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Macro and DOF
I'm using my first DSLR (D90 with a 17-70mm Sigma Macro) and am kind of confused about the Macro capabilities and DOF. I've taken some close up shots at relatively narrow f-stops (f11+) and have noticed a quite narrow DOF. Sometimes this is less than 1 inch! I would expect that at f2 but not at f11. Is this normal or do I have a lens problem? Perhaps it's also my ignorance.
It seems I also do not understand exactly when the macro aspects of the lens happen. I guess it's just another word for close-up?
It seems I also do not understand exactly when the macro aspects of the lens happen. I guess it's just another word for close-up?
A Nikon D90 plus some Nikon, Sigma & Tokina lenses.
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As you discovered, DOF gets extremely shallow as the subject gets closer and closer to the front lens element. DOFs get down to fractions of a millimeter, not inches when shooting real macro images.
Lens manufacturers use the tag Macro loosely. True macro lenses are, traditionally, thought of as lenses that create an image on the image plane that is the same size as the subject - a 1:1 relationship between actual subject size and image size. Most real Macro lenses are 'prime' lenses - single focal length.
Many variable zoom lenses can focus rather close, and manufacturers like to call these lenses 'Macro', although real macro shooters do not believe this usage is totally accurate, as they rarely shoot at 1:1.
Moderator of the Technique Forum and Finishing School on Dgrin
I thought I had a bad lens or that the cam was focusing on the wrong area of the scene.