reflected metering or incident metering for subject and film latitude

Discussion in 'Black and White' started by reza motaghedi, Oct 2, 2006.

  1. I have a question to understand concept of film latitude better. If i try to
    take a photo of a wall which is half white and half black on one side with
    some details on it and by reflected metering shows 4 stop difference but the
    wall is illuminated with the same amount of light (incident metering indicates
    same amount of light on black and white area). In this case if i use a film
    with a latitude of FOR EXAMPLE 2, will my film latitude cover the image in
    order to capture all details in both side of the wall?
  2. In my view, this isn't really worth the time, but if you really want to capture everything, put the low and high values on the straight line portion of the characteristic curve. Don't forget that you'll have to burn and dodge anyway, and there are seldom if never images that don't require dodging and burning for either corrective or creative control.
  3. Film will cover 5/7 stops easily and you can stretch more.

    Meter the darkest area where you want detail and put that reading two stops under middle grey. Meter the highlights and if they are within 5 stops they will print easily. If not overexpose some and cut development time.

    another method is to meter the lights and darks, if they are within 5 or six stops, average and shoot.

    or use the incident meter in the same light as the subject.

    I use incident 95% or a reflected reading off my palm and open one stop.

    rest of the time is Pentax digital spot as above for tricky situations.

    Remember KISS, keep it simple ...
  4. david_henderson


    I don't really get what you mean by a film with "a latitude of for example 2" but the reality is that you'll be hard pressed to find a film that won't cope with the example you've given if you expose it right. Even a contrasty colour slide film like Velvia will give you detail in a subject two stops over/under - though you'll have to expose it dead right to get both the brightest and darkest areas with detail. For B&W/ Colour neg film a 4 stop brightness range could be accommodated pretty easily without any post-exposure manipulation.

    In the specific example you've given, an incident reading, assuming you're metering right, is likely to give you the right answer- exactly half way between the reflected readings from the light and dark walls.

    But now consider this. Lets assume you're using a high contrast slide film with an effective latitude of 4 stops. Now lets say that the difference between your bright white wall and your black wall is six stops. Now use an incident reading. The reading you'll get is likely to be half way between the two extremes, so overexposing the white wall by three stops and underexposing the black wall by three stops. You're exceeding the available dynamic range at both ends. You'll have no shadow detail and no highlight detail.

    That amongst other reasons is why incident metering doesn't give the best answer all the time.

    Now if, using the same film, you took a reflected reading from the dark and light portions of the wall, you'd know that there is six stops difference between the light and dark halves of your subject. Incident metering won't tell you this. From your reflected readings you'll know that if you use a two stop ND grad over the light part, you can reduce the brightness difference to that which your film's dynamic range can cope, so getting detail in both white and dark bits.

    In my view the more your work approaches the limits of your films dynamic range, the more useful it is to use reflected metering rather than incident. Incident metering is a quick and easy way of getting a reading when the brightness range is well within the capabilities of your film and where you want to render the subject as it appears to the eye(I often don't). It tends not to work so well in complex, challenging situations that test your ability to get your subject onto your film- and these in my view at least, are often the scenes with the highest photographic potential.
  5. Actually i am neither going to take a photo of a wall nor have a film with latitude of 2. I just wanted to bring that example to understand concept of the latitude. What im trying to figure out is when we say a particular film has a particular latitude and a scene has a contrast which is out of that latitude, this contrast should be measured by incident or reflected metering. In fact in many occasions, by incident metering the overall illumination of the subject is the same(in all areas) and is inside lattiude of a film but the very same subject may be too contrasty(beyond latitude of the film) by reflected metering to be covered by a film which has a narrow latitude. In such occasions will the film be able to capture all details properly?
  6. david_henderson


    My response I think answers your question. First that you need reflected metering to really understand what the brightness range of your subject is. Second that if the brightness range of your subject exceeds that of your selected film then you will not get all the detail in both highlights or shadows, or maybe either depending on how you rxpose; and thirdly that you can influence the brightness range of your scene by using ND grads but alternatively potentially by fill flash or a polariser depending on the source and nature of the the light and dark areas.
  7. Thanks David and everybody. i got my answer.
  8. There is no such thing as film latitude. There is one and only one correct exposure if one is to get full information on the film so it may be fully interpreted in the print.
    All the articles about latitude fail to state that over or under exposure eliminates and/or compacts the information on one end of the scale or the other.

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