I've noticed lenses I've dialed in in the summer need some adjustment in the winter. The handy FoCal Setup Checklist shows you all the steps you need. One other thing, AFFT calibration can change with temperature. Then I'll do a quick field check and that's usually enough to get the results I need. In the end, I gave up and will only check AFFT if I'm seeing a consistent problem. The target gets small which makes very small differences harder to differentiate. With longer lenses you need to be quite far away and I find I need to do the serious calibration out of any wind and heat waves which means mostly indoors. The biggest problem is getting a decent working distance. Now I use the Lens Align rig but do my own analysis using fewer clicks. The computer program always seemed to indicate it needed more samples and you had to use jpegs. You need a good 10 samples at each setting. It is time consuming as well as eating up many shutter clicks. I also purchased the Lens Align and did use it. There are 5 of them each stepped 1/2" behind the previous one. Many years ago I built my own rig, targets glued to foam core blocks. While doing af fine tunes, I will de-focus in one direction and get slightly different results if de-focusing in the opposite direction. Put another way, the AF systems won't put the focus on the exact same spot every time, there is a little "slop" and it also depends on which way the focus is turning to get there. More often than not, my lenses are close enough out of the box that they are within the variable ability of the AF system. Look at it on the lcd and if the sharpest part is where I focused, no adjustment needed. I find one post and focus on it, take the picture with the lens aperture wide open. When in the field I usually am able to find something that will serve as a test subject. Does the lens need calibration? There are simple tests you can do before spending time and money to calibrate.
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