Adjusting time for a 23a red filter

Discussion in 'Film Discussion and Q & A' started by Zaphod2319, Nov 7, 2018 at 9:40 PM.

  1. Zaphod2319

    Zaphod2319 TPF Noob!

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    I have spent the night reading about compensating for having a filter. It seems like every article gives a different way to adjust. Adjusting f stops, adjusting exposure time.....adjusting both.

    I need a little help because this seems like a way to screw up my photos rather than adding some contrast, as I don't clearing understand what I am reading.

    I am using a roll of Ilford PanF 50 -120.

    What is the best way I can adjust exposure time when using a 23a filter?

    Thank you

    Dave


     
  2. vintagesnaps

    vintagesnaps Been spending a lot of time on here!

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    I haven't used red filters in so long I can't remember what a 23a is or what I have... (mine are for 35mm not 120) but it sounds familiar so I proably have one. Usually since a red filter is cutting light you'd probably need to adjust a stop (open up the aperture one setting). If it's a dense filter, maybe 2 stops. (edit - I looked it up and it's not that dense so maybe try one stop adjustment??)

    Shooting B&W film I often 'bracket' shots, shooting at least 3 images; using what settings the meter indicates, then one stop difference both ways (to let in more or less light). That can mean one f stop larger or smaller, or one shutter speed setting faster or slower (such as at f8, then at f5.6 and f11; or at 1/250, then at 1/125 and 1/500). Or maybe you already know how to do that.

    Try Tiffen's site or other filter manufacturers, or look up Ilford and see what info they have online. Ignore much of the crap online and read some Ansel Adams and you might be better off! lol
    52MM RED 23A FILTER
     
  3. dxqcanada

    dxqcanada Been spending a lot of time on here!

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    The 23a is a light red filter ... so I would agree with Sharon, 1 stop ... either slower shutter speed or wider aperture or both ... whatever works better for the situation.
    I am assuming you are not using TTL metering.

    When I did use a dark red filter (for infrared), it was about 2-3 stops.
     
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  4. 480sparky

    480sparky Chief Free Electron Relocator Supporting Member

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    Add 2 stops. Whether shutter speed or aperture.... or one stop of each.
     
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  5. petrochemist

    petrochemist TPF junkie!

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    My ancient Kodak Wratten filters book, shows 23a as an orange/red & reading between the lines for orange & red filters gives about 2 for tungsten balanced film & 3-4 for Daylight film. Results are higher still for orthochromatic films! Fortunately I just use TTL metering so don't have to deal with the guesswork.
     
  6. bhop

    bhop No longer a newbie, moving up!

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    If your camera has a built-in, through the lens, meter, then you don't have to do anything, the meter will compensate.

    When i'm using a filter with my meterless camera, I just set my handheld meter to a different ISO. For example, ND filter I use sucks away 1 stop. If i'm using 400 speed film, I change my handheld meter to 200.
     
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