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Old July 19th, 2013, 04:27 AM   #1
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big white balance calibration target

A pet peeve of mine is how poor many DPs are at doing white balance calibrations. They don't pay any mind to where they are pointing their calibration target, and often end up aiming it at the cast of a carpet or something nearby, and then the calibration is the opposite of whatever cast they pointed the target at.

Or they just point the camera at a white wall which hasn't been washed and was never true white. What's the point of doing that? Much better just to use the daylight or incandescent presets.

The target needs to be getting the same light as the subject we are trying to photograph, so it should be aimed upwards about 45 degrees toward the sun or wherever the main light source is (usually overheard).

In order to prevent DPs from doing bad color balance, ruining all the work I do getting the color right as gaffer, I'm thinking about getting a proper color balance target for use on set.

The features that I'm looking for are:

1. Big. a 12" card is just not big enough to fill the frame if you are shooting something human sized or larger.

2. Matte. Any shinyness will tend to reflect a cast.

3. Neutral. Obviously the material must not have a color cast.

4. Light Grey. 18% is actually a bit dark, and 100% white can blow highlights on cheap cameras, so I'd actually prefer about 40%, but other than the Robin Myers Imaging Digital Grey card I've not seen any other light grey color blancing targets.

The target that seems closest to meeting my needs is the Lastolite EzyBalance Lastolite, Manufacturer of Greycards for Colour Correction and Exposure Control. in the 20" middle size. But before I buy one I thought I'd see what others like to use for white balancing.
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Old July 20th, 2013, 07:24 AM   #2
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Re: big white balance calibration target

I use the white balance card from Portabrace. Its not big enough for your spec but durable and survives packing.
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Old July 20th, 2013, 10:35 AM   #3
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Re: big white balance calibration target

Tom, when doing your white balance you should have the camera set in the approximate position you'll be shooting from, have the white card facing the camera straight on. Set your exposure then do the white balance. Whether you are using an 18% grey or a white card will not make a difference for white balance as long as you set exposure before taking your color temp reading (which you have to do or you will not get a proper white balance).

If you angle the card you will not get a true white balance ready for the shot you are taking.

Generally though, it should be up to DP and director on whether you would do a manual white balance at all. There are many time when you would want to simply dial in the color temp depending on what you want the look to be. The most reliable way to gauge your look is to have a calibrated production monitor on set which you can use to judge your shot.

I've got the 20" Lasolite two sided card. I use it mostly for interviews, theatrical shoots, and multicam shoots where we need to match. For a lot of movie productions we will do test footage ahead of time and decide on what the setting will be with a given lighting setup.
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Old July 20th, 2013, 06:46 PM   #4
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Re: big white balance calibration target

Tom - thanks for getting a good discussion going over the ins-and-outs of white balance because this is one of the areas I need to work on. My kit consists of just one 6" x 9" Porta-Brace white card and it is about ready to break in half so I've been looking for something to replace it with or even add to it.

The set I've been looking at is the 6" x 9" one from WarmCards - White Balance Reference System, the large set, along with the instructional DVD. I'll be the first to admit that the card set is probably overkill for me at this stage but I like the larger size over the smaller size cards.

After reading that Garrett uses a 20" card I'm starting to have second thoughts about the 6" x 9" because the one I have seems small as one has to get it really close to the objective to get full coverage. Now my thought is to just get the Vortex DVD and a couple large cards then learn to work with them before adding more.

Again, thanks for starting these threads.
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Old July 20th, 2013, 08:28 PM   #5
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Re: big white balance calibration target

I have the 20" double sided Lastolite as well. Works great for me.
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Old July 20th, 2013, 10:49 PM   #6
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Re: big white balance calibration target

I've been happily using a 24" pop-up white/black/grey chart from Cowboy Studio. It's even got a silver reflector on the back for the occasional use as a bounce. For less than $20, I don't think you'll find a better solution.
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Old July 21st, 2013, 06:02 AM   #7
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Re: big white balance calibration target

I'm on the fence between the 20" and 30" lastolite ezybalance. My experience with 12" is that it's always way way too small to get at subject position with anything other than telephoto lenses, but I've never used anything bigger.

For those of you who use the 20" size, do you typically use it at subject position, and how far away is that typically from camera (lense focal length useful too if we really want to geek out over arcs of view)?

Garrett good to hear from you... I remember you using the lastolite on a few sets! I'm curious what you meant when you said

Quote:
Whether you are using an 18% grey or a white card will not make a difference for white balance as long as you set exposure before taking your color temp reading (which you have to do or you will not get a proper white balance).
I get why setting exposure first is good, but then once you have set your exposure lets say with an 18% grey card, wouldn't you agree that then replacing the grey card with a white card would give a higher sensor value and put you into a different part of your gamma curve (80-90+IRE ), potentially one that is less flat than 50% IRE middle grey... that was what I was getting at: measurement accuracy. I agree that if we assume color balance is perfect all the way up and down the gamma curve then the grey card is not preferable to a white card, but sensors aren't perfect and I find staying as far away from the nonlinearities useful when trying to measure things.

As far as aiming the white card dead at the camera, I still mantain that is bad practice since the lights are not typically behind the camera (that would be boring flat light); the goal of the card is to capture the light color, not the subtle environmental casts that add character and unpredictability to the light from around the camera wall and floor.

Case in point, I was on a shoot with an incandescent-illuminated wall behind the camera, but subject mostly illuminated by daylight from the side. Camera department kept asking me why the walls looked blue after they white balanced, and once we angled the card midway between the side daylight and the camera all the blue cast went away.
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Old July 21st, 2013, 10:03 AM   #8
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Re: big white balance calibration target

Tom, first, good discussion topic. May be doing another production basics class and need to remember to cover this subject.

Grey Vs. white card should not make a difference in theory if you first set your exposure level correctly. But that's theory. The reality is that you have to understand a lot of things that are going on in modern digital cameras if you wanted to really set your color temp to make true white record as white. The reason it doesn't really matter if you use grey or white is that both contain the same relative levels of red, green and blue. Basic theory of white balance is that you are telling your camera that a given subject is equal values of RGB. If you set exposure first (which you should always set rough exposure first), then you flip it to white, you may have one channel that is actually clipping. So lets say your green is actually at 108% IRE coming off of the card, then your camera will set the white balance so that the correction for green will be too low so you end up with a magenta cast. If you used a grey card you would be ok. That's why I have gotten into the practice finding my rough exposure level and if I'm using a white card to WB I drop my exposure by a 1/3 stop to do the WB. then set the final exposure.

If you want to get super technical you would have to look at the gamma curve of each channel separately. If, your camera's curves are equal all the way then it doesn't matter if you white balanced at 100% IRE or 2%IRE. All but, most cameras don't have RGB gamma curves that are uniform throughout the range. So I always think of taking my WB around the level that is my most important range. If a dialogue scene I usually try to keep the skin tones around 65IRE so I would want my WB reading down around there.

As for the example case regarding angle, this is a situation where they were not taking a WB reading of the key light. If your subject was being mostly lit by daylight then of course you would not assume that the light on the wall would be what you should WB to. Your camera department may have noticed the wall being blue but in reality your subject would have also been blue. You just may not have notice it looking through the camera or on a small monitor. Your editor and colorist would have seen it though. You should have actually turned off the light on the back wall, taken your white balance reading, Then turned it back on and if your DP and Director thought the light looked to orange they could throw a little CTB over the light source. Your mixing light sources so either your background light would look orange or everything else would look blue.

I'll try to address your angle of the card points in the other thread but in short your goal of white balancing is not to capture the color temp of a single light source, it is to capture the color temp of the light that is being reflected off of your subject. Then you use your knowledge of color and make an artistic decision about how you want your picture to look. One of the tools you have to do this is by setting your WB to taste. This takes experience and an understanding of your equipment. I use my WB setting to get a reading of the level then I tweak to get the look. That's why I like cameras that actually tell you what they're reading for WB. I've been thinking about investing in a color meter but they are pretty expensive.
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Last edited by Garrett Low; July 21st, 2013 at 02:50 PM.
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Old July 21st, 2013, 12:35 PM   #9
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Re: big white balance calibration target

Quote:
Originally Posted by Garrett Low View Post
... in short your goal of white balancing is not to capture the color temp of a single light source, it is to capture the color temp of the light that is being reflected off of your subject. Then you use your knowledge of color and make an artistic decision about how you want your picture to look. One of the tools you have to do this is by setting your WB to taste. This takes experience and an understanding of your equipment. I use my WB setting to get a reading of the level then I tweak to get the look. That's why I like cameras that actually tell you what their reading for WB. I've been thinking about investing in a color meter but they are pretty expensive.
(bold emphasis added)

I'd be even more specific; the goal of WB is to faithfully render the color of a subject's face. Hair can go off, shoulders, background, whatever, but the faces should be faithfully rendered. Almost always.

So, yes, I'd turn off backlights for WB, if a window is acting as a kicker on tungsten front light I would flag the window source out during WB and let that highlight later go blue, keeping to the tungsten balance. I'd consider this as something of an effect shot, needs to be managed carefully.

Artistic decisions with mixed lighting temps are for experienced ops, DPs and LDs. One of Tom's other threads addresses simplifying WB for novice cam ops. For them, "don't mix color temps" is the best advice.

I always think back to the very simple guidance of broadcast engineers when teaching the basics in an introductory class: "Can I see everything? Is it exposed correctly? Is it the right color?"

And what about post correction? I'm wary of getting too effect-y in camera unless I have time for good tests and a big monitor, would rather leave as many color decisions as I can to post.

Day-to-day, I use an in-camera tungsten or daylight preset about 60% of the time, a preset will get me to post just fine in many shoots. But it depends, what works for doc/journalism is different than magazine or corporate or narrative/feature.

I bought a set of warmcards, but don't use them much, I prefer post-correction over getting too wild at a shoot. I'm glad I have them, though, they've gotten me through to the best WB I could get under stadium & parking lot lights.
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Old July 21st, 2013, 12:48 PM   #10
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Re: big white balance calibration target

Gentlemen. Thank you all for this discussion. As an 'amateur', I appreciate the level of detail and insight into a very basic technique. Like most 'basic techniques' there's a warehouse of knowledge with years of practice that comes with how and when to properly push the 'little button'.

Again, thank you.

Best regards,

J.
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Old July 22nd, 2013, 07:44 PM   #11
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Re: big white balance calibration target

Quote:
if I'm using a white card to WB I drop my exposure by a 1/3 stop to do the WB. then set the final exposure.
Right on Garett. Thanks for taking the time to do that explanation. We're totally on the same page. Sounds like you're using getting a great signal for white balance, and you illustrate why grey cards might be better than white for novices who don't know how much or even that they should drop exposure for white balancing. Grey cards don't require that adjustment so might be better for novice DPs.


As far as angling the target towards the light, that's something I've come to by personal experience and I know that the convention is to keep it flat vertical with the focal plane. Since it's not the conventional approach and I'm not an expert in white balance, I don't want to argue too hard for it, but I do enjoy debating the merits of balancing for the light versus casts.

I agree that it's often better simply turning off lights that make color casts (leaving the main light on) while doing a white balance. In the particular case I was mentioning the incandescent was intentionally warming up the daylight though, so perhaps a colorbalance without it would have yielded too warm a capture. In most cases the cast is not part of the base lighting.

Mixing incandescent and daylight seems to be a hip thing to do now what cameras can work under low levels, and we are all used to seeing DIY videos with mixed lighting on youtube so it doesn't look as jarring as it did in the celluloid days. I think that white balancing needs to keep up with this trend. In the olden days when it was either daylight or tungsten but not both, it didn't matter as much how you aimed the target because all the light was approximately the same color temp.

But when you have vastly different light temperatures coming from different directions, intentionally, then I think you need to make a decision about which is going to be white, and then aim your target at that light source.

It's all well and good to just say don't mix light, but mixed lighting (especially when architectural flo lighting enters the picture) really happens in real locations, and it is often the time that the balance target comes out because the novice DP thinks "Oh, I don't know what should be white... I should calibrate with a card". They angle the card between the daylight and incandescent and wind up with a balance that is not correct for either. Or they don't pay attention to the angle and end up with essentially a random value depending on the angle.
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Old July 24th, 2013, 02:05 PM   #12
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Re: big white balance calibration target

Quote:
Originally Posted by Tom Morrow View Post
Mixing incandescent and daylight seems to be a hip thing to do now what cameras can work under low levels, and we are all used to seeing DIY videos with mixed lighting on youtube so it doesn't look as jarring as it did in the celluloid days...
On the early '90s TV show Twin Peaks, they used mixed color temps very often. In general, the back light would be bluish, motivated from a window. The color balance is set near tungsten, giving a slightly warm overall look (they were often in wooden rooms) with a clearly blue cast on the hair/back light.

I almost always do this, when appropriate. When it's not motivated, a 1/4 CTB gives a bit of depth without being obvious. A 1/2 CTB is ideal for a subtle, motivated look. A Full CTB is quite strong. I've used this for people in a dark room watching a TV or monitor. In each case, I'll balance to the tungsten fill/key.

A mixed temp setup offers the magical possibility of making a low contrast scene look dynamic. If you light with the fill nearly as bright as the key and add a subtle hair light - all matched, the contrast will be low and the look will be flat and boring. Bring up the key or hairlight and you no longer have low contrast. However, if you put a 1/2 CTB on the hair/back light, you can keep the contrast low while adding contours that bring depth to the subject. If there's a green Exit sign in the background, use a green gel for the same effect. As always, balance to tungsten, rather than to the colored splash light.

These days, when I see a back light with no gel, I can't help but feel that the job isn't yet complete. :)
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Old October 15th, 2013, 08:57 PM   #13
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Re: big white balance calibration target

I thought I'd update this with a test picture that I took with all the white targets I have. Attached is a pic with:

Going clockwise from upper left:
Lastolite tri-flip white panel
Lastolite Ezybalance
An old "white" sheet
A sheet of laser printer paper
The Gretag MacBeth ColorChecker white panel (in top of black plastic frame)
RMI digital grey card on top of a cheapo clapper.
(on the bottom are the cushions of a white leather couch).

This photo was taken at daylight color balance setting on a Canon s110 camera, and color not adjusted in post.

I am glad that I got the Lastolite Ezybalance; it seems to be well calibrated to proper color balance and I am surprised how useful the cross target is for framing. However I'm not happy with the way that the Ezybalance doesn't tend to lay flat; it has a tendency to curve into a saddle configuration reflecting different colors from different directions on different corners.
Attached Thumbnails
big white balance calibration target-grey-cards.jpg  
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Old October 16th, 2013, 09:22 AM   #14
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Re: big white balance calibration target

I shoot a little chart at the head of every scene. That way I have a calibrated source to work off of for first pass color correction.
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Old October 16th, 2013, 10:43 AM   #15
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Re: big white balance calibration target

I don't think anyone has mentioned scopes yet. Our eyes can be deceived but the scope is always correct. There is nothing like dialing in your white balance to a tiny dot in the middle of a vector scope. One of the most simple functions of a scope. And inexpensive with todays software. You don't have to buy an expensive, dedicated piece of hardware anymore. Some of you may already have scopes and never payed attention to them. They are built into most NLE software. For me, I still use Adobe On-Location (love it).

Last week I did a home tour video for a friend of mine who is a Realtor. I have never done one before so I explained to him it probably will not look as good as the videos he was used to watching. He said "come on Steve, you have been doing this for many years, I know it will be great". I said, "exactly my point, all of that experience has taught me you do not walk into a new specialty and create magic just because you are a pro".

Guess what my biggest challenge turned out to be? White balance. He wanted the great room shot at sunset with giant picture windows open to show the lake outside. Shooting from daylight to twilight over a two hour period was the challenge I expected it to be. If you think the sun does not set quickly and change color rapidly try balancing a massive surface of walls you want to stay true with the twilight. It was a challenge to say the least! And the color of those walls has to match the other rooms that do not get sunlight but are painted the same color.

Steve
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