Alley in Pisa, Italy

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What’s the difference between a regular lens and a macro lens?

what are the main differences b/w macro lens and normal lens. How a 100mm macro lens achieves more magnification than a 100mm normal lens. what are the factors effects magnification of a lens. what are the factors which limit minimum focusing distance

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marked as duplicate by Matt Grum, Nick Miners, Nir, mattdm, Dan Wolfgang Oct 28 '12 at 18:43

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
Your subject line and question body are non identical. It would be a good idea to edit your question so what you are asking is clear. Your subject line asks about macro and non macro lenses and the implication is that neither lens is zoom ("Normal" tends to suggest a certain range of possible focal lengths, but few woul dbe confused by your use of the term in this context.) You question body asks about normal and zoom lenses in the first sentence. But, your clarifying example talks about a zoom lens at 100mm compared with a macro lens at 100mm - so presumably it is a fixed 100mm macros lens. –  Russell McMahon Oct 28 '12 at 8:17
    
While a broad enough answer could be framed to answer the whole question area, you would be better served to more carefully ask about what you really want to know. –  Russell McMahon Oct 28 '12 at 8:18

1 Answer 1

I'll add to this and or alter it or delete it as the question becomes clearer.

A macro lens is a lens which allows you to focus on small objects such that they occupy a significant proportion of the image area. As the targets get smaller this implies either

  • The ability to focus at a closer distance than is usual "out of the box" without using any levers, buttons, cams or auxilliary lenses.
    (Image linear size is inversely related to distance from lens) or

  • a higher degree of magnification (more focal length)

  • Special modes which allow the lens to focus much closer than normal but over a very limited distance range. (Reversed lens methods arguably belong here).

Wikipedia - Macro Photography {here} says:

  • Macro photography ... is extreme close-up photography, usually of very small subjects, in which the size of the subject in the photograph is greater than life size (though macrophotography technically refers to the art of making very large photographs).[2][4] By some definitions, a macro photograph is one in which the size of the subject on the negative or image sensor is life size or greater.[5] However in other uses it refers to a finished photograph of a subject at greater than life size.[6]

The following example demonstrates that "Macro" lens can be as much a marketing term as a reality.

Closer focusing: A Sony 18-250, f/3.5-6.3 lens is not described as a macro lens either in Sony'd literature or on the lens. This is surprising, given Sony's penchant for marketing speak and the lenses capabilities when compared to some lenses described as "macros" lenses by their manufacturers. At full 250mm focal length and minimum focusing distance a target of 30mm just occupies the image width. This is a usful degree of macro capability.
The text above "Closer focusing: A Sony 18-250, f/3.5-" just fits across the image on a 1080p 29" monitor at default Chrome settings.

Special magic: Some macro lenses have special short distance focusing mechanisms that usually can be operated when the lens is at one extreme or other of its focal length range.
Example: The somewhat strange Nikkor AF 35-105mm f/3.5-4.5 (which I use as an example mainly because I have one to hand), has a minimum focusing distance at 105mm focal length of about 120mm - uncomfortably large in many cases. It has a macro mode which can be engaged with a pushbutton when the lens is at the 105mm end of it's travel. Turning the zoom ring then shortens the effective focal length to about 70mm over about 40 degrees of rotation BUT at the same time substantially reduces the minimum focal down to about 200mm and minimum focusing distance, a target of 50mm just occupies the image width on a full frame camera. On an APSC camera with a 2x area crop factor, the width would be about 50mm x 0.7071 ~= 35mm - just more than the Sony non-macro lens.

In my case the 18-250 lens is on an apsc camera and the 35-105mm lens is on a full frame camera, so the non-Macro lens provides a 50/30 = 1.6x linear gain over the macro lens, or 1.6^2 = 2.6 x area gain. eg an object with 3:2 aspect ratio that just fills the FF frame at maximum size, will fill only about 40% of the APSC frame. In my case the APSC is 24 megapixel (Sony A77) and the Nikon is 12 mp (D700) so there will be about 5 X as many pixels in a given cropped area. This overall combination makes the non-macro lens a better macro lens than the macro lens, all else being equal.


Your specific questions can probably be addressed by the above. If not, please advise.

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