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Matching Arri tungsten units to Arri M18


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#1 Ryan Emanuel

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Posted 15 March 2018 - 08:33 PM

I have a shoot where I'm going to need HMI's and tungsten to work seamlessly for color temp and green/magenta shift, but I will not have the time to test, wondering if anyone has had to do this already and has a gel cocktail that worked well.  Thanks.


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#2 Adrian Sierkowski

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Posted 15 March 2018 - 08:38 PM

It'll depend a bit on the HMI bulbs's life; e.g. how many hours it's been burning. Best bet would be track down a color meter and it'll tell you.


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#3 Mark Kenfield

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Posted 15 March 2018 - 08:53 PM

If you need them to match, you really need to make time for testing. If not, plan to have that testing eat up time on set while you're lighting.

You MUST bring a colour meter with you, or better yet a spectrometer, and have a healthy supply of CTO, CTB in full, 1/2, 1/4 and 1/8 densities, and the same for both Plus Green and Minus Green gels.

 

For colour-critical white-cyc work in the past I've had issues matching multiple Arri tungsten units (let alone throwing HMI into the mix). So make sure you come prepared.


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#4 JD Hartman

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Posted 16 March 2018 - 05:29 AM

I have a shoot where I'm going to need HMI's and tungsten to work seamlessly for color temp and green/magenta shift, but I will not have the time to test, wondering if anyone has had to do this already and has a gel cocktail that worked well.  Thanks.

 

A recipe for failure.


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#5 Chris Burke

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Posted 16 March 2018 - 05:53 AM

Why isn't there time to test? I read that here on this website and hear it time and again from all kinds of people with varying degrees of experience. Test? Yeah right? I am not picking on you, it is just that this is an area where people think they are saving time and money by skipping a test. Big mistake. Often one hears, "We want it to look good, but is it really necessary to test? Can't you fix it in post?"

Many different formats and cameras out there seem to make the differences in lighting instruments stand out more. You will pay for it one way or another.


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#6 David Mullen ASC

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Posted 16 March 2018 - 07:52 AM

I don’t think you can ever get a perfect match but it depends on how the lights are angled, etc. in terms of how noticeable the mismatch will be, plus exposure will have an effect, a hotter light will be less saturated so the color differences will be washed out a little.
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#7 Ryan Emanuel

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Posted 16 March 2018 - 10:00 AM

Why isn't there time to test? I read that here on this website and hear it time and again from all kinds of people with varying degrees of experience. Test? Yeah right? I am not picking on you, it is just that this is an area where people think they are saving time and money by skipping a test. Big mistake. Often one hears, "We want it to look good, but is it really necessary to test? Can't you fix it in post?"

Many different formats and cameras out there seem to make the differences in lighting instruments stand out more. You will pay for it one way or another.

 

If it were up to me, I would gladly test the units with the camera and a grey card and a RGB parade to know for sure.  The lack of testing for me is due to production department on tiny budget projects.  The tungsten units and the HMI are both coming from different owner operators so coordinating a test before the shoot would require an extra rental.  I tried to negotiate explaining the benefits of using a regular rental house, but with sites like sharegrid, some producers will browse for the best bottom line.   I'll have to do the test on set, I was just asking because I have a tight first day.  


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#8 Matthew Parnell

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Posted 17 March 2018 - 07:23 AM

How close a match do you require? Is it a color critical situation, or are you also working with natural light or have a litttle creative latitude?

If you have creative latitude you will be surprised at what you can get away with if you get them close, if its color critical then you will need to spend a bit of extra time dealing with it.

Generally speaking, putting CTB on Tungsten lamps will attain a better color match than trying to put heavy (full or stronger) CTO on HMI lamps. Heavy correction on HMI tends to accentuate the peaks and troughs in the lamps spectrum and can have some interesting, and difficult to correct results. Naturally CTB on tungsten does come at a cost in terms of stop.

You may be able to meet half way and start with a 1/2 CTO on your HMI, then CTB your tungsten to match.

It would probably easier to correct your colour temperature first, then when matched, fix your green bias with +/- green on the HMI Head.

There really isnt magic formula. Especially with HMI. Lamp to lamp you can have large variances, 2000 kelvin and 1/2 value swings in green from a new globe to an old globe are not unheard of.

Make sure you have a comprehensive supply of correction gel, and most importantly have fun!

If you can go with a tungsten balance, it may be worth checking the rental house you are getting the M18 from to see if they stock the coated Tungsten balanced 1800w Globes Osram make.
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#9 JB Earl

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Posted 26 March 2018 - 12:07 PM

what color temp are you trying to match them to?  how many footcandles do you need?  Your safest bet, without testing, would be to forget the HMI and get some minubrutes or something like  that.  They'll all match then.   


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