Exposing with Filters (B&W)

Discussion in 'Beyond the Basics' started by K_Pugh, Jun 21, 2008.

  1. K_Pugh

    K_Pugh No longer a newbie, moving up!

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    Firstly, excuse my ignorance if there's already various threads on here about this.. i have read pat VII of the B&W tutorial thingy.

    I just bought Cokin filters today. I use B&W film (HP5 and FP4) so i bought the following filters and as far as i've figured out the exposure corrections are listed next to them:

    P.001 Yellow. (1 stop)
    P.003 Red. (3 stops)
    P.197 Skylight? (came with the basic holder kit). (1 stop)
    P.121 ND Grad. (1/3 stop to 2 stops)

    I've done a quick test with my camera on aperture priority and it does work the correct exposure compensation according to the exposure increase factor required for each filter used. I thought it would have difficulty exposing using the Red filter but it appears to get it ok.

    No filter: F4@1/250.
    Red: F4@1/30.
    Yellow: F4@1/180.
    Skylight?: F4@125.
    ND Grad: 1/2 way down = F4@1/45. 1/3 way down = F4@1/90.
    Red & ND Grad 1/2way down: F4@1/6.

    Appears to me the camera has exposed correctly here?.

    My question is, is it ok to allow the camera to expose itself or should i take a reading with no filters and use Exposure Compensation to add the extra amount of Stops required?

    I'm guessing it's best to expose for the subject with filters off first, take the reading, add filters and compensate accordingly? I'm just thinking it would be difficult to expose for a certain part of the sky, or a certain subject if the filter were on?

    Sorry for the beginner questions but i just want to make sure before i shoot more film.

    Thanks,

    Kev.
     
  2. christopher walrath

    christopher walrath No longer a newbie, moving up!

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    I would meter through the filters. Because (and especially in the case of contrast control filters, the ones that are colored) if you meter through the red filter you will get a lighter reading if you are metering a reddish/orangeish subject and a a darker reading if you are metering a blue/greenish subject. Until you truly get an idea of what a filter will do to local areas of your negs I would meter through. Another thing you might do, and I, the great proponent of film photography, is cheat a little. Like the greats cheated by using instant film to see what adjustments they needed to make, I always carry my cell phone and make a quick exposure of a tough subject with the phone cam in B&W mode. If I want a certain area to appear lighter or darker I make appropriate adjustments.
     
  3. AndrewG

    AndrewG TPF Noob!

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    Your camera will calculate the correct exposure through the filters and will take into account the exposure factor; the effect you want to achieve will rely on your knowledge of which colours are affected by which filter in the subject you are photographing.
    I only use an orange (G) with XP2 which gives me good, contrasty sky/clouds.
     
  4. K_Pugh

    K_Pugh No longer a newbie, moving up!

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    Yeah thanks guys. I just read that sometimes the metering system doesn't work too well with red filters. Was also just making sure in case there was weird way of doing things.

    ta.
     
  5. christopher walrath

    christopher walrath No longer a newbie, moving up!

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    I have a couple of tutorials on my website (in the sig) that might help. Go to the tutorial section (text lower right) and check out 'Light and Color' and 'Filters'.
     

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