I recently invested in the
Sigma 50mm f/1.4 Art lens for Canon. I want to know which is the best way to focus for portraits. I am using a camera with APS-C cropped sensor. Should I use focal points to focus on the subject's eyes to maintain sharpness or go for manual focus ? I know that at f/1.4 I will really need to pinpoint my focus, else the details will be lost. What is the ideal way portrait photographers prefer to focus using a lens with such a narrow depth of field ?
I recently invested in the
With a shallow depth of field, the proper focus will depend on what the portrait is trying to communicate. For example at f:1.4 it will be difficult to achieve sharp focus on both the subject's eyes when using a typical oblique portrait pose (and impossible for a profile pose). In an oblique pose, which eye is in sharp focus will portray the subject differently.
This is part and parcel of the general nature of shallow focus lenses, what isn't in focus is as important as what is. The image is a gestalt. Great portraits are often made by what is in focus in addition to an eye or two...a hand, the weave of the subject's clothes, part of the hairdo, etc.
Should I use focal points to focus on the subject's eyes to maintain sharpness or go for manual focus ?
The most accurate will be live view with magnification.
Besides that, selecting the appropriate single focus point will most likely give best results. Some people prefer using the center point, which is usually the most accurate and then recompose. This "focus and recompose" technique may cause back-focus though.
Manual focusing with AF lens is usually not very comfortable and accurate. In addition, the typical matte screen is optimized for lenses with f/2.8 and greater and does not show depth of field correctly at f/1.4.
For very narrow depth of field (ie, when taking phitos at F:1.4, for exemple) autofocus is usually a must, as doing the focus by sight it is quite difficult to achieve (especially if your eyesight is not 20/20).
You may need to prefer the "best" focus point (old cameras usually have it at the center focus point, recent cameras have usually several good ones to choose from), focus using it (hald-pressing the button), then re-frame as needed (continue to press the button to actually take the picture when the framing is good).
But it is also possible to focus manually if you practice a lot (and is quite interresting to try).
Manual focus is especially important when filming with your camera, as you can quickly focus what you need to focus on, and not depend on the set focus point or the focusing speed of the autofocus)