Setting exposure with dark and light products (same props)

Discussion in 'Beyond the Basics' started by bobpotter, Dec 29, 2016.

  1. bobpotter

    bobpotter TPF Noob!

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    I'd be super grateful if you have any advice on getting the exposure right IN the camera so that I have less processing to do in Lightroom.

    Here are my questions with more info below:
    1. How do I get consistent color and exposure when there are different color products that are affecting the metering?
    2. All other factors being equal, is it OK/acceptable to adjust the exposure up/down?
    Here's my problem:

    I'm taking pictures of tea. Some are black, some are green, some are red - and there are varying darks and lights across those colors. I'm placing the tea in a cream colored teaspoon on a white-ish gray wood background.

    With the exposure set at "0":
    • When I take a photo of a black tea, the teaspoon is white, not cream, and it's washed out.
    • When I take the photo of green tea, the color and exposure are just about right.
    • When I take the photo of the red tea, the teaspoon is too dark and it's highlights are missing.

    While I've set the white balance and have consistent lighting, one of my struggles is knowing how to correctly set the exposure. If the manual setting is being used, shouldn't I just keep the exposure at "0"?

    But when I do, that is when I get a washed out teaspoon in the images with black tea.

    I've watched tuts on using the histogram and have attempted to adjust the exposure so that the "hump" is roughly in the same spot from picture to picture, but I still feel like there's still a bit much variation.

    Is it too much to expect to be able to get consistent exposure and color across images when everything but the tea color stays the same?

    Also, I've tried different metering modes and it doesn't seem to make a difference, but perhaps I'm doing something wrong.

    Here are some unedited images I've taken to show what I'm working with:

    [​IMG]
    This is an example of green tea. The color of the wood, teaspoon, and tea are accurate starting points.

    [​IMG]
    An example of black tea with exposure set to 0. The teaspoon and background are too white/washed out, but the tea is good.

    [​IMG]
    Exposure was set to -1. The background and teaspoon are close, but feel the tea is too dark.

    [​IMG]
    The example of red tea exposure is set to "0" and you can see that the teaspoon is darker/warmer than the green tea example above. Also, it has lost some of the highlights/definition on the teaspoon handle. Additionally, the background is a bit too dark.



    Thanks so much for your help!
    Bob


     
  2. Derrel

    Derrel Mr. Rain Cloud

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    I'm on my phone right now I'm not the best screen but I can see the density differences that you are talking about. One thing to remember when a photo that shot in raw mode is imported into Lightroom many people will have an import profile selected. I expect that that is the case for you as well otherwise if the exposure stayed the same the white background would look the same density / home / color in every image. The fact that there's a density difference makes me think that Lightroom and the import profile you have assigned is affecting your images.

    The second issue would be how the light metering is being done when set to zero. If you mean doing through the lens light metering which is reflected light metering, you could get variance in the zero-point based on reflectivity / color of the actual subject matter.

    The way I learned to shoot small products like this was using an incident light meter and setting a baseline exposure value on slide film with one specific type of processing done to the film. An incident meter will read the light that is hitting the scene, not the light that is being reflected from the objects in the scene. It's not clear what you mean specifically by 0. If the zero point is done by reflected metering off of such small objects as these teas,there could be density changes in the white wood. Or, the changes could be due to,again, the import profile Lightroom is creating for each image based on computer analysis.

    Again, one of the things about digital photography is that many times images are processed without us actually realizing it. Some cameras will attempt to read color
     
  3. Derrel

    Derrel Mr. Rain Cloud

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    Probably the easiest solution would be to take an in-camera reading off of an 18% neutral gray card and take that reflected light metering as BASELINE, and set the f-stop and shutter speed and lights and lock everything down. The idea of 0 as a metering Baseline really applies only to incident light meters, and not to reflected light meters. Today's smart digital cameras will read a scene and analyze the brightness and will modify the picture based on what the camera / computer thinks is the right exposure and the correct development of the subject matter and the image data. The film lab and how the film is developed is today, the Lightroom import preset.

    Brightness and contrast and tone can actually be determined quite a bit based on the Lightroom presetbapplied to imported Raw data.
     
    Last edited: Dec 29, 2016

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