• Laowa 25mm f/2.8 2.5-5X Ultra Macro vs 100mm f/2.8 2x lens

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    https://gilwizen.com/laowa-25mm-ultra-macro-lens-review/

     

     

    https://www.cameralabs.com/laowa-25mm-f2-8-2-5-5x-ultra-macro-review/

     

     

     

    • Pros:
      – Lightweight, small size for a high-magnification macro lens
      – Highest magnification lens available for non-Canon users
      – Excellent sharpness and image quality
      – Consistent working distance
      – Narrow lens barrel makes it easy to find and track subject
      – Affordable

     

    • Cons:
      – Manual, no auto aperture control
      – No filter thread (but still customizable with caution)
      – Dark viewfinder when closing aperture makes focusing difficult in poor light conditions
      – Magnification range is short 2.5-5x compared to the competition

     

    Combining a Laowa 25mm 2.5x lens with a Kenko 12mm extension tube

    To find the combined magnification when using a Laowa 25mm 2.5x lens with a 12mm Kenko extension tube, given the magnification of the lens itself, the extension tube length, and the combined setup, you can calculate the total magnification.

    First, consider the magnification of the lens itself, which is 2.5x.

    Then, to find the total magnification when the extension tube is attached, you can use the formula:

     

    Total Magnification = Magnification of the Lens + (Magnification of the Lens * Extension Tube Length / Focal Length of the Lens)

    In this case, the extension tube length is 12mm, and the focal length of the lens is 25mm. Using the values:

     

    Total Magnification with 2.5x = 2.5 + (2.5 * 12 / 25) = 2.5 + (30 / 25) = 2.5 + 1.2 = 3.7x

     

    Total Magnification with 5x    = 5 + (5 * 12 / 25)      = 5 + (60 / 25) = 5 + 2.4 = 7.4x

     

  • GretagMacbeth Color Checker Numeric Values and Middle Gray

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    The human eye perceives half scene brightness not as the linear 50% of the present energy (linear nature values) but as 18% of the overall brightness. We are biased to perceive more information in the dark and contrast areas. A Macbeth chart helps with calibrating back into a photographic capture into this “human perspective” of the world.

    https://en.wikipedia.org/wiki/Middle_gray

    In photography, painting, and other visual arts, middle gray or middle grey is a tone that is perceptually about halfway between black and white on a lightness scale in photography and printing, it is typically defined as 18% reflectance in visible light

    Light meters, cameras, and pictures are often calibrated using an 18% gray card[4][5][6] or a color reference card such as a ColorChecker. On the assumption that 18% is similar to the average reflectance of a scene, a grey card can be used to estimate the required exposure of the film.

    https://en.wikipedia.org/wiki/ColorChecker

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