Exposing - light meter

Discussion in 'Exposure Discussion' started by Caius Mihai Canea, Jun 9, 2018.

  1. Caius Mihai Canea

    Caius Mihai Canea Member

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    Hi,

    A little bit of backstory first..

    I recently found my grandpa's old SLR, a Praktica MTL5B with a Pancolar f/1,8 50 mm lens on it and thought I'd give it a go. The camera has an included light meter and on my first roll, it seems to have done a good job. Pictures came out nicely, or as nice as someone who's new to film photography could expect.

    In the meantime, I also found an old B&W expired film which I thought I'd try as well. The roll is a FORTEPAN SUPER 80 ASA. I know I need to go down 2 stops for every 20 years of age and since the film expired back in 1982, I have to go down to ISO 25. However, my in-camera light meter only seems to work if I set the ISO to 100 or above, so I though to myself I would just meter it with the camera set to 100 and then overexpose 2 more stops.

    Now. I also downloaded an app for light metering (Pocket Light Meter), but it gives me different results than the in-camera meter. For example, I set the camera to ISO 100, f/2,8 and to expose I had to set the shutter speed to 1/125. The app light meter however was telling me to go to 1/800.

    I tend to believe the camera since I already shot a roll and worked out fairly well, but you tell me...

    Can anyone tell me what's what?

    Thanks so much.
     
  2. R.Gould

    R.Gould Member

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    If your camera gives 125 at 2.8 for 100 iso then I would say your camera is out, assuming that the light is fairly bright I would estimate that it should be around 8 to 11 at 125, could be a battery problem with the camera light meter, but I would say that where I am, the sky is cloudy bright and I have just checked with my Sekonic and for 2.8 at 100 iso ti gives me 1000, so unless it is super dull then your app is closer than the camera, I would tend to go with your metering app
    Richard
     
  3. jnanian

    jnanian Advertiser Advertiser

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    Caius

    hi, welcome to photrio !

    sounds like you are having fun :smile:
    it could be that you in camera meter
    likes to over exopose a little bit, that's ok.
    i had an in-phone meter once, i deleted it/ found it to be no help.

    my maxim is that too much light is always better than not enough. ..
    so go with what you camera says, your expired ( and fresh ) films will be happier !

    you are correct about over exposing your film 1 stop for every 10 years.
    another way to check your camera meter is by
    thinking about "sunny 16" ( it works better if you do sunny 11 i think )
    https://en.wikipedia.org/wiki/Sunny_16_rule
    ( this website is also helpful, long, but helpful: http://www.fredparker.com/ultexp1.htm )

    good luck !
    john
     
  4. jeffreyg

    jeffreyg Subscriber

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    The built in meter and phone app may be reading at different angles of acceptance. I have used the Pocket Light Meter checked against a hand-held meter and they were both very close to each other. It's also possible that the cell in the camera meter or battery if it uses one is weak. I would try metering off a single surface at a close distance with both and see how they match up. Also try bracketing exposures with both and use a fresh roll of film and have a proof sheet made. If you are not processing and printing yourself whoever is doing it may be compensating in the printing to get acceptable results. There are ways to come up with a personal ISO for film/equipment you have but you will have to do the processing yourself. I'm not sure your twenty year rule is the most accurate because how the film was stored might affect it.

    http://www.jeffreyglasser.com/
     
  5. OP
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    Caius Mihai Canea

    Caius Mihai Canea Member

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    To make it easier to understand what light I was working with, here's the log from the app.
     

    Attached Files:

  6. jnanian

    jnanian Advertiser Advertiser

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    was the scene back lit ? i see behind the tables
    aer green leaves is there a ton of light too ?
    your pocket might have read a lot of the
    light spilling in from behind the subject, and your
    camera meter might have been reading more of the subject and the table
    you have to take these things into consideration whenever you
    use a meter or do sunn6 11/16 ..
    sometimes you can take your meter and get closer to the subject so there
    is less interference from "outside" what the photo is going to be about
    backlit can be a couple of stops difference
     
  7. OP
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    Caius Mihai Canea

    Caius Mihai Canea Member

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    It just got a bit cloudy this evening and got the chance to test the app meter, in-camera meter with the sunny 16 rule. When there's no light spill around the subject, they both indicate about the same values. I think things change a bit in extreme light, where I set the camera according to sunny 16 and the in-camera meter was showing me that the picture is underexposed. In ideal conditions, it's all working fine...i think
     
  8. wiltw

    wiltw Subscriber

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    A very simple way to assess if a meter is 'about right' or not, is simply to do the 'Sunny 16' principle!!!
    at ISO n, shutter speed 1/n f/16 should be the right exposure.

    If you are in bright mid-day sunlight and can see sharp edged shadows (few clouds in sky to momentarily block the sun and diffuse the light), aiming at a green lawn should give you something equivalent to ISO 100, 1/100 f/16

    (yes, not all grass reflects exactly the same amount of light, so this test is an approximation and NOT a assessment of ABSOLUTE accuracy!!!)
     
  9. jvo

    jvo Subscriber

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    welcome tp photrio - fondly rememebered as apug:errm:
     
  10. Sirius Glass

    Sirius Glass Subscriber

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  11. Poisson Du Jour

    Poisson Du Jour Subscriber

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