Question concerning 35mm film and digital projection

[Erik Lokegaard]

It seems like theaters are converting to digital where deemed feasible and cost effective - not least because of the new wave of digitally produced, stereoscopic features. What are the visually detectable differences between 4K digital projection with 35mm film material and film projection with a fine 35mm print?

 

[Rocco Schult]

Hi Erik - ideally: None!
While reality will prove me wrong and the likeliness you will be able to find a matched digital (4K) projection and a print outside the US is near to zero, a digital projection will be more of a subtle, very personal one. There are scientists who try find out what happens in our brain during the frames of a film (which is a black phase), when a digital projection gives you a constant 'light'.
Given, the print is from an intermediate in 4K, compared to an analog lab process which tend to loose some resolution down the processing chain.
Some people tend to see or better "feel" a difference, many do not.
A clear statement that can be given is, the digital projection won't get worn out during projection, so dirt, scratches and general wear and tear is minimized.

The 3D projection is another story - though I do not exactly know, I bet 100% of at lesst the european digital (3D) theatres are 2K.

 

[M Most]

It seems like theaters are converting to digital where deemed feasible and cost effective - not least because of the new wave of digitally produced, stereoscopic features. What are the visually detectable differences between 4K digital projection with 35mm film material and film projection with a fine 35mm print?

Digital: No weave, no scratches, no dirt, more consistency across theaters and screens.

Film: Better color depth and richness (subjective). Stronger blacks (depends on print and projector lamp).

I have been working in film for many years, but quite frankly, I prefer digital projection. However, as you might suspect, it won't become predominant for quite some time, due primarily to the current world economic climate. The transition even in the US is proceeding at a much slower pace than was predicted 2 years ago.

 

[Erik Lokegaard]

Thanks.

Some people tend to see or better "feel" a difference, many do not.

Does some argue that digitally projected film material partially loses its organic look?

 

[M Most]

Thanks. Does some argue that digitally projected film material partially loses its organic look?

I do feel that way, but I can't explain it in words. That's why I labeled the perception of better color depth and richness "subjective." For me, however, that isn't enough to negate its advantages. I just find myself less distracted when there's no dirt or scratches to visually contend with.

 

[David Mullen ASC]

If the original was shot on film, there's enough organic look right there, you don't need the film print adding more in my opinion.

I prefer digital projection but when I've hopped between two theaters, one showing the film print version and the other the digital version, I always notice how much richer the blacks are in a film print.

 

[Dan Hudgins]

Optics

Optics

From what I have noticed the blacks are better on film, and some of the warm colors like orange, less megenta skin maybe. Digital also can twinkle when things move sometimes, it depends on how close you sit.

One fear I have about the Digital projectors is that as they age the "brightness" will get turned up and not only will the blacks get more washed out but the highlights will go, that seems to be what happened at one place around here that have been digital for many years.

The optics in the projector can get dusty and the mirrors degrade from the heat of the lights so the contrast ratio can fall off as the projector ages. The bulb can also dim, they cost a lot to replace, making the "turn up the brightness" an easy fix. In a film print you get fresh color with each new movie that comes out.

The difference between film and digital projection is blured by the use of 2K or 1080p DI, film-to-film printing is better than even a 4K DI if done well, but without a projectionist the film projector will not hold focus for 2 hours to see the way film looked before DI came into use. Also color film has a softer MTF than fine grain Black and White film, unfortunately most of the black and white prints are made on color print stock from bad dups so you would have a hard time seeing what film looked like. Also the wide screen formats have reduced the film area to about half what it was, so making film look worse makes Digital look less like a loss.

Digital is cleaner, but does twinkle when things move sometimes and is compressed, so there will be a trend to use more and more compression as people no longer have a film print to compare the same move to. Look what has happend to TV, now we get blocks everywhere and bad lip sync.

Another issue is in the film recorders, before film recorders took like 45 to 90 seconds per frame to get sharpness that matched film-to-film optical printing. Now film recorders are going at 24fps in some cases, so there is a loss of resolution in pushing the film recorders past optimum image quality to maximum speed to get 2000' rolls through ASAP rather than just short shots used for special effects as before. This makes DI movies fuzzer. Also some DI are using compressed file formats, so all this levels the field by lowering the quality of the film print. Also the lack of 70mm prints makes a 2K digital projector seem on par with a 2K DI print, and so they are since the film print is made like recording the projection of a 2K digital projector, how could it be much better?

==

Another issue is that some film recorders are not using 2K in the image area,

http://www.celco.com/FormatResolutionTableKodakCineon.asp

You see in that link that flat prints would be made at 1828x1026, so the digital projection of the 2K DI would probably be sharper than the 1828x1026 print 2nd generation made form the same DI but down rezed for for the film print.

 

[scott william]

What are they playing these 4k digital files through, is it from a portable hard drive (like Red Ray will be) and what kind of files are they?

 

[Iannis Holwech]

Important to note that the only 4K projectors for cinemas are the Sony SXRD's technology so we have nothing to compare with.
The earliest Sony 4K's were not very good, the new Cine Alta is supposed to be better.
But we will have to wait to next year for the opportunity to see how good 4K projected can be, when 4K DLP in "light cannons" from Barco and Christi are released and we can compare 4KSXRD with 4K DLP, or 4K to 2K as "all" 2K projection in cinemas are DLP.

The new JVC 8K DILA are of course another ballgame (35mpx) but is not powerfull enough for big rooms.
Reports of the Evans&Sutherland's 8K laserprojector (world's first laseprojector designed for movies) presented at Infocomm shows the E&K still has some issues to be ready for cinema presentations, but when those issues are solved it should be scaleable for "big room" output.

 

[Bea Adams]

I would go with 35mm film 100% over digital. Digital pixelates, film doesn't. That's the differenece. Hope that answers your question. Plus, me and a couple of friends saw two separate shows of "Harry Potter and the Half-Blood Prince" and during the first performance, the digital projector broke down half way through!!! We subsequently saw it at another cinema on 35mm and the quality was noticeably better, beautiful in fact. So I will take film over video any day. Spielberg has also commented that while digital quality is great, it is inferior when projecting film. In other words digital is great, but should be kept for low budget arthouse films.

It seems like theaters are converting to digital where deemed feasible and cost effective - not least because of the new wave of digitally produced, stereoscopic features. What are the visually detectable differences between 4K digital projection with 35mm film material and film projection with a fine 35mm print?

 

[Brandon Kraemer]

Thanks. Does some argue that digitally projected film material partially loses its organic look?

It was tested early on in the history of cinema, the frame rate at which the human eye can no longer detect the shutter flicker is ~60 fps. So traditional film projection at 24 fps has flicker that your brain can detect. Digital projection has no flicker, so there is certainly a perceptible, if subliminal difference between film and digital projections on the audience.

It's a bit like the 3:2 cadence that you pickup on when your watching a TV show shot on film vs. one shot on video. In addition to contrast ratios and film grain, there is (was) a subtle difference that was sometimes difficult to quantify, a subliminal effect that watching a film transfer had on the audience compared to a video production. This is largely why video camera manufactures went out of their way to build cameras that simulated this effect.

 

[Brandon Kraemer]

I would go with 35mm film 100% over digital. Digital pixelates, film doesn't.

Or another argument would be that digital is compressed, and film is purely optical and chemical. Unless we are talking about lossless (uncompressed) 2k + digital playback, and we are not, dust and scratches not withstanding, digital projections are an "inferior" product to a film print.

I would bet that the next generation film projection, is not going to be a projection at all, rather a giant OLED type display playing back a digital file. The technology is rapidly catching up to this possibility.

 

[D'Arcy Foley-Dawson]

What are they playing these 4k digital files through, is it from a portable hard drive (like Red Ray will be) and what kind of files are they?

for all DCI-compliant digital cinema - ie. the standard created for digital cinema, [http://en.wikipedia.org/wiki/Digital_Cinema_Initiatives] - there is a proprietary file system. these files must be encoded with the special DCI-compliant software and are then loaded onto special DCI-compliant server-type machines, from portable hard drives. the server sits in the bio box (projection booth) alongside the projector, or is networked to it from a control centre somewhere in the cinema. this server then feeds the data through to a DCI-compliant digital projector. playback of these files is simply controlled through a computer, and it can even be done over a wireless network with a laptop or iphone.

but the entire chain comes under the control of the DCI specifications. for example, you cannot just take a 2k or 4k video file, ingest it into the server and play it. that file must be encoded into the DCI proprietary format. feature films are sent to cinemas on hard drives already encoded as such. but it can be a real pain converting ads and trailers, as it is incredibly processor-intensive. converting a full length high bitrate 2k feature film to DCI can take 48 hours or more on the best computer workstation, whereas it only takes a competent projectionist around 30 minutes to make-up (splice together all the reels) of the same feature film on a 35mm print.

DCI applies to both 2k and 4k digital projection, although as far as i know only sony does 4k stuff so far and i don't think they adhere to DCI (correct me if i'm wrong) and being the tricky bastards they are, have probably created their own proprietary format that they will hope to push as the 4k standard.

the funny thing is, digital projection has it's share of potential technical problems to rival the problems associated with film projection (scratches, dirt and dust, film path/platter faults/head wraps etc.) remember the first time you were watching a DVD and it suddenly went haywire, freezing frames, spitting up weird pixel garbage, refusing to play anymore? well imagine how annoying that would be in a cinema.... guess what, it happens.

imagine sitting there and halfway through the feature the screen suddenly fills with white noise like a television screen (DCI server loses the internet connection that allows it to read the key that decrypts the data), or suddenly one half of the screen is has a strong yellow or magenta or green hue (something wrong with the texas instruments board inside the projector, still don't fully understand that one).

 

[D'Arcy Foley-Dawson]

One fear I have about the Digital projectors is that as they age the "brightness" will get turned up and not only will the blacks get more washed out but the highlights will go, that seems to be what happened at one place around here that have been digital for many years.

I'm a little unsure as to exactly what you mean by this.

As far as I know, being a projectionist, none of the DCI-compliant digital projection systems allow any tweaking of 'brightness', nor contrast nor colour nor anything on the projector itself (or for that matter the file being played). The projectionist cannot do anything to adjust these values. Of course the Xenon bulb in the projector will age and weaken and flicker and eventually need to be replaced, but this is no different from film projection.

Now, as for E-cinema - a term applied to anything that is not DCI-compliant and will most likely become extinct as DCI and perhaps latter formats like Sony's 4k systems eventually take over - this has been possible. I've seen digital projectors have their brightness and contrast values adjusted like you would your television at home. But these systems I would characterise as a stop-gap solution that satisfied early-adopters of digital cinema before standards were created, more or less agreed-upon, taken up by manufacturers of equipment etc. In other words, E-cinema is going the way of 16mm theatrical projection, it will not be around much longer, at least not in large markets. I would suggest this accounts for what you have experienced.

Unless of course I am completely mistaken....!

 

[M Most]

..there is a proprietary file system. these files must be encoded with the special DCI-compliant software and are then loaded onto special DCI-compliant server-type machines, from portable hard drives. ...
but the entire chain comes under the control of the DCI specifications. for example, you cannot just take a 2k or 4k video file, ingest it into the server and play it. that file must be encoded into the DCI proprietary format. feature films are sent to cinemas on hard drives already encoded as such.

Absolutely nothing in the DCI specification is proprietary. It is completely based on open standards, one of the primary design objectives during its creation. The hard disk format is ext-3, an open standard used by essentially all Linux based computer systems, although per the specification, material can also be supplied on standard ISO9660 DVD optical disks. The files themselves are MXF - an open standard - and are compressed using JPEG2000, another open standard. The color space is specified in CIE XYZ coordinates. All of the control and documentation files are XML, and every relevant detail on all of these things is included in the freely distributed specification document. In short, it is one of the best examples around of a sophisticated specification based entirely on open standards. Not simple, but most definitely not proprietary.

but it can be a real pain converting ads and trailers, as it is incredibly processor-intensive. converting a full length high bitrate 2k feature film to DCI can take 48 hours or more on the best computer workstation, whereas it only takes a competent projectionist around 30 minutes to make-up (splice together all the reels) of the same feature film on a 35mm print.

The theater is not where the DCP's are made. In most cases, they come to the theater already made and ready to be copied to the server. Once on the server, the operator can create a "show playlist" that consists of all of these elements, complete with controlled transitions and black periods between elements. As for the time involved in the J2K compression step, there are a number of manufacturers of hardware J2K compression boards. These boards are used by a number of digital cinema mastering systems to reduce the time it takes for compression to real time, or at least close to real time. One example of such a board is the DVS Hydra board, a version of which is used in their Clipster product. There are also others.

DCI applies to both 2k and 4k digital projection, although as far as i know only sony does 4k stuff so far and i don't think they adhere to DCI (correct me if i'm wrong) and being the tricky bastards they are, have probably created their own proprietary format that they will hope to push as the 4k standard.

Sony projectors are fed by quad dual SDI from a digital cinema server equipped for that format. The DCP that is used for the source material, however, is a standard DCI specification DCP. It can be either 4K or 2K, as can all standard DCP's.

the funny thing is, digital projection has it's share of potential technical problems to rival the problems associated with film projection (scratches, dirt and dust, film path/platter faults/head wraps etc.) remember the first time you were watching a DVD and it suddenly went haywire, freezing frames, spitting up weird pixel garbage, refusing to play anymore? well imagine how annoying that would be in a cinema.... guess what, it happens.

Rarely. The studies I've seen, done over the last year and a half or so, indicate considerably higher than 95% up time. That's a very, very good track record, much more reliable in many ways than film projection, with its history of breakage, scratching, digital sound system failures, and other problems.

imagine sitting there and halfway through the feature the screen suddenly fills with white noise like a television screen (DCI server loses the internet connection that allows it to read the key that decrypts the data), or suddenly one half of the screen is has a strong yellow or magenta or green hue (something wrong with the texas instruments board inside the projector, still don't fully understand that one).

Although there have been some problems with key delivery messages, in almost all cases (from what I've been told) the key is loaded into the server locally and not constantly checked over a live internet connection. The color space issue (which is what you're referring to) is more often than not operator error. The fact is that digital projection is very, very reliable, far more so than you're implying.

 

[David Rasberry]

What is the bit depth of the 2k DCI/DCP standard? The latest gen digital projectors are 15bit and have an effective 11 stop contrast range.

My impression is that digital has higher contrast ratios but not as refined a tonal scale as a fresh film print. The contrast range for film projection is limited under SMPTE standards to minimize apparent flicker.

 

[M Most]

What is the bit depth of the 2k DCI/DCP standard?

Everything in the DCI spec regarding the image is based on 12 bits. But it should be noted that this is a distribution format. Essentially all post production in the DI world is done using 10 bit log format files, although the expansion of these to 12 bit gamma encoded (digital cinema gamma is 2.6) values should, in most cases, be rather seamless. This is to some degree dependent, of course, on the depth of the 3D LUT that is baked in to do that conversion.

 

[D'Arcy Foley-Dawson]

The color space issue (which is what you're referring to) is more often than not operator error.

in my case it was not. after weeks of scratching their heads, all we were told by the suppliers of the NEC projector that there was something wrong with the TI board inside and that they couldn't tell us exactly what because they didn't know. eventually they just replaced the projector and the problem never happened again.

The theater is not where the DCP's are made. In most cases, they come to the theater already made and ready to be copied to the server.

actually i already said exactly the same thing. i merely pointed out the difficulties inherent in converting material to DCI inhouse for cinemas.

The fact is that digital projection is very, very reliable, far more so than you're implying.

the point i was trying to make is that it's not a simple case of plugging in a portable hard drive and pressing a play button, as most people tend to (understandably) assume. things do go wrong and some of these things, like losing the connection to the key and therefore spitting up white noise, represents a far greater impact to the viewers' experience - imo - than say having a head wrap that forces a projector to stop running, or issues with the digital sound.

people who aren't in the know, who don't work with this technology, only have our word to go by. most of the time they only hear from those with a vested interest in the technology, who reassure them 'oh, it's extremely reliable, far more reliable than film,' and use statistics to prove their statements. but it's just spin. i'm simply stating my own conclusions, based on my own professional experience with film and digital projection. and my conclusion about digital projection is this: don't be surprised when you go see a film and weird stuff happens. don't assume that because it's digital it will run perfectly every time. don't assume it's as straightforward as opening up a quicktime file and pressing play. there are still kinks and flaws that will need to be worked out. and DON'T give us the 'operator error' excuse when faulty equipment is the real culprit.

the general public deserve to hear a little of the experiences of those on the floor working with this equipment, who have no special interest and can be 100% objective.

 

[Jeff Coatney]

I've seen two apples to apples comparisons with regard to film vs. digital projection.

The first time was Red footage from build 17 converted to 2K dpx's projected digitally vs. the same footage on a 35mm check print from Deluxe using 4K dpx's.

The second was 35mm film acquired 2K dpx's projected digitally vs. the same footage at 2K film out on a 35mm check print from Deluxe.

Two separate facilites, two separate projects, two separate colorists, DP's, etc. The only component of the tests that was the same is the lab work performed by Deluxe.

In both instances the digital projection was VASTLY superior to the film print. In the first test, we were shown the film first, followed by the digital immediately after with no delay between the two of them.

Unlike the others in this thread, I observed the digitally projected image to have much richer blacks, much more vibrant colors and no chemical stains or scratches or other artifacts. I also noticed there was no image floating or gate weave.

In both cases observing the film print, the blacks were milkier and the color saturation was surprisingly muted by comparison, even in the film originated footage.

Seeing the same footage back to back was amazing and ended all doubt for me as to the superiority of digital exhibition.

I expected the Red footage to under-perform when transferred to film, but when comparing the results of the film originated footage I saw later, I was amazed that the film originated footage fared no better than the Red footage in the transfer. The shortcomings I perceived in the film prints vs. the digital images matched from project to project and were basically your standard film print characteristics.

But, I have to say, with regard to the digital projection, I found no fault with the image. It appeared to be very warm and organic.

 

[David Rasberry]

in my case it was not. after weeks of scratching their heads, all we were told by the suppliers of the NEC projector that there was something wrong with the TI board inside and that they couldn't tell us exactly what because they didn't know. eventually they just replaced the projector and the problem never happened again.

At least in the high end Digital Projection DLP projectors we work with, the chassis are modular and all components are field serviceable.