How to use Manual Focus
In the previous article we looked at examples of when you might want to use manual focus instead of autofocus. In this article we'll cover how you can focus manually, with some tips to help you make sure that your focus is accurate.
The first thing to state is that not all cameras have manual focusing as an option. Most basic (point and shoot) compact cameras don't allow manual focusing, but most more advanced compact cameras do allow manual focusing. Nearly all lenses for interchangeable lens cameras allow manual focusing as well.
How to use manual focusing
For the vast majority of interchangeable lens cameras, manual focus is operated by using the focusing ring on the lens. Similarly, cameras with built-in lenses may have manual focus operation by a ring round the lens. Occasionally manual focus may be operated by a small lever (such as with Panasonic's 14-42mm X lens).
The positioning and size of the focus ring varies between lenses. Most zoom lenses have both a zoom ring and a focus ring. Normally the focusing ring has a textured rubber surface to allow you to grip and move the ring easily.
Many interchangeable lenses allow what is known as autofocus override. This means that you can use the camera / lens in autofocus mode, but you can interrupt the autofocus or modify the focus after the camera has focused just by moving the focusing ring.
So, you can half-press the shutter to autofocus and lock exposure. Then adjust the focus manually. Be aware that if you manually focus, and then half-press the shutter, then the camera will autofocus and your manual focus adjustments will be lost.
Full time manual focus
To set your camera to full time manual focus, most lenses have a focus switch on them that allows you to choose between autofocus and manual focus.
The focus switch on a Nikon lens - Autofocus is labeled as M/A to indicate that manual override is available in autofocus mode
Some cameras have a focusing selector on the camera body that allows you to choose manual focus. In the cases of interchangeable lens cameras where you have focus switches on the lens and the camera, if either the lens or the camera is set to manual focus, then it will operate as a manual focus lens. Both the lens and camera body must be set to autofocus for the lens to operate as an autofocus lens.
Focusing manually is just a case of twisting the focusing ring. Turning the ring in one direction moves the focus towards infinity, while turning the ring in the other direction moves the focus closer towards you. The direction that you need to turn the focus ring to move towards infinity or closer varies between manufacturers. For example, on Canon lenses you turn the ring left to focus towards infinity, while on Nikon lenses you would turn the ring to the right.
Many lenses feature a focusing scale, going from infinity to the closest distance that the lens can focus at.
When you look at the scale you will probably notice that there is a small distance between infinity and the next focusing mark, which may be something like 5 meters. But at the other end of the scale, near the lens' closest focusing distance, the gap between markings will often be larger, and the gap may only cover 20 cm or so.
This is because at close focus distances, depth of field is much smaller than it is at large distances. This means that accurate focusing is much more important at shorter focus distances. So lenses are built to have greater travel in their focusing range close-up, to allow the lens to focus more accurately in the range where precise focus is needed.
Not all lenses feature focusing scales, but all lenses do have greater travel in their focusing range at close focus than they do near infinity.
Fixed focus shooting
If your lens does feature a focusing scale, it can be useful. The main type of photography where it comes into use is for street photography. You can set your camera or the lens to manual focus mode. Then using the focusing scale, set the lens to focus at a certain distance that you want to photograph your subjects from, e.g. 3 meters.
Fixed focal length lenses (i.e. not zooms) with focusing scales normally have a depth of field scale as well. This indicates how large the depth of field will be at a given aperture. Using this you can work out how much of the image will be in focus.
If your lens has a focusing scale but no depth of field markings (or the markings aren't very helpful), then you can use a depth of field calculator to work out the depth of field. A good online one is the Cambridge in Colour Depth of Field Calculator.
When you know the depth of field that you will get at your selected focus distance and aperture, it means that you know the acceptable distance range a subject must be in for them to appear in focus.
For example, using the Depth of Field Calculator I entered 35mm (full frame) as the Camera type, f/8 as the aperture, 50mm as the focal length, and 3 m as the focus distance. The calculator tells me that this means that anything between 2.3 m and 4.3 m should fall within the range of acceptable sharpness for this combination.
So if I use the lens with those settings for street photography, I just need to try and make sure my subject is somewhere between 2.3 and 4.3 meters away for them to be in focus. The benefit of this 'fixed focus' way of shooting is that when you see an interesting shot, you don't have to focus on the subject. So long as they are within the range of acceptable focus, you can just snap a shot straight away.
Ya Dig!!! by andrew prickett on flickr (licensed CC-BY-ND)
You don't even have to look through the viewfinder or at the camera's LCD, so you can shoot from the hip. Shooting from the hip is sometimes preferred as it makes you more inconspicuous. Your presence is less likely to disturb people's natural actions and expressions than if they see someone with a camera up to their eye taking a photo of them.
I should point out that the majority of street photography is not done using fixed focus shooting. But it is a handy technique to have in your arsenal.
Another instance where fixed focus is sometimes used, is in landscape photography. Here a technique called hyperfocal focusing is used. The idea is to get as much into focus as possible, from quite close to the camera, all the way into the distance (infinity).
Fire Island Lighthouse - Long Island, NY by Bluesguy from NY on flickr (licensed CC-BY-ND)
The distance that the camera should be focused at to achieve this is known as the hyperfocal distance. It is dependent on the aperture that you will be shooting at. The smaller the aperture, the more will be in focus, and the nearer the camera you can focus.
For calculating the hyperfocal distance, there is a nice calculator and tutorial on the Cambridge in Colour website: Hyperfocal Distance.
I would like to stress that most landscape photography is not done using this fixed focus technique, but it can be useful in some situations.
Focusing using an optical viewfinder
Personally I find focusing using an optical viewfinder very difficult for anything other than macro photography. But there are plenty of people who don't have any problems focusing manually using an optical viewfinder.
For the purposes of this article, when I talk about an optical viewfinder, I mean a Through-The-Lens (TTL) optical viewfinder, as found on DSLR cameras. If, on the other hand, you have a camera with no linkage between the lens and the viewfinder, then you cannot see any changes in focus you make (so manual focus using the viewfinder would not be possible). For example, this is the case with the optical viewfinder accessories available for some mirrorless cameras.
Cherry blossom in central NJ by Dr. JS (addicated to vantage tamron glasses) on flickr (licensed CC-BY-SA)
Focusing using an optical viewfinder is quite simple, just turn the focusing ring until the image looks in focus in the viewfinder. Normally you will probably want to turn the focus ring so the image looks in focus, then keep turning until it just starts to go out of focus. Turn the focus back the other way just a little to where the focus was sharpest, and you should be back at the correct focus distance.
The ease of manual focusing using an optical viewfinder depends quite a bit on your camera model. Lower end DSLRs often have small and relatively dark viewfinders that can make manual focusing difficult. High end full frame cameras have much larger and brighter viewfinders, which make it easier to focus manually.
Focusing screens for Manual Focus
The focusing screen used in the camera is another thing that affects how easy it is to get accurate manual focus. DSLRs come with a focusing screen that gives a nice bright view, but is not necessarily the best for accurate manual focus (particularly for fast lenses used at an aperture larger than f/2.8).
Some DSLRs have interchangeable focusing screens, with a range of screens available. Super precision Matte screens and split prism focusing screens can both make manual focusing easier than the standard focusing screens. Usually it is a case of using a small tool to pop out the old focusing screen from the camera, and then snapping the replacement screen into place.
Example of an interchangeable focusing screen - the Canon Eg-S Super Precision Matte Focusing Screen For Canon EOS 5D-Mark II Cameras
Other DSLRs don't officially have interchangeable focusing screens, but a range of third party companies manufacture and offer installation of screens suitable for manual focusing. The disadvantage here is that you can't easily switch back to a normal focusing screen.
There are a couple of disadvantages of split prism and super matte focusing screens though. They give a darker viewfinder view with lenses that have a smaller maximum aperture than f/2.8. In some cases (more often with third party split prism screens), they can also throw the camera's metering system off, so you can't rely on auto exposure so much.
Overall, the main way to get better with manual focusing when using an optical viewfinder is practice, practice, practice.
Focusing using an electronic viewfinder or the camera's rear screen
Other than older DSLRs that don't have a liveview function, this method of manual focusing is available on most cameras that allow manual focusing. Personally I find this method easier to focus accurately with than using the optical viewfinder.
Advanced compact cameras, MILCs, and SLT cameras all show in the viewfinder or on the rear LCD what the image sensor will capture. With a DSLR, you need to enter Liveview mode, which will show the live feed from the camera sensor on the rear LCD.
Focus the lens so that the image looks in focus. Now zoom in on the area where you want the critical focus to be. Most camera models have three zoom levels - the full image, 5x zoom, and 100% zoom. At maximum zoom you should be able to make sure that you get the focus spot on where you want it. Then take the picture!
Some cameras also have a feature known as focus peaking. The exact way this works differs between camera manufacturers, but generally a colored outline is shown around anything within the plane of sharp of focus. This makes it quick and easy to see where the focus in the image is.
For more information on how focus peaking works, see this article on the Luminous Landscape website: How 'Focus Peaking' works. You can see an example of focusing peaking in action on a Sony NEX camera in the video below:
Stopped down or wide open?
Different camera manufacturers implement their liveview systems slightly differently. Some show the live sensor feed with the aperture of the lens set to wide open. This means that you don't get an accurate preview of the depth of field, but does allow you to easily place the plane of critical focus in the image where you want it.
To see what the depth of field will be like, you can press the depth of field preview button on the camera. This will temporarily stop the lens down to whatever aperture you have set for shooting at.
Other manufacturers automatically stop the lens down to the shooting aperture when showing the live view display. This allows you to easily see everything that will be in focus in the final image, but can result in a slightly noisy liveview preview in low light. (Because the lens is stopped down, less light enters the camera, and so the image has to be gained up more to create a preview at the correct brightness).
If you are using a manual lens with an aperture ring, then the liveview image will show the preview with whatever aperture you have set on the lens, since the camera has no way of changing it.
There is no clear cut winner between manually focusing with a lens stopped down to the shooting aperture versus a lens opened to its maximum aperture. Focusing with the lens wide open is good for nailing critical focus exactly where you want it. Focusing with the lens stopped down is good for seeing exactly how the image will look and what will be within the plane of acceptable focus.
Manual focusing for macro photography
As discussed in the previous article, focusing manually is often the best way to focus for macro photography. Focusing on macro subjects is very difficult due to the shallow depth of field.
Hello Friend by Yogendra174 on flickr (licensed CC-BY)
If you are shooting macro handheld, use the focus ring to get your subject in focus. Now gently rock back and forth, gradually narrowing down on the precise point that you want in focus. Then hit the shutter when the part of the subject that is most important (normally the eye for insects) pops into focus.
Using this technique you still won't get every single shot in focus, but it does result in more keepers than just using the lens focusing ring.