Technical Articles and Editorials
- Written by Chris Heinonen
- Published on 08 May 2013
Introduction to the Spears and Munsil HD Benchmark Setup and Test Disc - Version 2
Readers of Secrets of Home Theater and High Fidelity are likely familiar with the names Stacey Spears and Don Munsil. They authored the Secrets DVD Benchmark and brought to light issues like Chroma Upsampling Errors, as well as our recent HDMI Benchmark for Blu-ray players. They also authored the Spears and Munsil HD Benchmark Blu-ray, which was included with the Oppo Blu-ray players and so many people have a copy. Now they have gone back and released the 2nd Edition of the HD Benchmark, with far more tests and features. They sent along a finished disc so I could do an overview of it and how you can utilize the new features.
Be sure to check out the video interview with Stacey and Don, hosted by Scott Wilkinson on TWiT TV.
For The Beginner
If you're new to the idea of calibration, or of optimizing a display, what does the Spears and Munsil disc offer you? The first two sections of the disc, Video Calibration and Audio Calibration, are designed to help you get the most out of your system with almost nothing extra required. By following the on-screen guides, or using the articles they have published on their website here, you can go through and properly set the Brightness, Contrast, Color, Tint, and Sharpness controls. Many of these patterns have 3D versions included, so you can calibrate a display for both 2D and 3D viewing.
Some of these use the included blue filter, though many displays have a Blue-only mode that makes them even easier to do. There is also a Color Space tool that helps you select the proper color space from a Blu-ray player, which people typically don't know.
Once these are set, there is a section called Equal Energy Gamma that helps you to correctly set the gamma of your display for midtones. Gamma is an area where people often disagree about what is correct, but a decent rule of thumb could be considered 2.2 for a normal room, and 2.2-2.4 for a darker, dedicated home theater room. If your display has a gamma control, the only way to get it perfect is using more advanced hardware, but this test pattern will let you choose the preset that gets the mid-tones closest to your gamma target.
This version of Spears and Munsil also includes audio test tones. I know most people have receivers now that have some sort of automated setup, but those should always be double-checked because the reliability of them isn't always great. I've also found that Audyssey gets confused if a speaker is in phase or out of phase, and test tones to verify that are included as well. Ideally you will have an SPL meter to do this section correctly, but there are SPL tools available now for smartphones that likely are as reliable as the small measurement microphones that Audyssey and others include with their systems. You can also verify if there is any audio delay in your system, and adjust it easily in your processor or receiver to eliminate that common issue.
Once you've gone through all of these screens, which might take you 60-90 minutes, your system will likely be better configured than it was before, and you can get more performance and enjoyment out of it than before.
For The Expert
If you are familiar with these controls on your display, or you already have the first Spears & Munsil disc, there are still many more features included on this disc that are very useful. First on that list for me are the new Equal Energy windows for doing measurements for calibration. Typical measurements for calibration are done using windows or fields of the specific color you are looking to measure. For most display types, this works fine, but for plasmas in particular, they are not ideals.
All plasma displays have an automatic brightness limiter (ABL from here on) that regulates the amount of light output from the screen. With small windows, even a 100% white pattern may not cause it to kick in, but with full fields, it will certainly kick in. Because all displays work differently, and the ABL is different on all of them, you can calibrate using windows but get a different result because of how the ABL works.
One solution to this is to use equal energy patterns, where the light output is the same no matter which pattern is up. Most films have an average picture level of around 30-40% for brightness, so a 100% white field almost never comes into play. Using patterns that more closely mimic that level of output can help to more accurately reflect how the ABL works, and give you better real-world performance, even if test charts look identical to windows. Spears & Munsil has a new set of equal energy patterns that can be used for this, and have been designed to be more accurate than any others out there. Not everyone finds that equal energy patterns produce a better result, but for those with a plasma, it is a good approach to try and see how they work compared to windows.
Another important setting to check is the video-processing mode on your Blu-ray player and display. On Blu-ray movies, we now get the film in 24p format instead of 60i, so 3:2 pull-down isn't as essential as it once was. However, we still get a lot of 60i content for concerts and some TV shows, and movies on TV are 60i so 3:2 pull-down on your display need to work correctly to get the full resolution there. Using the 2:2 and 3:2 test patterns, you can determine if your devices should remain in the Auto mode that most ship in, or if you should choose one of the other modes that they offer to get better performance. In testing these devices, we've often found the default mode to be incorrect, but most people that buy them never know this, and endure worse performance because of it.
For The Reviewer
As a reviewer, I want different things that most users do. Most test discs are only structured for the end user, and getting some of those initial settings correct, and not for the reviewer or someone trying to seriously evaluate a product. Thankfully Spears & Munsil come from a background of evaluating a product to determine its performance, not just to get it setup correctly, and there are a ton of features in there to help me in my job, and help you find out what all a product can do.
One request I made to Stacey Spears was to include this uniformity test pattern, which is found in EBU Tech 3325. Using 13 squares located all around the screen, I can determine if the light output of a display or projector is uniform everywhere, or if it's too concentrated in the center. Usually people just measure the center of the screen, but in projectors, the cheaper the lens the less uniform the light output will be across the screen. Expensive lenses take expensive glass and most people don't realize the cost of getting a better lens on a projector, but this helps to measure this and show it to the reader.
Similarly, with 3D reviews we have been forced to rely on describing material that we have seen and hoping those artifacts that we see are caused by the display and not from the material itself. Now we can use these 3D test patterns to determine the amount of crosstalk in a 3D display and be certain it is from the display and not the source, and more easily use this number to compare different devices. We still watch 3D content, of course, but this is bringing an objective measurement to our subjective opinions.
One under-measured feature of displays is how well they handle motion. LCD and Plasma displays might both be 1080p, but that is with a still image. Start to have objects that move and LCDs will quickly start to smear details, while plasmas will remain sharper. With OLED and other technologies coming out, this will become more important for people to test to see the distinction in those.
I can also use these tests to evaluate the motion interpolation that many sets offer. Often you'll start to see sharper details when it's enabled, but also see artifacts that appear at the same time. Being able to partially quantify the benefit they offer but also see the drawbacks helps us to communicate how these perform to our readers. These patterns let us begin to assign numbers to a topic like motion, and let you easily see the difference with different settings enabled.
There are also a number of useful color ramps in Spears & Munsil that don't really let you calibrate off them or fix anything, but show the errors in the color handing of your display. For example, I can find that my display does blue perfectly, but red and green have slight bits of banding introduced into them. It isn't possible to correct this, at least without expensive outside video processors possibly, but it lets me better evaluate a display and decide how well it works, and if I should recommend it to readers or not.
Another problematic area for me as a review is evaluating scaling on a display device or Blu-ray player. I can go back to DVD transfers that I thought were incredible back then, like The Incredibles, but then I enter a realm of being purely subjective, and possibly not always looking at the exact same frame as before. On Spears & Munsil there is now a scaling test image, available at 480, 720, and 1080 resolutions, which has definite criteria to meet. Certain parts of the image should scale a certain way, and other objects in the image are designed to cause ringing, moiré, and other artifacts in poorly designed scalers. It still is a bit subjective, without a number we can assign to it, but it does have certain features that let us assign a passing or failing grade to a device we are testing.
Spears & Munsil HD Benchmark, Version 2 is the most complete setup and evaluation disc out there today that I have seen. There are many discs that can help you setup your display or audio system, but no others that allow you to so thoroughly analyze all aspects of its performance. For the beginner or expert, or the reviewer that wants to know all the limitations of a product, Spears & Munsil is a disc that deserves a place on your shelf. I have used the original now since it was originally released for every single Blu-ray player and display that I've tested, and I plan to use the new version even more. The new disc is $30 and available now directly from OPPO, and is highly recommended for anyone who is interested in getting the highest performance from their system.