Small OLED TVs do not perform as well as big ones – and it's not just about brightness

Some TV review websites (most of them, actually) review one size of a TV and act like it covers all sizes.

So, you'll find, for example, an 'LG C5 review', a 'TCL C8K review' and a 'Samsung S90F review', and you, the reader, would reasonably expect that review to cover all sizes of the TV.

In fairness, this is pretty reflective of the way manufacturers sell their TVs. Broadly speaking, you go onto the company's website, select a model, and a page appears that covers all sizes.

The thing is, there can be (and often are) big differences as you go up or down in size, and this really isn't talked about enough.

This is most pronounced with backlit TVs – the so-called LED or Mini LED models.

Sometimes, elements such as the number of dimming zones will go up and down depending on the size of the TV, but this is rarely exactly proportional to the increase or decrease in panel size.

And sometimes, the number of dimming zones doesn't change depending on the size of the TV.

Given how much impact the number of dimming zones can have on a backlit TV's performance, this can make a tangible difference to picture quality.

But it can be much worse than that. Many brands source their panels from other manufacturers, and we've seen plenty of cases where panels sourced from one manufacturer have been used at one size, and a completely different manufacturer's panel at another. Yet these TVs were still being sold under the same name.

It's a problem for OLEDs, too

While OLED TVs are generally much more consistent (the self-illuminating pixels help here), to the extent that in almost all cases (I'll get to the major exception shortly), 55-to-77-inch versions of the same model are very alike, size aside.

That's why we will generally (again, we're clued-up to exceptions) review either a 55- or 65-inch version of a TV and feel comfortable also recommending the other and the 77-inch version, assuming there is one.

But that doesn't mean that OLED TVs are immune to performance differences at all sizes.

By now, most people know that smaller OLED TVs (as in, 42- and 48-inch models) go less bright than their larger siblings, which is quite a big deal, but the differences can be greater than that.

Earlier this year, we were fairly blown away by the performance of the 55-inch LG C5, which we found to be a surprisingly large upgrade on its C4 predecessor.

But when we got the 48-inch C5 in for review, we were curiously disappointed.

It was less bright, of course, as we'd expected, but we also found the approach to colours to be different, with the 48-inch model rarely matching its 55-inch sibling for vibrancy, particularly in the darkest and brightest parts of the picture.

Combined, the differences in brightness (and therefore contrast) and colours give the 48-inch C5 quite a different character to the larger versions.

It's still a very good TV for its size class, but a review of the 55-inch model shouldn't be taken as covering the 48-inch or 42-inch models, which is why we have separate 48-inch LG C5 and 55-inch LG C5 reviews, and are working on a dedicated review of the 42 incher.

It gets worse...

If it seems as though I'm picking on the LG C5, it's only because this is the most recent example of the small-versus-large OLED conundrum that I've encountered in out test rooms. There are, unfortunately, much more troubling examples of this sort of thing.

The most troubling has to be Samsung and its S90 range of OLED TVs, which this year is the S90F.

Not only does it have the usual brightness inconsistencies as you move below 55 inches, but Samsung actually uses entirely different panel types at different sizes.

The brand is intentionally ambiguous on all of this, which makes matters even worse, but we know that most sizes of the S90F use a WOLED panel, while some sizes feature a much more advanced QD-OLED panel.

In short, in some regions, the 55-, 65- and 77-inch versions of the S90F all feature QD-OLED, but in other areas, just one size of the S90F is QD-OLED. In the UK, it's just the 65-inch model; in Brazil, it's the 55-inch version. Confusion reigns, and even those in the know could easily buy the 'wrong' TV.

And while the S90F is the most egregious example of all of this in OLED land, it's also a problem for other models, such as its stablemate, the S95F, and LG's G5.

Samsung produces the S95F in sizes ranging from 55 inches to 83 inches, but unlike the smaller models, the 83-inch version has a standard WOLED panel rather than QD-OLED, so it will have quite a different character.

The LG G5, meanwhile, goes both smaller and larger – 48- to 97 inches. But, unlike the others, the 97-inch model lacks that fancy new Primary RGB Tandem OLED tech. And while the 48-inch model does feature a Primary RGB Tandem panel, it goes much less bright than its larger siblings.

Something needs to change

These manufacturers could take a leaf out of Sony's book. When it launched its 42- and 48-inch OLED TVs, it gave them a different name (A90K) to the larger OLEDs that were launched at the same time, immediately flagging them as separate.

And when it launched the Bravia 8 II QD-OLED this year, rather than launch a 77-inch version with different, WOLED panel tech, it decided to keep the older 77-inch A95L in its range instead.

This sort of transparency should be the norm, not the exception.

Manufacturers need to stop selling fundamentally different TVs under a single name, and we reviewers need to be clearer about the specific TV size tested and be more open about the differences buyers can encounter by choosing a smaller or larger version.

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Here are our 48-inch LG C5 and 55-inch LG C5 reviews

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