Dennis C. Boyd » An adventure into Photography

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FoCal and Micro Adjusting my Lenses


Last year I saw a post about a new software coming out that was supposed to speed up the micro adjustments of lenses.  Sure enough a month or so again someone mentioned the company/product on one of the forums and I had to check it out.

Why… because I’m picky… and something just seemed off with certain lenses I owned.

I like eyes in focus, know that at f/1.2 there is such a shallow depth of field one has to be soo careful on focusing but even taking the utmost care… some of the lenses still just seemed off.

I wasn’t sure if the lenses were front focusing or back focusing… not even sure which ones but time and time again I found shots that should have been crystal clear and they weren’t.

I thought… my 50D and my 5D mkII have the micro adjustment feature built into them… why not try it out?

Off I went to the FoCal web site to see what it was all about (they also have a Facebook page here).

What is FoCal?

  • FoCal is a utility which can fully automatically calibrate the Autofocus Micro adjustment value of your camera and lens combination quickly at the touch of a button!


  • Live, real-time assisted target and camera positioning to ensure the best possible test results
  • A target designed closely with the image analysis algorithm to optimise performance
  • Complete control of the camera during testing to help speed up calibration
  • A fully automated micro adjustment calibration test which does everything at the touch of a button.
  • New Manual Mode allows AF microadjustment analysis without connecting your camera to the computer!

I found out that yes, my Canon 5Dmkii was supported and the 50D support was on the way (the program has been updated and now the 50D has been included).  Actually, the company has been continuously working at updates, amazing how often they are coming out with support for more and more cameras and from the looks of things Nikon gear will be included soon as well.

So… i’ve tried my lenses out a bit more, kept an eye on the focusing issue and sure enough… there were noticeable problems when using shallow depths of field.  Since I hadn’t tried any micro adjustments yet I ended up watching what I was shooting at, giving myself a bit more leeway in the DOF area and shot at f/8 a lot more than f/1.2-2.8.  Ha… I know, I know… but I’ll have you know I didn’t give it up completely for the time being, I just pulled back a bit and shot a bit further away to give myself more DOF by giving myself some more distance and zoomed in when I could (I couldn’t do that on the prime lenses, just the zooms).

Tonight I decided to fire up the program once everyone was in bed and give it a go.  I set up the target on a wall in the basement, the camera on a tripod (middle of the lens was 46 1/2″ so I set the middle of the target at the same height) and decided to try out the 85mm f/1.2 first.

I fired up the program and put it on automatic mode… only to have it come up with errors telling me it couldn’t get accurate focus on the calibration target I had put on the wall.  Hmm… then I tried the live view mode to calibrate it on the target and Whoa!!!  No wonder it couldn’t get accurate focus, the furnace had kicked on and the target taped to the wall was blowing all over the place :).

Ha… next up I found a solid place mat, one of those 1/4″ thick ones and taped the target to it and then clamped it to a lightstand.  Next problem… not enough light in the basement, may give inaccurate results so threw a 580exII on the hotshoe.  Arghh…. guess I should have done this during the day?

Screw in another lightbulb on the ceiling over the target just in case and… voila… off we went again.  After about 30 or so shots… the results were in for the Canon 85mm f/1.2 L and wow… it needed +20 on the adjustment scale which the FoCal program did automatically for me on the 5Dmkii.

Hmm… might as well try the 28-70 f/2.8 as well… but at which end should I do the measurements at?  28mm or 70mm or somewhere between?

A quick trip back to the FoCal web site gave me the info I needed.

 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!

Incidentally, Canon have acknowledged the need for multiple microadjustment points on a zoom lens by allowing you to calibrate at both ends of the zoom range on the new EOS 1D-X camera

Interesting… I only get to choose one focal length on these current Canon cameras… looks like I’ll be doing it at the 70mm mark.

Wow… after all these years… the old Canon 28-70 L lens… was spot on at 70mm.  Not bad for a used lens I bought from one of the guys here in town, not bad at all!

Next up the Canon 50mm f/1.4.  Right off the bat… the Focal program popped up some information on the screen about the target to camera distance not being optimum and thus… I followed their advice and moved the target a bit closer to the camera.  Voila again… now it was at optimum distance and off we went again for another 30 or so shots  and …the Canon 50mm f/1.4  sat at -16  needed and done for the automatic adjustments.

Hmm… why not try out the 70-200 lenses next?  So… sure enough…. the basement just isn’t big enough to extend the target out far enough to the recommended 10m (as per Canon recommendations the Focal software tells me) but lets me try it at about 4 meters or so.  Flash on camera to add light, good light from the room on the target… and the Canon 70-200 f/4 IS L comes in at needing +11 to bring it into focus.  Wow… and this lens has been my absolute favourite for so long due to it’s sharpness, guess now that I have been using it so much at the longer distances I hadn’t noticed how off it was with the focusing 🙁

Lastly… my brand spanking new Canon 70-200 f/2.8 mkii IS L lens… set at 200mm… was spot on!

Phew… now I can rest easy… here I always thought it was me simply being too picky… ha… ok… maybe it still is… but now the lenses are as close to spot on as can be with the use of Focal and I can enjoy perfect clarity in the eyes when I want it 🙂

I’ll give the 50D a go in the next couple of days to set up it’s micro adjustment features with the lenses as well but for now… the 5Dmkii is set up with my most common lenses and really, quite a painless ordeal that really opened my eyes.

Thanks FoCal… can’t wait to try out that 85 f/1.2 again now that things are more in line 🙂

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