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Author Topic: AF Microfocus Adjustment with Canon 1Ds Mark 3  (Read 4716 times)

rod edwards

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AF Microfocus Adjustment with Canon 1Ds Mark 3
« on: January 09, 2009, 07:46:17 PM »

Hi everyone,

After reading Michael's interesting review of the Lens Align Pro focus calibration unit, I was very keen to buy one and try it myself.

Having experienced focus issues with my Nikon digital gear (D2x, 85mm f1.8 & 70-200mm f2.8VR), I spent a small fortune switching over to Canon 1Ds 3 (and 5D 2) in the hope of reaching photographic Valhalla and getting perfectly focused images most of the time.

Whilst i'm very pleased with my Canon gear, I was finding the autofocus system was still letting me down more frequently than i would have hoped. I therefore sent the whole kit to Canon UK to have it tested and calibrated (on two occasions) ... but it still wasn't quite right.

I realise that the 1D 3 and the 1Ds 3 have both had moving predictive focus issues, but i was experiencing static focus issues at wide apertures on many of my lenses (24-105mm f4, 85mm f1.2, 50mm f1.2). When i therefore read about the new Lens Align Pro kit, I was very keen to get my hands on the new product and get to the bottom of my autofocus problems.

The Lens Align Pro kit is very well made and was shipped quickly from the USA to my home in the UK and very useful it has been too. It has allowed me to consistently and repeatably check my autofocus using a perfect black & white static vertical target and a horizontal ruler scale to measure front and back focus. However, whilst the kit seems great (and Michael Tapes of has been very helpful), I have noticed continuing problems with the Canon AF system.

I've tried using the Lens Align kit to adjust the front & back microfocus of my factory calibrated Canon 1Ds Mark 3 and my factory calibrated lenses at close focus distances (1m) and longer distances of 2.5m+. After considerable testing, i've concluded that the microfocus adjustment required for close focus can be very different to the microfocus required for larger distances. For instance, with the 85mm lens @ f1.2 at 1m distance from target, I need to set a microfocus adjustment of +20 to get the optimum focus, but at a distance of 2.5m it needs no microfocus adjustment at all. Needless to say, distances between these two extremes all need different micro focus settings to achieve sharp focus. This problem is repeated with my other lenses and my new Canon 5D mark 2 as well.  

It seems that Canon's AF microfocus adjustment is therefore largely useless since it changes with the distance from the subject. Nice idea, but as far as i can see, i doesn't quite work. Am I expecting too much from my expensive equipment to focus correctly at wide apertures when, for instance, shooting close up head & shoulder portraits AND then stepping back and shooting full length portraits ? It seems so ... and this makes me ask the question as to why i spend money on fast f1.2 lenses when repeatable sharp autofocus cannot seem to be achieved.

I'd be interested in other user comments and experiences about Canon (or Nikon) AF Micro Adjustment's and autofocus issues. Does anyone else find repeatable sharp focus of static subjects a real headache when shooting with fast lenses, wide open at close distances or with long focal lengths ? I know I can always use manual focus, but this isn't what it's all about & AF should, in theory, be more accurate !

Many thanks ... look forward to your replies and advice ...

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