Major Exposure Confusion

Discussion in 'Beyond the Basics' started by carmeyeii, Sep 16, 2008.

  1. carmeyeii

    carmeyeii TPF Noob!

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    Hi Everyone!

    I've got a few questions that keep bugging me as I can't find a reasonable answer to them. I hope someone is wise enough to provide the answers! Thanks!:blushing:

    1. When you are shooting with strobes, using a main light and a fill light, you typically expose for the main light. Supposing the main light is at F11 (outputting more light), and the fill light is at F8 (outputting less light), if you set the diaphragm to F8, what would the areas that are being lit by the fill light look like? Would they look as illuminated as the parts lit by the main light? Or just well exposed, still less lit? And so, when you do shoot at F11, this means that the fill light parts are actually being underexposed? Or just being lit less? :grumpy: So, does the meter indicate the aperture needed for that specific output to get to a standard lighting point? Or does the strobe have the ability to actually light a subject more subtly or intensely?

    2. This brings me to my second question: Sometimes, when you're trying to shoot a dark photograph, if you overexpose, it may not look as if you had overexposed, it actually looks like there was more light than there really is at the place of the shot, so a dimly lit cup might look really lit and its surroundings as well, without that light actually being there... so what's going on? It doesn't look overexposed, but I know it's not real... but is it the correct exposure?:confused:

    3. I shot a portrait of a girl which was reclining on the wall, so her left side (looking from the camera) was nicely lit, but her right side (the one she was reclining on) was shadowy. I liked the look of this lighting and took the picture, but it appears to me that the camera exaggerates either the shadows or the highlights, so if I shoot and expose her left cheek correctly, her right side will be too dark, and if I expose for her right cheek, her left will be way too light, and these extremes are not what is going on in reality. My question is, at what point does the camera begin to bias toward an extreme and stops being able to record detail in both areas as we do?

    I hope this was sort of clear, I know it is confusing, but it is killing me!!
     
  2. Moglex

    Moglex TPF Noob!

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    You really do need to find this out by experiment. The relationships between the different areas you want to expose can vary almost infinitely with respect to various parameters. When you have experimented (fast and cheap now with digital) you will get a feel for things. If you haven't got that feel it's very hard to answer your question in a way that will be meaningful in different situations.


    If you expose it 'correctly' it should look 'normally' lit. If it looks dark you've under exposed it even if it does look correct. The reason you should expose correctly (even if it looks too bright) and alter the effect in post processing rather than under expose (so it looks 'correct') and not post process is that doing the former retains the maximum amount of detail which may allow you to produce a far superior result in post processing.

    What you are noticing here is the superior dynamic range of the human eye.

    You will need some method of 'fill in' (flash, reflector, etc) to alleviate the shadow to some degree. Again you need to experiment to get a feel for how the DR of your eye relates to the DR of your camera's sensor (or the DR of your film).
     
  3. djacobox372

    djacobox372 No longer a newbie, moving up!

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    ;) "reality" is subjective.... the camera and your eyes see and process differently. One could argue that the camera is representing the "physical reality" of the light more accurately then your own eyes and brain. Humans have the ability to vary exposure across their vision which means that we don't really precieve the "reality" of contrast that exists, our brains instead adjust the image so that we can better precieve the detail, which is far more important information.
     
  4. carmeyeii

    carmeyeii TPF Noob!

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    OK, but let's say you're taking a picture of a table in the dark. The only thing you can see naturally are the highlights from some streaks of light that might be hitting it. To say that you-ve exposed it correctly, are you supposed to allow to enter as much light as needed for the table to look as if it were lit? Or is the correct exposure of the table one of a dark table with only some highlights?

    I'm just a bit confused as to what a good exposure actually is, in cases of darkness. So is a dark picture always underxposed, even if the subject did look dark in reality?
     
  5. JerryPH

    JerryPH No longer a newbie, moving up!

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    It is not only different from picture to picture, but place 4 people in the same studio with the SAME picture to take a shot of the SAME subject, you will get anywhere from 1-8 PROPER exposures, and 4 correct ARTISTIC exposures.

    The answer is... it depends on MANY things. There is NO one fixed correct answer here. You are looking for answers from others where YOU should be finding the answers YOURSELF.

    Depends... on the camera and the engineer many years ago that decided that your model of camera should react a certain way to a certain circumstance. Now if you do not like the way this engineer decided this for you, you *could* expose it in the manner YOU want. That's called taking control of the camera yourself.

    :)

    I strongly suggest you read Understanding Exposure by Bryon Peterson. ;)
     
    Last edited: Oct 4, 2008
  6. carmeyeii

    carmeyeii TPF Noob!

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    Will definitely check that out, Jerry. Thanks! Aso for the taking control of the camera myself, I don-t know if you mean by this using the Manual modes... because I do. I never work with the Auto Modes...
     
  7. Moglex

    Moglex TPF Noob!

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    A good exposure is one that captures the maximum dynamic range (in the areas of most interest) so that as many options as possible remain open to you when you 'process' the resulting shot.

    So, for example, if you are interested in seeing detail in the light streaks then you should expose for those and allow the dark area to lose most of all of their detail.

    If on the other hand you were most interested in the detail in the darker areas you would need to expose for those and accept that the highlights would probably burn out completely.

    I think it's fair to say the in extreme lighting conditions, unless you are used to working with the specific conditions in question, or definitely want maximal highlight or 'shadow' detail, there will be some trial and error involved, both in taking the initial picture and processing it.

    You need to go beyond using something like the centre weighted meter reading and maybe use spot metering and use your own judgement to add or subtract exposure (or maybe bracket).

    With the cheapness of digital your best initial solution is almost certainly to take a series of shots going several stops either way from the centre weighted meter reading and playing with the results.

    This will give you a far better feeling for what is happening with the particular lighting with which you are working.
     
  8. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Good exposure is getting the exposure that would be best for realizing your vision of the scene. Different photographers shooting the same scene may have very different opinions as to what is best.

    With digital I'd suggest studying up on the histogram. It's pretty simple, and gives you a lot of info about your exposure.

    http://www.cambridgeincolour.com/tutorials/histograms1.htm
     
  9. JerryPH

    JerryPH No longer a newbie, moving up!

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    ...but you are following the camera's meter suggestions, I bet. ;)
    Do you also know the differences between all the metering modes your camera has to offer?

    There are times to follow it, there are times not to. Thats part of the fun process of learning. I am in the same boat. Part of my picture taking process is deciding if for any particular picture, what exposure mode is best and whether or not I want to follow it's suggestions. :)
     
  10. carmeyeii

    carmeyeii TPF Noob!

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    Thanks to everyone for their replies! :hail:I'm definitely getting a better understanding of this... this is the last question I'll add to this thread, I promise! Going back to the "table in the dark" example, let's say the most accurate representation through the camera of what you see with your eyes comes at F5.6 at 1/10. I've noticed that if I lower the speed to let's say half a second, (technically, this would be overexposing the image), it won't look overexposed, as in blown out highlights or whites, but rather it will appear lighter, showing a table that APPEARS TO BE ACTUALLY LIT as if there were a 100 watt bulb in the room. It gets to me because I don't know 1) wehre that "lighting" is coming from, since I [barely] see a table in the dark and 2) if that made-up light counts as a proper exposure even though I know the scene is nothing close to what is in the real world. Make sense...? :meh: Note that the "overexposed" half of a second image actually looks real and shows no signs of fake elements. I really looks as if I wee holding a light bulb for the scene. Hope this isn't too much.. I really appreciate you sorting out my confusion knots...
     
  11. Moglex

    Moglex TPF Noob!

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    There is simply enough ambient light enough to light the scene.

    Think about it the other way around: If you took a shot of the same scene normally lit and greatly underexposed it you would get a photograph that looked like your dark room.

    We happen to see a certain range of light levels as 'normal' but by adjusting the exposure, film or a sensor can see a great range of light ranges as 'normal' and record what it sees.

    ---

    It might help to imagine that you are in a camera obscura, looking at a scene that is so absurdly brightly lit that you can see nothing but white.

    You have a large number of ND filters that you can place behind the lens aand you do so, one by one.

    As the image gets dimmer you will begin to see it.

    Then, for several filters you will see it roughly 'normally' illuminated - it may appear to get a little darker as each filter is added but the various adjustments you own optic system can make easily handles this.

    Eventually, though, you get to the stage where you can only see the extreme highlights (rather as in the scene you describe).

    Now, which number of ND filters show you the 'real' or 'correct' picture.

    The answer is, of course, none. There is no 'correct' way of looking at such a scene, or, indeed, any scene.

    The only way you can get an exposure that you deem correct is to get one that retains the maximum amount of detail in the area of the scene that you deem to be most important.
     
    Last edited: Oct 5, 2008
  12. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    If you were outdoors on a sunny day, and "correct" exposure was f/11 @ 1/250 @ ISO 100, but you set your camera to f/22 @ 1/1000 the photo would look more like night time.

    Your eyes and mind are constantly reassessing the world; the images continually refresh and don't burn in as time passes. The scene in front of a still camera burns into the film or sensor as time passes; it does not refresh.

    If f/5.6 @ 1/10 would create an accurate representation of how the scene looks to you, but you use f/5.6 @ 1/2 then you have overexposed by 2.3 stops. Each stop doubles the light, so your 1/2 sec exposure will be over 4 times brighter than the exposure at 1/10th. In my example above I have under exposed the scene by 4 stops, or made it 16 times darker (each stop is half or double the light/exposure, 2x2x2x2=16).
     

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