Super Macro >=2x with MFD >=1ft @ a budget

Discussion in 'Macro' started by markriemann, Feb 3, 2020.

  1. Because of the reduced optical distance there is a magnification effect. The image magnification will be 1.33 times the magnification in air if the front of the lens is adjacent to the tank wall, and the magnification will be lower if the lens is further away. So, if your macro lens is set for 1:1 magnification in air, the actual magnification will be up to 1.33 when focused in a fish tank.
  2. Stuff and nonsense. I've been shooting fish in aquaria since 1971. Shooting through glass into water, 1:1 set on the lens gets 1:1 on film.

    Have you taken pictures of fish in aquaria?
  3. air water magnification.jpg
    Here is a simple demonstration of what I was attempting to describe, using a rectangular cross-section jar with inside dimensions approximately 9cm x 9cm and with a 100mm macro lens with the front element placed approximately 10cm in front of the jar wall. The top photo shows a ruler placed next to the back wall before the jar is filled with water. The bottom photo shows the ruler when water is added. The magnification effect of water is the ratio of image dimensions between the 2" and 3" marks and, in this case. is equal to approximately 1.18. The magnification effect is less than 1.33 because the front element of the lens is not close to the jar wall.

    This was a quick and dirty tabletop (in this case stovetop) experiment which can easily be improved and expanded upon for better accuracy and better photographs. I encourage you to try it yourself.

    For an explanation of the optics see slides 26,27 and 28, using Google to find (pdf file),
    Optics for Engineers Chapter 2 - Northeastern University
    Last edited: Mar 26, 2020
    steve_gallimore|1 likes this.
  4. Here is a photo of my setup (with water in the jar). air water setup.jpg
  5. Thanks for the reply. I just did the experiment, got the result I expected, not yours.

    Nikon N8008S. 55/2.8 MicroNikkor AIS fully extended, so magnification = 1:2. Photographic aquarium 1" thick. Stainless steel ruler. Focus by, um, teetering.

    Ruler in air, ~ 1.5" from bottom to top of frame as visible in the camera's view finder. Ruler at back of tank pressed to back of tank, i.e., vertical, water in tank, same view. In both views the film plane was parallel to the ruler.
  6. Not sure what you mean by "focus by teetering". If you are changing the lens to window distance, that's not the same experiment.

    If your distance from the front window to the ruler is only 1" and the lens to window distance is greater than 1", then your results are not surprising. The magnification effect is only significant if the front of the lens is close to the window and the distance through water is similar or larger than the lens to window distance.
  7. With fixed magnification, the only way to move the plane of best focus is to move the camera+lens assembly. I do this by teetering back and forth. Do you move the plane of best focus by moving the camera+lens or by changing extension (= changing magnification)?

    Lens to subject distance was approximately 2", lens to front glass distance was approximately 1", not that different from your setup.
  8. In my setup the camera is fixed on a tripod and the macro lens focuses internally (I used auto-focus). So, camera lens to window and camera lens to subject are fixed. So, that accounts for the difference in results. Interesting.
  9. From the picture this looks like whiskey tumbler to me?
    This setup will always give a magnification because a round glass is used, when filled with water the glass-water surface will produse a lens like effect.
    In addition, a normal drinking glass is not optically optimized, so the results may vary by just turning the glass a bit, or moving up or down.
  10. The container had a rectangular cross-section and a flat front wall. Only the screw lid was round.

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