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Reproduced from EOS magazine October-December 2012
Reproduced from EOS magazine October-December 2012
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All you need to know about full-frame and APS-C formats
nina bailey
There is a lot of confusion about crop factors, extended
reach and telephoto effects when using lenses on APS-C
cameras. First, let’s dispel the myth that the focal length
of a lens changes when switched between a full-frame
camera and an APS-C camera. It doesn’t. Focal length is a
characteristic of the lens and is not affected by the camera.
Field-of-view
What does change is the field-of-view. Take a look at the
image above left, shot with an EF 400mm lens. A full-frame
camera captures the full image. An APS-C camera only
records a part of the full image (as shown by the white box
on the left hand image). There is no change to the image
created by the lens – it’s simply that the smaller sensor only
captures the central area of the image. The rest of the image
falls outside the area of the APS-C sensor.
Magnification effect
When you come to display the image to fill a computer
screen or a print, the result from the full-frame sensor is
shown above centre. The result from the APS-C sensor
is shown above right and appears to show an increased
telephoto effect. In fact, the APS-C image has been enlarged
more than the full-frame image to match the display size. It
is a magnification effect, not a change of focal length. You
could get an identical result by enlarging and cropping the
full-frame image.
Crop factor
A crop factor of 1.6x often talked about with APS-C cameras
can be explained like this: If you are using a 50mm lens on
an APS-C camera and you want to shoot the same scene
with the same field-of-view with a full-frame camera you
need a focal length of 50 x 1.6, which is 80mm. But how
often do you need this information? Our advice is to put a
lens on the camera and get used to the field-of-view it gives.
Forget about crop factors.
Standard lenses
A standard focal length for a camera is usually taken as the
diagonal of the image frame. On a full-frame camera this is
43mm. On an APS-C camera it is 26mm.
A focal length greater than the standard is telephoto and
a focal length less than the standard is wide-angle. This is
much more useful than knowing the crop factor.
Above left to right
These photographs show that an APS-C image is
simply a cropped full-frame image. There is no change of focal length.
See the main text on this page for more details.
Lenses and full-format cameras
EF lenses are ideal with full-frame cameras, in that you are
using the maximum coverage of the lens. However, there
is a downside. Some older EF lenses were designed for
film cameras and their performance with full-frame digital
cameras is less than perfect – especially at the corners. To
get the best from your digital EOS you need to use the more
recent EF lenses – these have been optimised for digital
cameras. We will not cover the technical side here, but it has
to do with the angles at which rays of light hit the sensor.
If you were using EOS film cameras before moving on
to digital, one advantage of a full-frame camera is that the
coverage of EF lenses is unchanged.
Lenses and APS-C cameras
EF lenses can be used on APS-C cameras, though with the
cropping effect shown above. This can be useful for older
lenses as the reduced edge performance is cropped. The
downside is that you lose wide-angle coverage. The ultra-
wide EF 14mm lens gives a field-of-view similar to that of a
22mm lens used on a full-frame camera. The EF-S 10-22mm
lens has been introduced to restore the balance. A 10mm
focal length on an APS-C camera gives the same field-of-
view as a 16mm lens on a full-frame camera.
EF-S lenses are generally smaller and lighter than EF
equivalents, but the image they produce only covers an
APS-C sensor, not the larger full-frame sensor.
EF-S lenses will only fit APS-C cameras (excluding the
early D30, D60 and 10D models). If you have an APS-C
camera, but think you might move on to a full-frame camera
in the future, it is worth staying with EF lenses.
The higher-quality L-series lenses are only available in EF
mounts. EF lenses fit full-frame and APS-C cameras.
Format choice
Full-frame cameras give the best of both worlds – wide-
angle coverage and the option to enlarge part of the image
for a closer view of the subject. However, full-frame cameras
are more expensive than APS-C cameras. In terms of image
quality, you can get great results from both types – the
format used will not be obvious in the photographs.
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EOS 6D
briefing
YEAR
APS-C FORMAT
APS-H
FULL FRAME
ENTRY LEVEL
MID-RANGE FLAGSHIP
ENTRY LEVEL MID-RANGE
FLAGSHIP
2000
EOS D30
2001
EOS-1D
2002
EOS D60
EOS-1Ds
2003
EOS 300D EOS 10D
2004
EOS 20D
EOS-1D Mark II
EOS-1Ds Mark II
2005
EOS 350D
EOS-1D Mark II N
EOS 5D
2006
EOS 400D EOS 30D
2007
EOS 40D
EOS-1D Mark III
EOS-1Ds Mark III
2008 EOS 1000D EOS 450D EOS 50D
EOS 5D Mark II
2009
EOS 500D
EOS 7D EOS-1D Mark IV
2010
EOS 550D EOS 60D
2011 EOS 1100D EOS 600D
2012
EOS 650D
EOS 7D*
EOS 6D
EOS 5D Mark III
EOS-1D X
Full-frame and APS-C
Full-frame and APS-C
formats originated with
film cameras. Full-frame
is a format of 35mm film.
It first appeared in the
early 1900s and became
popular with the launch of the Leica camera in
1925. The frame format is 36 x 24mm (35mm
refers to the width of the film). Before digital,
most Canon cameras – SLR and compact – used
this 35mm format.
The term full-frame was coined to
differentiate it from the 24 x 18mm half-frame
format, which gave twice as many frames as
full-frame on the same length of 35mm film. The
Canon Demi half-frame camera was introduced
in 1963 and was followed by a number of similar
models, including the popular Canon Dial 35.
Easier loading
Some camera owners found it difficult to load
35mm film. The Advanced Photo System
(APS) was introduced in 1996 to overcome this
problem. There was no need to thread the film
manually across to a take-up spool in the camera
– the APS camera and cartridge system did this
automatically.
All the original Canon IXUS models were APS
film cameras – the IXUS name is now used for
Canon digital compact cameras. There were also
two EOS APS cameras – the EOS IX and IX 7.
There are three APS frame formats:
APS-H – 30.2 x 16.7mm (16:9 ratio)
APS-C – 25.1 x 16.7 (3:2 ratio)
APS-P – 30.2 x 9.5mm (3:1 ratio)
In fact, all the images are captured at the
APS-H format, but a camera setting determines
the format used for printing.
The difference in price
Full-frame digital cameras are more expensive
than their APS-C counterparts in part because
the sensors cost a lot more to manufacture.
Sensors are not produced individually, but on
a large circular ‘wafer’ which is then cut into
rectangles of the required size.
You can get many more APS-C sensors from
the wafer than full-frame sensors. The cost of
the full-frame sensor is a lot more than double
that of the APS-C sensor.
The transition to digital
Some people believe that the Advanced Photo System was introduced to
get photographers ready for the transition to digital photography. The first
Canon digital single-lens reflex camera was the EOS D30 (see table below).
It features a digital sensor with a size of 22.7 x 15.1mm – similar to the
APS-C film format (see left). This has the same 3:2 ratio as the 36 x 24mm
full-frame format.
Inevitably, models with the smaller sensor are now known as APS-C
format cameras (see table below for a list of all EOS digital models).
A year after the EOS D30, the EOS-1D was introduced. The sensor in
this camera measured 28.7 x19.1mm, not too far removed from the original
APS-H format, but adjusted to keep the 3:2 ratio.
Canon would probably have preferred the EOS-1D to have a full-
frame sensor, but larger sensors generate more data, all of which needs
processing. Processors at the time were relatively slow and a full-frame
format would not have allowed the 8fps continuous shooting provided by
the APS-H format and required by the news and sports photographers
adopting this camera.
The first Canon full-frame digital camera was the EOS-1Ds. The
maximum 3fps continuous shooting was adequate for the more sedate
studio environment where many of these cameras were used. (It was said
that the ‘s’ was short for ‘studio’, though we are not sure that this has ever
been confirmed by Canon.)
Now that the full-frame EOS-1D X camera and its Dual DIGIC 5+
processors are offering up to 14fps, it is likely that the EOS-1D Mark IV will
be the last of the APS-H models.
Below
This chart shows
the introductory date and
format of every EOS digital
camera (except the new
EOS M, which needs its
own category). The EOS
7D* refers to the EOS 7D
with firmware update 2.0
(see page 66). Although
not a new camera, the
updated EOS 7D offers a
range of new features. You
can see that the new EOS
6D starts a new category.