I've seen enough comments posted in various places to believe that there are some who have the misconception that the Phase One AFr (autofocus-recompose) feature is the same as Hasselblad True Focus. Or, as prominent Phase One dealer posted a couple of months ago, "the XF also has a dedicated mode for this called AFr (same idea as True Focus)". However the two features are
not equivalent or the same idea.
There are a variety of things that can effect focusing accuracy. Hasselblad has worked to improve focusing accuracy by addressing first, factory calibrating the sensor position (and its specific optical characteristics), body, and autofocus module as a complete unit. Each component in the chain has very tight tolerances, but within these tolerances there are variances. All of these tolerances add up and need to be calibrated together for maximum accuracy. Spare bodies can be calibrated in the same manner.
Second, aperture dependent focus shift is compensated for automatically for the selected aperture setting of the lens being used. All lenses exhibit focus shift and this adds to previous list of variables that need to be considered to achieve best focus. These functions were termed "ultra focus" when introduced in the H3D/H3D II in 2006.
https://www.getdpi.com/forum/medium-format-systems-and-digital-backs/38555-diglloyd-focusshift-compensation-hasselblad-h-mf.htmlIn 2009, Hasselblad introduced the H4D with True Focus to address the problem that has always existed with autofocus-lock when recomposing. The plane of focus shifts when rotating or tilting to recompose after locking focus. True Focus uses accelerometers in the body to measure the precise degree of angle change and corrects the focus to the locked focus point. This allows center point autofocus lock and repositioning of the subject anywhere in the frame with more confidence of getting what you want in focus. True Focus is one of the most important features for many Hasselblad users due to their increased percentage of images with optimum focus.
In 2012, The H5D / H6D added True Focus II correction which compensates for lens field curvature (again, all lenses exhibit this to some degree. wide-angles more and teles less) to ensure consistent focus accuracy to the edges of the frame. True Focus processes the measurements and calculations,
then applies those focus corrections to the image you are currently capturing. This last statement (especially the underlined part) might seem obvious, but this is where the difference lies.
In 2017, Phase One introduced AFr (which functions only with "Blue Ring" lenses). Their website and release notes both say this feature allows you "to focus on a subject and then recompose the frame while retaining the desired focus point". Sounds like True Focus, doesn't it? It isn't. It does
not measure your angle change and calculate the focal plane shift and then apply
that change to your
current shot. On your current shot, AFr is going to
change your focus based on one or more of the previous shots you've taken and
NOT on the movement you made in your current shot. Huh??
https://www.getdpi.com/forum/medium-format-systems-and-digital-backs/62504-first-experience-afr-focus-recompose-phase-one-xf.htmlHere is how it works from the XF manual... "the compensation that AFr Mode applies to your captured image is anticipated
based on your preceding captures." "The XF Camera will automatically adjust the plane of focus for you, based on your
anticipated movement, prior to capturing the image." "This tool is designed to learn the movements of the XF Camera over the course of a shoot, and therefore
the more you repeat the same movement within a sequence of images, the greater the success." "The initial capture from when the camera is turned on, may be imperfect in terms of AFr success."
I cannot think of any reason why I would ever want focus adjustments being made based on anything other than the conditions of my current shot. Maybe I'm just not predictable and repetitive enough to benefit from this feature. Maybe I'm just too set in my habit of adjust focus, then shoot; to adapt to shoot first, then adjust focus.
Of course, the change in focus is often very small when using autofocus lock and recomposing. It depends entirely on the amount of angular change. So, it's mainly of concern at closer distances with shorter focal lengths. But where it makes a difference, it can be very noticeable and can make the difference between an excellent image and one that isn't what you wanted.
http://static.hasselblad.com/2015/02/using-true-focus.pdf]
http://static.hasselblad.com/2015/02/using-true-focus.pdf[/url]