A portrait can look soft because the camera moved, the person moved, or focus landed at the wrong distance. Each failure needs a different response. Before increasing shutter speed, inspect a frame closely enough to identify where the softness occurs. A sharp wall behind a blurred face tells you something different from a frame in which every edge trails in the same direction.
Set the shutter around the movement the photograph needs to stop. A person listening quietly and a person turning their head require different tests. Even a held pose contains small changes in balance, expression and breathing.
Find the pattern in the blur
Look at a stationary detail near the subject as well as the eyes. If both show similar directional smearing, camera movement is a likely cause. If the stationary detail is crisp while a hand or face is smeared, subject movement is more likely. A sharply resolved ear with soft eyes suggests that focus may have landed behind the intended point.
These clues can overlap. A frame can contain camera shake and a moving subject, and a distant background may already be blurred by depth of field. Make a comparison photograph of a stationary object at a similar distance if the portrait does not provide a useful reference. Keep your posture and framing comparable.
Judge the softness at the size that matters. A small preview can hide movement around the eyelashes, while extreme magnification can overstate a defect that disappears in the intended output. Check both before deciding a file is unusable.
Choose a starting speed and test it
For a mostly still person, a trial at 1/250 second can be a useful starting point in adequate light. It is an example, not a guarantee. Longer focal lengths, tighter framing, an unsteady camera position or a moving expression may call for a faster speed. Make a short sequence because one sharp frame can hide an unreliable setting.
Keep the aperture appropriate to the needed focus depth. Increase ISO if the light cannot support that aperture and shutter speed together. A modest increase in visible noise may be easier to manage than a face blurred beyond the detail you need. Inspect exposure as well, especially when dark clothing or bright sky occupies much of the frame.
With automatic exposure, confirm that the camera continues to use the intended shutter speed as the framing changes. Some automatic combinations can lengthen the exposure when the available ISO range is exhausted. Learn how your own camera indicates that limit and check the recorded settings in the test files.
Allow more speed for an action
Ask for a repeatable movement, such as a slow turn from the window toward the camera. Compare 1/250 with 1/500 second while holding framing steady. Inspect the moving eye and any loose hair. If the movement still looks smeared, try a faster exposure or photograph a deliberate pause within the action.
Movement across the image often produces more visible displacement than movement toward the camera, though movement toward you can make focus tracking harder. A walking portrait may therefore have sharp clothing but missed eyes even at a fast shutter. Check the focus sequence separately from the exposure sequence.
The City Light Portraits series uses a night setting and a balance of movement and stillness. When using that kind of visual reference, decide which visible movement belongs in your own image before judging every soft edge as a failure.
Use support for the problem it solves
A stable support can reduce camera movement during a still portrait. Image stabilization can also help with camera shake within its limits. Neither freezes a person's gesture. If a tripod-mounted portrait has a blurred face and sharp background detail, shorten the exposure or ask for a still moment.
Improve your stance when working handheld. Hold the camera comfortably, avoid reaching far from your body and release unnecessary tension. A permitted wall or support may help, provided it does not force an unsafe position or obstruct a route. Review the result after changing posture.
If the first frame in a sequence is consistently softer than the following ones, review how you press the shutter and settle the camera. Make another short comparison while releasing it gently. Keep testing subject movement separately; a steadier release will not stop a person turning their head.
Build a small reference sequence
At one location, photograph the same person holding still and making the same turn at several shutter speeds. Keep exposure comparable with ISO, and label the frames with the action and recorded setting. Compare the sequence before making a large batch of portraits.
Use the photography portfolio when choosing the framing for this exercise. Repeat your test when changing from a wider portrait to a tight crop, or when the light fades. Make a dependable sharp frame before experimenting with slower exposures so the session has a usable option if the motion trials fail.