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IR film, I have forgotten which filter

Discussion in 'General Equipment Chat & Advice' started by Stephen Rundle, Jul 5, 2020.

  1. Stephen Rundle

    Stephen Rundle In the Stop Bath


    REALLY appreciated

    I incident read with my Weston Euromaster
     
  2. Stephen Rundle

    Stephen Rundle In the Stop Bath

    As I couldn't cancel the order in time (can always return them) they arrived today.

    Glass and aluminium, as usual with Chinese, well made, and in case anyone comments about me not buying Chinese, I don't buy rip off items, but they don't look like Hoya etc. :) :)

    I will do as advised and try the am starting with the 720.

    Bought largest, I don't buy the thread size as I prefer step up rings to use on many lenses.




    IMG_20200707_101626497.jpg IMG_20200707_101636039.jpg
     
  3. Stephen Rundle

    Stephen Rundle In the Stop Bath

    My light meter goes down to 3 asa :)

    OK anyone

    Using a hand held meter and assuming that the filter has a filter factor of 4 stops, approx !, then the meter should be set to 50 ASA....................... 25 ?

    400..... 200..... 125....... 50 ........ 25
     
  4. neilt3

    neilt3 Well-Known Member

    Again , it depends on the scene your shooting as to how much ir light is reflected , and what effect your after .
    If your after leaves if trees and grass the typical white , you need to meter at ISO 6 .

    If you meter at ISO 25 then that's effectively the 18% grey that you shoot ordinary B&W film at .
    In which case expect the same results as HP5 with a red filter on for contrast .
    Shooting infrared is different .

    Oh , and don't forget to adjust for focus shift .
     
  5. Stephen Rundle

    Stephen Rundle In the Stop Bath


    Thanks, glad I asked you

    Then you don't simply take into account a 4 stop difference

    My Nikon lenses have the red dot :)
     
  6. neilt3

    neilt3 Well-Known Member

    Even without a filter , that film doesn't do well exposed as an ISO 400 film .
    It depends what your developing it in .

    But it really does depend on what your shooting to how much exposure is needed .
    Don't forget , your light meter is measuring visible light .
    Once the filter is on the lens , the light you measured us all blocked out from the film .

    On a cloudy day , it might need a bit more exposure , so sometimes meter at ISO 3 .

    Before you rely on your meter , take a reading at ISO 125 and work backwards in your head to ISO 6 .
    Then take a reading at ISO 6 on the meter and check the resulting shutter speed is still the same .

    Likewise , with the filter on the camera and it's ISO set to 320 , see what shutter speed that's giving .
    Anything less than a one second exposure doesn't need adjustment for long exposures .

    I'm typing on my phone now so I don't think I can add a picture , but this one was done with the Rollei i.r @ ISO 6 on a cloudy day .
    You'll notice the grass reflects a lot more IR than the tree leaves .
    [​IMG]
    https://flic.kr/p/Zz2VcN

    Your other filters let much less light threw than the r72 , so would need much longer exposures .
    However I don't think you'll get much of an image .
    On this link , click on the PDF for the film .
    It has a chart for the spectral sensitivity for the film .
    After 720nm it drops like a brick .
    https://www.firstcall-photographic.co.uk/rollei-infrared-ir400-135-36-iso-400/p1001
    Mix into that reciprocity failure and with the 800nm filter even half an hour might give a blank exposure ( depending on how much light it really blocked out ) .

    The red dot on your lens is for high sensitivity ir film , somewhere around 800nm .
    For 720nm you don't need to adjust it quite as far on the Rollei film .
    So I stead of going all the way back , just try 2/3 correction .
     
  7. Stephen Rundle

    Stephen Rundle In the Stop Bath

    Adox Rodinal, I use it for HP5 and FP4

    and thanks

    GREAT images
     
  8. Petrochemist

    Petrochemist Well-Known Member

    In many cases the IR intensity is completely unrelated to the visual intensity - trying to use a meter to estimate IR exposure with fluorescent lighting would be meaningless. Fortunately the sun produces black body radiation where IR & visual energy is related, but adding cloud cover into the equation complicates matters & introduces the need for experience or bracketing.
    I think your post explains why so many IR references suggest copious bracketing.

    Thankfully digital IR is so much easier. In my shooting framing, focus & metering can all be done directly from the sensor signal. Even allowing macro IR & shooting in complete darkness (with a IR torch/flash) It doesn't stop the camera throwing surprises at me, but at least I have a fair chance of spotting them while the subject is still available.

    My hat certainly goes off to those who can manage good results from Infra red film.
     
  9. neilt3

    neilt3 Well-Known Member

    Thanks .
    I use Rodinal myself , I use it for most of the film's I use .
    Don't forget to pre-wash with the Rollei .
     
  10. neilt3

    neilt3 Well-Known Member


    It is a lot easier with digital , I've a couple if Sony NEX 3's I've converted .
    One to full spectrum , and one to infrared ( 720nm ) .
    I've just bought a used Sony a3000 that I'll convert to IR as it has a viewfinder .
    Trying to focus on the rear screens are a pain in the sun .
    The EVF will make life a lot easier .

    As you say , with digital you know if you got the shot you wanted straight away .

    I find the film very satisfying to use though .
    I'm going to try a bit if experimenting with it when I'm away on holiday again to try get the wood effect more .
    I'm going to do a double exposure , with a slight change of either aperture or focussing .
    I've also got a soft focus lens to try .
    Both one for large format , and one in Canon EF mount .
    Trouble as you say , it'll be a few weeks before I develop them to see if my ideas work .
     
    Petrochemist likes this.

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