Alastair Arthur Photography

Week 3


Week 3

It can be one of the biggest frustrations when you think you've captured a great image just to find that your subject is blurry. Absolute sharpness doesn't necessarily make a great photograph, but it's important to understand the reasons and how to control the outcome.


What makes an image blurry?

These are the most likely reasons:

  • Camera shake
  • Motion
  • Inaccurate focus

There could be other reasons such as dirt on the lens or a camera/lens malfunction but we're going to look at these three in more detail.

Quick Tip:
If you find that the image in the viewfinder (or lcd) looks blurry even when you're sure the focus is correct, check the diopter. Most cameras allow the viewfinder to be adjusted to correct for imperfect eyesight, and on some it's easy to knock by accident making the image look blurry.)


How to hold a camera

It might sound trivial, but how we hold a camera can make a difference to the image. Many of us initially tend to hold the lens in our left hand with our thumb underneath and fingers on top. But switching our hand around so that the lens is resting on our hand and fingers gives a more stable base with your elbow tucked into your body. This page goes into much more detail and has some useful suggestions:
How to hold a camera and take sharper images


Shutter Speed and Camera Shake

Even using the techniques above, none of us have perfectly still hands. There will always be some small vibrations, as we hold the camera and as we press the shutter to take a photo. So even if your subject is perfectly still, those vibrations will blur the image if the shutter speed is slow enough. They are also amplified by the focal length, so a long (telephoto) lens increases the movement just like holding a long stick from one end and trying to keep the other end still.

There is a rough guide to help, and it is very rough. If you're using a 50mm lens (or have your zoom lens set to 50mm), then you ideally want a shutter speed of 1/50s or faster. If you're using a 35mm lens, you want 1/35 or faster. 100mm, 1/100s. And so on.

Unfortunately 50mm on one camera might not be the same as 50mm on another (it couldn't be that simple now could it), which brings us to...

Sensor Size: Crop and Full Frame

Unfortunately there is a technical complication when talking about lenses and focal lengths. You might hear the terms 'full-frame' or 'crop sensor'. Different manufacturers use different size sensors and the size of the sensor makes a difference to the results that a given lens produces. A smaller sensor acts like 'zooming in' to a smaller part of an image captured by a larger sensor.

The term 'full frame' comes from 35mm, so a full-frame sensor is roughly the size of 35mm film. Anything smaller is considered a 'crop sensor'. The most common sizes (excluding phones and simple pocket cameras) are Micro Four-Thirds (used by Panasonic and Olympus) and APS-C (used in some but not all Sony, Fujifilm, Canon and Nikon cameras). A 25mm lens on a Micro Four-Thirds camera is roughly equivalent to a 35mm lens on an APS-C camera and a 50mm lens on a full-frame camera.

There's a good explanation on Techradar here.

It's also about time you all heard from the one and only Zack Arias with his take on the subject.

Subject Movement

Once you're confident you're avoiding any blur due to camera shake, you might still want or need to push your shutter speed higher. Why? In bright conditions you might need to anyway to prevent too much light getting to the sensor and making the image too bright (over-exposed). Aside from that though, you might need a faster shutter speed if your subject is moving.

A faster shutter speed is capturing a shooter moment of time in your image, so the faster the subject is moving the faster the shutter speed in order to show that subject as sharp rather than blurred. Assuming that you want to freeze the motion of your subject in your image, here are some guidelines for the shutter speeds you might need:

1/125s - 1/250s    - Person walking
1/500s - 1/1000s  - Person running
1/500s - 1/1000s - Falling water
1/500s - 1/2000s - Sports (e.g. soccer or basketball)
1/1000s - 1/2000s - Moving car
1/1000s - 1/8000s - Motorsports

Here's a more detailed guide.

This does all assume that you're keeping the camera still while taking the shot. Another option is called panning. Panning means moving the camera to follow your subject while you take the shot. The aim is usually to show the motion of the object by blurring the background, so will generally be done with a slower shutter speed.

Slow Shutter Speeds

There are a few other tricks and tools you can use if you want to have a slow shutter speed.

You might see the acronyms OIS (Optical Image Stabilization) or IBIS (In-Body Image Stabilization). These are technologies that use small movements within the lens (OIS) or the camera body (IBIS) to counteract any small vibrations so can enable you to use a slower shutter speed than you might otherwise.

Beyond that, for long shutter speeds to create effect such as the 'soft water' you've probably seen in waterfall images, or a cityscape at night, you'll need to use a tripod.

Tip: To create the little 'starbursts' of light that you might have seen on some images, use a very small aperture.

Autofocus Settings

So to the third potential cause for not getting a sharp image, focusing.

There are two main settings that you'll be able to decide on, your autofocus point and whether you use 'single' or 'continuous' autofocus.

Single or Continuous modes determine the behavior of your camera when you press the shutter button half way. It either focuses then maintains that focus point until the shutter is pressed or released (single), or it constantly re-focuses while the shutter is half-pressed.

The autofocus point (or area) is telling your camera where to look to try to focus on an object. You might choose to be very specific (single point autofocus), or allow the camera to choose from a wider area.

Most commonly you'll probably choose to shoot in single mode with a single point autofocus. This allows you to focus first then recompose (or move the focus point) and have full control of the outcome. You might choose continuous autofocus with a wide focus area for a fast moving object, especially if the object is moving towards or away from you.

Check out this page or this video for more info. 

Although you might not often choose to use it, it is worth learning to focus manually. Occasionally, in low light or if you're shooting through a window for example, your camera might not be able to autofocus so manual becomes your only option.

Choosing a Lens

The quality of lens makes more different to the image quality than the camera body. You've probably got a 'kit' zoom that came with the camera, 18-55mm or something similar. They're useful, covering a decent range of focus lengths, but the quality is usually relatively low.

Choosing a second lens is tricky. You might want a higher quality zoom or longer focal lengths if you're planning to specialize in sports or wildlife for example. My personal recommendation for learning is to get a prime (non-zoom) lens. They're typically smaller, cheaper and higher quality than a similar zoom, although obviously you don't have the same flexibility. The constraint of using one focal length can be useful though. You start to learn that focal length and how close you need to be from a subject.

A 'nifty fifty' - a 50mm lens - has long been recommended as a great all-purpose lens, being similar to how we see the world. (Remember a 50mm full frame would equate to about a 35mm on APS-C or a 25mm on micro four-thirds). Another option would be to go a little wider, with 35mm being another popular option (23mm on APS-C). Look for a widest aperture of f/1.8 or f/2, check some reviews. There aren't many bad lenses around, but some are still better than others in terms of image quality and focus speed.


Try out different autofocus settings and get a feel for when you might use them and how to change quickly from one to another on your camera.

Try using manual focus. Your camera might have additional features (such as 'focus peaking') to make it easier to get right.

We've covered lots of technical detail so far, I hope it's not been too overwhelming. Take your time, make sure you enjoy experimenting and don't worry if you're struggling to get to grips with something. It'll come. For a little light relief, here's some photo-related chat that you might enjoy:
The Grid
This Week In Photo

(The critique sessions on The Grid in particular can be very informative).