Thankfully, though, both these distracting problems were down to options in the onscreen menus rather than being endemic to the SP8604's optical engine. The brightness shifting was caused by the DynamicBlack option, while the motion issues were caused by the Motion Smoothing feature. Turning the DynamicBlack option off and setting the iris to around its 3-4 level sorted stability out without spoiling black level response, while deactivating Motion Smoothing got rid of all motion processing artefacts.
It should be said that turning the motion smoothing off entirely definitely does lead, inevitably, to the appearance of judder. Personally we don't have a problem with this, but if you find it irritating, there's no harm in experimenting with the lowest-power mode of the Motion Smoothing option.
Aside from the easily avoidable teething problems, though, the SP8604's pictures are absolutely outstanding for its price point.
Perhaps their single most startling strength is the way they produce exemplary sharpness and fine detailing when showing HD sources without suffering with video noise. Most affordable DLP projectors tend to suffer with various types of dot crawl, be it greenish dotting in dark areas, fizzing over skin tones during camera pans, or general pixellation over skin tones. But the SP8604 delivers its sharpness while being almost completely free of all these common problems, a fact which speaks volumes about the skill with which InFocus has blended the SP8604's DarkChip 3 DMD, six-segment colour wheel and UNISHAPE lamp, among other things.
Not having to see overt DLP noise in dark areas of the picture also boosts the image's perceived contrast to a level beyond what we'd normally expect for the SP8604's money. Yet post calibration (having used the movie preset as a starting point) there's also no sense that the impressive black levels are forced, for dark areas of the picture still contain plenty of shadow detail.
Colours are very good too for £2,500, in terms of both their general naturalism of tone and the subtlety with which tiny tonal shifts and blends are portrayed.
InFocus has built PixelWorks DNX scaling into the SP8604, and this does its normal good-to-very-good job of upscaling standard definition feeds into the SP8604. Though obviously you should try to stick with HD sources where you can with any projector.
Yet another area where the SP8604 scores a palpable hit is with its rainbow effect. Or rather, the lack of it. For it was only after we'd been testing the projector for 8 hours or so that we suddenly realised we hadn't even thought about single-chip DLP's usual problems with colour striping. Even when we forced ourselves to look for the rainbow effect we still hardly ever spotted any, so we'd say it shouldn't be an issue at all for the vast majority of viewers.
Really the only complaints we can muster about the SP8604â€™s performance bearing in mind its price are that panning quickly around while playing video games can cause a momentary bluish shadow to appear around some objects in the frame, and that it runs a touch noisily and very warmly even with the lamp set to its lowest power output.
While we certainly welcomed InFocus back with open arms with last year's SP8602, it was a bit too clumsy in places to feel totally like the old InFocus we used to know and, for the most part, love. The excellent SP8604, though, while not totally original, feels much more the product of a company with a genuine masterplan. We await their next move with interest.