If you’re a photographer and you’d like to know more about lenses, then you’ll love our free course, What Every Photographer Should Know About Lenses. In this lesson, you’ll learn all about ultra-fast focusing motors, fancy lens coatings, and image stabilisation—and whether you really need them!
Fancy Photo Lenses: Do You Really Need Stabilisation, Coatings, and Focusing Motors?
Stabilisation
Image stabilisation is a fantastic feature to have in a lens. But what exactly is it? Lens-based image stabilisation or optical image stabilisation are techniques used to reduce blurring associated with the motion of a camera during an exposure. The sensors in the lens analyse vibrations and then apply correction via a special stabilising lens group that shifts the image parallel to the focal plane. Motion blur is cancelled, resulting in a sharper image, and this allows you to shoot at slower shutter speeds and still get sharp images.
Different lens makers have different names for these techniques, such as:
- OIS (Optical Image Stabilisation)
- Mega OIS
- Optical Steady Shot
- SR (Shake Reduction)
- VC (Vibration Cancellation)
- VR (Vibration Reduction)
- IS (Image Stabilisation)
There’s also stabilisation that can be done in the camera, but what we’re talking about here is done with the lens. Let’s take a look at how this helps make sharper images.
Stabilisation in Action
This image of two horses on a playground was shot with a 270 mm lens, handheld from around 10 or 25 feet away, at a shutter speed of 1/30 of a second.
If you’re shooting at a focal length of 270mm, handheld, on a crop sensor body, that will be really slow, because the general rule of photography when you’re shooting handheld is you shoot one over your effective focal length, and that’s about 420mm on the crop sensor compared to a full-frame camera. What that means is that the threshold shutter speed with good technique would be somewhere around 1/500th of a second.
If we look at a 1:1 pixel crop, this is not sharp and there’s motion blur in this image, but that’s because image stabilisation was off for this shot.
If we look at this photo of the same subject, again at 1:1, you can see that it’s much sharper, and that’s with image stabilisation on. It may not be as sharp as if it were on a tripod, but it looks perfectly usable and much better than the previous one.
1/30 of a second was too slow for that shot, but even if we were at 1/500 of a second, half of that would be 1/250 of a second and even at 1/250 of a second it would be very, very difficult, probably impossible to get a still shot using that kind of focal length, hand-held. Cut that in half again, and you’re down to 1/125 of a second, and half of that would be 1/60 of a second, so that’s three full stops, and four stops would be 1/30 of a second. Even with really great technique, there’s no way you can shoot a still image at 270mm on a crop sensor body at 1/30 of a second and have it be sharp.
This one was photographed at 1/50 of a second, and on the left you can see there’s definite motion blur. The image on the right has the same shutter speed but with image stabilisation turned on, and it’s hard to see any signs of camera shake at all in this image. It’s a good image to compare because it has some very high contrast and sharp lines, so it’s easier to see any tiny amounts of motion blur.
You can see what a dramatic effect IS can have on your images. It won’t stop motion entirely, because things in motion are not going to be affected by image stabilisation; what will be affected is your own camera’s movement, especially when shooting handheld.
Lens Coatings and Filter Coatings
Lens coatings are treatments applied to the outer surfaces of lens elements to reduce reflections. Reflections occur whenever a ray of light moves from one medium to another, such as when light enters a sheet of glass after travelling through air. Some portion of the light is reflected from the surface. Without coatings, each air-to-glass interface would reflect about 4% of the light reaching it. This is important because lenses are made up of several glass elements.
A complex lens without coatings would have as much as 70% of the light absorbed or scattered before it reached the image sensor. Most lenses these days have multi-coatings, at the very least, and better lenses will have nano-coatings, which do a better job of reducing reflections.
You might want to pay attention when it comes to filters. The cheapest aren’t coated at all. Some have a single coating on just one side. The vast majority of even lower-priced filters have single coatings on each side. The very best have multi-coatings or nano-coatings on both sides.
If you’re shooting in the direction of the sun, for example, and you use a cheaper filter, you’ll lose a lot of contrast and quality in your images, so lens coatings and filter coatings are something to consider.
Focusing Motors
Finally, let’s talk about focusing motors. One of the many acronyms you’ll see listed on lens models refers to the focusing motor:
- SSM: Supersonic Motor (Sony)
- SAM: Smooth Autofocus Motor (Sony)
- USD: Ultrasonic Silent Drive (Tamron)
- PZD: Piezo Drive (Tamron)
- USM: Ultrasonic Motor (Canon)
- SWM: Silent Wave Motor (Nikkor)
- AFS: Auto-Focus Silent (Nikkor)
- SDM: Supersonic Drive Motor (Pentax)
- HSM: Hypersonic Motor (Sigma)
- IF: Internal Focusing (Various)
These lenses are constructed so that they don’t change in length as the lens is focused. It also means that the front lens element doesn’t rotate, which can help with the use of some attachments like a petal-shaped lens hood and polarizing filters. The main point here is to distinguish these fast-focusing lenses from the older servo-style focusing mechanisms.
These older focusing motors are easy to spot as they make a lot of noise and are quite slow. You can still find this older style of focusing system used on lenses that are being made and sold today.
Having a lens that focuses really quickly is a fantastic feature when you are shooting moving targets or anything dynamic. Slow focusing systems will not work for these shooting situations. If you are looking for a lens, having one of these ultra-fast focusing systems is a definite advantage.
Learn More About How to Use Lenses
How to Use Medium Telephoto Lenses for Photography
Primes vs Zooms: Pros and Cons of Fixed Focal Length Lenses for Photography
Setting the Standard: What’s a Standard Zoom Lens?
How to Use a Telephoto Lens (to Photograph Far-Away Things Nicely)
About the Video Author
David Bode created the video course that includes this lesson. Dave is an expert on video and audio production, and he lives in the upstate NY area. He works as a camera operator, editor, inventor, motion graphics designer, recording engineer, and studio musician.
Marie Gardiner wrote the text version of this lesson and it was edited and published by Jackson Couse. Jackson is a photographer and the editor of the Photo & Video section of Envato Tuts+. He lives in Canada.
