Word of mouth on the 'real' IMAX experience is a good one, and rightly so; I can't dissent - I love the BFI's IMAX screen at Waterloo in London, and seeing a 3D film there is about as disinvolving as the cinema experience can get - even Earthbound and non-3D movies feel out of this world on the 20-metre high screen. If you're in Mumbai in India, you can see an even bigger picture - the screen there measures 12,700 sq ft!

Screen sizes do vary amongst IMAX theatres, many of which have been custom-built to accommodate the large screen dimensions, and others of which have been adapted from pre-existing structures. Therefore, one can't go in with a measuring tape and ask for one's money back because you're getting a metre or so less in Waterloo than you are in Mumbai.

However, I was interested to be directed at this admittedly rather ferocious blog yesterday, which criticises most vocally the 'IMAX Digital' experience as offered by AMC and Regal theatres.

The IMAX Digital experience is a rather humbler one than regular IMAX, as we'll see in a moment.

The strength of original IMAX has always been the uniquely generous proprietary film format, which measures 69.6 mm wide x 48.5.

Over the decades since its debut in Osaka in 1970, the increased surface area of the IMAX frame has combined with increasingly less grainy film stock to offer a cinema-projected resolution incomparable in terms of detail and sharpness. On the negative side, IMAX format is wasted on smaller screens than it can effectively govern, and building or restructuring to accommodate the format has thus far kept the IMAX brand in the same category occupied by Planetariums and the 'Laserium' experience in the 1970s and early 80s: an interesting curiosity, and a fascinating experience that the entire world might enjoy if it could only be diffused on a global level.

The most important point is that IMAX has nearly 40 years of positive word-of-mouth to exploit at will; it seems to have begun to do so - and begun well:  the inclusion of IMAX scenes in The Dark Knight were no minor technical matter for Christopher Nolan. IMAX-format celluloid cameras are enormous and come with their own set of strictures. Dark Knight co-star Gary Oldman even reported in one interview that he was given an IMAX handbook to instruct actors on the pitfalls of filming scenes in the huge format.

The IMAX push began earlier in the 2000s, as IMAX sought to more strongly associate itself with new and popular cinema, to leverage its huge advantage as a venue for 3D, and to turn its profile from 'curate's egg' to a Hollywood 'must-have'.

And Hollywood is very interested, in this decade, in any new cinematic wrinkle that can't be easily digitised and torrented - the IMAX experience fits the bill. Add 3D into it, and you can see the appeal; this is no common 'flea-pit' experience.

Hollywood films not actually shot in the IMAX format can still be blown-up to spec to (using the "DMR" Digital Remastering upscaling process) to exploit the spectacle of IMAX theatres, and this has been done with big releases such as Watchmen and Star Trek, and IMAX re-releases such as Apollo 13 in 2002. In 2004 Robert Zemeckis' CGI fantasy The Polar Express gave IMAX its biggest hit ever, making $75 million from 100 IMAX screens, a quarter of the entire take of the film.

Various scenes from Transformers 2 have been filmed, Dark Knight-style, with IMAX cameras, and we can expect these to be doing the press rounds erelong. Jon Favreau has also expressed interest in filming segments of Iron Man 2 in IMAX.

IMAX is hot. Everyone likes it. I like it - hell, I love it.

Which is why I was a little stunned to find this visual comparison of IMAX digital screens with original analogue IMAX screens…

Bit of a shock, isn't it? Contents may settle, weight/size may vary etc. but that's a quantum leap down by anyone's book. A digital IMAX screen weighs in at a paltry 28x58 ft - compare that to the 65 x 85 ft screen that I and various other writers at Den Of Geek are raving about when we get our IMAX experience at the custom-built premises in Waterloo.

It's clearly the moment for consumers to carefully distinguish between the real (or as Digital IMAX would like you to think of it 'old' or 'legacy') IMAX experience and the new lower-res digital set-up. What I've been saying for a long time, both on this site and in conversation generally is that IMAX = great. Now that's clearly like saying Sony = great. Sony make fine radios and a few good films, but we've learnt to distinguish between their different operating areas, and to judge accordingly.

So, sadly, with IMAX, who seem keen to spend 40 years of kind words to sell the public a lesser-experience than inspired them; one that's cheaper to set up, but requires just enough adjustment and building work to excite anticipation in the local populace. Unless you live in a major city, you may never have seen IMAX as it can be experienced in London or Mumbai, and all you may know is that IMAX is coming to your town. If it's IMAX digital, sorry - it isn't. I'm sure it's very nice, but it isn't what I was talking about all those years. At those ratios and dimensions, it simply couldn't be.

There's no earthly reason why IMAX can't consider itself a brand, if it likes. It can sell a new cinema experience if it wants to- one with a significantly lower resolution image; it can sell IMAX hotdogs and IMAX shoes if it likes, and God bless it. But if it is going to sell a short-weight cinema experience, that product could use a more telling name: IMAX Lite…?