Focusing accuracy

[Bill Pierce]

I recently got asked the most accurate way to focus small, hand-held cameras. It used to be that rangefinders were most accurate for high-speed wide-angles and normals; long lenses and macros worked best with SLR’s. (It was customary among many folks to send their rangefinder bodies and lenses to a top flight repair person for fine tuning.) That’s changed. When autofocus came about, in practice rangefinders lost much of their advantage.

However, various autofocus systems and their autofocus lenses range from god-awful to pretty good. On the bad side you get systems with tolerances that could only be described as generous and, on the other extreme, systems that allow you to customize the autofocus for individual lenses.

But the real focusing accuracy is in magnified live view, looking at a magnified version of the image actually produced by the sensor. For the first time, we can actually examine the image on the “film,” albeit digital film.

Not all digital cameras can do this, but I wondered how many photographers who could take advantage of this system do? Certainly for the landscape, nature, still life - and even street photographers who prefocus, it’s a possibility, and the results are pretty impressive.

Any thoughts?

 

[david.elliott]

My e-p2 has live view and magnifies at either 7x or 10x. In practice, it is -wonderful- for macro work. For landscapes, I find it unnecessary as I am usually focused at or near infinity. For any work in which the subject is moving, I find focusing with a magnified live view to be absolutely impossible. The 7x or 10x magnification is just too high and the subject jumps all over the place on the screen or in the viewfinder. Other systems which offer lower magnifications might be more useful in that regard.

That said, using the EVF on this camera it is very easy to manual focus even on moving subjects. Magnified focusing though is, as I mentioned above, impossible in those situations.

 

[Colin Corneau]

It just seems too unwieldy and time consuming to do, considering how accurate AF systems are now. The few times I've shot HD video on a DSLR, I used that feature a few times, but found it easier to simply autofocus first and then go on working.

Occasionally I've zoomed in on a frame after I shot it, to make sure...that's more useful, but YMMV.

 

[splitimageview]

I do. It does take time, and yes, the image can be shaky at high magnification.

This was shot hand-held with Panasonic G1, Carl Zeiss Opton Sonnar 50/1.5 (100mm equivalent.)

 

[charjohncarter]

I don't have live view on my DSLR but I zoom in after a shot to check for accuracy. It is amazing how easily these systems are fooled. I have had 5 digital cameras and all were/are easily fooled. Some times I think that the many focusing spots on DSLRs works against accuracy.

 

[Graham Line]

Have only used live view in the field to preview scenes and lighting; the autofocus on my camera is easy to manipulate in other ways if need be, by selecting focus points.

A couple of recent product shoots have been much easier with live view -- it allows more precise framing and composition.

On the D300, at least, the magnified view does allow careful manual focusing but it's kind of an eye-straining experience.

Using live view also eats batteries at about five or six times the normal rate, but it sure feels like using a view or technical camera.

The locomotive in the photo is about seven inches long.

 

[Arjay]

I also use a D300, but I have to admit I rarely ever use manual focusing. Granted, I only very rarely take any macro shots, but I almost always use autofocus with that camera, because it is very easy to control and it is very precise too - even when using a lens wide open. Autofocus in this class of camera can be calibrated if a lens exhibits focusing errors (earlier Nikons exhibited that problem more often), and this calibration actually for me would be the only occasion to use live view.

I find live view rather operator-unfriendly and clumsy, so that's why I hardly ever use it.

Modern phase change AF systems (such as those used in DSLRs) have reached a level of speed and accuracy that is fairly hard to beat using any type of MF. OTOH, these systems can be configured with such a large number of operating variables that one has to thoroughly read the user manual and follow a rather steep learning curve before one can successfully use the system. There's little chance to use the AF system without first having fully understood its functional details.

Given enough light, I even use autofocus on my D300 for stealthy street photography. This is possible because the camera's face detection function is rather powerful and can identify facial structures even if I am somewhat sloppy in pointing the camera (see my Oktoberfest shots in my gallery).

In lower-light situations, I still use AF, but I have to be more precise in how I point the camera at features that I want my camera to focus on, i.e. I can't use the camera without looking through the viewfinder.

So, scale or zone focusing is something I hardly ever need to use on my D300.

 

[gdmcclintock]

As I age and my vision deteriorates, I find myself relying on the focus confirmation light on my Canon 5DII when using both Canon AF and Zeiss MF lenses.