As a self-taught photographer I highly value the practical application of photographic concepts and tools. Of these concepts and tools, the understanding and effective use of shutter speed and the influence it has on focus, is without doubt one of the major differentiators in a photographers journey toward creating striking images. The effective use of shutter speed influences how sharp an image will be and this makes all the difference.
It took me years to truly appreciate what a sharply focused image is. Consider that focus is essentially a variable scale of how “in focus” or “out of focus” an image or element of the image is. Too often images are thought of broadly as “focused” or “not focused”, rather than considering it as a scale of how focused an image is.
When I finally grasped the concept and began to appreciate the difference between sharp and soft focus, it was what I consider to be my water shed moment in photography. I find that amateur or beginner photographers are much softer on the concept of focus and this is a huge distinction in the quality of images created. The big differentiator in how crisply focused an image will be comes from the photographers application of shutter speed. The focusing system is also of critical importance but first comes shutter speed which is the main focus of this edition. If your shutter speed is not correctly set, none of the other factors will be able to outweigh this in order to create a sharp image.
Shutter Speed, What it is:
Shutter speed represents the length of time that a cameras sensor will be exposed to light.
Shutter Speed, What it does:
- Affects the depiction of motion in an image and how sharp the image will be.
- Affects the exposure of the image, i.e. how light or dark the image will be.
Let’s get on the same page with our vocabulary around focus:
- Sharp Focus – Perfect, crisp focus. If you zoom into the shot the details will be in sharp clarity.
- Soft Focus – An image appears mostly in focus but when you zoom in on the subject a small amount of blur can be noticed on details which are slightly “soft” as opposed to “sharp”.
- Out of focus – Blurred image and/or subject.
Why sharp focus often slips by
Few people ever look at an image and state – “wow… look how sharply focused that shot is.” Sharp focus is naturally expected in an image, even if it goes by unnoticed. Unless of course, soft focus is being used as a creative tool to tell a specific story such as depicting motion through blur or with a shallow depth of field. Assuming this is not the case, the sharper the focus, the better, regardless of whether it is an action, portrait or landscape image.
The sharpness will in turn influence the relative effectiveness of the photograph, whether viewers are aware of it or not. A layman may not be able to pin point the problem in an image with slightly soft focus but they will know something about the image is not quite what a professionals image of the same scene would be. Even if they do not isolate focus as the problem.
How to Achieve Sharp Focus
Focus, is affected by: 1) Camera Shake 2) Subject Motion.
The faster the shutter speed, the greater chance you have of preventing either of these two factors negatively influencing your focus.
There is an old “rule of thumb” in photography when shooting hand held, i.e. without a tri-pod or something to stabilize the camera.
The shutter speed needs to be equal to or greater than the focal length of the lens in that image. Eg.
- 200mm focal length needs 1/200th of a second shutter speed or faster.
- 300mm focal length needs 1/300th of a second shutter speed or faster.
It is my belief that when focal lengths are less than 100mm the shutter speed needs to be double the value of the focal length. Eg.
- 30mm focal length needs 1/60th of a second shutter speed or faster.
I further believe that this rule is a shaky one at best and the reality is that if you are trying to achieve sharp focus the faster your camera will allow you to make your shutter speed while still achieving neutral exposure, the better.
Tip: It is easier to brighten areas of low light during post-production than it is to reduce levels of highlight or over exposure. The detail of over exposed elements is normally lost and no amount of editing will bring this detail back. Therefore even in cases when a faster shutter speed results in a less than neutral exposure, you will still be capturing the detail (so long as it not too underexposed) and you will be able to lighten the low lights during post production without losing detail.
Manual Mode – When shooting on Manual, remember the exposure triangle (ISO; Shutter Speed; Aperture) from my Learning to Shoot on Manual post.
Use the exposure meter to guide you here.
As you increase the shutter speed the exposure will start to reduce and appear darker. Adjusting the other two elements as you increase your shutter speed will allow you to maintain neutral exposure. Do this by:
- Increasing your ISO where necessary.
- Decreasing the Aperture Value. See my post on Depth of Field to understand the effects of aperture.
Shutter Priority Mode
Another option is to allow your camera to take care of the other elements of the exposure triangle and for you to prioritise shutter speed by shooting on TV (Canon) or S (Nikon). In this way you are only choosing the shutter speed and can insure that the speed is adequately fast enough to achieve sharp focus for the scene that you are capturing.
Be as critical as you possibly can be when it comes to the sharpness of focus in your images. Always strive to achieve sharper focus in a typical scene. Don’t wait for your water shed focus moment as I did, you are losing out on capturing some great scenes in the mean time. When you look back on those images in the future you will be disappointed once you appreciate a truly sharp image.