Sharpest Focusing Hacks
Episode #3 of the course The best photography hacks by Tom Ang
Image sharpness is one of the biggest preoccupations of today’s photographer. This is for a good reason. Today’s sensors are such high resolution, there’s nowhere to hide.
How Sharp Is Sharp?
We know intuitively when we have a sharp image: we can see details clearly. Drill down a bit further, and we start to look at separation of detail or resolution, edge features, and contrast. This subject can get too technical for a 10-day course, so here’s a good basic treatment.
For most photographers, what really matters is how much sharpness they actually need. As a rough guide:
• Acceptably sharp A4 print: all modern cameras and lenses are fine.
• Sharp A3 print: prosumer cameras of 18 megapixels resolution with good-quality lenses are needed.
• Critically sharp at A3 or larger: you will need the best both in gear and technique.
Whatever equipment you use, let’s look at two ways to get the best out of them.
Virtually all photographic lenses produce their best image quality with apertures somewhere in the middle of the range. Suppose your lens has a maximum aperture of f/2 going down to f/22. It’s almost certainly not going to be at its best at f/2 or at f/22, even at f/16. Around f/5.6 or f/8 is the sweet spot for the majority of general-purpose lenses.
• A useful rule of thumb is this: a lens’ sweet spot is around two stops smaller than the largest aperture, e.g. if you have a f/2 lens, the sweet spot is around f/5.6; if you have a f/4 lens, the sweet spot is around f/8.
• It’s easy to find your lens’ sweet spot. Make a shot of the same object at different apertures and zoom in on a computer screen to see which is sharpest. Try this on different subjects and distances to find a consistent result.
Moving to Focus
If you’re working close up—when making portraits or shooting flowers, for instance—manual focus is often the best technique. And auto-focus is often no match for little children on the move. This hack can help:
• Once you have obtained focus, keep focused by moving yourself, i.e. you keep the same distance to the subject.
You don’t focus by turning the focus control or using auto-focus. You simply lean back when they come closer, and lean forward when they move away. The distance covered isn’t great, but twiddling the focus control often overshoots the mark. Keep the camera away from your face if you have a rear display screen, as it’s easier to move your arms than your whole body.
Try it and see! You’ll get better with practice, and when you master it, you’ll find it a big saver in effort. Your hit rate for in-focus shots will also shoot up!
• Avoid using the minimum aperture of your lens unless you really need great depth of field effects.
• On all but the best-quality lenses, avoid using the maximum aperture unless you need very shallow depth of field.
• When working close in with subjects, it’s easier to keep in focus by maintaining your distance to them.
• Oh, and here’s a bonus third way to get the sharpest images: use a tripod whenever possible!
Tomorrow, I’ll tell you about something many people do—indeed, some say it’s the best thing digital did for photography. But you won’t catch me doing it!
May your focus be confirmed!
The Digital Photography Book by Scott Kelby
Share with friends