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Thread: Foot candle to aperture and ISO.

  1. #11

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    Re: Foot candle to aperture and ISO.

    "Basic exposure rule", as taught in film school back in the day:

    For ISO 100: 100 foot-candles = 1/50 @ f2.8

    We used incident meters, but sharktooth's recommendation of a gray card and reflective meter should yield the same results.

  2. #12

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    Re: Foot candle to aperture and ISO.

    Ansel Adams tells how to convert foot candles to f/stops and shutter speeds in your head.

    Use the square root of the film speed for the f/stop and use the footcandles for the shutter speed.

  3. #13

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    Re: Foot candle to aperture and ISO.

    There was a very well known local (Woodstock, Vt.) photographer, John Doscher, who started and ran a very well regarded photography school - who would always evaluate exposure (and express this to others) in terms of foot candles.

    John D. is long gone...but I seem to remember that many photographers - those born in the late nineteenth/early twentieth century, when evaluating or even thinking about a scene...both thought and spoke in terms of foot - candles, which a bit later transitioned to EV's...and then as simply f/stop shutter speed combos.

    Many photographers back in those days could also think and speak in terms of color temperature, and where I might photograph a grey card or color chart as the first snap of a series during a commercial color setup, especially if on location where lighting was iffy and not always in my control...earlier photogs would either whip out a color temperature meter (oh...how I wish I'd owned one!) - or just go by the seat of their pants, and just nail it!

    But I think we've lost something in our more recent means of evaluating light and color values - because Foot Candles, EV's, and Color temperature values all exist prior to interpretation, and thus could become more closely alloyed and more naturally ingrained during the life of a practitioner.

    Makes me think of the old polynesian navigators...standing on the foredecks of their boats - watching and feeling...interpreting what the seas were telling them, guiding them home. Sad that those times, and those practitioners, are leaving us.

  4. #14
    Tin Can's Avatar
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    Re: Foot candle to aperture and ISO.

    Yes, and when did your location get the infernal wires

    Rural was last to wire and lamp

    Before we did use candles

    My local Grid ia all spindly poles and a web of wires

    I named this 'Wires' last week shot from my gravel driveway, I am letting it go to grass
    Wire Support by TIN CAN COLLEGE, on Flickr

  5. #15

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    Re: Foot candle to aperture and ISO.

    Ha! But among the ironies of this infernal technology...that with a few clicks of the clone stamp - those wires are gone! (or maybe ?)

  6. #16
    Drew Wiley
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    Re: Foot candle to aperture and ISO.

    Meters that read in footcandles are typically called Lux meters, and are mainly used for things like architectural lighting, not photographic applications, although some incident film meters do both.

    Going back to the Polynesian navigators, they did use instruments. Just because those were made of sticks, and floated in the water detecting subtle variations in wave patterns doesn't mean they weren't real instruments. They certainly got them remote places prior to anyone else.

    And just a few clicks of a pair of insulated pliers will get those wires down out of the scene too. But then you'll have to contend with some angry neighbors and perhaps electrocution burns too, or a dry pile of leaves and then your house on fire. But at least infernal Photoshop would be disabled in the process, so that's something to commend the manual method. The Polynesians didn't need PS either.

  7. #17

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    Re: Foot candle to aperture and ISO.

    I did a conversion from EV to Lux to FC and created this exposure chart. It even has reciprocity time adjustments for Ilford. Its based on 100 ISO and large format shutters normal working speeds and fstops. For ISO 400 move 2 spaces in either fstop or time.

    Click image for larger version. 

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    Adventure is worthwhile in itself. ... Never interrupt someone doing what you said couldn't be done. -- Amelia Earhart
    http://www.searing.photography

  8. #18

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    Re: Foot candle to aperture and ISO.


  9. #19

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    Re: Foot candle to aperture and ISO.

    Quote Originally Posted by EarlJam View Post
    "Basic exposure rule", as taught in film school back in the day:

    For ISO 100: 100 foot-candles = 1/50 @ f2.8

    We used incident meters, but sharktooth's recommendation of a gray card and reflective meter should yield the same results.
    At the start of my career, modern office interiors and industrial workplaces were illuminated by systems designed by lighting engineers. Whenever you photographed in one of these locations, you could bet that there was 100 FC on the desktop or workbench. That was the OSHA standard. The exposure with EI400 Tri-X was usually 1/60 at f5.6. Top light is not very flattering, so auto electronic flash was often used for fill.

  10. #20

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    Re: Foot candle to aperture and ISO.

    One consequence of the widespread use of LED lights for cinematography and still photography, and the abandonment of tungsten, is that watts are no longer a reliable indicator of light output. In my view, this makes understanding Lux essential to evaluating light sources. Foot candles is a U.S. thing that I suspect is used less and less frequently. When I'm purchasing or using artificial lights, I want to know Lux, not watts (except to determine how much energy the fixture/light draws) or foot candles.

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