If you're choosing a TV mainly for its performance with broadcast HD material or Blu-ray, don't forget that you will also want to watch DVD on it.
More to the point, you'll also want to watch broadcast TV, and since that is mostly still in SD, how will your fabulous HDTV cope with that?
The Toshiba 42ZV555D is one of a range of Regza-brand LCD TVs claiming to have resolved the dilemma by offering Resolution+ technology; it aims to deliver top-class performance with HD pictures, but also to be able to squeeze impressive quality out of standard-definition using clever edge enhancement and contrast processing.
Toshiba's clever upscaling tech
The initial temptation is to be sceptical. After all, any attempt to upscale an SD image involves manufacturing picture data which is not present in the original; there's no 'hidden' information to be obtained. So how can the Toshiba do a convincing job?
The first hint of what Resolution+ might be capable of came with Toshiba's XDE (eXtended Detail Enhancement) DVD players; pushed as a way to get the best out of DVD (though Toshiba, still smarting from the demise of its HD DVD format, was reluctant to describe them as an alternative to Blu-ray), the XDE players did indeed do a demonstrably fine job of enhancing DVD pictures; a simple side-by-side comparison of the picture from the XDE and the previous generation of disc-spinner convinced me of this at the launch.
The question, then, is whether Resolution+ can work similar magic when built into a TV, and dealing with SD broadcasts as well as DVD.
The 42ZV555D (there's also a 46in model available) is a 1920 x 1080 Full HD IDTV with a glossy black finish; on the left-hand side is an eco-friendly(!) Full Off button.
On the back is the usual array of connectors; two HDMIs, two RGB Scarts, optical digital audio, PC WXGA, RGB, S-video, component video, audio input and subwoofer output. The remote control is a familiar, comfortable design.
The Picture menu has the usual adjustment parameters, plus the enigmatic Resolution+. The Resolution+ system isn't identical to the XDE used in Toshiba's DVD players.
The ZV TVs use a processor known as the Spurs Engine, which incorporates some algorithms similar to those used by the Cell processor found in the Sony PlayStation3. Don't get carried away thinking that the ZV555D essentially contains a PS3 chip, though just to confuse the issue, Toshiba is working on just such a system for a more upmarket TV.
The ZV's version of Resolution+ reviews adjacent areas of an image to determine waveforms of a similar nature, before combining pixel information to enhance edge detail. This does a bit more than just making the picture sharper; it improves the perceived depth and texture, giving a more defined image.
Further picture tweaks
Of course, the Toshiba 42ZV555D has further picture processing functions designed to make the most of all types of sources from broadcast SD to movie HD.
The Active Vision M100 system is a standard 100Hz picture mode, designed to double the screen refresh rate to reduce flickering. Other manufacturers are introducing 200Hz modes, so this isn't groundbreaking.
The Dynamic Contrast system automatically adjusts brightness to enhance reproduction of fine detail without compromising the rendering of colourful, high-brightness scenes by dimming the backlight. Conversely, for bright scenes the backlight can be brightened to give greater intensity.
There are also MPEG noise reduction, digital noise reduction, x.v.Colour compatibility, and a full range of colour temperature adjustment functions.
So what does Resolution+ bring to SD performance? (incidentally, before you ask, it's disabled when you're using an HDMI input, so you can't use it on a HD source - or for that matter on an SD source from an HDMI-equipped DVD player).
Resolution+ can be switched on or off, and can be adjusted in level from 1 to 5. At 1 to 3, I found the effect very subtle; at 4, it's quite obvious, and at 5 it can be too much.
With a fairly solid picture from DVD or a strong SD TV broadcast, the tech does indeed add perceived detail; pictures seem sharper without the addition of unsightly ringing, and there is an impression of enhanced depth and contrast. Text becomes easier to read and background detail becomes more obvious.
But with a grainy image, Resolution+ simply enhances the grain, so poor analogue TV signals cannot be enhanced. I also noticed that on a 4:3 picture, Resolution+ adds a visible line to each side of the picture, which is disconcerting.
So though I wouldn't entertain for a second any suggestion that Resolution+ upgrades SD material to genuine HD, I think it's a valuable tool. Some Freeview pictures I watched looked as impressive as anything I have seen on a set of this price.
Stunning HD performer
Resolution+ aside, this TV is a cracker with HD material. Watching my favourite Blu-ray demo disc of the moment, the Second Sight edition of Ron Fricke's sublime eco-diatribe Baraka, I was stunned
to see detail of a level I hadn't seen before; gorgeously deep colours, subtly intricate detail, smooth movement, and enormous contrast.
Switching to the Blu-ray of The Dark Knight, I was again impressed by the level of detail in the opening sequence, the strong handling of the dark street scenes, and the confident presentation of bright explosions against dark backgrounds.
The claimed contrast ratio of 17,000:1 may be a little optimistic, but the set's dynamic gamma curve correction function seems to do a particularly good job of dealing with images with dark and bright sections.
The savior of standard-def
Sound was confident without being overpowering; the 2x10W speaker system was never going to be overwhelming, but at least you can say that however far you crank it up, it doesn't start to distort.
So is the Toshiba 42ZV555D the saviour of standard-def material? Will it make you want to stick two fingers up at Blu-ray and stick with DVD? No way.
It will, though, not disappoint, and will make the process of watching SD material a bit more acceptable as we make the transition into an HD environment.