We are back with Part 2 of our 3-part series on taking sharp pictures. To recap, we are focusing on seven common causes of less-than-sharp images and how to address each. Part 1 focused on the notorious “camera shake”. Part 2 will introduce causes #2-4. With a reminder that I am only touching briefly on each, let’s jump right in…
CAUSE #2 – MOTION BLUR. While camera shake relates to movement of the camera, “motion blur” is about elements in your composition moving. Motion blur can happen with both your subject and your background. Your moving subject might be a person walking, while your moving background may include trees or grass blowing in the wind. Now, not all motion blur is bad. In fact, some of it is downright cool. However, it is important for you to have control over whether you want to freeze or blur the motion.
Motion blur happens when the shutter speed is too slow to freeze moving elements in the image. In addition to the speed of the moving elements, the space that the moving elements take up in the frame is a key factor. So, the distance to the subject and your lens choice play an important role. Once again, below is a link to a recent blog on shutter speed which deals with both camera shake and motion blur. For those that do not feel like clicking on the link, some starting points for freezing motion are to use 1/125 – 1/250 for slow moving objects (walking people)… 1/500-1/1000 for fast moving objects (running people and moving cars) and 1/2000 for very fast moving objects (race cars).
CAUSE #3 – INACCURATE FOCUS. Getting good focus isn’t quite as straightforward as it would seem. Here are some guidelines for getting good focus, starting with some tips which hold true whether you are using autofocus or manual focus:
- Zoom in when focusing. If you are using a zoom lens, you will get better focus by zooming into your subject to lock focus and then zooming back out as necessary to take the shot.
- Use “live view”. If your camera has it, you can get more precise focus using “live view”, which is Canon’s terminology. Live view (or whatever it may be called for your camera’s manufacturer) allows you to view and focus via the LCD screen on the back of the camera. You can zoom into a very small part of the image for precise focus. Live view is typically used when you are photographing still subjects on a tripod, as hand-holding the camera and looking at the LCD screen is not a stable way to hold the camera.
Here are some tips which apply to auto-focus only:
- Test (and adjust if necessary) the autofocus of each lens on each camera. Don’t assume that your autofocus is working perfectly. I had to send a brand new top-quality lens back for repairs because the autofocus was WAY off. It is a good idea to test each lens’s autofocus with your camera on a tripod. There are some relatively inexpensive tools which will help you determine if your focus is off and by how much. Most of the better cameras will then have a micro-adjustment tool, where you can adjust the focus of your lens (or camera) and re-test to help it focus properly.
- Be careful when re-composing with very wide apertures. Generally, photographers using autofocus will lock their focus, then recompose for the shot. This recomposing means a slight movement of the camera. For very wide apertures, such as 1.2 or 1.4, this slight movement can throw the image out of focus. So, be as careful as possible not to move forward or backward. If you are aiming the camera at an angle (as opposed to straight towards you subject), this is even more of an issue. If re-composition is necessary, some photographers using f1.2 will snap a few images, moving very slightly back and forth between each shot in an attempt to get one shot in focus.
Now, here are tips for manual focusing only:
- First, try using manual focus. Many people never use it. However, you can sometimes get better results than with auto-focus. I always use manual focus when shooting macro subjects and some of my landscape images.
- Getting good focus on manual is dependent upon two things: 1) Your eyesight; and 2) the diopter being adjusted properly if your camera has an adjustable diopter. The diopter is the little window that you look through when composing your image through the viewfinder. Adjust this until it is sharp to your eyes.
I know this might be “link overkill”, but I did do one other blog on focusing for moving subjects. Here it is:
CAUSE #4 – ISO AND APERTURE COMBINATION. We’ve discussed shutter speed. However, ISO and aperture can certainly affect the sharpness and quality of your image.
- Use a lower ISO when possible. Your ISO setting determines the sensitivity of the camera’s sensor. The higher the ISO, the more sensitive it is to light. However, as you raise the ISO, the picture quality suffers in the form of “digital noise”. Shoot with as low an ISO as possible under the conditions, without compromising the image from an inappropriate shutter speed or aperture combination. Newer cameras, such as the Canon 5D Mark III, can handle high ISOs with minimal noise.
- On a related issue, it is worth a brief mention here that aperture determines depth of field. Wider apertures (lower f-stops, like 1.8) have less depth-of-field, meaning relatively less of the image outside of the plane of focus will be sharp. Narrower apertures (like f/22) will have greater depth-of-field, meaning most or all of the image front to back should be in focus.
- However, many people are not aware that lenses have differing levels of sharpness across the range of apertures. Generally, the sharpest aperture of your lens is 1-3 stops above the widest aperture. So, if your widest aperture is f2.8, then f5.6, f7.1 or f8.0 will typically be the sharpest. This does not mean that your pictures will be blurry at f/16, but it is useful to know that these apertures produce the sharpest images and factor that into your choice of aperture. You may still want to shoot wide open or at a small aperture to get the depth-of-field you want.
That is more than enough for today. We’ll deal with the last three causes of less-than-sharp pictures in Part 3.