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"DigiPhoto Guide For Beginners" is now availableThe MYTCARD METHOD for the book is now released free to the public
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t-photo.com "Macro" Oct.1, 2000--Reference |
Quick Guide |
Reference |
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1 Magnification 7X (approx.) set up |
2 This is the edge of the flower bud |
3 Taken by normal lens (insert) and the center of this image |
4 Lens double extension result |
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Magnification is calculated by extension/focal length, e.g. for 25mm extension with 50 mm lens, magnification is 25/50=0.5, for 50mm extension with 50mm lens, magnification is 50/50=1. Square of 1 plus Magnification is the Exposure Factor. Log value of the Exposure Factor is the exposure compensation in stops. In fact, for macro, the calculation is not that simple. However, since general photography is a scientific research, and there are lots of deviation for the whole process, e.g. shutter speed, processing etc. There is a double extension requirement in normal lens (50mm for 135). Double extension means that normal lens with extension same as focal length. It is expected to have a good quality. In other words, if extension is greater than the focal length, there will not be any guarantee. Therefore when longer extension is required, we must use better lens, bigger format or better film to compensate. Image 1 shows a Canon (FD) 35mm Macrophoto Lens with 200mm extension tube. According to the manual, the Magnification for 175mm extension tube, therefore with 200mm, the Magnification is about 7X. |
The insert at right bottem of Image 1 is taken with macro lens at the same distance. We can see the flowers and the bud. Image 2 is the picture of the edge of bud. Image 3 is the center of the picture taken with normal lens 50mm, full frame as insert. Image 4 is taken with normal lens 50mm and double extension (50mm extension). The image quality with double extension remains high. Image 2, 3 & 4 are taken with Kodak E100S. |
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