Increase contrast in a barco spk4k projector

[Steve Guttag]

Third, the choice of a 0.98" chip projector with small light output is not the most clever way, the 1.4" chip machines offer a superior contrast out of the box. With the 0.98" chipset the HC lens does not really get the premium price tag resolved. Go for the good projector, if you want contrast. With Barco, that is the 27 HC model.

You are in error on this one. The Barco SP4K-C projectors (SP4K-12 through the SP4K-25)...are .98" projectors and are 2300:1 contrast ratio, out of the box, using standard "C" lenses. Conversely, the SP4K-35 - SP4K-55 are merely 2000:1 contrast ratio out of the box, using "B" lenses (High Brightness). Furthermore, the SP4K-C projectors, with a high contrast lens move up to 3000:1 while their SP4K-B counterparts merely move up to 2600:1. It is true that the SP4K-27HC can achieve 5000:1. It is an SP4K-40B with an very-high-contrast lens and an iris in the light path. However, Barco has now released the SP4K-13HC, which also has an iris and uses the Very High Contrast lenses (I believe it is based on the SP4K-20 projector with the iris). It too boasts a 5000:1 contrast ratio.

To my eye, there is a very noticeable contrast improvement on the SP4K series (all of them) to the DP4K series (or any other brand of 4K xenon projector). I, presently, have an SP4K-25 with a HB B-lens and an SP4K-35B with an HC lens (theatre 1 versus theatre 2) and they have a very similar appearance on screen, in terms of contrast. Believing Barco, it is 2300:1 versus 2600:1. I also think the HC lens has an overall corner-to-corner better appearance with less aberrations than the HB lens. That said, the lens shift between the two theatres is significantly different due to limited range one can shift a lens on a 1.38" chip versus a .98" chip. A Barco SP4K-C projector with a B-lens can shift up to 110% in the vertical direction...which is a lot, particularly for 4K. In the theatre in question, that amounts to nearly offsetting nearly 5.5-degrees of tilt and the resulting keystone distortion. Due to the 1.38" imager/lens combination, we could only get less than half of that lens shift.

Everything comes off of contrast. How the light gets through the lens, the port, the screen the wall fabric and anything the light reflects from...even exit lights and ambient lighting. 14fL (48cd/m^2) sets the upper limit...the lower limit is a function of the above. I would caution about promoting or advertising "high contrast" or High Dynamic Range (HDR), at this stage. To the lay person or even a typical exhibitor, without increasing the luminance reference, there will not be a perception of high contrast. People don't seem to notice or care too much about the black levels and detail unless it is so poor that it gets lost in the sea of grey that the S2K projectors specialize in. And, if one uses a 1.8 gain screen to high the crappy contrast (but lose all of the detail with the resulting hot-spot) the exhibitors seem to be okay with the inferior projection quality.

A key thing that Dolby Cinemas have are those high contrast projectors with a significantly expanded dynamic range (contrast) improving both white and black levels. Barco, pre-pandemic, demonstrated a light-steering projector that looked quite promising, if content would be made for it. I wouldn't use it on normal DCI content as the contrast looked exaggerated...just like leaving a TV set on HDR for SDR content.

[Dave Macaulay]

Tilting against windmills again, Mark?
Exhibitors are going to laser. Purely economics - mostly the electricity cost advantage. TCO for xenon lamps vs laser will kill xenon: new builds and replacements of aged out units are pretty much all laser now. We are doing a LOT of laser conversions on Barco S2 projectors now... although the economic benefit is sketchy IMO. You still have a decade old light engine, ICP, and everything else... a new laser projector costs about double but is all new with full warranty.
Lab colour grading? We can calibrate screen colours now and that's great. With film projectors nobody did that and what was on screen was whatever the lamp, reflector, lens, port, and screen gave us. I did colour grading room 35mm projectors years ago. We would get a dozen new in box reflectors to find two that matched colour temperature closely then add correction filters in the light path. I expect that the thousands of prints struck by Deluxe in Toronto did get close to being colour matched but that went out the window when they went to cinemas where what you got was what you got.
There are still old timers with fond memories of carbon arc and nitrate prints, that the image was so much better. But you could see the colour temperature shift on changeovers and often through a reel. Economics killed carbon arc light, and nitrate film ... yeah ... having explosive film was not a good idea.
What they do in studio screening rooms is great but don't imagine that it means much to the audience in your local multiplex.
On the actual question here, contrast is more a room issue than projection in most cinemas. Yes large chip imagers have better contrast. Higher contrast (and higher $$$) lenses may be available. Optical glass kept clean should be used. Sweet!
Then you use light colour wall paint and seat fabric, put in Tivoli lights on the stairs and illuminated exit signs (as required by law everywhere)...and your on screen contrast goes down the shitter.
Yes I would love to get a perfect image in a perfect room but like the rest of us I live in the real world.
/rant

[Steve Guttag]

Mark's points about laser color issues are valid and true. Laser projectors are not suitable for color grading. They don't represent true-to-life colors...furthermore, how everyone sees the colors of them are different...which again, makes them unsuitable for color grading. The fact that new cinemas are going laser is of no consequence, Hollywood has always done things based on their own screening rooms and dub stages...not for commercial cinemas. I do hope that the laser color issue is solved but it definitely isn't there yet.

As for laser conversion...I agree, it is a dubious proposition...unless you can catch the projector in the 6-7th year of operation. THEN, you could make the argument, particularly on larger lamp projectors (over 2KW) because Barco will allow one to warrant an upgraded projector out to 13-years...so at year 6-7, you are just at the half-way point to recoup your laser investment (which is substantial). And, if you do get the extended warranty, the worry of light engine and ICP failures are then minimized (cost wise). But if your projector is now in year 10-11...it's a bad investment. Buy a new S4 RGB laser projector and move your xenon one down to a lesser screen or turn one into a spare parts machines for the remaining ones.

[Stefan Scholz]

Then, regarding colors, I recently got an older book on color TV background, published around 1967, so at the time of worldwide introduction of color TV in most markets. Based on the pre WW2 research, the kez point, simplified was, a contrasty BW image background is mandatory, with a soft overlay colors to get a successful result on the TV receiver. The color bandwith, about 1/5 th of the BW bandwith, color vectors limited to 65% red and 75% green and blue being all you need. The human color sensing is the most underdeveloped sense, according to the author.
Thinking of this, we can go for economics in projection. I personally love Xenon projectors and the beautiful white they create, but have also learnt that many patrons prefer the new laser image, that has more contrast, "more vivid" colors. Modern lasers offering around 10 lumens per watt are in the range of a classic light bulb of the past, when it comes to efficiency. Xenon projectors are a fraction of that.
I have been given two perfectly good NEC Xenon projectors from a friend, who just told me he will retire in 6 years, and until then "never wants to swap another xenon bulb". Plus, due to the savings in electricity bills, it did also make economical sense. (Our country has the highest electric prices in the world.)
Even though there eventuallz will still be a few modern Xenon units available, the train towards modern, advanced laser projector systems is in full motion.
It may be, some colorists and DOPs in their own world are not a friend of mercurz light, or phosphor or RGB, looking into the above mentioned statement from the TV industry, their words will be ignored.
These people do a great job, but looking on sound mixes, which I loved to support as one of my consultancy tasks, the end result was always spoiled by the theatre exhibition side.
Exhibitors were always keen on saving cost. When new, they fought color, Scope, Stereo sound. Surround sound in theatres, a reality in living rooms in 1994, was mainly unheard in most movie theatres at the time.
When we started doing conversions to digital projectors, we still had to adopt the multichannel PCM to a Mono sound system in a few, but rare cases, being 2010 or 2011. It was easz to sell the projector, as it was an obvious cost saver, but not the sound.