4K projection on a small (20') screen

[Skyler Hunt]

We're about eight months out from opening a second location with two new 20' screens. Writers of the original plan (drafted in 2020) assumed 4K laser projection was the way to go. Now that construction is actually underway, the debate between 2K and 4K has resurfaced, specifically because Barco does not recommend 4K projection for screens under a certain size.

What I'd like to know is whether anyone is running 4K projection on a screen 20' or smaller, and if so, whether the impact is notable. If such a thing doesn't exist (doesn't in the PNW, as far as I know...), it would be helpful if someone could help me understand the math behind Barco's recommendation (assuming that math is not merely economic, i.e. the market for 4K laser machines for little cinemas is too small to support their manufacture).

In all likelihood, the cost difference of several tens of thousands of dollars between an SP2K-9S and an SP4K-12S will decide for us. The other wrinkle is brightness. Our techs tell us we'd have to reduce the max brightness of the 4K machine to 22%. They only go as low as 30% on their own, which means we have to figure out how to compensate further with certain lenses and low-gain screens. All this has me leaning toward 2K anyway, but the non-techie stakeholders aren't fully convinced by my admittedly basic explanation of the facts.

[James Gardiner]

I assume the recommendation is based on arc-angle visible resolution based on distance from screen. I expect Barco have done some small screens specifically in post facilities where it's a more matter of projected quality at 4K over if the cinema-user can actually see the difference.
I would expect 4K would have some minimal improvement for those with exceptions eyes, but it would be in the lower single figures (%).
As cinema is a commercial business. The numbers are likely to bare out that 2K is adequate for the use model. And why it is recommended.

Also, cannot the new Barco's go to 20 or 25% now? I remember hearing the number and being surprised it was so low now.

[Steve Guttag]

Thus far, the smallest screen I've done a 4K on (SP4K-12C) has been 14.25-feet wide (6-foot tall). Barco's S4 projectors will go down to 20%. Not everyone's current projectors go down to 20% but Barco's will. I would, absolutely, use (and did) a High-Contrast lens. In addition to the higher contrast (about 50% higher than high-brightness), the overall image is better (including convergence). I haven't run your numbers but using a matte-white screen (1.0 gain) would be preferred in all situations but there are grey screen options as well (has the benefit of making ambient light less of an issue too as it will reflect aisle lighting/exit signs less). I still prefer matte-white as grey screens tend to have some gain characteristics of hot spotting some.

Consider thing, 35mm film running a 1.85 (Flat) image is about 4K in resolution. 4K is not a luxury/premium feature. It is what every consumer already has in their homes. Additionally, you aren't going to get a true RGB laser projector in the 2K models. They are all using phosphor wheels and some form of additional blue lasers to get the "other" colors (smaller ones using two blue lasers with a yellow wheel and the medium ones using two blues with a green phosphor wheel and a red laser. It isn't that the laser/PE projectors look bad but they do not have the same look as RGB laser (or straight up xenon).

While some will argue that you can't see the 2K pixels on a small screen so there is no benefit to 4K, I'd counter that if you are seeing the pixels, then you are in a bad situation already. What I see different in 4K versus 2K is that 2K images have so little information on them that they look hyper-flat. There is no depth to anything. With 4K, you start to get that film-like depth back where things behind other things look more like they do in real life rather than picture cutouts laid on top of each other. 2K projection, for me, at least, isn't hard to spot due to that visual aspect of it. It isn't a focus thing, it's a depth thing.

I'd say that, at least, 50% of the features being released are now 4K. As mentioned previously, it isn't a premium format. It is becoming the standard one.

The only time 2K is being considered in our systems is where physical size and budget are the primary considerations.

Since you mention Barco...just know, their smaller 4K projectors, the SP4K-C series (e.g. SP4K-12C) are still on hiatus due to the TI TRP chip issue (stuck pixels) so Barco is substituting their "B" frame projectors (e.g. SP4K-12B) to bridge the gap until the SP4K-C series returns with the new SST style DMDs). So, you can still get a 12K lumen projector. Just know that it is physically HUGE (seriously, it is something like 5-feet long and is a 6-person move) and since it is a "B" projector it uses the 1.38" DMDs...which are good but also means less lens-shift than on a "C" projector. You might also find that on a small theatre you run out of choices on the longer lenses to make the image small enough (with the "C" projectors, the picture starts out smaller due to the .98" chip). Depending on when you actually need the projectors, the SP4K-12C may return. Barco, at this time, hasn't announced when as I'm sure they want to ensure they don't have the same debacle they had on the TRP chips. Speculation is they'll be back in 2025..but there was speculation that they were going to be back at the end of 2024 and that didn't happen.

[James Gardiner]

Yes forgot about the TI manufacturing fault. Defiantly puts 4K in smaller screens as a problem for the industry. A problem for every manufacturer. I hope TI can sort this out in the next revision.

However, I would put more weight behind the capability of the eye and the resolution it can see over a specific arc able is quite important.
Just because people have 4K at home, they rarely sit close enough to see the difference. With Cinema this is very much a variable that is used to judge what resolution screen is required to archive the required pixel count per arc-angle.

[Steve Guttag]

James, as I indicated, what I notice on 2K versus 4K is how flat the image looks. It isn't that I can resolve down to the pixel but how the overall image presents itself to me. While a 2K picture will appear in focus/sharp as all of its pixels can be sharp, the image itself just looks hyper flat, on almost any sized screen.

[James Gardiner]

Steve, I don't doubt your personal opinion. I am just more reliant on scientific analysis and measurement, as it's a way to remove the human element of.. non of us see exactly the same. That's why we have measurements like arc-angle/resolution. It's how we test the effectiveness of a Lens or the accuracy of telescopes for astronomy. It is also used to judge how far away from a screen you have to be to actually see a specific resolution it can present.

Obviously it would be used to calculate what resolution is needed for a specific result, as why make the resolution more than it has to be. It is a waste of money. I imagine this is what the projector makers would apply to help chose the right projector for the right job.

Personally, I feel the better contrast results in the separation like you have suggested works for you based on resolution. But again, it's the human condition. We all see things a little differently.

[Stefan Scholz]

For every screen the required resolution is only dependend on the viewing angle in the hall.
A 50 ft screen viewed in a long theatre of 180 ft will not really benefit from 4 k in the rear seating, but quite likely a lot of seats will be in the front rows to the center that will have a visible benefit.
Theatre building standard emphasize on a 90° viewing angle in the front, and 36° minimum in the rear seats.
A 40 ft long room, featuring a 28 ft screen will benefit on all yseats from the higher resolution. That also applies to any other room with a short viewing distance compared to the image width.
With abn average eye resolution for the majority around 60 px per arc angle of the viewing field, 5400 px is required in the front row, in the rear still more than 2k (2160) to conceal the fly grid.
This is, why 4 k was the compromise for digital reproduction, and 2 k intended to be a bridging technology until the industry was able to deliver 4k in quantities (which was in 2007)..

In 2024 I do only recommend 4k High contrast projection, the image looks better on any screen. It is just the fact, that small power projectors do not really exist in 4K.
Most or nearly all venues intended for 2D only eventually will be served with a 12000 lumen machine, as these worked with 35 mm, where this about as much light as you can get through a flat aperture in 35 mm projection.
So from that point a 0.69" low contrast DLP might do the job for a bright enough image, but the overall image quality will not satisfy.
Modern RGB laser can be trimmed down to 20 % light with Barco, Christie is about 30%. The value is stated with the standard focal range, Ultra High Brightness lenses. Using Ultra High contrast lenses, you are loosing a lot of light, it's mor than 1 T stop to 2 over Brightness lenses.
I Barco is the projector of choicer, the SP4K 13 model is the one of choice for the 20' screen, combining enough light reserves for future enhanced dynamic range and enhanced contrast to values, that make movies look great. It eventually is a price issue for such a room.
My recent projects, if it wasn't a rural group or community with limited screenings per month/ week has always been 4K RGB with Ultra High Contrast projection, running on 22 to 27 fl, regardless of size of the room. The feedback I got, the audience notices the difference over the common screens in the surroundings, and increased turnover at the box office. It must be accompanied by a good sound system.

So, I do not see any discussion here.

[Steve Guttag]

I apologize James. If Stefan and I are starting to agree on things, I know I must be heading down the wrong path.

In all seriousness now, I don't question the scientific part but when one comes up with measurements, they are measuring what they are trying to measure. It does not completely quantify all aspects. For instance, I can measure two speakers to have the same frequency response but it doesn't mean that they sound the same. If I were to make many more measurements for distortion, resonances...etc...eventually, I'd get closer and closer to quantifying the sound in a predictable way but likely never get there as there would need to be so many types of measurements.

Likewise, when I hear someone say that they have this way of determining what one can resolve based on a smaller number of parameters, I question if that is sufficient to quantify. I see what I see and I don't consider myself particularly blessed. I've been in rooms where color-timers have looked at an image and saw (or claimed to have seen) a gazillion more things than I ever did. And, I've noted those sorts of people are pretty consistent in their observations too. When I see 2K images, I see hyper-flat images. If your measurements don't reflect that observation, then your measurements are insufficient to fully describe what people are seeing.

Truth be told 4K images almost always are lower-contrast than 2K ones (it is MUCH harder to keep the light well controlled when everything is so small). The xenon 4K projectors had a 2000:1 contrast ratio with a wink and nudge. There is no way they were achieving that and even the measurement is bogus as it is full black compared to full white. Try it with a 50% checkerboard pattern on screen and merely alternate the checkerboard between measurements to get an excited optical system. You're in the 100s:1. Most anyone can see that the 4K xenon doesn't have the contrast of a 2K xenon. With the RGB lasers, 4K finally can get up over 2000:1 and with HC lenses, starting at 3000:1 and going up to 6000:1, depending on the optical path and lenses used (if the theatre doesn't pollute the screen with light).

I have also found that, in terms of contrast ratio, without increasing the white point above 48nits (14fL), you get a diminishing returns in customer perception as to the difference above 3000:1 I've had a customer look at back-to-back 3000:1 versus 5000:1 and they couldn't tell the difference, despite the extra $30K it would have cost to get the better system. I agreed with him. Conversely, without exception, if you can get the lumen output up over 100nits (e.g. Dolby Vision) and combine that with a higher contrast...everyone notices and seems to prefer it (if the content is really mastered for it). People are much more sensitive to things getting brighter than they are to making dark, darker, after a point. If you projector's contrast ratio is below 2000:1, it is going to look bad...you don't have anything that appears black...just grey. The worst are the lamp based S2K projectors at about 1600:1. They're just horrible.

[James Gardiner]

As a cinema operator myself. All well and good if an installer says Do X to get no compromise. However, that's not a commercial stance. Projectors are expensive, and High Contrast 4K projectors are super expensive. In this new world of compressed attendance levels, needing more catchment to service a cinema at pre 2019 levels. It is only common sense that a commercial cinema operator may consider a compromise in that the first 1/3, closer to screen may be compromised over the typically used seats 1/3 and back. Its a commercial decision based on viability of actually running the cinema at a profit.
Due to this, I expect Projector makers calculate and present best banks for dollar, 2K vs 4K etc.

Don't look down on it, look at it as the harsh reality of running a cinema today.

[Steve Guttag]

James, it isn't that I look down upon it, it is that I fear that as the cinema becomes less-and-less quality conscious, there becomes less and less reason to go to it and spend money on it. With respect to 4K. It isn't special. It isn't high-end. It is only as good as consumer grade. Putting in 2K in 2025 is wanting to serve fast-food at sit-down prices. My fear is that patrons will not see the value in the cinema experience (presuming the issue of release windows is resolved). Going up to 3000:1 in contrast ratio isn't pie-in-the-sky either. That is just a HC lens...a relatively small incremental increase. In film days, did you use junk or ISCO and/or Schneider? There was a significant difference between those lenses and the rest.

Mind you, I'm not advocating ripping out existing equipment and putting in the latest projectors. But, if you are putting in a new projector, in today's world, I wouldn't recommend a 2K unless, again, size and budget are paramount (particularly in non-traditional cinema spaces).

Projector companies will make 2K projectors because they want to capture people at the lower end of the price spectrum too. If you take the Sony stance of just the one-level of projector, you get the Sony result (out of the business). As such, the survivors do have the range from low to high end machines. I'm continually amazed, however, how one of the three continues, in the laser era, to have found a way to make sub 2000:1 projectors.

[James Gardiner]

Steve, on this point I do agree. I was hoping by this time, TI would have been able to produce cheaper and better DLP chips, and likely only at 4K. (Larger and smaller versions)
Unfortunately that has not worked out at all. The TI efforts in this area have need very unfortunate and costly. I wish them luck in the next attempt.

[Steve Guttag]

The whole DLP market has been precarious ever since they lost the home TV market to flat-screen. If you look at the entire cinema market...let's be generous, 200,000 screens...world wide. That is 600,000 chips divided up amongst 4-5 or so models of DMD. Furthermore, the churn rate is going to be in the 1000s per year...we into the "sample-size" of a chip manufacturer. There is no economy of scale. The need in the A/V markets for a projector gets smaller and smaller. Most have moved over to flat panel (smaller screens) and LED wall. The projector market is sort of in the middle of those and for particular displays where LED/micro-tile type technologies haven't taken over, yet.

I seem to recall seeing Christie showing an SST based projector (a non-functioning carcass with the information of the SST chip) at Cinema Con 2024. We'll see when Barco brings their SP4K-C projectors back. Thus far, they've been keeping quiet about it since they have their interim projectors (SP4K-B that go down to 12K lm).

[Carsten Kurz]

From my experience, typical small screen auditoriums are often set up with people sitting a lot closer to the screen than in larger size auditoriums. As such, it makes more sense to use microperf or woven screens and 4k projection, if the budget is there. 4k is certainly not spoiled for these smaller screen sizes. However, contrast is important just as well.

[Skyler Hunt]

Thanks, all, for the thorough responses and back-and-forth.

[Marco Giustini]

In this new world of compressed attendance levels, needing more catchment to service a cinema at pre 2019 levels. It is only common sense that a commercial cinema operator may consider a compromise in that the first 1/3, closer to screen may be compromised over the typically used seats 1/3 and back

You do not gain audience by compromising on quality when a reasonably expensive large TV can provide infinite contrast ratio and 350fL Yes, I know many do think this is the way to go.