Can You Trust Auto-focus?–Revisited

About 9 months ago I published a piece called “Can You Trust  Auto-focus with Your Digital Camera“. In the article I concluded that using Live View to focus a digital camera gives much sharper results than using the camera’s auto-focus. Indeed, one of the huge benefits of Live View has been an increase in the technical sharpness of my images because lens focus can be set so precisely. I stopped trusting auto-focus.

Several photographers wrote to me and suggested that I just needed to use the AF microadjustment feature built into my camera, the Canon EOS-1ds Mark III, to calibrate my lenses for more precise auto-focus. I balked at the suggestion: I expected an $8000 camera to function properly from the factory! Why should I need to give it a tune-up? To me, this is like buying a car but needing to calibrate it for the roads I drive on! Besides, none of the photographers who wrote to me about this actually knew how or had even tried to do the AF microcalibration themselves.

Time passes and I am happy using Live View because for me, a landscape photographer, there is no need to rely on auto-focus.  I admit though that I was dismayed by the slightly soft images I got when using auto-focus to shoot dogs and kids, something I dabble in on occasion.

On Dec. 12, 2008, a new product, Lens Align was introduced over at RawWorkflow. To see how to use this product please watch the videos at RawWorkflow or this one at Luminous Landscape. I ordered a Lens Align kit and ran my lenses through the easy calibration process. The photo below was done using auto-focus at the default factory settings in the camera. Here I used a Canon 135mm F2.0L lens, and the results show that on my camera body this lens is focusing behind the zero mark at around the “2” mark.

Sharpness Results before Lens Align Calibration
Sharpness Results before Lens Align Calibration
I then manually focused the lens at 10x magnification using Live View (see below). The results were perfect and I could obtain precise focus on the zero point. Live View really lets you get the best focus possible!
Manually Focused Esing Live View at 10x Magnification

Manually Focused Using Live View at 10x Magnification

After calibrating and testing the lens with Lens Align and then using  the AF microadjustment in my camera, I got the lens to give me consistent auto-focus performance that nearly matched what I could get from using manual focus in Live View (see the image below).

Sharpness Results After Lens Align Calibration

Sharpness Results After Lens Align Calibration

Interestingly, some of my lenses were focusing behind the zero point, some were focusing in front. I calibrated each lens and retested rigorously, and now all of my AF lenses hit the zero mark everytime! Some lenses, like my 135mm f2.0L, needed a moderate adjustment (+7 units of microadjustments) while some needed very little adjustment (e.g. the 24-70mm f2.8L only needed -3 units of change). Others lenses needed a giant adjustment like my 180mm macro lens (+15 units!).

In the end if you own any of the following cameras –  Canon 1D MKIII, 1Ds MKIII, 5DII, 50D, or Nikon D3, D3x, D300, D700, or Sony A900, or Pentax K20 you owe it to yourself to calibrate your camera with Lens Align–why spend big bucks on camera and lenses and not have the most precise performance possible?? Darwin

5 Responses to “Can You Trust Auto-focus?–Revisited”

  1. But how did you do it? Was it easily found in the instructions?

  2. Rick, To see how it is done simply watch the Luminous Landscape video posted in the story above. Darwin

  3. Well, I guess the lenses make the difference, not the camera body… some front-focus, some back-focus… Should be consistent on any camera body though.

  4. Glenn Cratty Says:

    Hi Darwin,

    On the verge of a major upgrade of my system, I’ve been digging through your blog and really enjoying your impartial, practical and thorough take.

    Having said that, what I’ve just read here might just be the revelation of the decade of camera gear for me. Now I know why I’ve never been able to get get my 24-70 tack with autofocus! Thanks a million: sad to say but you may have just improved my professional life by measurable percentage points!

  5. […] using Live View at 10x magnification than I can get with the camera using auto-focus even after focus calibration . I also turned off Optical Stabilization (Sigma) and Image Stabilization (Canon) for all tripod […]

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