Spears & Munsil Calibration Advice - Page 5

I guess thats why I am here. Using the disc for calibration my contrast comes out high 30s low 40s, but everyone else over in the GT25 thread seems to be using a higher contrast. I've seen ranges from 41 all the way up to 66. Using the contrast pattern on the Spears disc you can clearly see clipping of whites with anything over 42. Also the clipping pattern with red, blue, green and white shows clipping of those colors. Not saying one is right one if wrong but honestly I am struggling to find a setting that seems correct for most of my viewing which is sports, tv shows etc. I'm definitely a novice at all this thats for sure.

Also question for Stacey, any patterns on Spears and Munsi that I could use in conjuction with the WB controls in the user menu ?

If it clips, it's wrong. If clipping cannot be eliminated, set contrast for proper light output and live with it. What else you gonna do?

True

Those are pretty much your choices.

Back in the day there were ~30" BVMs. The standard said to set contrast until you hit 30fl. These displays would go into blooming around 23fl. Some post houses would set to 30 because the standard said so while others would set to the point below clipping so they would have all of the detail.

Contrast control on a digital display is really more about getting the full dynamic range. An LCD has a backlight that can let you control the overal light output independent of setting contrast to get the full dynamic range.

I get around 2-3fl in 3D mode, which is really dim.

My primary display is set to 15fl, but is is a projector. Again, I set contrast to get the full dynamic range, and then the manual IRIS to hit 15fl. As the bulb dims, I open the IRIS.

We spend most of our time talking about movies. If you play video games, then the clipping is even more of a problem since games are 0-255. Games have a lot more pixels above 235 than movies do.

At the end of the day, set contrast as high as you can so that you are happy with the light output on your plasma since you don't have a backlight or an IRIS. Clipping RGB is worse than clipping white. The reason is because those RGB squares are all within 16-235 in YCbCr. (Way it is stored on the disc) The white goes above 235 in YCbCr. The RGB squares are closer to what you will find in real content, usually in specular highlights.

Stacey thanks for all the info

So for movies (in YCbCr), avoid clipping RGB between 16-235 and avoid clipping white up to 255?

In Y'CbCr, it is Y 16-235 and CbCr 16-240. These values can produce RGB that go up to 255. The RGB squares are 16-235/240 in YCbCr but are 16-255 once converted to RGB.

My head is spinning in both directions

Disk work on a PC with bluray drive how come?

Not sure I understand. Are you asking if it will work on a PC or are you saying it does?

As long as you have Blu-ray software, the disc should work like any other Blu-ray. PCs have all kinds of problems getting video right. From PC vs. Video levels to software players scaling the image even at native resolution.

Just got the disc and a quick question, it seems I am able to the contrast screen right, but when switched back to the Low Plunge screen the brightness is off, can't seem to get one to agree with the other so to speak, is that possible ?

Sometime they interact and you have to make adjustments back and forth between brightness and contrast to get it right.

Brightness and contrast interace as do color and tint. I takes a few back and fourths with the Panasonic plasma I have to get them to right. After a grayscale calibration, you need to tweak them a bit more.

There is a simple way to expand the dynamic range of the image beyond the limitations of the display device itself. The most recent entertainment system setup/calibration discs neglect sufficient discussion of human perceptual issues and viewing environment principles. Display calibration should always be understood to include the entire video system. Display system calibration must address viewing conditions and the limitations of the human visual system. These are fundamentals in any balanced understanding of video imaging. The consequences of neglecting such considerations are unavoidable, while the benefits of incorporating these principles into the design and use of video systems are assured.

Two techniques will expand the perception of dynamic range in a video system. Firstly, lower the brightness of room lighting. Dark-adapted vision will require less peak brightness from the display. A lesser light output from the display will be perceived as brighter by the viewer in a darkened room. Secondly, provide correctly implemented bias lighting behind the screen with a darkened room. This will make the dark portions of the image appear darker but not affect the bright areas.

"Contrast could be considered to be the most significant quality that impacts not only the perceived depth of an image, but also affects the apparent sharpness.....While the luminance level of a given image affects how the eye perceives contrast and detail, the ambient conditions surrounding the image can also have a dramatic impact. This phenomena was studied by Bartleson and Breneman (1967) to examine the impact of perceived contrast based not only on the luminance level of the image but taking into account the surrounding ambient luminance levels as well. Their results showed that the perceived contrast increased as ambient luminance increased. With the increase in ambient luminance, the eye interprets black levels as being darker while the impact to the white level is minimal. Since the perceived difference in dark areas is greater under the higher ambient luminance conditions, the perceived contrast is higher. It is a natural tendency to want low ambient luminance levels to strive for "better" perceived image quality and what is thought to result in higher contrast. However, in reality, the opposite is true. This tendency may be justified for current direct view CRT televisions due to the issue of glare that results from the glossy surface of the glass tube [also true for certain flat panel displays today]. With less ambient luminance, the glare is reduced- but it may be important to keep some ambient luminance behind the television [as in the case of bias lighting] to keep the perceived contrast higher.....While sharpness can affect the apparent contrast of an image, the converse is true in that contrast can also impact the apparent sharpness of an image. Images that have lower contrast will appear to be not as sharp as an image of the same content, but with higher contrast.....A subjective study was then conducted to verify the impact that ambient lighting has on perceived contrast. Several non-technical (and thus presumably non-biased) and technical observers were asked to compare a series of images with various ALL [average luminance levels] under different ambient luminance extremes in order to understand the impact that ambient viewing conditions might have on the perceived contrast between the two television technologies [CRT and DMD (DLP RPTV)]. Under dark ambient conditions, the result for images with an ALL > 5% was found to be equal between the CRT and the first DMD display. However, under bright ambient conditions (about 250 nits of luminance on the wall behind all of the units), the DMD display was favored over the CRT by 50% of the observers as having higher perceived contrast.....This proved that ambient conditions have the effect of potentially raising the black level threshold of the eye above the actual black level of the television such that the perceived contrast ratio is higher." from the SMPTE Journal, 11/02. 'The Importance of Contrast and its Effect on Image Quality' by Segler, Pettitt and Kessel

"Their experimental results, obtained through matching and scaling experiments, showed that the perceived contrast of images increased when the image surround was changed from dark to dim to light. This effect occurs because the dark surround of an image causes dark areas to appear lighter while having little effect on light areas (white areas still appear white despite changes in surround). Thus since there is more of a perceived change in the dark areas of an image than in the light areas, there is a resultant change in perceived contrast.....Often, when working at a computer workstation, users turn off the room lights in order to make the CRT display appear of higher contrast. This produces a darker surround that should perceptually lower the contrast of the display. The predictions of Bartleson and Breneman are counter to everyday experience in this situation. The reason for this is that the room lights are usually introducing a significant amount of reflection off the face of the monitor and thus reducing the physical contrast of the displayed images. If the surround of the display can be illuminated without introducing reflection off the face of the display (e.g., by placing a light source behind the monitor that illuminates the surrounding area), the perceived contrast of the display will actually be higher than when it is viewed in a completely darkened room." from 'Color Appearance Models,' by Mark D. Fairchild, Ph.D., of the Chester F. Carlson Center for Imaging Science: Munsell Color Science Laboratory

These techniques are used commonly by video program mastering technicians and colorists. Emulating professional best practices in home systems always yields better image fidelity and picture quality for the viewer.

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.
A Lion AV Consultants affiliate

"Advancing the art and science of electronic imaging"

I employ bias lighting and I use the Spears and Munsil calibration disc.

How do I properly calibrate using the Spears and Munsil calibration disc since there is no bias light level test pattern on the disc?

A 30% digital level window pattern can substitute for the 10% (SMPTE recommended) ambient light level patterns found on the 'Digital Video Essentials' series or 'Avia' series test discs. Set contrast, brightness and gamma for dark room viewing conditions, then display the ambient light level pattern, then adjust the bias lighting to compare by eye between the display screen and the level of illumination reflected by the wall behind the display. Double check black level with a pluge pattern after adjusting the bias light.

Thank you for your help.

I looked and I haven't been able to find a "30% digital level window pattern" on the Spears and Munsil disc yet.

If there's not one, should I search for one online, burn it to a DVD and use that (although it won't be in high definition - but, if it's just a solid white screen, I guess it won't matter)?

You can use the free download of the AVS HD709 program: http://www.avsforum.com/avs-vb/showthread.php?t=948496 . Also, I strongly recommend 'Digital Video Essentials: HD Basics,' available for a very small investment. It contains unique and worthwhile information not included with the 'Spears & Munsil HD Benchmark' program. I own both programs and recommend any serious student of video quality to do the same.

Thank you so much for that information.

Is there a notable difference between a bias light calibrated using a 10% display on the screen and a 30% display?

The 30% digital signal level displayed on the screen is closer to emitting 10% of peak white light output visually, due to the gamma curve used for video.

Perfect.

Logical advice and information as always. Thank you.

This disc just got delivered today and I'm planning on going through the calibration this weekend. I'll be using a PS3 for blur-ray player through Onkyo TX-NR808, and finally into a Panasonic G15 plasma, all via HDMI.

I've heard that tweaking in Panasonic's THX mode is best, so this is the mode I'll be using. I'm wondering if there are any video or other PS3 settings I should have enabled/disabled on the PS3? What about the other devices in my setup?

This is the info that is apparently correct as it was given to me by more than one person whom I trust to know what they are doing.
PS3
Video Settings

BD Internet: "Allow"
BD/DVD Cinema Conversion: "Automatic"
BD/DVD Upscaler: "Normal"
BD/DVD Video Output Format (HDMI): "Y Pb/Cb Pr/Cr" for TVs, "RGB" for PC Monitors
BD 1080p 24Hz Output: "Automatic"
BD/DVD Dynamic Range Control: "Off"
BD/DVD Audio Output Format (HDMI): "Linear PCM"
BD/DVD Audio Output Format (Optical Digital): "Bitstream"

Display Settings

RGB Full Range (HDMI): "Limited"
Y Pb/Cb Pr/Cr Super-White (HDMI): "On"

Sound Settings

Audio Output: Varies/Automatic

Thanks, this is essentially the information that I was looking for.

I'm not sitting in front of the PS3 right now to view all of the possible settings, but I believe I remember having the ability to set options for Noise Reduction. Any idea about this?

Also, can anyone either confirm or refute THX mode as the best way to go?

THX locks out some settings. But, THX is a fine mode to use.

But is it ideal? More specifically, does THX mode introduce any pros/cons during calibration vs another picture mode such as "Custom"?

Obviously, if the settings needed to make adjustments are locked, I suppose I would need to change into custom, but perhaps there are other internal/unchangeable settings in THX mode that would result in a more accurate display?

eh hi been reading your post and wanted sspears please if you could give me an orientation to the configuration of the bluray player and VT20 BDT300 I read that you have it , these are my questions based on your test drive with spears and Munsil (unfortunately I have not).

tests based on your output should be in 4:4:4? or 4:2:2?

must be on the deep color in the blu-ray???

the button to display BDT300 when watching a movie is a configuration image which appears as follows:

- Chroma process: advanced
- Detail clarity: OFF
- Super resolution: 1

this should go on like this? so leave the factory default, which should make changes in that part?

VT20 in my image in a and a configuration option called: HDMI / DVI RGB range and have these 3 options:

-Auto
-Standard (16-235)
-Nonstandard

which should be in for watching bluray via HDMI?

these would be my questions, however if at any post configuration d is its image for the VT20 in THX would appreciate a lot.

sspears greetings and thanks in advance

4:2:2 into VT20 works best. If you look at the Chroma Alignment pattern you will see half a pixel shift when sending in 4:4:4.

Chroma Process - Off
Detail Clarity - Off
Super Resolution - 0 or off (dont recall what the choice is)

Leave the VT20 in auto.

Any further word on the 3D disc?

Way off topic question, but in the race car test section, is that a clip from Super Speedway?