The Truth About Inflated HDTV Contrast Ratios

Just as resolution continues to increase on HDTV sets, so it seems does contrast ratio. I few years ago, digital displays were exclaiming how impressive a 1,000:1 contrast ratio was. Now 10,000:1 is not that uncommon. And since contrast ratio is more important to resolution in the production of a great picture, it sounds like these new displays should be amazingly fantastic. Unfortunately, these extremely high contrast ratios have little to do with real world performance and are, to a great extent, marketing hype.

First of all, it’s necessary to understand the difference between the two types of contrast ratio measurements. The one used by pretty much every manufacturer out there is full on (100% white) / full off (100% black). While this can give some amazingly high numbers, people don’t watch all-white or all-black screens. Comparing the brightest whites in one scene to the blackest blacks in another scene is not representative of the picture quality available at the exact instance the viewer is watching each scene. (Measuring the screens at 2 different times also allows further manipulation of the display between tests, such as switching to a different color wheel setting, changing the aperture of an iris, or taking the measurement at a more favorable location on the screen.)

The contrast ratio that matters most for the most common viewing scenarios is ANSI contrast ratio [1]. With ANSI contrast ratio, the black and white levels are measured at the same time on the same screen using a 16-square black and white checkerboard image. What this means is that it is representative of the contrast ratio achievable at any one point in time; this is what is really important to viewers. [Edit: see AlenK's comment below regarding situations where On/Off contrast ratio become important.]

The reason ANSI contrast ratios are not published is because of marketing. ANSI contrast ratios are much lower than on/off contrast ratios. An ANSI contrast ratio of 250:1 would be an impressive result and 600:1 would be outstanding — but much too low of a number if casually compared to an on/off contrast ratio of 6,000:1.

This info is for front projection and does not directly relate to flat panels:

One last point that is critical is the impact ambient light has on perceived contrast ratio. Ambient light kills contrast ratio on any and every display. If you make out the beige carpet below your flat panel, your contrast ratio is being negatively impacted. If there is 1 lux of ambient light in the room (i.e. a small candle), the max perceivable contrast ratio is 500:1. A dimly lighted room with 30 lux of lighting would squash the maximum perceivable contrast ratio to 50:1 [2]. Unless you have a completely dark room covered in black velvet, you’ll never be able to perceive the high on/off contrast ratios claimed by manufacturers — those numbers are meaningless otherwise.

Conclusion: If you’re looking to buy a new HDTV, don’t place much merit on the contrast ratio published by the manufacturer; it is pretty much meaningless for real-world (a little bit of light in the room) viewing. Plus, I’ve never seen a review of a calibrated display meet or exceed the manufacturer published contrast ratios. Look for independent test results that measure both ANSI and On/Off contrast ratio on a properly-calibrated display. If you are always watching TV in a well-lit room, the contrast ratio doesn’t really matter anyway; display brightness is more important the brighter the room is. But if you like to enjoy the full performance of your display by turning the lights off, high contrast ratio is extremely important.
If you’re considering a model for which no reviews listing ANSI and On/Off contrast ratio exist, use this rule of thumb:

  1. CRT displays are pretty much the king of on/off contrast and give the best black levels, have great color reproduction, but lower ANSI contrast ratios [edited 2007-05-29]
  2. Plasmas offer almost the same (and often better) on/off contrast ratio performance as compared to CRT and can offer better ANSI contrast ratios.
  3. DLP is the best for digital front/rear projection displays
  4. LCoS (aka SXRD, DiLA) are very close to DLP
  5. LCD (both flat panels and front/rear projection) offers the poorest contrast ratios (especially on/off); however, they can be among the brightest flat panels and that makes them great for bright rooms where it is difficult to perceive contrast ratio.

Like always, there are some exceptions. Always look at a display yourself before you purchase it. LCD flat panels have great bang-for-the buck and look pretty good on a bright show-room floor. See if you can view and compare it in your normal viewing environment (a completely dark room, a very bright room) before you make your final decision. Plasmas have great black levels but are terrible for glare and reflection off the glass front screen; plasma + direct sunlight = unwatchable combination.

Written by in: Home Theater | Last updated on: 2007-January-04 |

21 Comments »

  • lbfh says:

    I have never liked a single LCD TV picture… Ever. It is the Emperor with No Clothes, in that when someone shows me their newest $4000+ prize, it is virtually impossible to say, “You have been suckered, your TV sucks.”

    Aside from projection, the 36″ tube is my favorite for viewing.

  • Carlton Bale says:

    From what I understand, the newest plasmas can meet or even exceed CRT contrast ratios. The models that Pioneer will release in mid-2007 are supposedly the best displays ever made; their current plasmas are awesome as is.  Here is a link: http://www.twice.com/article/CA6405089.html?nid=2402

  • curtis says:

    Carlton,

    Thanks for the site. Great info.

    The link you posted in the comment is just a Pioneer press release. It’s a good teaser, but so far just Pioneer’s word. We’ll need to wait for independent tests (like the ones you mentioned) to verify the claims.

    Good article, Carlton.

  • AlenK says:

    Great site, Carlton, and this blog entry a nice attempt to educate about contrast ratios. But, you shouldn’t dismiss on/off contrast ratio so easily. Both numbers are important. While people don’t watch all black or all white screens, the average picture level for a lot of video content is fairly low (some movies more so than others). For that kind of material, poor on/off is immediately obvious (assuming a low ambient level in the environment). Poor ANSI generally has less of a negative affect. And these two figures of merit are nearly independent – it is easily possible to achieve a good number for one and a poor number for the other (either way).

    Second, CRT projectors are the “kings” of on/off contrast ratio, not ANSI. Their ANSI ratios are actually relatively poor, although rarely were the numbers ever published. A model with air-coupled lenses would be typically 50:1, a liquid-coupled model maybe as high as 200:1. In comparison, ANSI contrast for a well-designed DLP projector (for instance) is typically over 400:1. Yet there is no question that CRT projectors, even air-coupled ones, produce subjectively “punchy” pictures with good contrast.

    Please take my comments as constructive criticism, based on over 20 years as a display engineer designing projectors (starting with those antiquated CRT models!).

  • Murdo says:

    Good point, AlenK, about on/off contrast. Many movies have low-light scenes.

    Carlton said CRT/Plasma has the best contrast for displays, DLP for projection. Do you disagree?

    I’m curious why CRT projection has poor ANSI contrast compared to DLP. If it is due to the lens system, how is the DPL lens system able to do better?

  • AlenK says:

    CRTs, whether direct view or projection, still have among the highest on/off contrast ratios, but Plasma (see Pioneer announcement at CES) and even direct-view LCD (see Sharp 1,000,000:1 on/off CR prototype) are catching up. Among non-CRT projection displays, JVC’s current 1080p HD-DILA front-projection models currently hold top spot: 15,000:1 on/off without dynamic control. But TI demo’d a 100,000:1 rear-projection display (presumably with dynamic control) at CES, so the game of leap-frog and specmanship continues.

    Projection CRT has low ANSI CR, even with liquid coupling, because of this: The CRT phosphor emits light in an essentially lambertian pattern (i.e., diffusely). Some light from a high brightness feature will thus reflect from wherever the refractive index changes (glass-to-air-to-glass = a lot of reflection, glass-to-liquid-to-glass = less but not zero reflection) at a severe angle and illuminate some other part of the phosphor.

    In the case of a micro-display, be it based on DLP, LCD or LCoS, light from the lamp is focused onto the panel, arriving from a far more limited cone of angles. The light which transmits through or is reflected off is thus much more efficiently captured by the lens – not as much of it is bouncing off at odd angles. There is still some, and there are still reflections within the lens itself because of all the glass-to-different-glass and air-to-glass interfaces, so it’s not perfect. But it can be much, much better. (Note that anti-reflection coatings are typically used in both cases.)

  • Carlton Bale says:

    AlenK: Thanks for your great comments. I updated the original post to correct/clarify some of the mistakes you noted.

  • AlenK says:

    One other thing: You say “I’ve never seen a review of a calibrated display meet or exceed the manufacturer published contrast ratios.”

    Here’s at least one: Greg Rogers’ review of JVC’s DLA-RS1U in Widescreen Review, Issue 120, May 2007. I quote: “In the Normal lamp power mode, the RS1 produced 595 lumens, which is equivalent to 27.2 fL (foot-Lamberts) from my 1.3 gain screen, with an extraordinary 16,400:1 full-field (on-off) contrast ratio.” JVC’s spec is 15,000:1.

    There have been other displays reviewed in WSR by Greg Rogers that meet or exceed their published CR’s. Greg knows how to calibrate and measure displays properly and he’s no stooge for the manufacturers.

  • Andy says:

    Pretty good information in general….. but:

    ….If there is 1 lux of ambient light in the room (i.e. a small candle), the max perceivable contrast ratio is 500:1. A dimly lighted room with 30 lux of lighting would squash the maximum perceivable contrast ratio to 50:1 [2]. Unless you have a completely dark room covered in black velvet, you’ll never be able to perceive the high on/off contrast ratios claimed by manufacturers — those numbers are meaningless otherwise….

    That may be true if the otherwise black area of the TV reflected 100% of this ambient light source (which it obviously does not) thus the contrast does not deteriorate NEARLY as fast as the above quote would have you believe.

    To put that in perspective, pretend you have a white surface / screen and are using a projector mounted behind you.

    In a dark room, the contrast is going to be pretty average, like you would expect from a movie theater.

    add ambient light (a candle or otherwise) and the contrast will suffer fast, just as mentioned above in the quote.

    HOWEVER

    Nearly every screen in existence will filter or absorb / re-direct that light, thus maintaining a good percentage of the original ratio.

    Think about it… 30lux leaves you only a 50:1 ratio??? Typical room lighting could provide over 1000lux…. do you honestly think in that condition your only getting about 2:1 contrast ratio? common with a front projector maybe!

  • Carlton Bale says:

    Andy: Very good point; those contrast ratio numbers are for front projection (white screens) which much higher ambient light reflection. The black screen of a flat panel would be impacted much less. I’m not sure what the equation is to calculate the exact impact, but it would be interesting to compare the difference. I’ve updated the post to reflect this info.

  • jdub says:

    So after all the extensive research you have all conducted on the HDTV’s, for Joe Consumer; which is the best CRT, LCD, Plasma tv’s “currently” on the market. In other words, if you were going out to your local electronic store, no special order items, which tv’s would you buy today?

  • Phillyblunz says:

    I think that the samsung dlp’s with the led engine is a great option. And apparenty getting better and better. I have read a few bad reviews and dont get where they are comming from. I bought a hlt-6189sx in late 2007, most of the bad reviews where from earlier in the year so maybe those issues were fixed? All I know is my one buddy has the jvc dila 61″ close to same specs(10,000:1, 1080p, etc) but my led engine is so much brighter and the colors are extremely vivid and accurate in comparision. with DLP you get the fastest response times, longest life before deterioration, low power, sharpest picture and absolutely no visible picture structure. (the LED’s are icing on the cake)

  • Jackie Jay says:

    This is all fine and very educational. However I am now more confused than ever as there are NO t.v.’s that offer all of the “good stuf” within one unit. Gentlemen what is the bottom line?

    • Carlton Bale says:

      It is absolutely true that there is no perfect TV. The bottom line it to consider your viewing environment and trust your eyes. Most people want a thin flat panel TV, so that means LCD or Plasma. If your room is extremely bright with lots of windows, a matte finish screen on an LCD is probably your best option; a LCD with a LED backlight instead of the traditional florescent backlight is best if you’re willing to pay the extra price. If your room is fairly dark with few windows, plasma will provide a stunning picture with deep blacks, very fast refresh rates, but slightly less brightness overall. Understand your criteria and then go look at some models. Don’t be afraid to turn them off so you can more easily detect screen glare.

  • Charles Gatchell says:

    I have a Sharp projector that is Native 1024 by 768. It accepts 720P and 1080P HDMI Input. Would I see the difference if I purchased a 1080P Native projector? I am using a Blue- Ray Player 1080P feeding the projector. The Picture looks great. The Projector is 2500 lumens 2000:1 Contrast ratio.

  • Aldo Lammy says:

    I would like to ask about Dynamic Contrast Ratio. Manufacturer nowadays are more to show the DCR instead Contrast Ratio, since it claimed to be like millions compare to one DCR. I’m thinking of buying a computer external display, and I couldn’t find the CR shown in specs area, only a millions DCR. What should I look in the spec area? For example, the display I interested in has a 5.000.000 : 1 DCR, and a 250 cd/m2 brightness and a 5ms response LED backlight display. What can you tell from this? And after all, do you think the best decision to make is to look at the display itself?
    I have a Sony KLV-40W400A, with a 30000:1 DCR (VESA standard) and 3000:1 CR and 450 cd/m2 brightness with 8ms response LCD HDTV. How to read the different between them? Thank you

    • Carlton Bale says:

      You can tell pretty much nothing from a Dynamic Contrast Ratio spec. You either need to find a professional review of the display that tests it, compare it with your own eyes, or use something like a Sypder 3 to perform the test yourself.

  • Rob says:

    Dynamic contrast ratio is a technique used to increase the on/off contrast ratio of a backlit LCD screen. Basically it takes a look at the scene currently displayed, and if it’s generally a dark scene it reduces the brightness of the backlight to prevent the dark shadows from being washed out by light from the backlight leaking through. For brighter scenes then the backlight is brought up again. This is great for giving higher contrast ratio numbers, but if you ever watch a movie on a TV with DCR enabled it is incredibly distracting – when there are light and dark areas on the screen at the same time, you can actually *see* the backlight go up and down.

    Good write-up, by the way Carlton :)

  • [...] hace, es un excelente producto (al igual que los sinto-amplificadores que muestran potencia RMS). Según Carlton Bale una pantalla con un ratio ANSI de 250:1 es más que [...]

  • JGood4u says:

    Good discussion of this topic. I have worked with TV projectors going back to the 1960s when NASA used them in flight simulation. I traveled around America and Canada doing video presentations in large arenas and other venues. I have done engineering on TV projectors. As you have discussed, recently we have begun to see there are increasingly unrealistic contrast ratios, with virtually no meaning that I can understand. I would be interested in how these DCR measurements are actually made, if someone has experience with that.

    Typically, the contrast ratio is limited by the maximum brightness emanating to the viewer’s eyes divided by the minimum light from the same screen surface with black content or even switched off. A screen can’t get any blacker then when it is switch off, but even when it is off, it can reflect ambient light in the viewing room. So in your “real world living room” your screen will never get darker then it is when it is switched off with the ambient light you will typically use to view your screen. There have been a number of innovations to help screens reflect less ambient light beginning with black surrounding the phosphor dots on the CRTs. The best I have ever seen is the rear projection consoles with a flat lens/screen. In that case, the ambient light falling on the screen surface is conducted through to the inside black box and absorbed, rather then reflected and dispersed to the viewer.

    When considering the factors in the black contrast, you might consider the light from the screen image as it reflects off the surroundings in the room and back to the screen to illuminate it. If the viewing room has light colored walls, carpet, drapes, or furniture, then those will effectively reduce the screen contrast in all cases except the rear projection lens system. I designed a rear projection system in a church sanctuary using a special “screen” which was really a Fresnel lens on the inside surface and a lenticular lens on the front viewing surface. This has the feature to gather the projected light from the projector, columimate it as it passes through the screen and the lenticular structure disperses it into the seating/viewing area. This sanctuary not only has white walls, but a cove along the back with florescent lamps washing the wall in light! Only glass windows and outside light could have been worse. However, even with the wall-wash light on, the video image is very viewable from the seating area, including the main floor and the balcony. Because of this ‘expensive’ lens/screen system, super bright projectors were not required and the less expensive projectors in the 2000 lumen range have worked very well on this 8 ft x 6 ft projection screen.

    Front projection screens also present variables in how they effect contrast ratio. Screen gain is an important factor in directing the projector’s light back to the viewer’s position. You might think at first, that you should select the highest gain available, but not so. Gain comes at the expense of viewing angle, and if the gain is high, the project needs to be placed very close to the viewer’s head position to get the maximum reflected light back to the viewer’s eyes. Still, this may produce a bright spot near the center and dimmer towards the outsides of the screen. If you don’t get the light from the projector to the viewer, you’ll loose contrast ratio as well.

    Some of you have asked “what’s the bottom line in selecting a TV.” The reasons this is not so simple are that there are various factors and values that go into such a decision:
    * how much can you afford,
    * how is your room decorated,
    * what time of day will you do your critical watching,
    * how much outside light can you control,
    * what kind of program material do you watch,
    * do you care about how efficient your system is,
    * how much resolution do you require,
    * how big of viewing area do you wish to have,
    * and how good are your eyes and mind at discerning these values???

    Our eyes are very adaptive, especially when it comes to color and brightness, as well as other factors. We don’t do well at seeing something, like a TV in one viewing environment, and comparing it to another.
    What you see in a store may be very different in your living room in the daylight.

    Recently, I bought one of those DCR LED/LCD 26″ for my kitchen. The sharpness is very good, but I get very annoyed by the dynamic “breathing” of the brightness as the backlight changes during a program. Charley Rose, an interview format with a completely black set except for a table, is very noticeable as the camera is switch from close up to wide shots. I wish I could disable that feature on this set.

    Most of what you buy a TV to view is entrainment, and you will very likely be well entertained as long as you can see the subject matter reasonable well. Control and select those factors you can at reasonable cost, and sit back and enjoy the program!

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