Now, should we be concerned that a $2000 and change projector can slightly out black, the LS-10? Not a chance.
And that is to say, the LS-10d is real good at both. Despite the wimpy number Runo claims for contrast, 10,000:1, black level performance is easily that of what we call around here - "ultra high contrast" projectors. As is also the case with the lower cost Runco, this LS-10 projector cannot match the deep blacks of the JVC RS25 and RS35 (and we presume their RS50 and RS60 replacements). To deliver the blacks it does on those darker scenes, the Runco LS-10 does rely on a dynamic iris.
The black level performance of the LS-10 projectors is more likely that of the best of other projectors with dynamic iris solutions, such as the Epson 8700UB, Optoma HD8600... As noted above, based on the LS-7, does come up just a bit less capable than the Epson, but, close enough! I say that because the Runco LS-10 projectors have a very nice, smooth iris action, about as good as it gets, something those other projectors cannot equal. That's because Runco doesn't want their iris closing down as far - for the sake of invisibility. They've succeeded. I could even be wrong, the LS-10 may very well match the Epson. It's just that it's so many times brighter in "best" modes that it's really hard to compare. After all, if the brights are 3 times as bright, so are the blacks and letterboxes, if the black performance is the same.
I haven't had a problem at all with the blacks of the LS10d, beyond the desire to always appreciate better still. The point is, the black level performance is really, really, good, considering the brightness of what you are watching if on a screen smaller than say 130 inch diagonal.
Image time: First is a normal shot of the starship in The Fifth Element. It's followed by the usual heavily overexposed version. Even with the heavy level of overexposure, the blacks in the image and the letterbox are still pretty dark gray. That's what happens with projectors both extremely good at blacks! In this first image below, I have left in part of the letterboxing, so you can see the basic black level more easily. Immediately below, from The Fifth Element, our favorite starship image - overexposed. There are slight differences in the overexposures. Certainly, the JVC is a touch more overxposed than the Runco or Epson, although all three are close (hint, look at the "blown out" pause indicator in the lower left side of the screen - the more smearing, the more overexposed).
The point here, is that all offer great black levels. Without having a JVC RS50 here, my take is that the RS50 (and RS60, like my RS20) will have a slight, but real, black level advantage over the Runco. The Runco image definitely has more "pop" than the other two projectors, which to me, more than compensates in this case. Note, the blacks on the Runco, look blacker than the RS25 below it, but also note that the RS25 image is definitely the more overexposed of the two. The easiest way to tell is to look at the pause marker in the lower right. See how it's more blurred on the RS25. From much back and forth between my RS20 and the Runco, yes, the RS20 (and therefore the RS25) does do a blacker black on this scene (ok, all scenes) than the LS-10d. That they are close enough that I need to clarify, is good indication that the LS-10d is where it needs to be, a first class - ultra-high contrast projector capable of excellent black levels, based on DLP chips and a dynamic irs.