Lighting 2nd Edition

Posted: February 25, 2013 in Everything else
Tags: , , , ,

Just arrived with me are early copies of the 2nd Edition of Basics Photography: Lighting (ISBN 978 2 940411 95 5) which is published this Thursday 28 February by Bloomsbury under the recently acquired ava imprint. This is my first look at the printed version – material from the 1st edition has come up crisp and fresh with some excellent new imagery looking great on the page. Thanks to all who contributed. Now looking forward to seeing this and Basics Photography: Composition 2nd Edition together in the book stores.

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Comments
  1. Jose says:

    I read your lighting book, but I can´t understand the exposure value table at page 32. In this table, at same f number, the EV decrease while shutter speed increase.

    If I go up, by example, in the first column of the table (f1) at 1 second I see EV=0, it´s correct, but over this, f1 and 2 seconds EV in the table is -1.

    And If you go down, at f1, 1/2 second, EV is +1…

    This is very confuse to me… is a mistake?

    • David Prakel says:

      Hi Jose

      Thanks for your enquiry

      Any one EV number represent all possible combinations of shutter speed and aperture that will give the same exposure.

      If you look at EV10 in my table – all possible combinations are:

      1/1000 at f/1
      1/500 at f/1.4
      1/250 at f/2
      1/125 at f/2.8
      1/60 at f/4
      1/30 at f/5.6
      1/15 at f/8
      1/8 at f/11
      1/4 at f/16
      1/2 at f/22
      1sec at f/32
      2sec at f/45
      4 sec at f/64

      All these combinations will delivery the same amount of light energy to the sensor or film. 1/1000 at f/1 is very short duration and high intensity. 4 sec at f/64 is very long duration but very low intensity. PIck any EV number and go diagonally through the table and check out the combinations of shutter and aperture – they’ll always give the same exposure.

      This all operates according to the Law of Reciprocity where a halving of either duration or intensity needs to be matched by a doubling of either intensity or duration to achieve the same exposure for a fixed sensitivity. Any halving or doubling is a ‘one stop’ which is the same as one EV unit.

      EV numbers always represent possible combinations of shutter speed (duration) and aperture (intensity). Minus EV numbers are very ow light conditions, high numbers are very bright conditions.

      • jose says:

        First, thanks for the reply.

        I understood what you say, it is very well explained in the book.

        What was confused to me is the fact when I move up the same column of the table, by example in f1 value column, at 1 second I get EV=0, but at 2 seconds, same f1, EV is -1 at the table.

        It must be 1 second at f1 EV=0, and 2 seconds at f1 EV=+1, So, the right values are only if I go diagonally, right?

        Is not ony in your book, I see the same confusing table in a lot of places…

        Anyway, EV by itself means nothing, or I can´t see how it works.

        If I think in EV=0 like “Only a value of light” then I understand EV=+1 is “the double of ligh at EV=0”, and EV=-1 is “the half of light at EV=0″… and so on…

        BUT I see EV=0 is defined like 1 second at f1 everywhere… and this say nothing about how much light I get….

        As far as I know, 1 second at f1 (EV=0 in the table) maybe a dark or burn photo depending on how much light is in the scene… is not the same one second at f1 in the forest at night than one second at f1 in a beach at 11:30 AM.

        So is confused to me this definition of EV=0 like 1 second at f1….

        Let me give you thanks again for your support, and sorry for this long comment

      • David Prakel says:

        I think the issue is you are seeing this in human perceptual terms when its all to do with the science of sensitometry – you have to see if from the point of view of the photosensitive material. It takes a certain amount of energy to turn film black or to produce a voltage from a digital sensor. The sensor or film integrates energy over time which is why the relationship is always ‘how bright for how long’.

        The Table of EV numbers is not read as columns or rows it doesn’t make sense. An EV relates to the light energy available to make a photograph in the world. How you divide that up between intensity and duration is up to you as a photographer. You use aperture in conjunction with focus and depth of field and shutter speed to emphasise or freeze motion.

        Your comment about 1sec at f/11 maybe a dark or burn photo depending how much light is in the scene – you’re absolutely right but ‘how much light is in the scene’ means different EVs. If the EV measures 7 with 1 sec at f/11 you get a correct mid-gre exposure – that’s what the table tells you.

        I’m sure you’d get this if you try it with a real meter – just go and measure some scenes in terms of EV and look at the possible combinations of shutter speed and aperture you could then use to get a good exposure of that scene. There are some free light meter phone apps that are great to play with.

      • Jose says:

        I think not only for my eyes, the energy received by the sensor at EV=0 (IF EV=0 definition is the exposure at 1 second f1, ) will be different at day or night…

        Maybe the right definition of EV=0 is when the subject reflects 18% of light, and one second at f1 is some kind of old definition?

        I am thinking about that, trying to understand.

        Or maybe EV=0 really is the ammount of light needed to get a 18% of light reflected at 1 second f1? This will have sense for me….

        This way I KNOW the ammount of light we are talking about… but with only the definition I read of EV=0 (1 second, f1) without the reflecting 18% part I can´t imagine how many light goes to the sensor.

        I will play with a light meter, maybe the problem of digital age photographers like me is we never use light meters… to be sincere I only use the histogram on the live view screen to adjust exposure, and when I tried to proof in EV concept, is a little confuse to me.

        Let me give you the THANKS again. You are very kind with me, and thanks for your patience too.

      • David Prakel says:

        No – the energy received by the digital camera sensor at EV0 will always be the same – if its day the EV will be higher, if its night it will be lower.

        Go back to the idea of why we need to make mid-grey images – its to get an standardised average exposure that captures both shadow and highlight detail. Every single photographic item is calibrated around this concept whether it’s a light meter, a minilab or a digital compact camera.

        The EV number represents any combination of time and brightness (duration and intensity) that provides the right amount of energy to create a standard mid-grey exposure for the light being measured at that moment. That is for a specific sensitivity.

        Forget the 18% reflected bit as that applies to reflected (camera) lightmeters only and confuses the basic issue – the EV number tells you how much light energy is present – how you divide it up between aperture and shutter speed is up to you the photographer. This is the absolutely fundamental concept behind photography.

  2. jose says:

    Ok, I was playing with a light meter for two hours… as you said the meter EV values change. I can see EV4, EV7, or EV15 depending the ambient light.

    Anyway I understood when you wrote “The EV number represents any combination of time and brightness (duration and intensity) that provides the right amount of energy to create a standard mid-grey exposure for the light being measured at that moment. That is for a specific sensitivity.”

    But the EV definition I found said EV0= one second at f1 only… My mistake was because this words alone don´t give me and idea how much light there is.

    The amount of light needed to get a mid-gray tone in a photo at 1″ f1 is always the same…. is something I can messure, or imagine.

    To create a mid-gray exposure (what I called 18% reflected light) is the lost data I need to understand the EV concept.

    Now I see the light 🙂 even if I know how much lux have in EV0, I can know the EV with a given lux.

    THANK YOU very much again. You really helped me a lot.

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