So what is sharp tack focus?
(Natural light, 50mm, ISO 640, f/3.5, SS 1/80)
See how sharp and clear her eyes are? That is sharp tack focus. Now, to really test how sharp my focus is, I typically blow up and crop the photo. How sharp is it now?
Here's another one.
(Natural light, 50mm, ISO 640, f/3.5, SS 1/100)
How does a photographer achieve sharp tack focus?
- Select your focal point. You are smarter than your camera so you should be the one deciding where the focal point should land. Be sure your camera is set to a single focal point. And one that you choose! For most portraits, your focal point should be on the eye closest to you. I've seen some photographers complain how they can't get the eyes in focus but then they reveal that they focus in between both eyes. Aim for one eye. (Note that in some portraits you may want to focus on another part of the face - lips, freckles, lashes, etc - and that's okay too.)
- Don't shoot too wide. I know some get obsessed with using an f stop of 1.8 but your image is more likely to be a bit soft the more wide open you shoot. Most lenses are not sharp at 1.8. In fact, you may need to play around with your lens to find its sweet spot - where it becomes super sharp. I've given you my settings on all the photos here in this post. As you can see, I prefer an f stop of 3.5. I feel like my lenses are at their sharpest and I still get that shallow depth of field.
- Be sure your shutter speed is not too slow. Yes, it's possible to shoot sharp images with slow shutter speeds handheld but you're more likely to get some blur. Play it safe and bump up your ISO if you have to.
Here are a few more examples.
(Natural light, 105mm, ISO 200, f/3.5, SS 1/200)
(Natural light, 105mm, ISO 400, f3/5, SS 1/200)