Sharpness - Tips for Beginners

 

Unfortunately, even the most advanced cameras and photographers get blurry pictures every now and then. We have these advanced auto-focus features now, and it happens nevertheless. Here are my favorite reasons for those mistakes. In order of frequency those are

• wrong focus spot,
• not enough depth of field,
• motion blur,
• camera shake.

Let me fight them in turn.

Wrong Focus Spot

Putting the focus to the wrong spot, i.e., too short or too far, is more frequent than you think. It happens daily to those who always leave the camera the choice. They might be thinking that the AF system will do its job. It often doesn't, not even on the best cameras. The wrong thinking may arise from our experience with eye detection which really works very well. But if there is no eye or face in the scene, the camera might struggle to detect the subject. And even with eye detection, it might be the wrong eye or the wrong person.

To counteract this problem, there are two measures you can take: A large f-stop so that more will be in sharpness, or closer attention to what the camera does. I opt for the latter. The critical situations to pay attention to are fuzzy foreground objects, where the AF occasionally focusses on the background, some textures, or no texture at all, especially in low light.

Believe it or not, my Z5 misfocussed the image above with AF set to wide area and automatic selection of focus points. It showed me green squares all over the trees. But on close inspection of the image, the result was way softer than it should be. My solution was to use the zoom key and focus with my back-button-focus technique while being zoomed in. I can then release the AF-ON button and zoom out to see the full image again. The result of this technique is always perfect. 

Another idea is to use a single focus point and position it to a well-textured area in the trees. We used this all the time before the automatic selection of the focus point mislead us to thinking we need do no work or checking anymore. 

Not enough DOF

Even if you are well aware that the camera cannot focus everywhere and you learned to estimate the depth-of-field from the aperture and the focus distance, there are still occasions when you underestimate the problem. Some images simply look too blurry in important regions, even without pixel-peeping. There may be this object in the background which is neither blurred nor sharp. So, it draws the attention of the viewer without looking good. Another problematic scene are group portraits of persons which are not at the same distance to the camera. 

The solution to this problem is to increase the f-stop and thus increase the DOF. If that makes the background too intrusive, your only option is to rethink the composition. The best images have only one object in sharpness, or all objects. There is also a balance between DOF and background bokeh. You can shoot portraits at 135mm and f/1.2. But that might yield one eye in sharpness and the other blurry. If you are close, you might get the eyelashes sharp, but not the eye. Personally, I restrict myself to f/4 for portraits.

By the way, the DOF does not depend on the focal length if you keep the subject at the same size in the frame. A longer focal length will however blur the background more and show less background. It is the preferred way to shoot portraits.

Motion Blur

Everything is moving. Even in landscapes, some leaf may be shaking in the wind. Usually, you do not notice unless you print or view large. But when shooting kids, sports or wildlife, you will have to handle with motion blur.

The solution is to increase the shutter speed. For kids, I prefer 1/200. For sports, 1/500. Obviously, you need to compensate the missing light. You can use a faster lens, but only with restricted DOF. For sports, a very thin DOF might not be a good idea, even if your camera focusses very fast. How should it know if to focus on the ball, the leg or the face of the player?  

It might thus be necessary to increase the ISO instead. Do not be afraid of doing that. Everybody knows that dancing events in low light are difficult, and does not expect a well-lit image. It is better to get a sub-optimal image quality than an image lost by motion blur.

Note, that you might take advantage of the motion and show it. This is often done with splashing water which will look smooth at anything above 1/5 second. If you use this technique for moving dancers or objects, don't stop halfway. Make it blur enough to see that it is intentional. You might want to use a tripod or put the camera down somewhere to get the other areas in your image sharp like I have done in the image above.

Camera Shake

This point is now much less important than 20 years ago. Most modern cameras or lenses feature some type of image stabilization now. Moreover, we can now use higher ISO values with confidence. It does still happen, especially with prime lenses on cameras that do not have IBIS. Optical image stabilization is rare in prime lenses.

The old solution was 1/focal length for the shutter speed. So, the nifty-fifty requires 1/50. This rule applies only if you are a steady shooter and hold the camera firmly against the eye. A more modern solution is to use a camera or lens with image stabilization and to shoot not too hastily. You can also switch to silent shooting on modern mirrorless cameras which eliminates the shutter. Moreover, you can add a delay before the release which will prevent camera shake by pressing the shutter button. Of course, it is still helpful to hold the camera steadily, use a tripod, or lean against something solid.

Focusing Techniques

There is manual focus (MF) and auto-focus (AF). But there is also a mixture of both which is called focus override. It is best accomplished with back-button-focus (BBF). Let me explain.

Manual focus is now easier then ever. The mirrorless design allows focus the same hints  on the display and the viewfinder. The simplest hint is an indication of correct focusing, sometimes even arrows showing the direction to turn the focus ring to. Usually, the focus point is a single point, changing color if the focus is considered good by the focus element. 

A more advanced hint for MF is focus peaking which colors areas of correct focus. The color can usually be selected, as well as the intensity of the effect. After some practice you may find this an excellent way to get sharp images.

Auto-Focus is depending the processor of the camera. More modern cameras are more capable and faster. They are able to track objects which move through the image, often even predicting the movement. There are two modes for AF, area mode and object detection. The area modes usually select the closest object in an area of selectable size. The systems with object detection can detect faces, eyes and other objects, depending on the camera. 

Tracking works either by pressing a dedicated button to enable a tracking rectangle which will stick with the object underneath it when focused on, or simply by focusing in tracking mode. Tracking is an easy way to avoid having to set the focus point off-center to an object. Note, that focusing with a center point and recomposing is not precise enough. In tracking, you can place the track rectangle on the off-center subject and recompose.

I told you that is possible to combine AF and MF. In auto-focus mode, you can turn the focus ring on the lens simply. Most cameras will switch to MF then. That is called manual override. You can then use the focus hints to get a more precise focus.

Another trick is to use back-button-focus. When AF was introduced, the half-press of the shutter was invented to do the focusing. This allows a point-and-shoot operation of the camera. Many photographers prefer to have a dedicated focusing button and get the focusing off the shutter operation. This allows to precisely focus if there is enough time and then take the image. The focus button is usually easy to reach with the thumb. After a bit of practice the method is as fast as the half-press method, but easier to use precisely. It has more advantages as you will discover when you use it.

We also need to distinguish single AF and continuous AF. The latter causes the camera to continue focusing when the shutter is pressed half-way down, or the focus button is pressed. The confirmation of correct focus in continuous mode is usually weak. But you can set most cameras to release only if focus is acquired. By the way, BBF makes it get single focus in continuous mode. Simply let the focus button go to fix the focus. 

Finally

This ends my tips for sharper images. A final remark should be that you can always check your images on the camera. If you do not want to do this, use a setup where you are confident that it generates sharp images, something like a 35mm lens with 1/125 shutter speed and F8 on full frame cameras. You can use AUTO ISO to compensate for bad light. The crime scene below was taken on such a setting for street photography.

Most of all, have fun!