David Cardinal: Saving Your Photo Safari with Datacolor’s SpyderLensCal
Jun 2012 10

A common complaint among serious photographers is that their cameras don’t focus accurately. “Back-focus” and “front-focus” are both dreaded ailments that can plague any SLR (digital or film) and lens combination. Fresh from the factory, lens and camera are supposed to be calibrated so this doesn’t happen. However, not only does that not always occur, but once a lens and camera are in the field, it is only a matter of time before slight changes in the alignment can cause focus to drift.

To help address focus issues, starting several years ago Nikon and Canon began adding the ability to fine-tune the auto focus on their mid-range and high-end DSLRs. By setting a custom adjustment the camera owner can tweak the AF either forward or back by a few inches. Most importantly, this is done for each lens and camera combination, or even for each combination of lens, camera and teleconverter.

Until Datacolor introduced the SpyderLENSCAL, I used the crude method of placing several identical objects in a row

Since sending a lens and camera body to the vendor’s service organization for a checkup and retuning costs hundreds of dollars in fees and shipping – and leaves you without a lens or camera for days or weeks, the idea of being able to tune the AF yourself was incredibly appealing. Unfortunately, it was also complex, time-consuming, and error-prone. I have always advocated that photographers verify their lenses were focusing correctly before a trip, using a row of bottles, cans, or in my case Burmese lacquerware bowls. However my advice if there was a problem was to send the lens and possibly the camera in for adjustment.

That was before Datacolor introduced the very clever SpyderLENSCAL. The idea of a LensCal is quite simple, but the implementation is very elegant. Essentially a calibrated ruler placed at 45 degrees, with its zero point placed exactly next to a focus target, the LensCal folds flat for easy transport and features a mount for attaching directly to a tripod baseplate. When popped up for use it can also be placed on a shelf at camera height for use.

The clearly labeled 0 to 6 (in each direction) axis on the ruler makes it more convenient to use and less likely to produce errors than home-brew solutions involving household rulers taped to targets and propped up at an angle. Because they are so close to the focus target it is possible to evaluate test images and tweak your camera settings from looking at the test images on the camera’s LCD. There isn’t even a need to load the images onto your computer.

The Adjustment Process

The process for testing and adjustment is fairly simple, although the specific menu items for setting the adjustment varies by camera maker and model. Start by shooting an image centered on the small focus target of the LensCal that also includes some of the numbers on the ruler. To maximize the visible effect of the focus point, it is ideal to start out near your camera’s minimum focus distance from the target (if your lens has multiple focus distance ranges, set it to Full to make sure you are truly at your MFD).

For best results, insure that your lens is at the same height as the focus target, and that your shutter speed is fast enough that you won’t be getting blur from lens or camera movement. You can set your camera up on a tripod, or on the same surface as the SpyderLENSCAL, or hand hold as long as you can achieve a high-enough shutter speed. Make sure it is set to Autofocus, as that is the feature we’re testing. Then aim at the center of the target (for a telephoto you’ll want to aim at the center of the smaller bullseye target so you can still see the ruler in the frame).

Participants took turns using the SpyderLENSCAL to fine tune the AF on their cameras during my recent workshops

Once you’ve taken a good image, zoom in on your LCD (or download to a computer and check by zooming) and look at the image of the ruler. You want to see if the “0” mark is the sharpest. If it is, you’re finished. If not, then add or subtract points from the AF fine-tune setting in your camera and repeat the test process until the “0” is sharpest – meaning that the AF on your camera is correctly focusing on the target.

If you prefer to see a video walkthrough of the process, Datacolor has thoughtfully provided one as a companion to the User’s Guide: http://www.datacolor.eu/?id=398.

Case Study: Participants on my Texas Photo Safaris

After using the LensCal to adjust the AF on my cameras – with two lens combinations out of the 8 I tested requiring a tweak – I was ready to take it on the road. Since one of the most frustrating things for a workshop or safari participant is non-sharp images, often caused by mis-adjusted AF, it was a no-brainer to bring the LensCal along when I headed to Texas for my annual Hill Country and Rio Grande Valley photo safari and workshops.

Ideally of course, everyone would have checked out their gear in advance and evaluated the auto-focus performance. But not everyone has a LensCal of their own, at least not yet. So the first day of each safari we set the LensCal up for everyone to use. It was unbelievably easy to explain compared to the old way of doing lens calibration. Everyone had at least one long lens (200-400mm, 100-400mm, 500mm, 600mm, or similar) to calibrate, and many of the participants also had a shorter “flight” lens (either a 300mm f/4 or 70-200mm f/2.8) they also wanted to check. Even with all the possible combinations of lenses, cameras, and teleconverters, it didn’t take us too long to run through the exercise.

As expected, most of the lenses and cameras were fine. But around 20% of them required an adjustment. These were all pro grade Nikon and Canon lenses, coupled with prosumer and pro bodies. And all were owned and maintained by conscientious photographers. So the fact that 1 in 5 benefited from a correction of up to 2” in auto-focus showed the value of the LensCal. I expect that most of the folks on the trips will have ordered their own by now.

Imagine the difference in spending a week, or even a day, shooting with your autofocus off by anywhere from ½” to 2”, especially with birds, small mammals, or even human faces. You’d be stuck blaming your technique, or your shutter speed, or dialing in an extra stop or two of aperture to try to make up for the camera focusing in the wrong place. There is no question that using the LensCal really helped make the safari happen for at least one or two of the participants whose lenses were fairly far off. I’m looking forward to bringing it along on my Alaska Bear & Puffin safaris and my Botswana wildlife safari, so participants can make the most of their time in the field!

is a veteran travel and nature photographer who specializes in Southern Africa and Southeast Asia as well as North American mammals and birds. His images of creatures in the wild help communicate the importance of our natural heritage and our responsibility to preserve it. You can learn more about David on our Friends with Vision page, or on his own website, Cardinal Photo, and its sister site, Nikon Digital, which are both full of tips, reviews and forums where photographers compare notes and tips. Or you can follow David on Facebook or join him on one of his Photo Tours and Safaris for plenty of experience