Reprinted without permission but I'm sure I am forgiven...
Focusing Using Live View
Tack sharp focus, we've all marveled at the optical clarity of photos seen in magazines. It's amazing how every
detail is perfectly recorded. Autofocus has made the life of photographers much easier. Especially, as our eyes
start to age to the point of needing glasses.
While autofocus can be great at getting it right most of the time, tack sharp critical focus still needs the human
eye to get it spot on consistently. For sports photos or activities with lots of movement, autofocus is still the
best bet in town because of the need to focus quickly, but when the action dies down, there is a new methodology that should be considered and exploited.
With the advent of DSLR cameras that can record video, a new method for manually focusing the lens to
achieve tack sharp focus has emerged. It utilizes the Live View video mode of these new cameras. It's extremely accurate and helpful when shooting more static type photos such as landscapes or macro shots. Read
on to find out how to leverage this new feature that is revolutionizing focusing.
Live View mode turns the back viewing screen of the camera into a TV screen. The viewscreen displays the
data that is being received by the camera sensor. Changing the autofocus switch for the camera lens to manual
puts the responsibility for focusing in the hands of the photographer. Trying to focus the lens with a 3 inch
screen may sound like an impossible feat, but Live View offers the ability to zoom in on the screen to both five
times (5x) or ten times (10x) magnification. With just a couple of touches of a button, the vision of an eagle is
suddenly in your hands making it easy to get tack sharp focus. Once the focus is set, compose and press the
shutter button. It's that simple, and for those photographers with glasses, it also means you don't have to fiddle
with them when taking a photo.
There is no other method of focusing the camera that is more accurate than Live View. There are two reasons
why: First, as stated above, is the ability to zoom in to five/ten times (5x/10x) magnification when focusing.
This allows the photographer to see, in minute detail before the image is made, exactly what will be in sharp
focus. The second reason is, Live View utilizes the same optical path to the camera sensor as is used when the
image is made. This is significant because of the design of DSLR cameras and is explained below.
Member Article: Jeff Claypoole
Page 9 Camera Club of Richmond — Southern Exposure Newsletter
- May 2011 Camera Club of Richmond — Southern Exposure Newsletter Traditionally, with DSLR cameras, the photographer looks through the viewfinder to see the image through the
lens. In actuality, the image/light entering through the front of the lens is redirected off a mirror, hanging inside of the camera body, up into the viewfinder where the image is seen. The viewfinder is also where exposure meter and autofocus systems are located. When the shutter button is pressed, the following sequence of
events happen:
1. The autofocus system determines the subject distance and focuses the lens.
2. The exposure meter determines the correct ISO, aperture and shutter speed.
3. The aperture blades inside of the lens are stopped down to the correct aperture size (f/stop).
4. The mirror inside of the body slaps up allowing a direct path for the image/light from the lens to reach the
camera sensor.
5. The shutter curtain opens and closes thus exposing the sensor to light.
6. The camera saves the recorded image to the camera's memory card.
The recorded image is displayed on the back viewscreen of the camera.
When the camera is autofocusing, during step #1 above, the redirection of the lens image by the mirror up into
the viewfinder is one of the main factors that can introduce focusing errors. In step #4, the lens image/light direction is changed when the mirror slaps up out of the way to allow the light to pass to the back of the camera
body and onto the camera sensor. If there is a distance difference between the mirror to viewfinder and the
mirror to camera sensor of more then 10 microns (millionths of an inch), it will affect the camera's ability to
critically focus. Using Live View eliminates this possible error from the image taking process.
When focusing in Live View mode, the light/image from the lens is always directed onto the camera sensor.
The plane of critical focus that is seen on the viewscreen and set by the photographer when manually focusing
the lens is what will be recorded.
It should be noted here that there may be other factors that can affect critical focus. Issues such as lens field
curvature, focus shift, as well as camera shake, can all contribute to less then optimal focus. Live View is not a
panacea for tack sharp images, but it's the best method for critically accurate focus.
Using Live View, when possible, to attain tack sharp focus is well worth the extra few moments to takes to
focus the camera. Speaking personally, it has put the "Wow Factor" back into my images. I am taking more
"keepers", and it has brought my photography up to a new level. I can not recommend it highly enough.
If you have any questions or comments, I would truly enjoy talking with you further at our next meeting.
Cheers, Jeff Claypoole
amandadams 1 post
