compare with, which I own, and also had been tested. CPF member MrGman did extensive testing with an actual integration sphere, including tests of Quark Mini and Preon lights:
As you can see, the Mini and Preon are both apx. 20 lumens on the medium mode. Just by eye, I figured the P60 on a single Li-ion was somewhere in the 30 lumen range, maybe as much as 40. On a single 18650 (not fresh), at 4.08 volts unloaded, I measured an initial current of a bit over 0.9 amps. This was in a SolarForce host, measured from the body to the battery (tailcap bypassed).
So, assuming that under load, the voltage drops to 3.7 volts at that current measurement, the wattage would be about 3.3 watts. Assuming a poor efficiency of only 10 lumens per watt (since it's underdriven), that should still put the lumen output in the 30-ish lumen range.
Since I don't have an integration sphere or a light meter, this was the best I could think up. A plastic jug filled with water, and the light shining down through the cap of the jug. The cap diffuses the beam to eliminate effects of thrower vs. flooder. The water and plastic of the jug evenly distribute the light. Then I take photos with my camera, locked to the same settings for each shot, to allow the brightness of the image to be compared. All brightness test photos were shot in black-and-white mode on the camera to eliminate the effects of color on brightness perception.
The SF host may be at a slight disadvantage, since (1) the crenelated bezel allows a tiny bit of leakage out the sides, and (2) the larger head diameter may be causing some light to hit the threads of the jug and not be distributed into the water as well. Probably negligible for the most part though.
Click the thumbnail images for a larger size; with a photo open in each tab of your browser, it allows easy A/B comparison.
First, the Mini AA on medium:
Now the Preon on medium:
You can see that the Mini and Preon are essentially the same output, confirming the results of the table above.
And now the P60 x 18650 SolarForce:
When you open these in separate tabs and click from one to the other, you can tell that the P60 is noticeably brighter than the 20 lumen modes on the Mini and Preon. Now for grins, let's check the max output of the Mini AA, which is somewhere in the mid-60 lumens range according to the table above.
Mini AA, high mode:
As expected, it's noticeably brighter than the P60x18650 combo, but perhaps not as much as you might think.
Now let's look at color temperature. An under-driven incan will typically have a lower (warmer) color temp, right? Let's compare the P60x18650 to a couple of LED lights, on a "still life" setup. I don't have a color checker card, but I've found that food product boxes are good for this sort of thing, since they tend to be bright and colorful.
The camera is set to a white-balance color temp of 3000 K, trying to hit a happy medium between light sources. These photos were shot in raw mode, then converted to jpg on a PC, to make sure there was no unexpected variation from shot to shot caused by the camera jpg conversion.
First, a Cree PAR-style LED lamp, 2700K, shining upwards at the white ceiling to illuminate the scene. The lamp is just off-camera about 2 feet to the left. The door in the background is glossy white.
As you'd expect, the scene appears just slightly warm since the light source is 2700K vs the camera setting at 3000K.
Now, a Quark Mini AA Warm (exact color temp unknown)
The whites look just about true white in this shot, indicating the Mini color temp must be very close to 3000K. There's just a hint of ugly color tint though. You would hardly notice it unless you were doing direct comparisons to another light source.
Now the P60. Slight disclaimer: it was really hard to evenly light this scene with the spotlight beam of the P60 and not get it too dark, or have weird shadows, or blown out. This was the best I could do after at least a half-dozen attempts. I had to push it about 1 stop brighter in post processing, so that the overall brightness would look similar to the other scenes. Shouldn't affect the color temp though. The ISO was set the same for all shots.
This looks VERY close to true white, indicating the P60 is pretty much bang-on 3000K for all practical purposes. Also, if you do a direct A/B compare of this image to the Mini-Warm, the ugly greenish tint of the Mini becomes much more apparent. On a personal note, I've found that almost all photos I've taken under LED light sources have issues with tint. It can be a real nightmare to correct if there are multiple LED lights with different tints. The worst I ran into was a highbay lit by Cree parking-lot area light assemblies. Despite being all the same product, there was enough tint variation to give me fits trying to make the whites in the scene look somewhat normal.
If I was a pro photographer, I think I'd still be using incan lights in some situations since there appears to be less issue with tint, and all you have to do is set the camera white-balance to whatever Kelvin value you want to make the scene warm, neutral, or cool. I was surprised by how nice the colors look in the P60 lit scene, despite being underdriven.
So there you have it. The P60 on a single Li-Ion is definitely viable if you want a lower output, longer running incan using a single rechargeable.
