Through trial and error I have discovered what conditions produce the sharpest shot at a very shallow depth-of-field ~ meaning how close can I get to my subject so that a small area takes up the entire frame and still produce a sharp image? All this talk about aperture, f-stop, depth-of-field, resolution, exposure can seem unwieldy, complicated, confusing, overwhelming to the untrained photographer. Here's what I've learned along the way ~ what works and why.
First of all, let's talk about the sunny 16 rule. What's that? Essentially, it means that, on a sunny day, an aperture of f/16 and a shutter speed equivalent to the the inverse of the ISO speed of the camera's film, will suffice. Digital cameras use image sensors and so ISO refers to the light sensitivity of the camera's image sensor. An ISO of 80 suits our purposes for a sunny day. This means low light sensitivity, minimal visual noise ~ fast shutterspeed, short exposure.
A close-up shot requires a shallow depth-of-field, which decreases with f number. This implies a smaller aperture. Sunny conditions produce the best quality close-up shots. This makes sense because we need a smaller aperture for our shallow depth of field. As we reduce the distance betweem ourselves and our flower subject, with a smaller aperture, so that small details fill the frame, we need maximum light. NATURAL LIGHT WORKS BEST. The highest resolution possible will also reduce the depth-of-field. So, we want an f-number smaller than 16 ~ as in somewhere in the range of 4.5 to 8. A longer focal length also helps achieve a shallow depth-of-field ~ an effect we want in macro shooting.
I hope this makes sense and helps to demystify the science behind macro photography. I leave you with an visual example from my photo gallery.
|Camera:||Nikon Coolpix L110|
|Exposure:||0.013 sec (1/76)|
|Focal Length:||15.1 mm|