No matter what digital SLRs you own or exist today, two nagging issues continue to plague owners — sensor dust and autofocus accuracy. Sensor dust is a subject that has been talked to death and is very much an unavoidable part of living on planet earth. For the latter, issues involving focus issues are a hit and miss. Some experience it, some don’t. Most don’t even know what it’s about. Until the day Canon and Nikon began equipping dSLRs with Autofocus Microadjust (“AFMA”) capability, focus accuracy issues had been an incredibly frustrating to deal with that required returning both body and lens to respective service centre for calibration. Goes without saying nobody likes doing this given a choice.
AFMA capability immediately gave birth to a slew of tools that help perform manual calibration more accurately but are at best products that leave many users confused. I know for sure if I had to use one of those 45° angle charts it wouldn’t take me long to smash it to pieces. Thankfully Reikan understands this frustration and makes the calibration process much simpler. For the mathematically challenged user like me there’s the Fully Automatic mode and for those who can understand numbers better there’s the Semi Automatic method. I thank Richard of Reikan has given me an opportunity to trial and review this release (ver 1.1.0.40). There’s also an FAQ that may contain answers to your burning questions.
I printed out the chart provided onto an A4 paper, mounted it on cardboard and held up the entire duration of the calibration on a boom stand. Here FoCal confirms the chart is correctly setup.
Any change in AFMA setting previously registered by camera can be changed easily via FoCal. I didn't have to keep getting up from my seat to reset the on-camera menu.
The first lens I calibrated was the EF 50mm f/1.4 and FoCal determined after analyzing 40 or so shots that the optimum AFMA setting is -6.
Post calibration report (PDF): FoCal_FullyAuto_Canon EOS 5D Mark II_EF50mm f_1.4 USM_50mm
FoCal determined my EF 100mm Macro f/2.8 Hybrid IS didn't need any adjustment.
Calibration Report: FoCal_FullyAuto_Canon EOS 5D Mark II_EF100mm f_2.8L Macro IS USM_100mm
Calibrating prime lenses is straightforward. The challenge and question is how would FoCal handle telephoto lenses. I have two long lenses I often use — EF 70-200mm f/2.8 L IS and EF 100-400mm L IS — and I’ve found calibrating the EF 70-200mm to be quite an interesting learning experience (at this posting I have not tested the EF 100-400mm).
How do you calibrate zoom lenses? Most cameras only support a single micro-adjustment setting for the whole lens at all zoom positions, which is not ideal. What you tend to find is that the ideal microadjustment values are different at each ends of the zoom range. Whilst FoCal cannot address the lack of support in a camera for multiple microadjustment values, you can still calibrate a zoom lens and get a better result than uncalibrated. It’s easiest to explain this with a quick example… Suppose you have a 24-70mm lens. If you calibrate at 24mm and get a result of +10 and at 70mm and get a result of +15, then any value between +1 and about +17 will almost certainly make your lens better at any focal length than it would have been at the default setting of 0. So which value is best? Well, focus errors have a greater effect at the telephoto end of a zoom lens as the depth-of-field is shallower, so it’s better to shift slightly towards the telephoto end. In the example above, the recommended value would probably be +13 or +14 – in real shooting you probably wouldn’t notice a difference between the two so either would work. What you would notice is a huge improvement over the images compared to an uncalibrated setup!
At 70mm f/2.8 my EF 70-200mm lens needed a AFMA value of -10 (same value on second run)
Calibration Report: FoCal_FullyAuto_Canon EOS 5D Mark II_EF70-200mm f_2.8L IS USM_100mm
At 135mm lens needed +3 for sharpest image while at the longest end (200mm) FoCal decided +10 on the first run and +7 on subsequent run. What's interesting is when I increased the camera to target distance to 3.5m, AFMA value dropped to +4 at the 200m end.
Calibration Report: FoCal_FullyAuto_Canon EOS 5D Mark II_EF70-200mm f_2.8L IS USM_200mm
As soon as I find time to calibrate the EF 100-400mm I’ll update results here.
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