Flourescent lighting

Discussion in 'Beyond the Basics' started by smilesforlife, Dec 30, 2015.

  1. smilesforlife

    smilesforlife TPF Noob!

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    I just changed the location of my studio and my previous was pot lights.. white walls..high ceiling.. new studio is fluorescent lights with cream walls, low ceiling.. had to change my kelvin temps in the new studio, have never before. I do not use strobes or studio lighting but have always bounced my flash. Always,, even in ppls homes. always been happy.
    So frusterated as my images are no longer consistant in the new studio.. same settings one could be yellowish, one could be perfect.. I wondered if it was because I was bouncing my 580 EX flash off the lighting... some say it's the flickering bulb.. I don't want to put money into changing anything until I am completely sure. Bulbs are not cheap and fixtures to change are $300 per fixture and there is 7.


     
  2. 480sparky

    480sparky Chief Free Electron Relocator Supporting Member

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    Your color shifts are due to the alternating-current cycling. If you live where it's 60Hz, your fluorescent lamps will dim 120 times a second. When they dim, the color output changes slightly. Your camera is picking up this difference when you use a high enough shutter speed.
     
  3. WayneF

    WayneF No longer a newbie, moving up!

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    Based on technology change in the 1990s, fluorescent lights are either old or new.

    Old ones use magnetic ballasts, and new ones use electronic ballasts.
    Speaking of builtin larger ceiling fixtures, which might be either type. Complicated, because some older magnetic ballast is still sold. Compact CFL bulbs use electronic ballast.

    The old ones with magnetic ballast will flicker with the line voltage, either 60 Hz (North America) or 50 times a second (much of rest of world). Technically, the flicker is at twice that rate. Our shutter speed needs to be either that exact 1/60 or 1/50 second, or perhaps exactly twice faster. But NOT any inexact partial multiple. Because, unless our shutter mimics the same frequency, or exactly double it, we capture partial cycles and will see serious random color shift. Every shot will not be the same, often yellowish, brownish.

    New electronic ballasts are tremendously faster, maybe 20,000 Hz, and are not any issue about flicker.

    See Color Filters on Flash

    for details of a simple shutter test (which intentionally does it wrong to cause the problem) to decide which your your lights are. Don't use Auto white balance for the test. Doesn't really matter which WB is used, we are just looking for differences in several shots, but Auto WB tends to hide differences.

    Using the shutter speed same as the cycle duration works. Or just the ballasts can be replaced (less expensive), the rest of the old fixture is not a problem.
     
    Last edited: Dec 31, 2015
  4. smilesforlife

    smilesforlife TPF Noob!

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    Thanks so much for chiming in and helping this all make sense to me.. it's still rather confusing.
    How does one person shoot under 1/125 when shooting children who non stop move.
    I am willing to try whatever it takes if I know it will work.
     
  5. dennybeall

    dennybeall No longer a newbie, moving up!

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    If you're handy and allowed to by the building owner, you can open one of the fixtures and see which ballast is in there. The old ones are big and very heavy (for 2 -8 foot bulbs the ballast will be about a foot long and 2" X 2"). You can buy a new electronic one at Home Depot or Lowes and change it out. It's very easy but the new electronic ballasts are not cheap. I've got over 200 of the fixtures at my self-storage facility so have changed out a bunch of them over the years.
     
  6. WayneF

    WayneF No longer a newbie, moving up!

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    Well, magnetic fluorescent is far from the best lighting, but you said bounce flash, and flash is fast (faster than shutter speed - the shutter just has to be open to pass the flash), so more emphasis on flash power will stop action pretty well. If actually needed, you could add a second flash unit. You would want full size regular speedlights (like the 580), not the little toy ones for bounce.

    The continuous light is what lets slower shutter speed blur action that the flash could have already stopped. Continuous light cannot stop action, but the speedlight flash can. In this case, it is NOT the faster shutter speed that stops the motion anyway. It is the flash that stops the action, and instead faster shutter just keeps out the contribution of the continuous light that could blur whatever motion that the fast flash already stopped.

    But in this case, faster shutter speed messes up the flicker situation, but you can turn off Auto ISO, and use lower ISO (maybe ISO 400 for bounce, or ISO 200 is sometimes possible), and do pretty well (lower ISO keeps out the continuous, but the flash power can simply be turned up to compensate). The bounce will usually light up the whole room in the same way the ceiling lights could.

    Mixing flash and fluorescent is bad anyway, because they are different colors. We can only set one White Balance, so more flash and less fluorescent is good for that reason too, with Flash white balance.
     
    Last edited: Jan 1, 2016
  7. DB_Cro

    DB_Cro No longer a newbie, moving up!

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    You can freeze motion using 2nd curtain flash sync at virtually any shutter speed, the flash will "bake in" the image.
    I've been shooting like that in nightclubs (people dancing), often at 1/4 to 1/8th of a second.

    Only need to be sure that the flash output is above the various ambient lights that might be flying around or you might
    get ghosting.
     
  8. WayneF

    WayneF No longer a newbie, moving up!

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    2nd or rear curtain sync does NOT "bake in the flash". Each pixel simply accumulates all the light that hits them, and shows the one value of total accumulation. It does not matter to the total when it occurred.

    Since the 2nd or rear curtain sync flash occurs at the end of the open shutter duration, it does cause any motion blur recorded during the longer continuous light exposure to be located "trailing" the moving subject instead of leading it out in front. Looks very much more natural. Examples at Flash Sync mode, including Rear Curtain Sync
     
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  9. DB_Cro

    DB_Cro No longer a newbie, moving up!

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    I adjusted my post to the obvious level of expertise of the person who asked.
    I think he got the point.
     
  10. petrochemist

    petrochemist TPF junkie!

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    You can get colour balancing gels for either the fluorescent lights or the flash to reduce the WB issue. Might be a pain to get right & it won't solve it if there's flicker involved.
    It MIGHT be that shooting a couple of test videos could check for flickering. I think they'd show quite well if the video frame rate is at odds with the mains cycle. Many cameras allow video rate to be adjusted to work with 60Hz or 50Hz.
     
  11. smilesforlife

    smilesforlife TPF Noob!

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    So what I do know is the bulbs are 4100k is the flourescent bulb temp. They put 3700k in my waiting room to see if it was better on my head (migraines) and the room looks yellow. I can find out whatever I should ask.
    Yesterday I shot with white backdrop.. and all pics looks pretty good,, I was happy.
    I didn't change anything so this didn't help me figure things out..
    1/160 3.5 ISO 250 RAW bounced 580 Ex no window light
     

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  12. smilesforlife

    smilesforlife TPF Noob!

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    That bad?
     

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