Scale focus solution

Discussion in 'Miscellaneous Equipment' started by blockend, Oct 13, 2018.

  1. blockend

    blockend Member
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    Although this is a d*g*t*l solution the application is 100% analogue. The latest iPhone firmware contains a distance measure. Simply point the screen dot at your camera, then at the subject. The phone gives a precise distance measure.

    This is a great solution for old folders or any camera that lacks a rangefinder or Fresnel focusing screen. No more guessing.
     
  2. Svenedin

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    Good tip. I often use a light meter app on my iPhone anyway when out with an old folder so this makes it even more useful. Most of my old folders do have coupled rangefinders though but for the odd one that is "guess the distance" an excellent tip. Must get my Minox 35mm out too -that is guess the distance......

    Edit: I had a play with this and it is hopeless. Woefully inaccurate and guessing would be better. Perhaps I am doing something wrong.
     
    Last edited: Oct 13, 2018
  3. OP
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    blockend

    blockend Member
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    Strange, it was accurate when I tried. You point at subject a and drag to subject b. The measurement is additional, it accumulates as it goes.
     
  4. Billy Axeman

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    If you like something more in style, consider a Watameter.
     
  5. jim10219

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    The only scale focus camera I use is my underwater camera. So this wouldn’t help me. And I’m pretty good at judging distances. It helps to just think of objects that you are familiar with of known sizes, and imagine them between the lens and the subject. I can do anything from an inch (the width of my middle finger’s nail) to 300 feet (a football field). It’s a skill that comes in handy for more things than just photography.

    I wonder if the reason why it works on some phones but not others is because of the phone’s design. In order to get an accurate reading, you’d need two cameras on the same side of the phone to calculate distance through a trigometric function. Either that, or you’d need a wide aperture and software calibrated to the lenses focal length as well as a way of accurately measuring the lens’ position relative to the sensor.
     
  6. OP
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    blockend

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    I need focus assistance with wide apertures at close distance. Medium format cameras have a relatively shallow DoF wide open, which has meant doing tests to determine the exact focal range. There are a number of such cameras, some of high quality, whose original price didn't run to the addition of a rangefinder. If a pocket phone measure keeps those cameras alive, it's a bonus. I do have separate rangefinders, but they're not very reliable at close distances and have to be realigned for the camera.

    My wife demonstrated the iPhone app last night and the reading checked out. There appears to be a knack to getting the correct measurement, I'll give it a more thorough test today.

    Edit: The app worked in six different situations, checked with a tape measure to the nearest centimetre.
     
    Last edited: Oct 14, 2018
  7. Bill Burk

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    It’s a clever combination of using the camera’s internal focus distance and measuring point to point what you pan across. I think some of the newer phones estimate focus distance over the whole picture (it’s used for fake 3-D).
     
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