Overexposure for beginner

Discussion in 'Exposure Discussion' started by polkor, Aug 5, 2017.

  1. polkor

    polkor Member

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    Hello
    i might sound dumb but as a newbie i tried to figure out depth of field and over exposure thing. Cannot find info online to this particular problem.Hence i have b&w film Iso 100 and it's a sunny day.
    I want to take portrait photo with person standing 1-2 m max.
    I want to have deep DOF.
    Should i change aperture from f/16 to f/1.7 . What about shutter speed? Does it stay at 100/125 according to sunny 16 rule? I have 50mm lens. Definitely dont want photos to be overexposed. Please help !
     
  2. Elondonphoto

    Elondonphoto Member

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  3. Mr Bill

    Mr Bill Member

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    Hi, for "deep DOF," where more of the scene is "sort of in focus," you want a physically small lens aperture - if you could look into the front of the lens when the photo is being taken, you would see only a small opening in the aperture. But to set your aperture for the small physical opening, you need a large f-number, like f/16.

    So to take the photo in sunlight, yes, you can use the "sunny 16" rule. So with film ISO = 100, you should expose at roughly 1/100 or 1/125 second at f/16.

    (Like Elondonphoto says, f/22 gives even more DOF, but you would need to increase the exposure time - to about 1/50 or 1/60 second, in direct sunlight with ISO 100 film.)
     
    Last edited: Aug 5, 2017
  4. mpirie

    mpirie Subscriber

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    Correct exposure is a product of the sensitivity of the film, the intensity of the light allowed to reach the film (aperture) and the time it's allowed to reach the film (shutter speed).

    For a given film speed (ISO/ASA) the relationship between the aperture (f-stop) and shutter speed (time) are linked.

    If you reduce the f-stop to increase depth of field, (e.g. f8 to f22 = 3-stop reduction) then less light is allowed to reach the film, therefore to retain exposure, you need to increase the time the light is allowed to reach the film by the same amount (e.g. 1/125th sec to 1/15th sec = 3-stop increase).

    Mike
     
  5. Chan Tran

    Chan Tran Member

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    Did you mean you don't want any DOF. You want paper thin DOF? Because if you want deep DOF you do not change from f/16 to f/1.7 but rather changing from f/16 to f/22 or f/32

    Now but supposed you do want to change your aperture to f/1.7 and you are using the sunny 16. Okay. f/16 @ 1/100 is EV 14 and 2/3. f/16=8 and 1/100=6 2/3. You change to f/1.7 which is 1 1/2. So 14 2/3 - 1 1/2 = 13 1/6 which the shutter speed must be about 1/9000. You can use 1/8000.
     
  6. OP
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    polkor

    polkor Member

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    Thank you all for your explanations. :smile: I hope i wont ruin any more films.
    Frankly as a newbie i followed this https://www.gimp-werkstatt.de/galerie/saijin/upload/Fotowissen/Cheatcard.jpg
    So I thought if i change to f/1.4 or 1.7 i will have deep DOF

    . I dont have 1/9000 . Max is 1/1000 . So i guess this will be corresponding shutter speed .
     
  7. OP
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    polkor

    polkor Member

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    Ok i guess i messed up with my explanation. My apologies. What i meant was blurred background and I thought it's called deep DOF. Its other way round and it's called shallow . I didnt know that :sad::sad::sad:

    So i need shallow DOF on the sunny day . I guess its all the way to f/1.7 and shutter speed 1/1000?
     
  8. E. von Hoegh

    E. von Hoegh Member

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    For the moment, you need to separate depth of field and exposure.
    You want to make a portrait, so you meter the scene. Say for the sake of discussion the meter reads f:8 at 1/125th, using ISO 100 film.
    Hold this thought.
    Now, you want "deep depth of field". It sounds like you have a lens with a maximum aperture of f:1.7. This lens likely has a minimum aperture of f:16.
    f:1.7 gives you the least i.e. shallowest DOF. f:16 gives you the deepest DOF.
    Now remember what the meter read - f:8 @ 1/125. This is equal to, in exposure value, f: 11 @ 1/60, or f:16 @ 1/30. You want deep DOF, you use f:16 @ 1/30. You want the shallowest DOF, you use f:2.8 @ 1/1000 - this is the largest aperture you can use for the scene you metered, because that is the fastest shutter speed on your camera; it gives the film the same amount of light as f:8 @ 1/125 by using a faster shutter speed and a wider aperture.
    You really need to study the relationship between aperture and shutter speed and exposure separate from the DOF issue.
    Using 1/1000 when an exposure of 1/8000 is indicated will give you film 3 stops overexposed, you can't just pick these numbers arbitrarily.
     
  9. Bill Burk

    Bill Burk Subscriber

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    Yes that is shallow DOF (depth of field) that you want. f/1.7 is good for that.

    At 1/1000 you might overexpose the 100 speed film in daylight. A filter might help avoid overexposure.

    But overexposure is not that harmful. If you really want to use f/1.7 for a shot then just do it and make up for the overexposure when you print.
     
  10. E. von Hoegh

    E. von Hoegh Member

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    The OP has no idea what "Exposure" or "DOF" mean, he/she needs to learn the very basics first. "Filters" and "printing" will just lead to more confusion.
     
  11. RalphLambrecht

    RalphLambrecht Subscriber

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    I can offer this free read to you; it may help understanding the issue of exposure; if needed, I have another one on DOF; sorry 'file too large error;I can send it via email upon request to :rwlambrec@gmail.com
     
  12. pentaxuser

    pentaxuser Subscriber

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    I remember two good rules for DoF that I read somewhere that helps clear up the confusion - I hope. Think of the f in f number as representing a fraction so the fraction of 8 as in f8 is thus bigger than the fraction of 16 as in f16. Second rule: the smaller the fraction, the greater the DoF

    I don't wish to complicate matters at this early stage but depending on the size of you lens i.e 24mm;28mm; 50mm; and format of film i.e. 35mm film or 120 film then a very large aperture thus a very small DoF such as f1.7 gives and at a subject distance of on only 1-2 metres might even result in not all of the person from front to back being in focus.

    It sounds as if your shutter speed range will require a smaller aperture than f1.7 anyway but I'd certainly move to a smaller aperture. At 1-2 metres even a much smaller aperture such as f4 or f5.6 will ensure that unless there are objects immediately behind the person they will be out of focus as you intend them to be

    It is worth getting a general book on photography which will explain exposure and its relationship to shutter speed and aperture.

    pentaxuser
     
  13. Chan Tran

    Chan Tran Member

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    No! If the correct exposure was f/16 and 1/100 sec. Then if you use f/1.7 and 1/1000 you over expose by 3 1/6 stops. You need 1/8000 (which still overexpose by 1/6 stop).
     
  14. tedr1

    tedr1 Member

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    to the OP: photography is complicated, get a book, a good one is Black and White Photography by Horenstein available at amazon used for a few dollars and very helpful for the beginner.
     
  15. TheRook

    TheRook Member

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    A neutral density filter on the lens can help you adjust the aperture for a shallower depth of field while avoiding sever over-exposure. I use this approach quite often, especially with cameras that have a maximum shutter speed of 1/500 sec or less.
     
  16. OP
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    polkor

    polkor Member

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    alright everyone, thanks a lot! many comments are very helpful and i have some idea by now
    however profound study is essential to succeed. Thumbs up
     
  17. Steve Smith

    Steve Smith Member

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    I was going to write that.

    Don't worry too much about over exposure with negative film. It's preferable to under exposure.


    Steve.
     
  18. Chan Tran

    Chan Tran Member

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    under sunny 16 condition it's over 3 stop overexposure which is a bit much.