Teaching Photography - Technical Basics

 

This page contains basic technical information on cameras. It is mostly stills oriented, and does not contain much for videography. It will be a work in progress.

I added exercises to the page. Even if you use this page as a reference, you might profit from reading and especially from doing the exercises. Of course, all this is for beginners. Most older photographers will know almost everything I explain here.

If you want to learn more about the author, please see About Me.

Content

• Start
• The Camera
• Exposure
• ISO
• Aperture
• Shutter Speed
• RAW and JPEG
• Focal Length
• Focusing
• Bad Photos

Start

This is most useful for photographers with some experience. But it might be beneficial to give a few hints up front for those who want to start with photography. You may be coming from a smartphone and want to explore photography deeper. Or you may have been given a used camera and want to explore it. I don't know your intentions. So, feel free to skip anything that does not apply to you.

Photography is a wonderful hobby that will keep you engaged, e.g., making you walk outside, like a dog does. Just take your camera and go. You will be able to keep precious moments, things you see and would otherwise forget, or even document events for others. There is so much you can do.

If you want to buy a camera for a good start, you can do so by spending less than 1000€. An example would be a Nikon Z50 with the 16-50 VR lens. But there are others, especially on the used market. If it is not a too cheap or too old camera, you can hardly go wrong. I'd recommend a mirrorless APS-C camera for the start, however, because it offers a good balance between size, cost, and weight, and image quality.

Once you have the camera, go exploring with it. Set it to full AUTO and take pictures. Just try everything out. You can also read the manual. Most have a manual online. E.g., here is the one for the Nikon Z50. If you are new to photography, you won't understand everything. Then you can come back to this page to learn. The first target at that stage would be to get out of AUTO. But it is a good start to let the camera make the technical decisions for you.

You should also immediately start learning a good composition for your image. For a start, fill the frame with your subject and keep anything out that could distract the viewer. Be critical of the results, and keep an eye on the background. If you Google "photographic composition", you will find enough reliable material to read and learn. 

Most of all, have fun!

Exercises

• Rent or buy a camera with a standard lens (ask if you do not know what this is), reset it to factory settings, and set it to AUTO. Go out and shoot pictures. Do that at night or day and in all sorts of light. Learn how to transfer the pictures to a device with a larger screen, like a tablet or a computer.
• Learn how to print some of the pictures. There are lots of shops that will print the pictures for you. You just have to bring the camera or a smartphone, or upload to a web-based printing service.
• Compare the pictures with pictures of your smartphone in the same situations. Compare the printed results, especially those in difficult light.
• Judge your pictures artistically. Were you close enough? Does your image contain distracting elements? Is the composition pleasing? Is your subject sharp enough? Get critical!
• Read on only after going through these initial exercises.

The Camera

A modern digital mirrorless camera with interchangeable lenses (MILC) works differently from the film camera in the image above, although the central elements are still the same. Here are the main parts of such a camera:

• A sensor sitting inside the housing on its back side.
• A lens to collect the light beams from a light point in your scene and project it to a single point on the sensor.
• A display that can often be flipped partly or completely to show the image that the sensor received.
• A viewfinder through which the user can see the image on a small LCD screen via an ocular, usually mounted on top of the display at the center of the back of the camera.

There are many variations of this design. The most important one is the single-lens reflex (SLR) system, which dominated the market for decades. It has an optical viewfinder, and you look via a pentaprism at the image reflected by a mirror on a ground glass. The SLR is increasingly vanishing as mirrorless designs are more compact and allow additional information to be displayed in the viewfinder. We call these MILC (mirrorless interchangeable lens camera) in the sequel.

There are also compact cameras without any viewfinder at all. The photographer needs to use the display to compose the image. Since displays are touch-sensitive now and can be flipped, these cameras can be nice travel cameras. The main disadvantage is that the display can be obscured by bright sunlight. Moreover, its light might be unwanted in some situations.

Another, rarer type has an optical viewfinder that sees the scene through a different lens, like the camera in the picture above. Leica has made that design popular with its rangefinder technology.

The most frequent type of camera today is the smartphone. In principle, they have the same components as the MILC, except for a viewfinder. Of course, the lens and the sensor are very much smaller. The lens cannot be changed or zoomed optically, but there is often more than one camera with different lenses.

We need to identify two other parts of the camera that are important for the photographer.

• The aperture can close the lens, allowing less light to pass through. It consists of small blades that close from the edge of the lens, leaving a small circular opening in the center. Smartphones often lack an aperture and control light only with the shutter speed.
• The shutter sits in front of the sensor. It is a curtain that closes when the sensor is cleared to receive an image. Then the curtain opens for a precise amount of time, allowing light to shine on the sensor. After the images have been read, the shutter opens so the viewfinder can continue working. We call the time of the exposure the shutter speed. Most shutters consist of two parts, allowing a slit to move over the sensor for very short exposure times. Recently, there are cameras without a shutter, controlling the exposure time on the sensor. 

Older cameras and smartphones might have a different type of shutter built into the lens itself. Very modern cameras don't have one at all. They do the exposure electronically. The shutter of an SLR is closed unless an image is taken, but the mirrorless cameras leave it open to allow the sensor to see the scene.

Exercises

• Learn to identify the mentioned parts in your camera.
• Have a visit to the camera store to see and identify other types of cameras. 
• Ask technical questions about cameras. Can the lens be changed? Does it have a viewfinder? How does the viewfinder work, and where is its image coming from? What size is the sensor, and how many MP ("Mega-Pixels") does it capture? What storage is used? Can the display flip out?
• Listen to your shutter. Is the screen dark during the exposure? Does your camera have a silent shutter, and how does it work?

Exposure

The exposure is the amount of light that reaches the sensor, measured in light per area. It can be changed via the aperture and the shutter speed, i.e., the opening of the lens and the amount of time the shutter is opened for the sensor to be exposed.

For example, an average daylight exposure can be achieved with an aperture of f/8 and a shutter speed of 1/60 of a second. As you will learn below, an aperture of f/4 yields 4 times more light, and the shutter speed can thus be decreased to 1/240 (usually denoted 1/250 on the camera).

The sensor, just like the old film, has a specific range of exposure where it works best.

• The minimal exposure a sensor can record is determined by its noise level. Every electronic part produces noise. The light itself can only be measured with noise. The signal, i.e., the exposure, must be brighter than the noise.
• The maximal exposure a sensor can record is determined by the capacity of the sensor elements.

Thus, we obtain a range of good exposures, called the camera's dynamic range. The job of a good exposure is to fall inside that range. To achieve that, the aperture and the shutter speed can be changed. 

• Overexposure means that the exposure was too high. Some areas or spots in the image may be washed out in blank white ("blown out"). Most colors will look less saturated or distorted when they are overexposed.
• Underexposure means the exposure was too low. Details in the shadows are lost because they are below the noise level of the camera. The image looks sad and muted, and very grainy due to the noise.
• Correct Exposure usually uses the full dynamic range of the image.

But it can be artistically desired to over- or under-expose for a special effect. This might even be necessary if the camera's dynamic range is insufficient. An image with lots of blown-out white areas is called a high-key image. Likewise, not all shadow details are important. If all shadows remain pitch black, the image is low-key. These terms are often applied also to well-exposed images that are primarily white or black.

One should not be afraid to make artistic choices. E.g., it is more important to get the main subject in good light than the background. This can sometimes be achieved only by exceeding the dynamic range, unless we are willing to make two images with different exposures and combine them later in post-processing. This is called high dynamic range (HDR) photography. Some cameras can do that automatically. Especially smartphones like to do that. Images can look unnatural, however.

On modern cameras, good exposure can be achieved automatically using light metering. Most smartphone users will never care about aperture or shutter speed. But to learn photography, it is important to get acquainted with these concepts as soon as possible. The reason is that aperture and shutter speed determine the photographic output in more ways than just by the exposure.

For newcomers, let us first talk about automatic exposure modes. The explanation applies to cameras with a PSAM-AUTO dial. On retro cameras with specific dials for each setting, modes are handled differently.

• The fully automatic (AUTO) exposure handles everything for the photographer. On cameras with a mode dial, it is usually marked as AUTO. Besides the exposure, it restricts access to various other settings. Nevertheless, it can be useful for starters or for very quick access to reasonable settings. On smartphone cameras, it is the default mode, and most leave it there.
• Aperture Priority (A) lets the photographer fix the aperture and select a correct shutter speed. It is used because we may want to handle the aperture ourselves for reasons explained below, mainly to isolate our objects.
• Shutter Speed Priority (S or T) lets the photographer fix the shutter speed and select a correct aperture. It is used because we may want to handle the shutter speed ourselves, mainly to freeze or show object motion.
• Program Mode (P) is a mix that selects a reasonable combination of aperture and shutter speed. Like in A or S mode, there is usually a wheel to change the combination. This mode works like AUTO, but without the additional restrictions and the ability to change the selection.
• Manual Mode (M) lets the photographer handle both the aperture and shutter speed. There is usually some feedback to get the right exposure, either by a simple indicator or by a histogram. If the light is not changing much, this mode can be more reliable than the automatic ones.

Since all modes rely on metering, it is important to know where the camera meters the exposure.

• Average metering meters the entire scene and aims for a good balance.
• Center weighted metering uses only an area near the center.
• Spot metering uses only the very center. This is useful for low- or high-key images. Most cameras use the focus point for the metering.
• Preserve Highlights is a special metering that some cameras feature. It does not overexpose any part of the scene. It is good for dark scenes with bright spots, like on a stage, where the bright areas need to be exposed correctly.

For example, see the image below, where the camera's dynamic range does not meet requirements. It is important to expose for the tulip in the foreground. There is no problem with the background going completely dark. Beginners often fear losing information in dark areas. But photography is not about information, but about art and beauty.

Exposure Compensation is available on all cameras, including smartphones. Often it is marked as +/- on some button or wheel. 

The modern way is to set exposure compensation visually. If the image looks too bright or too dark, adjust it and take a second image. Most cameras feature a preview that lets you judge exposure on the display or viewfinder while composing your image. If you do not trust your visual experience, a scientific way is to use the histogram, which modern cameras can display.

Often, the exposure compensation is memorized for the next shot even if you switch off the camera. Do not forget to check this! On Nikon Z cameras, one wheel sets the aperture, and the other sets non-saved exposure compensation. Many cameras can define user modes with fixed settings. Switching to such a mode should also reset the exposure compensation.

Exercises

• Look through your images to identify pitch-dark areas and blown-out highlights. Does this look okay to you? Was it intended?
• See if your camera has an HDR mode. Use it and see if you like it. 
• Try setting your camera from AUTO to A mode (aperture priority). Learn to set different f-stops, and try them for a portrait. How does the shutter speed change when you change the f-stop? Do the photos look different?
• Set the camera to S mode (shutter priority, sometimes denoted by T). Try setting different shutter speeds on a moving subject, such as flowing water. How does the aperture change? How does it change the image?
• Learn how to set the metering to spot metering, and find scenes that clearly show the difference.
• Check if your camera has a button to lock the exposure. Often, it is locked when the shutter is half-pressed, i.e., during focusing. 

ISO

We need to talk about a much-discussed feature of modern cameras, the ISO setting. The abbreviation comes from the organisation for international standards for film sensitivity. It is also used for sensors.

In a modern digital camera, ISO is used to simply brighten the image, including sensor noise. This might be necessary if there isn't enough light to expose the sensor to its full dynamic range. E.g., you might not want to use a longer shutter speed because that would blur the image due to subject motion or camera shake. Moreover, it is necessary to increase ISO if you only have a limited aperture to work with, or if you want to close the aperture to achieve greater depth of field (see below).

If you underexpose an image, you are not fully using the sensor's dynamic range, so you lose useful light range in your image. Some cameras, however, switch to a different sensor technology for higher ISO, which helps a bit.

The end effect is that you see an image that is correctly exposed, but has more noise. Now, modern cameras have a very large dynamic range. Moreover, there is clever noise reduction that effectively covers the noise with only minor loss of detail. Thus, you should not be afraid to increase ISO within limits. Test this on your camera!

It is important to repeat that there might be good reasons to underexpose an image and help with higher ISO. You may want a high aperture to create a large depth of field, or a fast shutter speed to freeze motion. In both cases, it is better to increase the ISO than to end up with an unusable image. Also, hand-held images at night almost always require an increase in ISO.

Most cameras have an AUTO ISO setting that selects the ISO to keep the image correctly exposed. E.g., in aperture-priority mode A, the ISO will be increased if the shutter speed drops too low. In this case, camera shake might spoil the image. The photographer can set a limit for this increase or specify how the focal length is weighted into the increase.

Exercises

• Which minimal ISO does your camera allow? Which is the highest ISO possible, and what do images look like at that ISO?
• Set the camera to manual mode M and to ISO AUTO. Set a reasonable combination of shutter speed and aperture (such as 1/120 and f/8 at daylight) and watch how the ISO changes depending on the scene.
• Print high-ISO images or view them on large screens. See if you can see the increased noise.
• Learn how to set a limit to your AUTO ISO. 

Aperture

We now want to talk about the artistic aspects of the aperture. We already know that it determines the exposure.

Aperture is measured in f-stops. Most denote the apertures by f/2, f/2.8, f/4, f/5.6, f/8, etc. The fraction indicates that we can compute the aperture diameter by dividing the focal length by the aperture number. However, we just simply need to remember that f/2 is a very wide aperture, f/8 is a normal one, and f/32 is a very closed aperture. The f-stop determines the amount of light per area on the sensor. Going from f/2 to f/2.8 means doubling the amount of light per unit area.

A lens can only focus on points at a specific distance. I.e., only points at that distance will appear exactly sharp on the sensor. Closer or wider points will appear blurred. We use that to isolate subjects from the background. 

There is an interval of distances, where the objects appear sharp enough. This is called the depth of field (DOF). It becomes larger with closer apertures. So, f/2 has a very shallow DOF, and f/32, a very large one. It also depends on the focus distance, the focal length, and the sensor size.

Related to the DOF is the background blurriness in your image, which is part of the so-called Bokeh. The way the background interferes with your subject is important to isolate subjects. 

• A wider aperture decreases the DOF and increases background blurriness, thereby isolating the subject more. Note that this means a smaller denominator in the f-stop, i.e., f/2 instead of f/8.
• A closer distance to the main subject results in a smaller DOF and more blurriness in the background. Macro shots can have very small areas of sharpness, measured in millimeters.
• A longer focal length can be used to blur the background. Adjusting the distance so that the subject has the same size in the frame yields almost the same DOF. But the background will look much nicer with the longer lens. There is also less background in the frame, and it can be selected more easily to avoid distraction.
• A larger sensor allows a shallower DOF. Smartphone cameras, with their tiny sensors, tend to render everything sharp and often isolate the subject solely through artificial blurriness. 

There is a so-called crop factor that can be used to get equivalent f-stops for different sensor sizes. It helps translate DOF in f-stops across different cameras. It can also be used to translate the magnification effect of different focal lengths. APS-C cameras have a crop factor of around 1.5, so that f/4 on the APS-C is equivalent to f/6 on a film camera (also called a full frame camera, FF).

Good photography uses the DOF in artistic ways. Sometimes, we want everything to be sharp; often, we don't.

Exercises

• Look at your images and try to identify the DOF when printed or viewed on a large screen.
• Try a wide range of apertures for portraits and view the results. Which did you like best?
• If you have a modern smartphone, it may be able to blur the background in "portrait mode". Compare that to the results from a camera with a "fast" lens (say, f/2.8).

Shutter Speed

The choice of shutter speed also has an artistic meaning beyond its effect on the aperture. Shutter speed ranges from 1/4000 to 30 seconds. The most natural choices are between 1/30 and 1/250. 

There is a practical reason to select a high shutter speed for hand-held photography. Camera shake can easily ruin an image's sharpness. Today, many cameras have some sort of image stabilization (IS). It can be in the camera body (in-body IBIS) by moving the sensor, or in the lens (called optical OIS or VR) by moving lens elements. The latter is more effective in the telephoto range. Without stabilization, a good rule of thumb for shutter speed is 1/focal length. With stabilization, shutter times up to 6 stops (64 times) longer might be possible.

Here are some artistic considerations for the shutter speed.

• To freeze motion, you need very fast shutter speeds. It depends on the length of the lens and the speed of the subject. As a guideline, use at least 1/200 for anything that moves, e.g., for kids. Sport action may even require 1/2000 or less. To achieve such short shutter speeds with reasonable ISO settings, you need a fast lens, i.e., one with a wide maximum aperture. The problem is that you will then get a small DOF. There is always a compromise to be made.
• To show motion, you need a slow shutter speed. This helps smooth out water. You need more than 1/15 for this. If your image stabilization is not very good, you need a tripod. Often, the scene is too bright, and you cannot stop down enough at a basic ISO. In this case, you need a gray density filter to darken the scene. Pushed to extremes, you can smooth the movement of clouds and achieve an effect falsely called fine art by some photographers.

The author of these pages is a travel photographer and rarely does smooth water. Below is an attempt. I had to use a polarizer because I had no gray-density filter with me to manage the light at a reasonable f-stop, and only a tiny tripod.

Exercises

• Experiment with different shutter speeds on a running kid or dog. Be critical of the sharpness.
• Set the camera on a tripod or on a solid surface. Which long exposures can you take and still get a properly exposed image? Note that f-stops beyond f/16 are usually avoided due to the diffraction, which softens images.
• Take an image of a moving car or bicycle with a long exposure while panning the camera along with the subject. This should blur the background.
• Find a neutral density filter for your camera, and try really long exposures of waves or clouds. Even moving traffic might look nice, especially with lights.

RAW and JPEG

For a page like this, focused on the technical aspects of photography, it is essential to discuss what happens to your image after it leaves the sensor. You have two choices.

• JPEG output. JPEG is a standard image format for the internet and computers. The format reduces the storage space required for the image through compression, losing image data along the way. The conversion of sensor data to JPEG is performed by a processor inside the camera. You can adjust many aspects of this compression, such as sharpness, brightness, and brilliance. You can even change the image size and format in the camera. This kind of shooting is called out-of-camera photography (OOC).
• RAW output. This format contains all sensor data (or at least much more than JPEG) plus information on the lens used, the f-stop, etc. The format is specific to the camera. However, there is now an effort to standardize a RAW format, called DNG, which some cameras support. RAW is later converted on a computer by software like Lightroom or free camera-specific RAW converters.

Smartphones use OOC almost exclusively. Only a few smartphone photographers take the time to process their images on a computer. It is usually not worth it. The high noise levels require aggressive noise reduction, and modern smartphones can do that very well. Also, the artificial blurring of backgrounds often depends on additional sensors. It is best done on a smartphone. The results can be strikingly good, especially when viewed on the phone or printed at smaller sizes.

Exercises

• If you do not have Lightroom, consider learning this mighty editor and subscribing to a photography plan. It will also give you access to Photoshop and Lightroom Classic, which is the version I use on desktop computers, iPads, and laptops. 
• I understand that you want a cheaper alternative. One option is to use the processing software that comes with your camera. It will be good enough for most purposes. You may need to download it from your camera maker's home page. 
• There is also Darktable, which clones Lightroom. It is a lot slower and misses some features or camera profiles, however.

Focal Length

The focal length of the lens is defined as the distance to the sharp point behind the lens from incoming parallel rays, i.e., from points at infinity. It is denoted L in the image below.

The main purpose of knowing the focal length is that it determines the lens's angle of view (AOV). You get less with a telephoto lens and more with a wide-angle lens. I.e., a telephoto lens provides magnification.

• A focal length below 35mm is called wide-angle.
• Above 70mm, the telephoto range starts.
• In between, we have the 50mm normal lens.

These numbers apply to film-sized sensors of size 36mm by 24mm, so-called full-frame sensors (FF). For smaller sensors, a so-called crop factor needs to be applied. E.g., on APS-C 35mm becomes equivalent to 50mm, and on Micro Four Thirds (MFT) 25mm become 50mm etc.

Of course, wide-angle lenses can be used "to get everything in", and telephoto lenses "to get the subject closer". But besides those practical reasons, there are more important artistic reasons. Often, you can choose the distance to your photographed subject.

• A wide-angle lens emphasizes foreground objects. It makes them appear larger relative to the background, because you have to go closer. The best use is to show objects in their surroundings, while still emphasizing the subject. The feeling of depth will be enhanced. It will also create more DOF. A room can appear to be larger than it actually is with a wide-angle lens.
• A telephoto lens compresses objects at different distances. So, the background will appear closer to objects, and objects at different distances will appear closer together. The reason is that you go further away from your subject. Since it creates much less DOF and shows only a small part of the background, it is good for isolating, e.g., in portraits. A telephoto lens will remove the feeling of depth in the image. A building can appear to stand close to a faraway mountain with such a lens.

The zoom lenses combine both options but are usually not "fast" lenses, starting at f/4 or higher. To isolate something from the background, you may need other means, such as fog.

Exercises

• Do a portrait session with a zoom lens or different prime lenses at different apertures. Always keep the subject at the same size in the frame. Watch the effect on the background and DOF.
• Take an image of a long street with houses with a wide-angle and a telephoto lens. Can you create a sense of compression, making the houses look closer together?
• Get out on a sunny day with a 35mm lens or similar, set to f/8. Find a subject and try different compositions to isolate the subject from the background.
• Do the same on a foggy morning.

Focusing

As already mentioned, only points at a specific distance can be focused sharply. To be precise, the sharp points are ideally on a plane perpendicular to the lens axis. Ideally, only because the plane is sometimes slightly curved ("field curvature"). Closer or further points are not sharp. The interval of distances where points are sufficiently sharp is called the depth of field (DOF). We already explained how to use this to isolate subjects.

The optimal sharpness distance changes by positioning the lens or single lens elements forward or backward. There are several methods for the user to achieve the correct focus. The details may vary by camera, but we have the following options.

• Manual focusing. This is usually done by turning a focusing ring on the lens. In modern cameras, the user can select a focus point. For feedback, this point changes the color or blinks if the spot is in focus. The number of available focus points varies by camera. Modern mirrorless cameras can set this point almost everywhere on the screen. 
• Auto focus. In this case, the camera can select the focus point automatically, or focus automatically on a focus point set by the user. In any case, the camera will focus by default when the shutter is half-pressed. Optionally, this can be transferred to a special button (back button focus - BBF). There are several methods for telling the camera where to place the focus point.
• Single Point Focus. This sets one specific spot. Usually, this method is the most precise but the slowest.
• Area Autofocus. The camera will select a focus point in a specified area. Older cameras will simply select the closest point. Newer cameras may have more clever methods. The areas are usually available in several sizes and can be moved.
• Eye or Object Autofocus. Most modern cameras and many smartphones can focus on faces and even single eyes in the scene or in a predefined area. This technique has been available for some years and is continually refined. Now, cars, birds, and insects and their eyes can be detected.

Many lenses and cameras can use manual override. After the camera has finished autofocusing, the user can turn the lens's focus ring to change the focus. Often, this will enlarge the focused area, or the details in focus will be highlighted in some bright color (focus peaking).

There is not only the problem of selecting the focus point. It is also important to know when to focus.

• Single Autofocus. This mode focuses once when the shutter is half-pressed or when the dedicated AF button (BBF) is pressed. It is good for static subjects. The user gets precise feedback in this mode.
• Continuous Autofocus. In this mode, the focus is adjusted from the time the auto focus is activated until the shutter is released. This is good for moving subjects. The user feedback is not as precise as with single focusing, however. Modern cameras are quite good at determining the movement in advance. They can even change the focus point if necessary.
• Dynamic Area. Adjacent focus points can be selected if the subject moves out of the main focus point.
• Tracking. The camera will track a subject through the scene. This places a high demand on the camera's computational capacity. It is the most advanced technique available. Tracking might also be available in single autofocus and will select a focus point before the autofocusing even starts.

How to best use these autofocus areas and modes should be a topic for another posting. To learn the best use of the camera requires practice. In any case, focus should be achieved without much thought. Modern cameras, with their automatic focusing and tracking modes, are a significant help to photographers.

Exercises

• Enable eye detection on your camera and see if it works in portraits. Can you change the eye in your camera? Can you switch the face in group shots?
• Learn the quickest way to change the focusing mode on your camera. Try to switch between auto area and single spot quickly.
• Learn if your camera has tracking and how to use it. You need to quickly disable and enable tracking or change the tracked subject.
• Learn the difference between continuous and single autofocus. See how your camera indicates successful focus. 
• Learn manual override by turning the focus ring after the camera has autofocused. If possible, enable focus peaking. 
• If your camera can do it, learn how to zoom in for precise focusing.
• Try the back-button focus by disabling focus on the shutter and enabling focus on a button within easy reach of your thumb. 

Bad Photos

A list of the usual reasons for bad photos might be helpful.

• Motion Blur. To freeze your subject's motion, you need a high enough shutter speed. Sports may require 1/2000, and kids at least 1/200. It is better to increase the ISO than to spoil the image. The problem is too apparent to be neglected.
• Wrong Focus. If your subject is blurry, but other parts of the image are sharp, you have focused on the wrong spot. Modern cameras show the autofocus point they select. In extreme cases, use manual focus.
• Not enough DOF. This is another problem that spoils the sharpness in your pictures. In group shots of people, you want all of them to be reasonably sharp. You need to take a high enough f-stop to achieve this, even if it means increasing your ISO.
• Confusing Composition. You are responsible for the visible stuff in your image. Reduce the view to the things you want to show by changing the camera angle or lens. Take care of every detail, even at the borders of your image. Close one eye to avoid being fooled by your 3D vision.
• No Subject Isolation. Above, we talked about how to isolate subjects with a wide aperture and a longer lens. But also avoid distracting elements in the background.
• Bad Light. Light is crucial for good results. Some situations cannot produce a satisfying result. Move your subject, your viewpoint, or wait for better light. If necessary, use flash.
• Boring Scenes. Clearly, we cannot always get fantastic photos. In fact, we rarely do. But you should make the most of what you have. It is surprising how little it may take to make a boring subject interesting.