How do I calculate magnification ratio? (Photography)?

A

Alex

New member
Is there a formula to calculate magnification ratio?

My equipment:
- Vivitar 75-200mm Lens w/ a minimum focusing distance of 1.3m (4.3') resulting in a magnification ratio of 1:5 @ 35mm (according to box)

- Nikon D60 (DX sensor)

- Macro extension tubes... Not sure of the length, but here... http://www.dealextreme.com/details.dx/sku.12458


So, if I were to know the size of my sensor, the focal length, the distance at which the picture was taken, and the length of my extension tubes, surely there would be some sort of equation for that...
 
Actually Magnification ratios are measured by comparing the image size to the subject size used when shooting with macro lenses. Typical ratios are 1:1, 1:2, 1:4.

So knowing the size of the film or sensor is one half the equation.

With your figures, if the image size is 24x36 mm (frame size of a 35 mm camera or "full frame" DSLR) would mean that the subject you are shooting would be 1:5 or five times larger than the frame size (12x18 cm). Most lens makers have the grace not to call one of their lenses a "macro" unless it can resolve down to at least a 1:2 image to subject ratio.

With your camera's sensor that is 23.6 x 15.8 m, the subject would be about 12x79 cm.

Nikon still makes a zoom lens that can resolve to 1:2 (macro) and it is the Nikkor AF 24-85 mm f/2.8~4.

Extension tubes are an excellent way to decrease the image to subject ratio and you can use your standard zoom lens or a 50 mm prime lens for better edge focusing.

** Many generic makers of lenses, cameras and other photographic accessories use a certain marketing latitude when it comes to describing their products.

One of the most over promoted terms now days is "HD". High Definition was used in the professional video arena to describe video cameras that could be used to produce video that could later be released as 35 mm theatrical films. These cameras start at about $15,000 up to around $150,000 and have three different CCD sensors, which individually are much, much larger than any P&S camera which have now claimed to be HD, just because they produce one of the HD specs. like 1280 x 720p. No mention is made to the extremely tiny pixels that capture these images when compared to those on a proper, professional video camera, poorer optics and reduced control found on a professional video camera.

The Flip camera company has had the nerve to call one of their tiny sensored, non-focusing cameras HD. Try converting those videos to 35 mm films for release in theaters.
 
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