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How To Evalulate Correct Exposure

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  • John Friend
    Top Commenter

    I'd' suggest you read about the usefulness of the histogram (upper left of your screen shot).  That will show you the distribution of the pixels across the brightness range.  In your image above, you can see a peak in the histogram on the left side - that's your background.  Then, the rest of the little bumps in the middle of the histogram are your subject and there's not much to the right of the histogram (that I can see at this resolution).  As you mouse over the image, it should show you where you are in the histogram.

    For many images, you want the bright whites of your image to be near the right side of the histogram (in the 240-250 range) and the darker parts of your image (assuming a subject that should span the whole range of brightness) to be in the 10-20 range.  But, not all images (or all lighting) look best using the whole range, but that will generally give you the most "pop" or "contrast".  You can see what value any part of your image has by looking at the R, G and B values right above the image as you move your mouse around.  You can also drop "color readout" markers on your image, using the color readout tool (in the third from the right dropdown of the cursor tools tool bar).  That will allow you to see the RGB values for multiple spots in your image while you make adjustments.

    You also want to make sure you don't have a big spike at the very right side of the histogram because that might mean that you have too many pixels crammed into the very right of the histogram and may have lost detail there.

    You can stretch of compress the histogram using levels (easier) or curves (more flexible, but harder to master).  Levels is one of the first places I go with a lot of my images to tweak the endpoints and the midpoint.  Sometimes I'm looking at the histogram to achieve a specific movement in the histogram and other times, I'm just "trying out" the image with levels tweaks to see what improves it.

    Curves are levels on steroids where simple things are not quite as simple, but more complex things are possible.

    As for how to properly expose this before shooting, that's very dependent upon the type of camera.  For a mirrorless, you can actually see a rudimentary histogram before you shoot.  In dSLR or mirrorless, you can look at an approximate histogram after you shoot and then adjust.  In both, you can preview your first shot on the LCD and see if you appear to be getting in the right exposure neighborhood.  With this much black background, you may want to use spot metering or center weighted metering.  Whether or not it gets the exposure right using a full image metering (Nikon calls it matrix metering) depends entirely upon the camera's algorithm for identifying the subject in the image for whether it properly handles the black background or not.  That would be camera/brand specific and would also depend upon your camera settings.

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