Results 1 to 9 of 9

Thread: Measuring Color Temp

  1. #1
    Senior Member iND's Avatar
    Join Date
    Jan 2009
    Location
    ST LOUIS
    Posts
    400

    Measuring Color Temp

    I have been interested in finding technology that is able to read color temp much like a light meter.

    With the recent release of the Sekonic C-700 SpectroMeter my curiosity has been peaked.

    Does anyone have an expertise in the measuring of color temp, used any devices, or had a chance to get their hands on the new Sekonic

    SekonicC-700 SpectroMaster Spectrometer

  2. #2
    Administrator Sean Setters's Avatar
    Join Date
    Jan 2009
    Location
    Savannah, GA
    Posts
    3,347
    I've been interested in such devices, but I've never pulled the trigger. Previous products I looked at were right in this price range but weren't as full-featured. I think it'll likely be a popular tool, at least within its relatively small market. :-)

    Sean

  3. #3
    Senior Member iND's Avatar
    Join Date
    Jan 2009
    Location
    ST LOUIS
    Posts
    400
    Thank Sean

    So lets say we measure the light temp, and set our white balance appropriately.

    How would you modify your flash to keep a balance,

    If you are going to use gels, then can we produce gels with a wide range of color temps?

    How about a flash with a built in color temp setting?


    Thank you

  4. #4
    Administrator Sean Setters's Avatar
    Join Date
    Jan 2009
    Location
    Savannah, GA
    Posts
    3,347
    If you're going to spend $1,500.00 to know what color temperature the ambient light is, then you're likely ready to invest in a wider array of color correction gel filters. The C-700 tells you the product name of the Lee gel you need to most closely match your scene. However, most of us are unlikely to have the exact one (or multiples of the exact one). The best idea is to expand your own range in the color temperature locations you intend on working in and then use the closest gel you have. That's still better than ballparking it most of the time, assuming you have a wider array of color choices besides full-1/2-1/4 CTO/CTB and Plus Green. :-)

  5. #5
    Senior Member iND's Avatar
    Join Date
    Jan 2009
    Location
    ST LOUIS
    Posts
    400
    Rosco makes a range of gels

    http://www.rosco.com/filters/cinegel...V&CategoryID=2


    I would need to expand my range of existing gels, I just converted to the MagMod system and it may be sometime before they are able to expand for a limited market, so I would need some sheets of gels that I could cut to fit the system. Do you have any resources here.

    Also If I use stacked gels, how would I do that calculation.

  6. #6
    Administrator Sean Setters's Avatar
    Join Date
    Jan 2009
    Location
    Savannah, GA
    Posts
    3,347
    The good thing about buying larger sheets of colored gels is that you can cut them up to get several shoe-mount-flash-sized gels out of them (even accounting for the larger area of the Magmod). When it comes to stacking gels, though, I'm unaware of how to do those calculations.

    I suppose you could get the C-700 with the flash triggering option and simply measure the color of your flash when stacking gels to see if you're close to the ambient. I know it features a built-in PocketWizard trigger, but I haven't been able to figure out if it also features a sync port (that would allow you to plug in another manufacturer's radio trigger). I would assume it does...but I haven't found confirmation of that.

    UPDATE: Apparently, PocketWizard triggering isn't built-in. Take a look at this from the product announcement:

    The world’s first stand-alone spectrometer that measure the flash light with wireless Triggering with a PocketWizardⒸ Receiver Attached (C-700R Only).
    That would indicate that you could plug any radio trigger into it, wouldn't it? So confusing...

  7. #7
    Senior Member
    Join Date
    Jan 2009
    Posts
    1,156
    I've classically figured out my color temp the old fashioned way: shoot a gray card, review on screen with RGB histogram showing. Raise the K to move the Red to the right relative to the Blue, lower the K to move the R to the left relative to the B. When Red is stacked over Blue, I know the K. If I really care (i.e. I'm under icky fluorescents), I'll fiddle with the Magenta/Green shift to get the Green lined up with the Red/Blue, but I haven't experimented to see how many green shifts equals 1/4 plus-green, etc.

    Would I buy a meter to save me the time? Perhaps...some of the shooting I do might drive me to do that.
    We're a Canon/Profoto family: five cameras, sixteen lenses, fifteen Profoto lights, too many modifiers.

  8. #8
    Senior Member iND's Avatar
    Join Date
    Jan 2009
    Location
    ST LOUIS
    Posts
    400
    Thank you for keeping this discussion alive.

    I contacted Sekonic and was informed the C-700R will only radio trigger with Pocket Wizzards.

    In regards to auto white balance, if we choose auto white balance is there any way to read this Kelvin value on the LCD screen prior to the shot?

    Does anyone see a value in the lux reading?

    Next regarding stacking gels: my assumption is that stacking is additive in regards to color value.

    for example: stacking

    (CTO 1/8 converts 5500K to 4900K) + (CTO 1/2 converts 5500K to 3800K) =

    CTO 3/4 converts 5500K to 3200K

    I assume the stacking vs a single CTO 3/4 will stop more light but that can be adjusted in exposure.

    I really do not understand the Mired shift and whether those values are useful in calculating stacking values

    Mire shift CTO 3/4 = 131
    CTO 1/2 = 81
    CTO 1/4 = 42



    Thank you

  9. #9
    Senior Member
    Join Date
    Nov 2011
    Location
    Big Mouse Florida
    Posts
    1,055
    You know I had blocked this whole mental exercise in my memories, and you guys brought it back, now my grey matter has the consistency of refried beans.

    Who says photo is a only a craft, it is high science as well.

    If you see me with a wrench, call 911

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •