Sometimes you may have noticed that your lens doesn't seem to be pin-sharp on its autofocus.
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Well, this can
happen because lenses can drift over time now to overcome this problem we can
actually recalibrate the lens to be pin-sharp on that particular focus point. Now
to do this you just need a few simple things I recommend a low table such as a
coffee table, you'll need a piece of whiteboard, a ruler and a pen, and of
course a tripod, and your camera and lens so let's show you how to do this. So the
first thing you need to do is draw a very thin clear line on a piece of
whiteboard this will enable the camera to have a specific point to focus on and
nothing else after that you need to align maybe one or two rulers along that
line on a particular point here I've chosen to align them on the 20
centimeter mark. Following this you must make sure that nothing is going to move
either your board your rulers or your camera and then we'll set about using
the central focus point to focus on the line without the rulers in place so once
you've drawn your line simply select your central focus point and place it on
the center of that line. Now I recommend shooting in full aperture so in this
case this is a 1.2 lens so I'm going to open the lens to 1.2
for the shallowest depth of field possible, also switch your camera to
manual focus temporarily, defocus it so the line isn't sharp at all then switch
your camera back into autofocus so that it can try to focus on the line. So now
the camera has focused on that line, I'll now place the rulers and at this point you
have to be very very careful not to move anything on this table.
Now I position those rulers to be on the 20 centimeter mark exactly on that line
and we know that the camera is already focused perfectly on that line I can now
take a photograph and we can examine the results. So let's zoom in on the image we
can see here clearly that the number 21 and 22 are actually sharper than the
number 20 so what that means is that currently our autofocus is actually
focusing slightly too far into the distance than actually on the mark where
we wanted it to, but we can overcome this with our custom calibration. So we go
into the menu, find autofocus, autofocus micro-adjustment, select and then move
down to adjust by lens and then you'll see, in this particular camera, we need to
press INFO to register and then this graph appears which will show you the
going into the distance is the mountain symbol and then coming towards the
camera is the camera symbol so we're going to pull the focus back on here by
about -15 on the autofocus calibration adjustment and we're going
to say okay because the lens was focused too far in the distance so we're going
to pull the focus adjustment back towards us.
We take the shot again, we zoom in and we check the image and we can now see on
the new calibrated image at -15 on the autofocus calibration adjustment
that the number 20 and the line is sharper and we can see that focus is
pulled back further towards us away from number 22 and 21 so it looks now that
that lens is calibrated perfectly. So that's how I calibrate my lenses and if
you have a longer focal length lens you may need to be further away so you could
actually replicate this on the floor and also different cameras other brands
other makes have slightly different operations on their menu but the general
principle is the same. One final thing to keep in mind is if the image isn't still
not looking sharp to your eye through the viewfinder especially if you're
using a DSLR, if the image isn't looking sharp then it may be that you need to
adjust the diopter on the side until the picture looks sharp to your eye through
the lens as well. So I hope you found that useful, I'm Karl Taylor, thanks for watching.
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