Another snap of the shutter, another opportunity to exert control over your image capture...How you composed the image determines WHAT will be seen, but it’s your combination of shutter and aperture (and to a lesser extent ISO) that controls HOW it will be seen.You know all this already.The point is, do you apply this knowledge before pressing the shutter?
You know that shutter speed generally dictates the amount of motion-freeze or motion-blur you allow in your image.You also know that aperture choices generally dictates the depth of field, that is, what you allow to be in focus.So, once again, before you press that shutter, HOW do you want your resulting image to appear?
The two images here of grape clusters demonstrate the result of different decisions being made prior to pressing the shutter.Of the complete grape cluster, my desire was to be able to see the entire bunch of grapes clearly, and in focus.Because of this, a fairly broad depth of field was desired.By choosing an aperture of f/5.6, all grapes would be well within the depth of focus resulting in the desired outcome.(The necessary shutter speed for proper exposure under this condition was 1/250 sec. with ISO at 200.A focal length of 105mm was used.)
Conversely, the tight, almost macro image of the grapes was shot at a wide-open f/1.8 because of my desire to have focus only on the surface of a few select grapes, with the remainder of the grape cluster falling off into a gentle blur (an effect often referred to as “bokeh”).(For this aperture setting, a shutter speed of 1/750 was needed, also at ISO 200.A focal length of 35mm was used.)
With all the advantages that today's software gives the photographer in post-production (i.e. after the fact), it can’t make up for the important decisions you make as part of the initial capture.Photography is thinking, not just reacting or snapping pictures.That said, sometimes conditions are such that you don’t have the luxury of time to think, plan, or prepare for your shot, and that's ok—that’s when you need things like fully-automatic, aperture-priority, or shutter-priority.But if you have the luxury of time, indulge yourself by also taking advantage of the luxury of manual settings in order to exert full control over HOW you want your image to look.