Capturing LCD screen and white balance.

Liam_Vegas wrote on 1/31/2004, 12:48 AM
I am trying to capture the screen of an LCD monitor using my VX2000. I just cannot get the color to come out the same as is on the LCD. I know a few members of this forum do this sort of thing so I thought I would ask for your help.

Is there some trick to doing this in the camera or will I have to correct it in Vegas after capture?

Obviously the default white-balance settings do not work (tried those first). Doing a manual white balance seems a little pointless also as usually you hold up a white card under the specific lighting conditions under which you are shooting... but in this case of course the LCD itself is emitting the light so I think that just won't work (even though I had my doubts I still tried displaying a white screen on the monitor and using that as the white-balance "card"... but of course it made no difference).

I just know the answer is probably really obvious.

Thanks for your help!

-Liam
[edit] If I could trouble you to also read

[FINAL EDIT]
Thanks for all that helped me with this. If you want to jump straight to the (for me) final solution to my particular needs right now you can jump to this post.

Many people were a great help but I wanted to recommend the posts by farss (such as this one in particular) as they helped me understand more fully what was going on.

Comments

Grazie wrote on 1/31/2004, 1:18 AM
Hiyah LV - What are you ultimately trying to achieve? Are trying to send this off to Sony Cammie tech or what? Are you trying to gauge if your LCD screen is working as it should? Haven't got THE answer for you . .I'm interestied too . . but knowing what your final outcome you are wanting to achieve may just give others some other options in helping you. Does this make sense?

Regards

Grazie
Liam_Vegas wrote on 1/31/2004, 1:33 AM
I am trying to capturer to video an animation sequence which looks awesome on my LCD monitor.

I am using some special <beta> software of a product which will likely eventually have a capability to dump each frame as a still image but for now I just need to get a good looking video made from the real-time display output from it.

I have heard others in the forum have done this sort of thing (Spot? Rextilleon?) with good results. I know some have done this in order to capture the on-screen activity of a program... and perhaps the color is not so critical in those situations.

I have tried a cheapo "scan-converter" thingy to convert the VGA signal direct to s-video but it just does not look anything like as clear as it does when I point my VX2000 straight at the LCD screen and hit record. The only problem is that the color is incorrect on the stuff I captured off the LCD screen in this way.

And... in case anyone is wondering this... I cannot use a PC-based capture tool (such as Camtasia) as this animation is being "rendered" in real time and Camtasia would swallow up too much CPU to allow the animation to work.

Thanks for the questions... hopefully my answer will help others understand what I am trying to do.

[edit] I think I just figured out that what you were thinking I was trying to do.. which was to capture the actual display on the LCD screen of my VX2000 camera? Hopefully the above has cleared that up?
Zulqar-Cheema wrote on 1/31/2004, 3:42 AM
If you are trying to achieve the quality you are seeing on your PC LCD and capture that via a video camera, it is not possible, you are trying to put a quart into a pint pot, not possible the screen ress is much higher then video and so video will always look inferior, its about half the ress i believe of the LCD 720x576?.
You could say you are recoding the TV screen with a camera feeding a VHS recorder, while watching an off-air broadcast because it looks better then when to record it direct using your VHS recorder.

If you use a good scan converter, that may go toward archiving higher quality recording/capture then the cheap one you have tried, it does make a lot of difference to the final image.

FuTz wrote on 1/31/2004, 7:39 AM
GaryKleiner wrote on 1/31/2004, 8:23 AM
Liam,

Your best best is to use Camtasia to capture it.

If you do want to use your camera, display a white space on screen (e.g. empty text document) and use that as your white reference.

Gary
corug7 wrote on 1/31/2004, 8:46 AM
Liam,
I just taped off my LCD recently with my VX2000 and had a wonderful outcome. I'll just let you know what I did. Please don't think of me as condescending, because I'm just going over the list of events in order.

1) Make sure the room is completely dark (except for the LCD, of course)
2) Set camera at lowest F-stop without going into gain.
3) Make sure LCD is at the color temperature you want, and record away!

Don't let the camera go into gain! It will screw the colors up. I just did this to record a music video included on a cd at something like 240X180 which was rediculously hard to see (I only did it so I could watch it on my own TV, FAIR USE, FAIR USE!!!). You shouldn't need to white balance, just increase the F-stop to your own liking for contrast. Good luck.

P.S. I am using NTSC Equipment, and a MAG Innovision 15 in LCD. Not sure if it makes a difference, so thought you should know.
Liam_Vegas wrote on 1/31/2004, 9:52 AM
it is not possible, you are trying to put a quart into a pint pot,

Look mate. Thanks for the thoughful reply and all... but I can assure you that my eyes are not lying to me. I can only guess that you are talking about something you have not actually tried! Have you actually ever done this or are you just guessing what would happen?

I have done test captures from an LCD monitor and it looks FANTASTIC. Don't get me wrong... I am NOT expecting to get a 1024x768 or higher resoluti8on captured to my 720x480 DV resolution monitor..

However I can ASSURE YOU that it looks far better capturing the screen over using a cheapo scan converter. I don't have the money to purchase or rent a proper scan converter to do this. I DO HAVE a good camera.. I have achieved good results so far THAT I AM HAPPY WITH (apart from the color).

All I ASKED FOR (and I think it was a simple request) was help from someone on whether I can adjust the camera color/white balance before capturing rather than having to do this in Vegas. I did not actaully ask anyone to comment on how bad they thought the qaulity of this is.

Thanks...
Liam_Vegas wrote on 1/31/2004, 9:56 AM
Maybe try with CamStudio and set the app to "best" settings?

I guess I MUST REALLY be talking a different language today? Please re-read the statement I made about NOT BEING ABLE to use Camtasia. DOes what I said not make sense? I cannot use Camtasia on the PC.

And... in case anyone is wondering this... I cannot use a PC-based capture tool (such as Camtasia) as this animation is being "rendered" in real time and Camtasia would swallow up too much CPU to allow the animation to work.

Or simply make a Print To Tape?

Huh? What?

Please tell me how on earth I can do a print-to-tape from this animation software that I am using when it cannot do that? What are you talking about?

[edit]
Sorry... I must have fallen out of the wrong side of the bed here or something.

But I do wonder what I have to do to properly explain what I am trying to do so that I get relevant answers or suggestions. I am VERY WILLING to receive for a reply from anyone pointing out to me how I should have described this better than I have. RIght now I feel as if I have caused some of you to go off on large tangents giving me suggestions that are just so off the mark. I am really sorry!
Liam_Vegas wrote on 1/31/2004, 10:01 AM
No... I do not think you are being condesending. I am perfectly willing to accept that I am doing this stufff wrong.

However... on setting the "color temparature thing". I guess that is the EXACT question I am asking you. How do I do that? I mean that sounds like the white balance you are talking about and I did describe that I have tried a lot of settings in order to do this.

[edit]... or maybe you are talking about the color temperature of the LCD Monitor rather than a camera setting? I guess I'll dig around in the manual for the montor but I don't quite see how that impacts the color difference I see between how the colors look on the screen and how they look via the camcorder (plugged into a big TV monitor) that is capturing the LCD monitor. I am trying to get them to look the same... but I guess what you are suggesting is that I modify the color balance for the LCD so that it matches the appropriate color balance that my camcorder is set to?

The room was completely dark... no other lights were on. And yet the colors are quite a way off. An orange color looks more red on the screen. I did not let the thing go into gain at all and I did drop the F-stop a little as well.

Just checking... what were you capturing and in your assessment did you notice ANY difference in the color from what was on the LCD screen and what was captured.
Liam_Vegas wrote on 1/31/2004, 10:02 AM
gkVideoguy. Sorry you must have missed this additional explanation
Grazie wrote on 1/31/2004, 10:51 AM
. . .er . . . I'm outta my depth here . . but have you considered getting this up on a CRT monitor, and film that? - Sorry if this has been considered today . . .

Grazie
Liam_Vegas wrote on 1/31/2004, 11:04 AM
Yep. I have a big CRT monitor right next to the LCD monitor. Capturing off a CRT monitor looks awful in comparison to the LCD. You also get the problem of flicker induced by the refresh rate of the monitor.

I am REALLY REALLY REALLY happy with the contrast/brightness and detail when shooting direct off the LCD Monitor. It is only the color balance that is wrong.

Thanks for trying Grazie... I am grateful for the reply especially in light of the fact that it is pretty obvious I am having a "bad hair day" over some of the answers I have got so far today :-)
Grazie wrote on 1/31/2004, 11:28 AM
Yeah, at least yer got hair to have a . . bad day with!?!?! Hah!!

Okay, stupid idea No.3 - Have you tried altering the colour balance of the LCD screen . .don't tell me . .this is in a post above this? - If so .. .I'm outta here . . don't like to see grown men cry . . no, that's a lie . . I don't mind really . . . hang on in there Liam we're gonna kill this one . ..


Grazie
Liam_Vegas wrote on 1/31/2004, 12:19 PM
Thanks for bearing with me...

I think the color temperature of the LCD monitor was one of the suggestions (from curug7 above)... but I was not sure. I didn't initially think that was what he was suggesting but when I thought it through again I think that is what he was suggesting I do *I'm doing a lot of thinking to day... my head hurts).

I will try that (if I can find the darned manual for it).

Thanks again.
Zulqar-Cheema wrote on 1/31/2004, 1:36 PM
Liam you asked a questions I put some ides and technical issues forward if thats not what you require, that's fine, can live with that.

You are right I have not tried it, I have seen it and have pointed cameras at LCD's in the past and seen the quality, BUT i do need to fall of a cliff to know it hurts, and so i can offer suggestions as I have done in the past on how it could be or could not be done.

"I did not actaully ask anyone to comment on how bad they thought the qaulity of this is."

You did not ask for it in English but I notice all the replies are.

When you write your next post perhaps you could be so kind and write a very specific specification we can all work to thus not annoying you by wasting your time with our silly responses.

Remember there is more then one way to skin a cat.

You certainly did get out of the wrong side of the bed.
farss wrote on 1/31/2004, 1:48 PM
OK,
Lets ignore the camera part for a minute, if you don't understand all the issues up front then you'll be beating yourself to death for a long time on this one.
CRTs and LCDs produce colors differently, sorry if thats bleeding obvious but bear with me here. You've got a CRT and a LCD monitor. Put them side by side and run your animation program, does it look the same on both monitors?
Can you get ANYTHING to look the same on both monitors?
Color bars and a few other test patterns would be a good starting point here.

So here is your first hurdle. No matter what the camera 'sees', how it looks color wise is going to depend on how it's displayed to a large extent, thats one reason you went from the CRT to the LCD monitor to shoot from.

Now it may well be that the animation app / LCD monitor are producing colors that are out of gamut for video, ie they just cannot be reproduced in a video system, I say maybe OK.

What I'd suggest you try doing is this.
As has been suggested before, white screen on LCD to set WB on camera. All that ensures is the color temp of white is the same (hopefully!), it still doesn't fix how the colors track within that space.
OK now, color bars on the LCD and then greyscale test pattern. Don't change anything and then shoot your video.

Now capture it into Vegas. What you need to do is calibrate your clip of the animation video to match what those test patterns look like.

Put the same test patterns on a new track. Check how they look on the vectorscope, now apply CC to your video track. Adjust it to get the same readings on the vectorscope for each of those test patterns.

You may not be able to do this of course but this procedure is going to give you your best shot at it. This is what test patterns are for. You may need to use quite a range of test pattern to get the whole process to track correctly and you may need to do work on the gamma as well, LCD monitors have a pretty hot gamma curve compared to CRTs.

I'd say if you're lucky you'll get things to look close. My suspicion though without seeing the footage is that you'll never get it to look the same.
farss wrote on 1/31/2004, 2:02 PM
Your best bet is to start with the grey scale test pattern.
Use this to get the gamma corrected using the color curves, probably using the histograms scope. DO NOT rely on your eyes, they lie very easily because they adjust very quickly to balance out the differences.
Once you've got the gamma matching and you MAY have to adjust this for each color i.e. the gamma for R,G and B may be different as well, then start on getting the overall color balance correct using color test patterns. You should use bars at different levels as well ,again to check not only that 100% red is red but that 50% red is still 50% red.

Sorry if you think you've got a simple problem that should be easy to solve. Fact is millions are spent and millions of words written on this subject.

farss wrote on 1/31/2004, 2:16 PM
You did say you wanted do this WITHOUT doing anything to the video in Vegas.I'd deliberately avoided that. You could do it but you'll need a studio camera with separate CCU to have a shot at it and you don't want to know what that's going to cost.

Alternatively you COULD feed the output of the VX2000 through a color grading system but the studio camera would be a cheaper starting point!
Liam_Vegas wrote on 1/31/2004, 2:20 PM
Farss

I was hoping this was a simple problem to solve... but entirely prepared for the fact that it was more complicated than that.

It seems to me that I will have to do the color correction in Vegas after I have captured the animation direct off the LCD screen using my camera.

You are absolutely correct that the colors displayed between the CRT and the LCD are very different. However what I was trying to achieve was some way to at least get my camera to capture the colors from the LCD monitor in the way they are represented. That was my hope.

Thanks for the suggestions I will post some results when I get a chance.

In the meantime here are a couple of clips from the animation that may give you a better understanding of what is going on.

1: Video capture direct off the LCD Monitor

2: Video capture via a cheap scan-converter.

The colors coming through the scan converter look more like what I have on the LCD Monitor but as you can see the resolution/contrast does not look anything like as good as what I get by taping direct off the LCD Monitor.

Thanks so much for the help!

[edit]... corrected the URL link to the second image so that it is going to the right one!
Liam_Vegas wrote on 1/31/2004, 2:30 PM
Zcheema.

I really did ask some very specific questions in plain english. I guess I am now shocked that I end up getting a response from someone telling me that I am crazy even to be doing this.. and then I find out that person did not even try this themslelves. That just seems to me to be a very strange thing for you to do.

But... it takes all sorts of guess. Hopefully you have learned a little something from this and will think twice before bringing in some irrelevant opinions into the mix.

For your enjoyment and to prove the point that what I am saying about capturing off an LCD screen does have at least some merit to the issue that I had, please view the following sample images and tell me which one you would choose to use (barring color issues... which is the whole point of my post).

1: Video capture direct off the LCD Monitor

2: Video capture via a cheap scan-converter.


Liam_Vegas wrote on 1/31/2004, 2:36 PM
It wasn't really that I did not want to do anything in Vegas as far as color correction.

It was rather that I was thinking I was doing something wrong (even stupid) in the capture step that maybe someone who does this all the time would say "hey you dummy... don't you know you have to do it <this way>".

I am a great believer in capturing video right rather than trying to fix it in the edit stage... but... I am fully prepared to just tweak things in Vegas using the color correction FX until it looks the way I want.

Thanks again.

farss wrote on 1/31/2004, 2:59 PM
Scan converters even the most expensive ones are trying to do a difficult task. We've worked with some people capturing HiRes screens from poker machines and recently worked with uSoft capturing footage from XBox for commercials about new games.

For the uSoft deal they were using 4:2:2 sampling so you've got a fighting chance. The poker machine guys built a special version of the machine just to capture screen shots.

Anyways, you're not doing anything wrong with the camera and I hope I didn't sound like I was trying to scare you off having a go.
To shoot off a CRT screen and to avoid the flicker you need to use 1/50 or 1/60 second shutter speed or else a camera with a thing called 'clear scan'. The LCD screen doesn't have this 'problem' becuase they're so damn slow!

If you're going to this much trouble I'd make an effort to avoid any geometry errors up front as well, get teh camera dead cemtre and dead square onto the LCD. Also get the camera a good way back from the monitor so its about mid range on the zoom to fill the screen. The lens will give its best performance there and you'll avoid capturing the incident light coming out of the monitor.
I'll be interested to hear how it pans out for you.
Zulqar-Cheema wrote on 1/31/2004, 3:06 PM
Liam, the links both point to he same picture so a bit hard to judge the merits of what you are trying to say. the picture is bright and clear, but without the original its hard to judge how good.

Irrelevant is a matter of opinion, Liam
There is nothing strange in replying to a post having never having tried it before, that's how ideas are generated, never be scared to a have a shot at something no matter how wild it sounds.

Just a thought, have you thought of hiring a high quality scan converter for the day and achieving what you require? will be cheaper then a purchase.
Liam_Vegas wrote on 1/31/2004, 3:14 PM
Fixed the links. Thanks for noticing my mistake.

We will eventually be able to generate stills from the animation program so this is a short-term solution. I am doing this project with no budget so I have no money to spend on renting a scan converter. And... as I have said before I am perfectly happy with the quality (detail/contrast) that I get when shooting direct off the screen (sample1) but that I just want the colors to look more like the sample2 image.

I think Farss has come up with some great ideas for me to try,