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  1. #1
    Stephen J. Collier's Avatar
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    New: SLR TTL metering and Filter Factors

    *THIS IS THE CORRECT PLACEMENT OF MY EARLIER MISSPLACED THREAD*


    I have little experience using filters in my photography; the times that I have tried to use them I've been less than pleased with the results. I shoot mainly black and white and so I’ve only ever used an orange or red filter.

    I do know that using any filter other that a UV/Haze filter will require that a filter factor be computed into the exposure, but that in the case of a TTL meter on an SLR the filter factor is already computed because the light entering the lens and being metered first has pass through the filter. I’ve also read that in cases when a heavy ND filter or a dark red filter are used the TTL system can be thrown off, resulting in an erroneous meter reading.

    Well here is my problem: I shoot with a Canon “New” F-1 (mid to late 80’s center weighted meter screen) and also a Nikon N80 (bought 2005 with spot, center weighted and 3D matrix meter) and as far as I can tell neither camera’s TTL meter compensates for a filter being placed on the lens. I have taken readings of a scene with both cameras recorded the meter reading and then placed my orange (G) filter or my red (A) filter on the lens and with both camera using either filter there was no change at all in the meter readings (there was a slight change with the red filter, but no more than 1/3 stop).

    I have looked up using filters in my basic photo how-to books and tried to find information on filters and metering in the Nikon N80 manual and have had no luck with either approach.

    I totally assume that the problem is all of my own making; that there is something that I am missing, so please fill me in on where I am going wrong.

    Thank you for any help.
    [COLOR=DarkOliveGreen][SIZE=2]"We are not at War, we are having a nervous breakdown". Hunter S. Thompson[/SIZE][/COLOR]

  2. #2
    David A. Goldfarb's Avatar
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    That sounds odd. I have a New F-1 and it compensates correctly.

    Are you sure you're doing the reading the same way? Set the camera on a tripod aimed at an outdoor scene. The camera should be in manual mode, and don't use stopped-down metering. Take an unfiltered reading, and then without moving the camera, take a filtered reading.
    flickr--http://www.flickr.com/photos/davidagoldfarb/
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  3. #3
    Stephen J. Collier's Avatar
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    David-
    I have to confess that I did my test indoors; would the tungsten light change the meter reading? Wait, damn it would wouldn't it!
    [COLOR=DarkOliveGreen][SIZE=2]"We are not at War, we are having a nervous breakdown". Hunter S. Thompson[/SIZE][/COLOR]

  4. #4
    David A. Goldfarb's Avatar
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    Yes, tungsten is fairly yellow-orange so it would have a different effect, and meters tend to get non-linear at low light levels, so if you're indoors and then add a 2-3 stop filter the meter is likely to be unreliable.
    flickr--http://www.flickr.com/photos/davidagoldfarb/
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  5. #5
    Stephen J. Collier's Avatar
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    Thank you, I appreciate your help.
    [COLOR=DarkOliveGreen][SIZE=2]"We are not at War, we are having a nervous breakdown". Hunter S. Thompson[/SIZE][/COLOR]

  6. #6
    JBrunner's Avatar
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    A TTL meter may not compensate correctly depending on the meter's spectral sensitivity( or it might, depending). The safe bet is to use a handheld meter and add the filter factor manually, or use the camera meter without the filter and then add the filter factor, and the filter, and shoot accordingly with the filter in place, or run some tests so you know how far off the TTL is under the light you normally shoot in and compensate (It might be fine). I just use handheld meters as the other methods would be a PIA for me, personally.
    Most of my cameras don't have meters. I shy away from fancy stuff like that

    And yes, try again under daylight conditions.



 

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