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Sean Cubitt writes:

The software governing aspect ratios is more problematic: often based on the frame aspect, it can include the edges, which the (usually hand-cut) aperture plates and tabs of traditional cinema excluded.

That one is really horses for courses: often the plates in traditional film projectors were under- or over-cut to work with the screen and masking as it was, or the focal distance of an available lens (i.e. to avoid having to spend £500ish on a new prime lens that will actually project the correct ratio with a given throw distance and image size) not the ratio of the film as it should be shown.  This was a real problem with the 1930s picture palaces that were then twinned and tripled in the '60s and '70s.  The smaller auditoria were often pokey, with small screens and bad sightlines, and so the ratios would be tweaked to maximise the screen surface area in use.  In some of these places, 1:1.85 would be cropped to 1:2.0 or even wider, because if you actually respected the intended projection ratio, the resulting image would be little bigger than that of a large TV set.

The big problem with digital aspect ratios is that the DCI standard only supports two pixel aspect ratios, roughly equivelant to 1:1.85 and 'scope.  So if you want to show narrower ratios in a DCP, you have to 'windowbox' (vertically crop) the image using the 1:1.85 pixel aspect ratio.  So you effectively lose about a third of the resolution that the DLP micromirror array is capable of: in other words, in reality, your 4k picture is about 2.8K and your 2k picture is about 1.3k.  A FIAF group headed by Nicola Mazzanti did lobby the DCI consortium to include a native Academy ratio pixel aspect ratio in the spec when it was in development, but they weren't successful.

Both lenses and lamp housings are effectively identical between analog and digital projectors (at least at the top end) as they cope with delivering light under control from lamp to screen...

The lamp issue is controversial.  As this article hints at, xenon arc bulbs for DLP projectors are typically 30-50% more expensive than their equivalents for 35mm projection.  Furthermore, you can't do what your Australian venue did, which is to under-run them in order to maximise their life, or to keep running them beyond their rated hours, basically until they start to flicker.  With regular rotation and proper lamphouse ventilation, I could easily get 3,000 hours out of a 1.6k short arc (they're guaranteed for 1,500 hours, typically).  You can't do this with a digital projector: the bulbs have an electronic control system in them (a bit like modern inkjet cartridges that have chips in them to stop you from refilling them with a syringe, which tells the printer that it's been refilled and causes the printer to refuse to use it), and once they reach the end of their rated life, they shut down.  Furthermore, the system also controls the rectifier current automatically, effectively preventing underrunning.  Some more sophisticated ones are even linked to a spot photometer hung from the ceiling of the auditorium, and make automatic adjustments based on the reading, to maintain the light output at the regulation 16ft-l.  The manufacturer featured in this article claims that the arc in a d-cinema xenon has to be smaller and more intense, hence higher manufacturing costs.  But there's no doubt that lamp running costs are yet another example of the up-front cost of putting the image on the screen being transferred from distributor to exhibitor with the conversion to digital.

Leo
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Leo Enticknap
Institute of Communications Studies
2.35, Clothworkers' Building North
University of Leeds
LS2 9JT
United Kingdom
My personal website
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