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Lighting Difference in Two Cameras?

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Pat Ford
Lighting Difference in Two Cameras?
on Aug 14, 2009 at 7:21:01 am

Don't know if this is a lighting question or a camera question.

At a two camera shoot we were getting different levels, both luminosity and color from the two cameras. check out:

http://criterionweb.com/cameradifference.html

Further explanation on the page.


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John Fishback
Re: Lighting Difference in Two Cameras?
on Aug 14, 2009 at 4:00:24 pm

To me, it's a camera issue. Obviously, the cameras were not matched before the shoot. Even with the differences between the two cameras, this could easily be fixed in post.

John

MacPro 8-core 2.8GHz 8 GB RAM OS 10.5.5 QT7.5.5 Kona 3 Dual Cinema 23 ATI Radeon HD 3870, 24" TV-Logic Monitor, ATTO ExpressSAS R380 RAID Adapter, PDE enclosure with 8-drive 6TB RAID 5
FCS 2 (FCP 6.0.5, Comp 3.0.5, DVDSP 4.2.1, Color 1.0.3)

Pro Tools HD w SYNC IO, Yamaha DM1000, Millennia Media HV-3C, Neumann U87, Schoeps Mk41 mics, Genelec Monitors, PrimaLT ISDN


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Pat Ford
Re: Lighting Difference in Two Cameras?
on Aug 14, 2009 at 4:49:01 pm

Thank you sir.

The cameras were not matched before shooting as you suggest. We have shot this job two times with the same cameras before without this problem. I know that's no excuse; in the future I will certainly do it in the future.

As I think I mention, #2 camera would not white balance to match #1. #2 seemed to be washed out in comparison. We tried it with and without warm cards to no avail. At the beginning the iris on both cameras were at 4; I stopped down to 5.6 to no avail...then I just flipped it to automatic...that seemed best.

The main reason I posted here is to discover if the fact that the spot beside #2 was at close to the angle of the camera on the contestants. Whereas the spots struck the contestants more obliquely for camera #1....hope I made sense. Thanks again.





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John Fishback
Re: Lighting Difference in Two Cameras?
on Aug 14, 2009 at 5:22:57 pm

It's possible you were getting flares in the lens from the spot. BTW what cameras were used. As I said, you should be able to fix most of what you're seeing using color correction in post. If you have FCP, Color would be very helpful. I'm not sure why one camera wouldn't white balance. That might be caused by colored light "confusing" the camera. On our camera, if the light is out of the expected range, we get an error message.

John

MacPro 8-core 2.8GHz 8 GB RAM OS 10.5.5 QT7.5.5 Kona 3 Dual Cinema 23 ATI Radeon HD 3870, 24" TV-Logic Monitor, ATTO ExpressSAS R380 RAID Adapter, PDE enclosure with 8-drive 6TB RAID 5
FCS 2 (FCP 6.0.5, Comp 3.0.5, DVDSP 4.2.1, Color 1.0.3)

Pro Tools HD w SYNC IO, Yamaha DM1000, Millennia Media HV-3C, Neumann U87, Schoeps Mk41 mics, Genelec Monitors, PrimaLT ISDN


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Pat Ford
Re: Lighting Difference in Two Cameras?
on Aug 14, 2009 at 5:37:02 pm


Thanks, John, I appreciate it.

We will be editing on Premiere Pro CS3 if I do it...Final Cut if my editor does it.

The edited length of the final cut will be very roughly two hours. We had a deck capturing the output of the director as he chose the camera signal to send to the two large screens to either side of the stage. Ideally, we would just make corrections in that tape and burn a DVD. If we have to color correct it may greatly increase the time to do the edit. With that said...the director was favoring #1 camera.

The cameras were both Sony PD 150s. They have 70/100 zebra settings.

Another thing which I don't understand..I notice that overlimit ire setting would blow out the image...on my waveform monitor...there is much of the footage from #1 camera is overlimit but still looks good...has good color saturation etc.

I realize I am all over the board here...I appreciate the advice given....



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John Fishback
Re: Lighting Difference in Two Cameras?
on Aug 14, 2009 at 6:02:04 pm

You can certainly color correct the tape. The challenge is how to handle dissolves. I'd blade the clip before the dissolve to the next cut or after the next dissolve. Then color correct that clip and add dissolves as necessary so the transition to color corrected footage is smooth. If the cameras are consistently off, you'll be able to color correct one time and apply that to the rest of the clips to save time.

How a particular device handles video over 100% varies depends on how it's set up. Most cameras can record over 100% and still not clip. AFAIK, zebras are simply indicators. They're not a threshold over which clipping will occur. At least that's the way all the cameras I've worked with operate.

John

MacPro 8-core 2.8GHz 8 GB RAM OS 10.5.5 QT7.5.5 Kona 3 Dual Cinema 23 ATI Radeon HD 3870, 24" TV-Logic Monitor, ATTO ExpressSAS R380 RAID Adapter, PDE enclosure with 8-drive 6TB RAID 5
FCS 2 (FCP 6.0.5, Comp 3.0.5, DVDSP 4.2.1, Color 1.0.3)

Pro Tools HD w SYNC IO, Yamaha DM1000, Millennia Media HV-3C, Neumann U87, Schoeps Mk41 mics, Genelec Monitors, PrimaLT ISDN


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Pat Ford
Re: Lighting Difference in Two Cameras?
on Aug 14, 2009 at 6:16:57 pm

[John Fishback] "You can certainly color correct the tape. The challenge is how to handle dissolves. I'd blade the clip before the dissolve to the next cut or after the next dissolve. Then color correct that clip and add dissolves as necessary so the transition to color corrected footage is smooth. If the cameras are consistently off, you'll be able to color correct one time and apply that to the rest of the clips to save time.

Gotcha. ...the bid for the job is pretty tight...we'll experiment. One complicating factor is that I am color blind...I hate that...would have to have my editor do the color correction and not me.

[John Fishback]
How a particular device handles video over 100% varies depends on how it's set up. Most cameras can record over 100% and still not clip. AFAIK, zebras are simply indicators. They're not a threshold over which clipping will occur. At least that's the way all the cameras I've worked with operate."


I should add that the ire levels were checked on the software waveform monitor on Premiere Pro.





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Craig Alan
Re: Lighting Difference in Two Cameras?
on Aug 16, 2009 at 6:08:54 am

Hi Pat,

I'm not a lighting pro, but I have shot quite a few stage shows with pd170s (basically an updated 150). This line of cameras is very sensitive to light. When they light the stage for live affect, it often overexposes the Sony. These shots look overexposed to me.

When you start to close down the iris to the upper range (5.6), you loose a lot of detail. If at all possible, you should attend a dress rehearsal and experiment with your settings.
If not a dress rehearsal than at least meet with the crew running the lights and white balance without colored lights and experiment with your settings under the different lighting that will be used during the show.

If you can attach a broadcast monitor to your camera, you can show the director what he is doing to ‘his’ video. Not a bad idea for the camera operator either since there is nothing accurate about the LCD screen.

Did the lighting look good live? The faces look way blown out.

Did you try one of the built-in ND filters? This should allow you to have a more wide-open iris and thus more detail and a more shallow depth of field if you are zoomed in all the way. You could also try a matte box and filter in front of the lens. This will help with lens flare and you can cut through the glare a bit more.

I might also suggest using the second camera to shoot close ups on the contestants’ faces and set the camera for this purpose. Set the first camera to allow greater camera movement following the movement of the contestants. Since the images of the two cameras will be radically different, wide and close, the transitions will be much easier and capture more of the drama of the event.

Under a lot of circumstances the auto on the Sony works pretty good. But it is taking an average. Black curtain in b.g. will tell the auto exposure to open up the lens. Light to faces not b.g.

If you are in a hurry you can use the broadcast safe filter in FCP – should help a lot.



OSX 10.5.7; MAC Book PRO (EARLY 2008); Camcorders: Sony Z7U, Canon HV30, Sony vx2000/PD170, Canon xl2; Pana, Sony, and Canon consumer cams; FCP certified; write professionally for a variety of media; teach video production in L.A.


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Pat Ford
Re: Lighting Difference in Two Cameras?
on Aug 16, 2009 at 7:38:30 am

Craig,

Thanks so much for taking the time answer my post; you all have been generous with your time.

A saying I have is that with any major shoot you learn something new. This time it's to be sure the cameras match.

I have done this shoot twice before and we have have no problem with the cameras matching. This time we had trouble. I still do not know why. I could not get camera 2 to white balance the same as the other camera. It looked washed out. We became aware of this in the minutes before the show. The flash video is early in the program when the difference is most obvious.

Since I last posted, I went back to my camera tech shop and presented him with a tape of the same video as appears on the web. He ran the video through a vector scope and a waveform monitor. In a nutshell, he said that the chrominance was not far off; the problem was mainly in the luminance. Like you, he suggested I use a ND filter. I have tried to color correct to overcome these problems and have succeeded in improving the situation somewhat.

....time passes....

Eureka...maybe...One of the moderators of this forum kindly called and suggested that I check out the data code on the camera tape...heretofore I have been running the tape of the director's switcher output. So...I checked #2 camera. It appears early on that the iris was being rapidly moved to various settings as wide as 2. Also, the gain seems to be being messed with...it went as high as fifteen...the movement is so erratic that it is possible that it might be a camera malfunction.(?)In any case by the third and final tape the erratic iris movement has ceased; the camera is set at 5.6 and the gain at 6db. And, as I understand it, a setting of iris 5.6 and 6db gain would roughly equal an iris of 4 and 0 db on the other camera. The third tape on the #2 camera matches #1 fairly well.

Strangely the gain on the second tape on camera #2 is 15 db. There does not seems to be a noticeable amount of noise.

If the gain was the problem...and indications are that it is, it is unfortunately my fault. The camera guy did not notice it, but I was acting as a producer/production manager at this event. Furthermore, it's my damn camera. If the gain was set incorrectly...it was almost certainly showing on the camera lcd screen. The camera guy did not see it nor did I. Seems crazy and unlikely but that's the best explanation so far.

Anyway...it's up to me to fix it. Thanks for your help.





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Craig Alan
Re: Lighting Difference in Two Cameras?
on Aug 16, 2009 at 5:08:54 pm

Hey Pat,

If the gain kept changing, how was it the fault of initial set up? 15db? THat much always produces noise.

Great idea to check the meta data. One possible explanation for the erratic settings is auto exposure. Certainly with that much light there is no reason to raise the gain. But on auto with a black b.g. and talent moving to different areas of stage lights, auto can get wildly confused. Just like auto focus will.

Really the best way to handle this is with a broadcast monitor on location. WYSIWYG. And you should be able to get the metadata on the screen as well. For SD cams you need not spend a lot for the monitor. JVC makes nice CRTs for well under $1000. You can borrow the one you use for editing and if you don't have one they come in handy for both.

Curious: Was the more stable camera shown to be overexposed on the scopes as well?

One more thought: since you did not have trouble matching in this environment before and the cameras were on auto exposure, is it possible the shutter speed on cam 2 was accidentally set to manual at a different speed?

OSX 10.5.7; MAC Book PRO (EARLY 2008); Camcorders: Sony Z7U, Canon HV30, Sony vx2000/PD170, Canon xl2; Pana, Sony, and Canon consumer cams; FCP certified; write professionally for a variety of media; teach video production in L.A.


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Jason Jenkins
Re: Lighting Difference in Two Cameras?
on Aug 17, 2009 at 4:13:57 pm

[Pat Ford] "If the gain was the problem...and indications are that it is, it is unfortunately my fault. The camera guy did not notice it, but I was acting as a producer/production manager at this event. Furthermore, it's my damn camera. If the gain was set incorrectly...it was almost certainly showing on the camera lcd screen. The camera guy did not see it nor did I. Seems crazy and unlikely but that's the best explanation so far."

I am very familiar with the PD-170 and if the PD-150 works the same way I can tell you that controlling the gain is a little tricky. If you are not seeing the gain number on the LCD, then the camera is setting the gain automatically. In a situation with plenty of light, you should be shooting at 0 db of gain to minimize noise. You need to push the gain button on the back of the camera to see the gain setting on the LCD. Set it accordingly. Again, if it works like the PD-170, the camera is automatically setting gain if you don't manually set it.

Jason Jenkins

Flowmotion Media

Video production... with style!


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Pat Ford
Re: Lighting Difference in Two Cameras?
on Aug 17, 2009 at 4:58:37 pm


We might just have a winner!!!

I guess I knew this about the gain control...but it had not occurred to me.

I had left set-up for the cameras to the last moment. And in the flurry of activity I may have missed the fact that the gain number was not showing up. I rarely, if ever, pump up the gain. I may not have noticed that the gain number was not showing...

Thanks Jason!! And thanks to all of you for your kind help. You've been most generous!!



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Craig Alan
Re: Lighting Difference in Two Cameras?
on Aug 18, 2009 at 6:05:23 pm

Correct. On both the pd150 and pd170: IRIS, GAIN, and SHUTTER speed work this way. As does white balance. The camera defaults to auto when you “turn off” these manual controls.

Pat,
If you have a black b.g. and moving, colorful, hard-lit subjects, the auto sensors will be taking an erratically changing average. The camera might capture the black curtain, for example, with as much detail as possible and the costumes and faces will be blown out, just the opposite of the desired result. The ND filter works pretty well under these circumstances. If you find that you now do not have enough light, you can add about as much as 6db of gain without noticeable noise.

AE shift, if employed, will also make two identical cams no longer match.

If you do not have experience in a particular light, and you have no way to properly monitor the image, you can use the cameras’ meters. Zoom in on the part of the image that you care most about. Faces, for example. Put the camera on auto then back to manual. Take note of the settings. Turn on 70 zebra. The faces should show the stripes. Go wide, turn on 100 zebra—how much of the image is blown out?

The talent, here, is moving into radically different amounts of light. The camera operator needs to ride the iris control to compensate.


OSX 10.5.7; MAC Book PRO (EARLY 2008); Camcorders: Sony Z7U, Canon HV30, Sony vx2000/PD170, Canon xl2; Pana, Sony, and Canon consumer cams; FCP certified; write professionally for a variety of media; teach video production in L.A.


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Pat Ford
Re: Lighting Difference in Two Cameras?
on Aug 18, 2009 at 6:50:47 pm


Well said Craig, thanks.

In the future, if we do this job again, we need to have a production meeting regarding the stage set-up. We could avoid such things as:

1. Black background on the stage. The girls' dresses were light or white...against a black ground with a spot. As my #1 camera guy said...."It's like trying to shoot a supernova on stage!"

2. We tried to make the spots go away this year, but we were not successful. In my humble opinion, the spots add nothing to the stage presentation. The two huge screens to each side of the stage serve the purpose of highlighting the girls. I am not a stage lighting expert, but it seems to me that the use of the spots in a fairly brightly lit venue is well-nigh useless. In the old days, they were used to create dramatic pools of light in a dark hall. This ain't happening here.

By the way...none of this means that we could not have done our job better. That is certainly true. This shoot is a huge job...set-up takes a significant amount of hours over two days. However, we need to have the cameras matched. We need to have a video production meeting for 15 minutes or so before the start of show.

By the way, I have used the term "girls" throughout our discussion. I do not mean any disrespect here...you would not catch me performing in front of several hundred people...let alone walking down a runway in high heels wearing a two piece bathing suit.

They are talented and brave people. Kinda cute too, if an old geezer can say that without fear of getting arrested!



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