Mailbag: HD Movies and the resolution of film

April 3, 2006

Gump in HDWe often get questions from readers via email, some of the questions range from, “What’s the best way to incorporate surround sound into a whole-house-audio system?” to “Which is better, LCD or plasma?” and everything in-between. Recently I got an email from a JD in Maryland and I felt it deserved an in-depth response so I decided to make a post out of it.

JD’s question was: “Some of the movies on TNT-HD don’t look very good, specifically recent airings of Aliens and Forrest Gump. Weren’t these movies made before films were shot in high definition? Were they just up-converted or am I missing something? Oh and what is the resolution of the movies shown in theaters? Thanks.”

Ok JD here’s my answer, but you might want to grab a cold drink, you got me fired up with this one. First off as to your question about the quality of the HD movies on TNT-HD: While I didn’t catch either one of these when they aired, I have noticed a pretty wide range of image quality on TNT-HD and other networks. Some of the films do appear to be standard definition up-converts, while others appear to be recent film to HD transfers.

Obviously not having knowledge of the inner workings over at TNT-HD I can’t say for sure, but color saturation is often the first tell-tale give away of a SD up-convert. Also the grain in some of them smacks of SD to digital HD conversion as well. But before you fire off an angry letter to the network, keep in mind this isn’t always their fault. They have a “HD” network to run and true HD masters of these films aren’t always immediately available. In their defense I will say I have seen some great looking movies that were obviously true film-to-HD conversions.

This is one of the reasons I’m so excited about both Blu-ray and HD-DVD. We get a chance to potentially see some movies in a way we’ve never seen them before. Just as all home theaters aren’t of the same caliber, many of the movie theaters we frequented growing up were working with aged film projectors and worn copies of the film itself. High definition DVD gives us that rare chance to capture the magic again, or even potentially surpass the original experience.

The fact that a movie was shot in HD (Collateral and Star Wars: EP3 come to mind) or not, bears little weight on how the end product appears on video; at least in terms of resolution as film has more than enough resolution to be considered HD-worthy.

• The resolution of the movies shown in theaters

And now to answer your last question, “What is the resolution of the movies shown in theaters?” This one isn’t as easy to answer because well, there is no fixed answer. Film stock isn’t bound by the same rules that make up the pixels in a frame of video. Most of the data I’ll cite from here on out comes from a great study done by the International Telecommunications Union, specifically sub-group 6 which deals with large screen digital imagery. Their study titled ‘Image resolution of 35mm film used in theatrical presentation’ is as close to the definitive word as I’ve found on the subject.

One thing to keep in mind is that analog film has no ‘lines of resolution’ as we know them in the video world, but it is possible to arrive at a comparative resolution by using a resolution-chart in the frame that equates to fixed video resolutions.

The study indicated a 35mm negative has a resolution in excess of 2400 lines by picture height but obviously we don’t watch negatives, the film has to be processed into a stock reel. Those tested stock reels were found to have a maximum comparative line resolution of 1400 lines P/H, still considerably more resolution than 1080p’s vertical integer. (Note: the P/H formula is used because film has the same vertical and horizontal resolution, where video does not.)

Luckily the study also included real-world data collected at a sampling of movie houses. I say luckily because no matter how good the film stock, the theater’s equipment plays just as much into how the projected image looks as the film itself.
This part of the study only reinforces my anticipation for high definition DVD as the numbers indicated what we’re seeing at the theater in many cases falls short of 1080p. The study indicated a comparative, average line resolution of between 685 lines and 875 lines P/H. But again don’t let these numbers alarm you as the film stock itself is more than capable of bettering HDTV, it seems it’s the movie houses that have been letting us down.

So there you go JD, I hope that more than answers your questions.



Posted by Bryan Greenway | | Filed Under HDTV


Comments

  • Film Fan

    New comment on a real old post, but what I have noticed is that HD is not the same as it was when it was first launched. We bought our first HD set before the 2004 Summer games and the NBC high definition channel was playing stuff from the day before was un-believable. It was a new toy and they were putting every effort to make sure the image was as good as it can be. They don't have the money anymore for that anymore. Make up alone is tough enough without HD. With HD, I am glad I am not in the business anymore. The tonight show has had always the best camera set-ups in the business. Very few programs have looked better than the tonight show way way before HD. The compression schemes drive me crazy. Some programs like the disney channel, are turning up their SD compression past prime time to save money on bandwidth. It looks horrible.

  • Film Fan

    New comment on a real old post, but what I have noticed is that HD is not the same as it was when it was first launched. We bought our first HD set before the 2004 Summer games and the NBC high definition channel was playing stuff from the day before was un-believable. It was a new toy and they were putting every effort to make sure the image was as good as it can be. They don't have the money anymore for that anymore. Make up alone is tough enough without HD. With HD, I am glad I am not in the business anymore. The tonight show has had always the best camera set-ups in the business. Very few programs have looked better than the tonight show way way before HD. The compression schemes drive me crazy. Some programs like the disney channel, are turning up their SD compression past prime time to save money on bandwidth. It looks horrible.

  • westcott

    Compression on TNT HD has really ruined the 5.1 experience, their stretching the image and clipping the left and right sides of the film to fit a 16:9 screen, editing, and just plain bad film conversions all contribute to the overall bad video and audio quality found on TNT HD.

    I would think TNT would have been smarter than that. Most of us are used to the bars above and below the picture. Why degrade the video by stretching it and cutting it up? If you are going to go HD, it has to sound at least as good as the DVD version, not to mention have better video.

    TNT HD has been a real disappointment after watching it properly done by HD Net, Disovery, and others.

  • westcott

    Compression on TNT HD has really ruined the 5.1 experience, their stretching the image and clipping the left and right sides of the film to fit a 16:9 screen, editing, and just plain bad film conversions all contribute to the overall bad video and audio quality found on TNT HD.

    I would think TNT would have been smarter than that. Most of us are used to the bars above and below the picture. Why degrade the video by stretching it and cutting it up? If you are going to go HD, it has to sound at least as good as the DVD version, not to mention have better video.

    TNT HD has been a real disappointment after watching it properly done by HD Net, Disovery, and others.

  • B.Greenway

    I understand what your saying, but we’re talking about the variance of image quality on the same channel via the same source.

  • B.Greenway

    I understand what your saying, but we’re talking about the variance of image quality on the same channel via the same source.

  • Dan

    You must also factor in the compression ratio used if you are viewing via cable or satellite. I find this to be the biggest factor in the end result. Seems most cable at sats compress WAAAAAAAAAYYYYYYYYYY TOOOOOOOOOOOOOOOOOOOOOOOOO much to get in more channels.

  • Dan

    You must also factor in the compression ratio used if you are viewing via cable or satellite. I find this to be the biggest factor in the end result. Seems most cable at sats compress WAAAAAAAAAYYYYYYYYYY TOOOOOOOOOOOOOOOOOOOOOOOOO much to get in more channels.

  • hifidigital

    Excellent explanation. I’ve noticed some of the same issues when watching HD movies on Comcast. Most of the time, they tend to appear to not look as good as something like The Tonight Show, or live sports. I guess it really boils down to what the source was, and how it was converted.

  • hifidigital

    Excellent explanation. I’ve noticed some of the same issues when watching HD movies on Comcast. Most of the time, they tend to appear to not look as good as something like The Tonight Show, or live sports. I guess it really boils down to what the source was, and how it was converted.