Calibration and Adjustment

Before making any brightness level or color correction adjustments to your videos using filters included with Vegas Video, it is important to first calibrate any external monitor you are using to view adjustments, plus any televisions your videos will be played off of. While the best method is to use a color bar generator and other expensive equipment, that method is beyond the reach of most hobbyists. So the following information is presented to assist you on how to proceed manually adjusting your television's white and black levels, test sharpness and adjust color intensity and hue. While somewhat technical, do not skip over this tutorial if you wish to make the best possible adjustments to your videos. Vegas Video comes with several test patterns including SMPTE Color Bars. This tutorial includes some other test patterns including the EIA #1956 sharpness test pattern.

How To Best Take Advantage of the Preview window

Normally the preview window is displayed in the lower right corner. By clicking on the thin gray vertical line to the left of the preview window while holding down your left mouse button the preview window becomes undocked and can be dragged elsewhere and also resized. If you have a two monitor setup the preview window can be dragged to the second monitor. This is not the preferred method for video editing when working with FX filters adjusting levels and colors. The best method is to display the preview window on a external NTSC monitor (in the U. S.) or if you're on a budget, any small TV that has video-in capability. This allows you to see in real time* how your video will play off a television which is important for brightness levels and color adjustments. To have the preview display off an external monitor you'll need either a digital camera with a firewire (IEEE 1394) connector or a device that takes the place of the camera. Vegas Video online help and the full manual gives specifics for setting up an external monitor.

*Real time previewing on any external monitor is influenced by the power of your CPU, how many tracks you have set up, and by the type and duration of transitions, overlays and other more complex features. Some jerkiness and hesitation in the preview window is normal with the frame rate dropping substantially at times. Faster playback can be achieved by changing the playback quality to preview. This has no effect on the rendered quality of your finished video.

Many things effect how we perceive color. This series of tutorials isn't about the finer points of color theory, many books have been written to cover that topic. As you probably know, no two people see colors the same way. Nothing we can do about that, but we can have some basis to begin at before we start making adjustments to our videos. Several things effect how colors are displayed on television sets and computer monitors. The first thing you should be aware of is televisions and computer monitors display colors differently. Depending on where you live there are two main standards. In the United States there is the NTSC standard, most everywhere else they use the PAL standard. The picture tube phosphors for the NTSC world is STMPTE-C, while in the PAL universe the phosphors are EBU. You should also keep in mind that all televisions and computer monitors display darker and darker pictures as they age. While the changes are very gradual, if you do a lot of video work you may want to consider replacing your external monitor every couple years or so, especially if you can no longer achieve proper white balance explained below.

This and the next several paragraphs revolve around a simple yet very important question; how white is white, how black is black? If you're hardware isn't set to show whites and blacks properly without any distortion or unwanted shading, any attempt to make accurate color corrections to your videos is nearly impossible which is why proper calibration is so important.

Everyone knows when you take photographs or shoot video outdoors, colors look 'different' then they do indoors under artificial lighting, noticeably so in skin tones for example. Under certain lighting conditions colors look more bluish (cooler) or yellowish and warmer. You knew all that. What you may not have known is in an effort to make television pictures brighter, many television sets straight from the factory have a white point of 9300K (Kelvin) or higher while the broadcast standard is only 6500K. Your computer monitor may have yet another color temperature setting, a good reason why you don't want to adjust your video colors and brightness levels by looking directly at your computer monitor, because in part the default color temperature probably isn't 6500K, so if it isn't it will cause all your video colors to be distorted if you adjust off your computer monitor which is why you're much better off using an external monitor to make such adjustments, but only after said monitor is properly calibrated which this tutorial is all about.

Be aware that grabbing just any old color bar chart from the hundreds of web sites that offer them can get you in trouble. Even if they say they are SMPTE NTSC or SMPTE PAL, many are inaccurate. Vegas Video includes several color bar and other test images calibrated to be used with their DV codec. Their NTSC version is the second chart below.

This Color Bar has 100% saturation. It was offered on a web site as a SMPTE color bar chart. It is shown here along with an actual SMPTE color bar chart below so you can see the differences in the saturation of the colors. Do not use this chart to calibrate your TV!

Channel
Gray
Yellow
Cyan
Green
Magen
Red
Blue
Red
127
255
000
000
255
255
000
Green
127
255
255
255
000
000
000
Blue
127
000
255
000
255
000
255

 

This Color Bar is the Vegas Video SMPTE version for NTSC. To meet SMPTE standards (Society of Motion Picture and Television Engineers) the color bars are set at 75% saturation and reflect the following values shown in the table below. The letters and numbers on the chart won't show on your file copy and are for reference purposes in the adjustment steps that follow. Why not use the brighter bars? Chrominance amplitudes with 100% bars can cause distortions and they violate NTSC transmission standards.

Channel
Gray
Yellow
Cyan
Green
Magen
Red
Blue
Red
180
180
016
016
180
180
016
Green
180
180
180
180
016
016
180
Blue
180
016
180
016
180
016
180

Step #1 Setting White Level

Before making this adjustment or any that follow, check the room environment changing the ambient lighting to what you normally have for television viewing. Do not begin until your TV has warmed up for at least twenty minutes to allow components to stabilize. Do not have a freeze frame on the television while waiting for the set to warm up or you may risk burning in the image. This adjustment uses your television's contrast or picture control. Too low a setting results in a dim picture. Too high a setting distorts image with a loss of detail. Many people have this control set too high out of habit or to compensate for viewing television in a overly bright room.

The image at the left is comprised of two rectangles, the outer is absolute black, RGB value 0,0,0, the inner is set to SMPTE white, 235,235,235. You can also use Vegas Video's test patterns; White Porches, Pluge and Porches and Ramp. which are under the Text/Backgrounds tab under test patterns for this adjustment and the one that follows.

If your TV is relatively new this adjustment is simple to make. As your TV ages it gets more difficult because you'll need to increase the brightness which tends to distort the picture tube beams preventing them from staying in sharp focus. Your goal in this step is to use your TV's contrast or picture control to get the inner rectangle as white as possible while keeping the outer rectangle pure black. You want BLACK. Not a shade of gray. Avoid introducing any distortion or blooming which can happen if you set the contrast or picture control too high. What you want to avoid is seeing any vertical dirty white bar beginning to appear at the edges where the white inner rectangle meets the black nor do you want to see any out of square distortions. If you see any glowing or halos around the inner rectangle or some bleeding of the white into the black outer rectangle, then the contrast/picture adjustment control is set too high and you should reduce it until it the distortion disappears.

Step #2 Setting Black Level

This is a close-up of the lower right corner of the three vertical bars shown in the SMPTE NTSC color chart with the labels -4,0,+4. It it often called PLUGE, an acronym for Picture Line-Up Generating Equipment. If you look closely you'll see there are actually three distinct bars. They are used to properly set black level more commonly called the brightness control, a confusing name for this control considering the black level should not be adjusted to effect overall light output, what many people wrongly use it for. Rather its purpose is to set proper black level. Setting the black level too high results in a washed out image, setting too low results in a loss of detail.

When black level is set correctly you should not see any difference between the first two blocks labeled ,-4 and 0 on the SMPTE chart above with them both appearing to be the same shade of black. Only the rightmost block labeled +4, should appear just slightly lighter in shade than the other two blocks, just being barely visible. You can also use the test pattern labeled Pluge and Porches.

This is a gray chip chart. Once you set white and black points in the previous two steps look for any color cast. Next look very closely at the horizontal bar than runs across the middle of the chart. You should be able to see six 5% gray (very dark) "zebra stripes". Readjust brightness very slightly (if needed) until the stripes just disappear, then adjust again in the opposite direction until they just reappear. Alternate with tweaking white and black point settings very slightly using the other test patterns. This is as close as you probably can get to proper white and black levels without using expensive test equipment.

 

 

Note: If your television previously had improperly set white and black points you'll need to resist restoring them to what they were. After a few days, maybe up to a week your eyes should be get use to viewing at correct settings. If you can't achieve proper white and black points without distorting the picture, you may need to have your TV serviced. A common problem is improper convergence which prevents the red, green and blue electron beams in the picture tube illuminating the TV screen's phosphors correctly. A symptom your picture tube is showing its age or is badly out of convergence or something is amiss in some of its circuitry is bluish whites, greenish grays and reddish blacks that can't be removed.

Step #3 Adjusting Sharpness

After making the white and black level adjustments use this test pattern or a similar one to adjust sharpness. This control is sometimes labeled peaking, focus or detail. Many people think the higher the setting, the sharper the picture. Wrong! For most televisions the control more likely will be between a third of the way and a little past half way to maximum. If you set it higher you'll introduce video noise, distortion and shadowing resulting in a picture that is actually more blurry. Set too low you'll lose detail. To make doing this adjustment easier, first reduce color saturation to minimum settings. Most modern televisions display a value on screen. Record the value so you can restore it later.

Adjust sharpness by placing the control near its minimum settings to begin with. Note the pattern of wedges, three patterns of lines each at the top, bottom, left and right coming out from the smaller inner square at the center of the test pattern. Adjust sharpness to obtain the best overall image while looking at the entire test pattern and the most sharpness, separation and equal brightness of the wedges. As you begin to increase the sharpness control, likely at some point it will begin to distort the lines in the wedges and in the squares containing alternating thin white and black bars towards the ends of the chart in the medium gray area. Set too high the black lines in the wedges will begin to develop white outlines or shadows. Set too low the dark lines will become more blurry. The correct point is where neither effect is overpowering. Do not except to be able to clearly see the numbers or separation between the bars on your television as well as you do off the fairly high resolution image included on the web site.

Like changing white and black points, it may take up to a week or so for your eyes to readjust to the change. Once your eyes adjust, you should begin to see more subtle details especially in shadow regions.

Step #4 Adjusting Color Intensity

Now that you have adjusted white and black levels and sharpness you can proceed to setting color balance. If you skipped over the first three adjustments. Stop. Do not make the following adjustments without first setting proper white and black levels or adjusting sharpness! Restore the color intensity control to its previous setting as mentioned in the previous step.

The best way to adjust colors is to remove all traces of Red and Green generated by your TV by shutting off those two guns located in the neck of the picture tube if you have a CRT type television. Some more expensive televisions and most all true NTSC monitors have a blue switch either located at the front or back of the monitor that allows you to do this. Newer plasma type televisions and LED monitors obviously don't have CRT guns due to the design.

Most regular consumer grade televisions don't have a blue switch. Therefore you need an alternative method to adjust color intensity and hue. The best is to view the screen through a blue filter so you can properly adjust using the SMPTE color bars. If you television has a tint control that allows fine tuning of skin tones disable it. Larger photo supply stores should have the required blue filter or one can be obtained from various web sources. What you'll need is either a Wratten 47B Blue or a Rosco's #80 primary blue filter. The latter seems easier to find on the web and is generally less expensive. With luck you should be able to purchase just a single sheet for around $6 U.S. You hold it up to your eyes and view through it to make the following adjustments. Your goal is to have the color bar chart appear as show with only blue and black vertical bars when viewed through either filter described above.

We'll adjust color intensity first. Closely study the large SMPTE Color Bar Chart that has the keys, A, B, C, D. In the next steps the bars are also referenced by their relative position on the chart. The first is bar one, the next is bar two and so on through bar 7. The same applies to the blocks sometimes called chips which are immediately below the bars. Note the first bar at the extreme left (bar one) and the smaller block immediately underneath it, (block one) references A and B on the SMPTE Color Bar Chart demo, along with references C (bar 7) and D (block 7) on the right side of the chart. These are used to set color intensity.

When the SMPTE Color Bar chart is generated on a television and viewed with only the blue CRT gun on or when viewed through the correct type of blue filter, the intensity of bar A and block B along with bar C and block D should be the same or as close as you can make it. The smaller image of the SMPTE color bar chart (blue and black only) shows how the bars and blocks appear to merge into one solid area with only a tiny whitish line separating the bar and block. Do not confuse the bottom row starting with a darker blue block with this adjustment and only look at the the outer bars and blocks. Refer to the larger SMPTE color bar chart to see how it appeared as three rows prior to turning the blue switch on (if your TV has one) or looking through a blue filter.

Step #5 Adjusting Color Hue

To adjust hue, look at the two inner bars; Cyan and Magenta (bars 3 and 5) and the blocks immediately underneath them. Make very minor tweak if necessary to have bar 3 and block 3 plus bar 5 and block 5 at the same intensity. Again there will be a thin whitish line separating the bars from the blocks.

Alternative Hue Adjustment Without Blue Filter

If you can't obtain a proper blue filter you can still adjust off the Red bar on the SMPTE color bar chart. While less accurate, you can still adjust for obvious errors. Note the shades of blue on the outer blocks (-I) and (Q). If the red bar is over saturated usually some of the red will 'bleed' causing a little red to show up in either block -I or Q. A minor adjustment of color intensity should remove it.

Summary

Calibration sounds more complex in the explaining then the actual process is. After reading through this you may be a little skeptical if it is really worth the bother. I assure you it is, and encourage you to give it a try. While there are several DVD packages available that include more tests and better quality test patterns, you can make your own test video using the test patterns included with Vegas Video (under Text/Backgrounds, test pattern) and copying the white level, gray chip and EIA #1956 resolution charts from this web site or obtain different ones off the web. All that's necessary is making a small video using Vegas Video or Video Factory (of course) and dropping the appropriate charts on the timeline stretching them out so they appear long enough on screen for you to hit the pause button on your remote when you're actually doing the calibration.