Light meters for DV camcorders

[Ken Tanaka]

Extending Jeff's remarks back to your idea, Brad, there is such a round-about calibration solution. Some of the newer Sony production monitors, such as the PVM-14L5, can calibrate themselves if fed SMPTE bars. I have one and it does a very good job, certainly as good as I can by hand, when I feed it bars from FCP.

Calibration, however, in not something you should need to do frequently.

[Jeff Donald]

Calibration is checked daily with color bars and blue gun. If it has drifted then calibration is preformed. Newer models don't drift nearly as much and PPL circuitry to prevent drift. Older, more analog models will drift more frequently and require manual adjustments. Phosphors change over time on all models and will necessitate infrequent corrections.

[Brad Horner]

I guess the problem with me right now is that I am trying to understand the big picture of color correction from camera to NLE, so my questions are all over the place on the subject. This goes for another thread where I am grappling with the subject. I found a tutorial that will help me with the color bars, but they claim that Adobe Premiere 6.0+ has correct SMPTE bars are correct.
http://www.greatdv.com/video/smptebars.htm

Okay, now seperating the monitor calibration from my mind I (a little) I have some other quirky thing that I found. A waveform monitor and vectorscope in Premiere! Anyone use this in realtime correction to replace a waveform monitor?

[Roger Berry]

Brad: I've looked everywhere for the waveform monitor/vectorscope in Premiere 6 and can't find it. I'm not even sure what these do but I've read about them and would like to know more. Can you help?

Thanks in advance,
Roger

[Brad Horner]

Here is a link to a tutorial at the Adobe site. You need to sign up so I'm not sure that this link will just ask for a password or registration. The tutorial is "Correct color in video".

http://studio.adobe.com/tips/tip.jsp?p=1&id=400&xml=prepcolorcor

I haven't had good luck with my posts lately; they are off topic or just confusing. That seems to happen to newbie types in most any forum. Hopefuly the link works.

I can't answer any questions on the topic because I know little to none about it. I am hoping that with some card like the Canopus 2 that it would be possible to make "live" color correction using the aforementioned software vectorscope and waveform monitor. Maybe it's possible but not worth the trouble? Someone (you or I) could start a new thread to try and find out more.

signed,
Overwhelmed

[Josh Bass]

Have I been doing this wrong for all this time?

I've been following these instructions:

1. Allow the monitor to warm up for a few minutes

2. Dim the room lights and block any reflections on the monitor

3. Feed color bars to the monitor either from a camera or "house bars" from your editing system

4. Set the contrast also called "picture" to its midpoint

5. Turn the chroma also called "color" all the way down until the color bars are shades of black and white
6. Notice the three narrow bars labeled 3.5, 7.5 and 11.5 on the bottom right. These are the Pluge Bars which stands for Picture Lineup Generating Equipment. Adjust the brightness control until the middle (7.5 units) pluge bar is not quite visible. The lightest bar on the right (11.5 units) should be barely visible. If it's not visible, turn the brightness up until it becomes visible.

Since 7.5 units is as dark as video gets, you should not see any difference between the left bar (3.5 units) and the middle bar (7.5 units). There should be no dividing line between these two bars. The only division you should see is between 11.5 and 7.5 (Note this same technique is used in setting the b&w viewfinder on your video camera.)

7. The next step is to set the contrast control for a proper white level. To do so, turn the contrast all the way up. The white (100 unit) bar will bloom and flare. Now turn the contrast down until this white bar just begins to respond. The image below shows what it should look like at this point.
8. With the blue switch on (or your blue gel in front of your eye) turn the chroma or color until the grey bar at the far left and the blue bar at the far right are of equal brightness. One trick is to match either the gray or blue bar with its sub-bar.

9. Adjust the hue control until the cyan and magenta bars are also of equal brightness. You can also match either of them with their sub-bars. Now the four bars - gray, blue, cyan, and magenta should be of equal intensity. The yellow, green and red (which are black in the diagram below) should be completely black.




They're from some site. . .don't remember where; I know it's referenced here.

What happens if I do it this way and the setup is 0, instead of 7.5 as these instructions are made for? That additional step sounds difficult to do by eye, which is the only available method I have right now.

Also, does anyone know if I should recalibrate when color correcting in post (I use the same monitor in the field as I do for the color correction)--meaning should I use the camera's bars for shooting and the bars in Vegas 4 for editing, or is it all the same?

[Roger Berry]

Thanks for the feedback Brad. That tutorial was well worth reading even though I only have basic Premiere 6, not the Pro version. The controls mentioned are not included in my version -- the nearest I've got is a color correction workspace and no wave form monitor.

I'm not sure it's worth upgrading just for this feature, at least until I understand it's importance properly. Are there any other important reasons why I should shell out more dosh for the Pro version?

JOSH: I don't own a proper monitor... just use TV sets... but your calibration method is the same as mine and it seems to work. I too would like to know if we're doing it wrong.

BTW, I disagree, most of what you write seems to be right but then, who am I to say?

[Josh Bass]

Yeah, and also, I remember reading elsewhere on this forum that you had to LOWER the setup on the XL1s to get it to 7.5, like down two notches. I swear.

[Wayne Orr]

Sounds like you guys are doing it right, but are you certain you have accurate color bars? There are some bogus bars floating around the web, and even some supplied with software are NG. One of the best places on the web to get accurate color bars for FREE is from Synthetic aperture at http://www.synthetic-ap.com/products/tpm/index.html

Video University has some infor for setting up monitors for PAL, as I recall. Also try Tektronix website. They have an excellent technical tutorial.

Wayne Orr, SOC

[Josh Bass]

Like I said, I use the ones out of Vegas, or the ones straight from the XL1s.

[Wayne Orr]

Sorry, Josh, but that does not necessarily mean they are accurate. Best way is to check 'em out in Photoshop. Especially the ones from the camera.

W.

[Josh Bass]

Alas, I have no photoshop. I thought one of the big pluses of the XL1s is that it had honest to God SEMPTE bars.

[Wayne Orr]

That is very likely true, Josh. I didn't mean to imply otherwise. I am sure someone will come along and set the record straight. Can you run your cursor over the bars in your edit software and read the luminance values on the various chips?

W.

[David Ziegelheim]

A high res monitor is always nice...but not always there, especially with miniDVs. They are bigger than the camera.

Zebra's also nice, but not very exact.

The meters allow you to cover a large area, get objective readings on contrast and on shadow detail (usually impossible to see on the LCD, and difficult on a small field monitor being viewed in the native field lighting).

Last weekend I needed to light a table, and the meter quickly found some 1-stop holes that I don't think I could pick up with the camera, especially before the subjects arrived.

David

[Carlos E. Martinez]

<<<-- Originally posted by David Ziegelheim :
The meters allow you to cover a large area, get objective readings on contrast and on shadow detail (usually impossible to see on the LCD, and difficult on a small field monitor being viewed in the native field lighting).
-->>>

As I had a discussion over this question on another DV Info Forum recently, and got many attacks from it, I can say I absolutely agree with you.

People look at film tools, when used for video, as an "old" thing. And I think it's quite the opposite.

In my opinion some practical basic things are getting forgotten.

No doubt a CRT monitor and a waveform are excellent tools to work in video, probably some of the best.

But metering a frame using a combination of incident and spot meter may go a bit farther.

What can I say: maybe I have become an old bloke.

As long as you can use the right ASA reference (where do you get that for different camera models?) and know how to handle a spot meter (not many really do) what is the real problem?

They are all tools, folks. Like a screwdriver or a hammer. And they never got old fashioned.



Carlos