September 19, 2013
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Checking Your Autofocus Accuracy Without Microadjustment / Fine Tuning
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I recently purchased a Nikon 5200, only to discover that it lacked Autofocus Fine Tuning. Apparently there are others out there who are discovering this about their beginner / mid-range DSLRs, as someone posted online about their Canon T3i.
My Ramblings:
Yep, I’m very used to doing AF microadjustment with all my pro cameras for the work I do, and when I bought my D5200 a few days ago I was dumbfounded by this omission. Luckily the camera seems to focus perfectly with all my lenses.
Aside from the fact that your camera simply cannot calibrate your lenses, it would still be nice to know whether or not you can count on this lens to function without any calibration. I especially like the trick where you shoot at an angle to a perfectly flat surface. I’ve never used those fancy charts and graphgs and programs in my life; I usually just go up on my apartment balcony and take pictures at a shallow angle of the grassy area below. The trick is to focus on something that is much larger in the viewfinder than your selected focus point, so that there is no room for error. The important thing is that you compose the shot so that there is a visible transition from foreground to background.
I also have another tip: turn your in-camera sharpening all the way up to it’s max setting, and use one of the more vibrant picture styles too. This will allow you to check your focus on the back of your camera effortlessly, without using a computer or software to do any silly calculations.
Of course if you shoot JPG or video, be sure to turn your sharpening and picture styles back to whatever you usually prefer, because while this is great for RAW shooters who like to determine sharpness easily, this will ruin your images otherwise.
Honestly, I really do think charts and graphs and software are for people who have more money than they know what to do with. A simple test focusing on a tree trunk in the park will be perfectly accurate, as long as you understand simple geometry and get the angle correct.
Either way, if you set up your test right you should be able to clearly see where focus is, in relation to where it should be.
As with any test, be sure to eliminate variables that could cause error, and click multiple test shots. I use a solid tripod and a cable release that can perform autofocus. I perform my tests in bright sun and then also in dim light, but bright sun should be a priority of course for the best accuracy.
And there’s a very good chance that, even without any focus adjustment, your Sigma will shoot perfectly on your T3i. As it is a big chunk of glass, of course, you will want to keep in mind that no super-fast prime can nail every single shot every single time, when used on anything less than a flagship camera. (And even then your keeper rate at f/1.4 and close distances may not be 100%) So, in other words, even when you’re on the job and you know your lens is focusing perfectly, you should be clicking 2-3-4 shots depending on the overall reliability of your camera’s autofocus. I have seen many people get angry at their lenses for not focusing accurately, when it is the body’s overall consistency that is the problem.
Good luck!
=Matt=
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