O
84 http://www.digitalcameraworld.com
CANONSCHOOL
THERE ARE numerous occasions
where the precision of manual
focusing trumps autofocus, such as
when you’re shooting macro or
landscapes or shooting with a
very shallow depth of field.
While it wouldn’t be true to say
that accurate manual is impossible
using an optical viewfinder (you can,
after all, select a single AF point,position that over the detail you want
to be sharp, then wait for the green
dot focus indicator to appear in the
viewfinder as you focus the lens), it’s
a lot less hassle to simply use the
Live View feed.
Once you’ve moved the focus
point over the detail you want to be
sharp in the Live View preview, you
can magnify that area by pressingthe magnification/zoom button on
the camera – once for 5x
magnification, twice for 10x
magnification, and a third time to
return to the full view.
Canon’s mirrorless cameras also
offer ‘MF peaking’, which is a more
convenient manual focusing aid
when you don’t have the time to
magnify the image. Once this isactivated in the red Shooting menu
and the lens is switched to MF, the
edges of subjects that are in focus
will be outlined in a bright colour.Doing it by hand (and eye)
Make the most of Live View’s manual focusing aidsWB
SETAFISOne area of
performance where
an optical viewfinder
used to really show up an
EVF or Live View display is
autofocus speed.
As we detail in Super Test,
a DSLR has a standalone
autofocus sensor at the
bottom of the mirror box.
Some of the incoming light
is separated into a pair ofimages; the AF sensor then
measures the distance
between them, and uses this
information to drive the
autofocus mechanism. This is
known as ‘phase detection AF’.
When a camera is in Live
View mode, no light makes it
down to the AF sensor, and
there’s obviously no mirror at
all in a camera with an EVF. So
the camera measures the levelof contrast on the imaging
sensor to determine whether
the photo is in focus or not; the
higher the contrast, the
sharper the image. In order to
determine ‘peak contrast’, the
camera has to focus back and
forth across the image. So,
‘contrast detection AF’ is slow.
But Live View autofocus has
moved on. All current
mirrorless EOS cameras andthe majority of DSLRs from
the 250D upwards feature
Dual Pixel CMOS AF. Here,
effective pixels on the surface
of the imaging sensor feature
two photodiodes; they are
combined when creating an
image, but read separately for
phase detection AF. It’s
transformed focusing during
movie recording, although not
all cameras can use it with 4K.Live View autofocus
Most current EOS cameras use ‘phase detection AF’ for rapid response
UPPING THE GAME
Phase^ detection
The^ camera^ sees^ two^ ‘out of^ phase’^
versions^ of^ the^ image^ wh
ich^ need^ to^ be^
aligned.^ It’s^ a^ rapid^ form^
of autofocus,^
because^ the^ camera^ know
s in^ which^
direction^ the^ lens^ needs^ to
be^ focused^ for^
the^ image^ to^ snap^ into^ s
harp^ focus
Contrast detection
Only the (^1300) D, (^2000) D and (^4000) D
rely exclusively on (^) this slower type of
autofocus, where the (^) lens has to be focused
backwards and forwards across the scene.
The 750 D uses (^) a hybrid system, where a
number of individual phase detection pixels
are (^) embedded in (^) the sensor