Quote:
Originally Posted by R.A.D.
It's not the magnification but rather the ability of the macro lens to focus down to a few inches. Most conventional lenses have a minimum focus distance of 2-4 feet. A true macro lens will allow the user to focus within inches sometimes mm to the object. Although this may seem like an increase in magnification because you are focusing so close it is rather the macro lenses nature to focus down so tight and that is why they cost so much. If I selected a higher aperture on the lens ie f/16-f/22 and had enough lighting, the result would be a much sharper image that is focused front to back. Most photographers use f/2.8 as a setting when shooting close up is because they want their subject to be sharp but the background to be blurred so that it will not distract the viewer.
True magnification is dependent on the size of the lens that you buy. ie 50mm, 100 mm, 200mm etc..
If I had a 60mm macro and wanted to take a macro shot, I might have to be as close as 1 inch away from my subject. However, if I had a 105mm macro I can now shoot the same image but be further back. Both shots I can select f/2.8 and still get the same blurred and sharpness effect. The only difference is that one lens is magnifying almost twice the other and I can stand further back.
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I have to disagree the lens elements in the marco lens completely change the rules of normal lenses. Depth of field is dependent on the positioning of the lens elements and not f-stop. stopping down to f22 from f2.8 will gain you millimetres of depth of field where as minor decreases of magnification will gain you centimetres.
Anyway. This is usually not a problem with Tank photography as you are never mm from you subject.
Depth of Field Information
J