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Color chart test


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#1 Ashley Barron

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Posted 27 February 2009 - 12:24 AM

Hi there,

I just wanted a quick refresher as to how to do a color chart test. I know it must be evenly lit but I can't remember the other parameters.

Thanks,
Ash.
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#2 Satsuki Murashige

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Posted 27 February 2009 - 07:08 AM

Hi Ashley,

Do you mean an over/under stock test?

Basically, set up a grey card and color chart in the foreground, an actor or two with different skin tones in the mid ground, and maybe a black and white reference like some duvytene and gatorboard in the background. You can also do colors in the background or whatever else you want to see. Take notes of your meter readings so you remember later how over/under key the light and dark areas of the scene were lit.

Light everything evenly to f/5.6 and shoot at T5.6. That's your normal exposure. Then change the stop on the lens and shoot at T2, T2.8, T4, T5.6, T8, T11, T16. So now you have a range of -3 stops to +3 stops. Then can out that film and tell your lab to print the roll twice - the first time, with a one-light corrected to the 1st grey card (that you shot at T5.6), and second time, with every shot corrected back to normal. That way, you can see what each under/over exposure looks like uncorrected and corrected.

Here's what it should look like, roughly: http://www.flickr.co...N03/3196855469/

Just light your charts better than I did! I was fighting spill from overhead skylights and some underpowered lights. Big soft lights at 45 degree angles is best.
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#3 Scott Pelzel

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Posted 27 February 2009 - 08:28 AM

Hi Ashley,

Do you mean an over/under stock test?

Basically, set up a grey card and color chart in the foreground, an actor or two with different skin tones in the mid ground, and maybe a black and white reference like some duvytene and gatorboard in the background. You can also do colors in the background or whatever else you want to see. Take notes of your meter readings so you remember later how over/under key the light and dark areas of the scene were lit.

Light everything evenly to f/5.6 and shoot at T5.6. That's your normal exposure. Then change the stop on the lens and shoot at T2, T2.8, T4, T5.6, T8, T11, T16. So now you have a range of -3 stops to +3 stops. Then can out that film and tell your lab to print the roll twice - the first time, with a one-light corrected to the 1st grey card (that you shot at T5.6), and second time, with every shot corrected back to normal. That way, you can see what each under/over exposure looks like uncorrected and corrected.

Here's what it should look like, roughly: http://www.flickr.co...N03/3196855469/

Just light your charts better than I did! I was fighting spill from overhead skylights and some underpowered lights. Big soft lights at 45 degree angles is best.



This is a good way to do a color chart test, but another way is to leave you lens on T4 or T5.6 and leave there, but adjust your lighting in 1 stop increments either side of + or -

This method is a better way to test the stock with your ideal Tstop setting as much of the time you will want to stay within the same Tstop for most of your scenes if possible which will help with consistency. Adjusting the lights and not the lens gives you a more accurate ideal latitude reading of the stock or video you are shooting.

Have Fun!

-Scott
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#4 Mike Lary

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Posted 27 February 2009 - 04:59 PM

If it's strictly a latitude test and I'm shooting a gray card and/or color chart, I try to keep the light fixed and bracket exposures. If I'm shooting three dimensional subjects, I'll move the lights as opposed to opening up the aperture - only when the depth of field would diminish enough to put some of the subject out of focus. The problem with moving the lights instead of bracketing is that you have to constantly adjust the light to make sure the angle and area of coverage stays the same from shot to shot.
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#5 Scott Pelzel

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Posted 27 February 2009 - 05:20 PM

If it's strictly a latitude test and I'm shooting a gray card and/or color chart, I try to keep the light fixed and bracket exposures. If I'm shooting three dimensional subjects, I'll move the lights as opposed to opening up the aperture - only when the depth of field would diminish enough to put some of the subject out of focus. The problem with moving the lights instead of bracketing is that you have to constantly adjust the light to make sure the angle and area of coverage stays the same from shot to shot.


Mike, you don't have to move the lights, you can just knock them down with scrims or nets to start and then pull away the nets or scrims to get your + exposures and add them back and more to get your - exposures. It is not about moving them but cutting them down and you can leave your lights se for the most part. It's not that difficult if you have the scrims or nets and it is a better way to a latitude test for ideal exposure scenarios.


-Scott
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#6 David Rakoczy

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Posted 27 February 2009 - 05:23 PM

It's not real practical to light a shot to a t16 or t22 then scrim it down to a t1.4
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#7 Scott Pelzel

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Posted 27 February 2009 - 05:29 PM

It's not real practical to light a shot to a t16 or t22 then scrim it down to a t1.4


Why is that David? I have done it many times and never had any problems...
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#8 David Rakoczy

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Posted 27 February 2009 - 05:37 PM

Why is that David? I have done it many times and never had any problems...



Well, because there is not enough room for enough scrims to cut light from t16 to t1.4. You will need 7 Doubles. Basically, you need to place a piece of linoleum in the ears to cut it that much... and, after the 4th scrim you can see the scrim mesh 'effect' on whatever it is you are lighting. I use a combination.. light with two doubles in each.. then do a combo of pulling scrims and adjusting the iris... and nudge the Lamps around a bit...
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#9 Scott Pelzel

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Posted 27 February 2009 - 05:37 PM

Why is that David? I have done it many times and never had any problems...


I have to clarify that I am talking about just for a chart test and not an elaborate set up. Most chart tests are not that elaborate just to test stock.
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#10 Satsuki Murashige

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Posted 27 February 2009 - 05:39 PM

... but adjust your lighting in 1 stop increments either side of + or - ... this method is a better way to test the stock with your ideal Tstop setting ...

Sure, if he has the time and amperage to get away with that then I agree that testing at the shooting stop is ideal. I usually don't if I'm at the rental house because they want to me out of there in a few hours and I can only use a few 1ks that they have around, so I do it the easy way. On a rented stage or in a classroom setting it's a different matter. It also depends on how well you know the lenses, if you've never used them before then it might be good to see how they hold up at different apertures.
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#11 David Rakoczy

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Posted 27 February 2009 - 05:40 PM

It is not wether you are testing a chart or a face.. what Satsuki is sharing is the real deal on Stock testing and you have to go (well in the old days 3 stops over and under) but with today's stock you should go 4 stops over and under...
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#12 Scott Pelzel

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Posted 27 February 2009 - 05:44 PM

Well, because there is not enough room for enough scrims to cut light from t16 to t1.4. You will need 7 Doubles. basically, you need to place a piece of linoleum in the ears to cut it that much... and, after the 4th scrim you can see the scrim mesh 'effect' on that ever it is you are lighting. I use a combination.. light with two doubles it each.. then do a combo of pulling scrims and adjusting the iris.


It has to do with the lights your are using as well and not all fixtures and you start at cutting the light to the lowest level and then work your way up, so you are pulling scrims for the most part.

I think it has to do with what you are lighting the test with and a combo of scrims and adjusting the iris works as well if you start adjusting the iris on the far upper and lower end of scale in the test.

-Scott
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#13 David Rakoczy

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Posted 27 February 2009 - 05:45 PM

Sure, if he has the time and amperage to get away with that then I agree that testing at the shooting stop is ideal.


Amperage has nothing to do with it.. it is cutting light in half 7 times... Sure you can send someone to the truck and start hanging sheets of ND9 etc... but that is not efficient.
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#14 Scott Pelzel

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Posted 27 February 2009 - 05:45 PM

It is not wether you are testing a chart or a face.. what Satsuki is sharing is the real deal on Stock testing and you have to go (well in the old days 3 stops over and under) but with today's stock you should go 4 stops over and under...


Very true...
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#15 Mike Lary

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Posted 27 February 2009 - 07:17 PM

Mike, you don't have to move the lights, you can just knock them down with scrims or nets to start and then pull away the nets or scrims to get your + exposures and add them back and more to get your - exposures. It is not about moving them but cutting them down and you can leave your lights se for the most part. It's not that difficult if you have the scrims or nets and it is a better way to a latitude test for ideal exposure scenarios.

Good point. You can throw layers of ND on the lights as well. I didn't mean to imply that moving lights was ever ideal. It's just that in cases where you get stuck with a couple lights and stands but no modifiers (which has happened to me on a few occassions) moving the lights is a better option than losing image sharpness.
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#16 Scott Pelzel

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Posted 27 February 2009 - 07:59 PM

Amperage has nothing to do with it.. it is cutting light in half 7 times... Sure you can send someone to the truck and start hanging sheets of ND9 etc... but that is not efficient.


David,

As I said in my other reply, I am referring to a basic color chart test and there are all sorts of variables that can be added and subtracted to the equation and I was just giving one of those.

Much of what we do in Cinematography is not very efficient or practical (lighting for film and video is not a very efficient or practical concept when you break down what has to go into it), but I too like finding ways to do more with less and it's worked for me and made me more efficient and practical in an impractical, but creative job title.
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