Hi all,
Sorry, again...
In the interest of keeping each posting on this overall topic short...ish, I
have broken this
section
into sub-sections. This might also mean that each part arrives at the 'press' a
bit quicker; there
is a lot to tell and I keep thinking of more points to raise in the hope that
anyone contemplating
purchasing a Digital Camera will be aware of at least a few of the 'traps' for
the unwary and will
be able to cope better with the camera salesperson.
Digital Bird-photography with Compact Cameras (Sub-section 1):
The definition of a 'Compact Camera' is a bit difficult these days.
Essentially, I believe that a compact camera is one which:
- is small;
- has a non-interchangeable lens;
- has a viewfinder which does not view through the lens;
- is relatively easy to use.
Most of the cameras which I would place in the 'compact' category have those
features but there are
some which are not so small and at least one soon-to-be-released model from
Epson will have
interchangeable lenses.
I know of no 'compact camera' currently available which has an optical 'through
the lens' (TTL)
viewfinder, however, an increasing number have 'Electronic Viewfinders' (EV)
which simulate TTL
viewfinders.
Learning to use a Digital Camera is not necessarily 'easy' to do considering
the common use of
electronic 'menus' for getting access to many of the facilities and features.
Incidentally, Compact Digital Cameras (or Digital Compact Cameras) are often
referred to as
'Consumer Digital Cameras'. This is probably because this type of digicam is
intended to be used for
personal pleasure rather than for commercial gain. However, some of the better
'Consumer' cameras
are capable of producing 'commercial (or professional) quality' images and are
therefore often
referred to as 'Prosumer' (Professional Consumer) models.
Many people think of Compact Cameras as 'Point and Shoot' cameras made for
tourists. Considering the
'auto-everything' nature of this category of camera, this seems to me to be a
reasonable
association.
Basically, Compact Cameras are the type of camera you use when you simply want
to take general
photos and don't want to think too much about photography.
Having said that, there are some truly remarkable digital compact cameras on
the market which can be
used to take photos anyone would be proud of (even bird photos).
Digital compact cameras come in a bewildering range of shapes, sizes and
capabilities and are often
marketed as if they are the 'silver bullet' of photography!
I say: "Close, but....."
For many people wanting a general-use camera there will be a digital compact
camera model which will
be ideal but for the bird-photographer the range is severely restricted.
For effective bird-photography (apart from Digiscoping which is discussed in
detail on my web-site:
http://users.tpg.com.au/inglisrc ) the most important features in a digital
camera are:
- powerful telephoto lens (at least the equivalent of 600 mm in 35 mm camera
lens terms but I prefer
a minimum of 800 mm);
- fast, accurate auto-focus with easy to use manual over-ride;
- spot-focus;
- very short shutter response time (the time between when the shutter button is
fully pressed and
when the shutter operates, commonly called 'shutter-lag');
- high shot rate (frames per second, fps);
- high resolution sensor (CCD/CMOS/etc, the electronic equivalent of film).
- ability to record image files in RAW format (a type of file which is more a
'data' file than an
image file) and/or uncompressed, un-enhanced image files;
- an LCD (Liquid Crystal Diode) screen for 'instantly' reviewing the images as
soon as they are
recorded.
Unfortunately, not one Consumer Digital Camera has, to my knowledge, all of
these features. In fact,
I doubt that there is even one model which has more than two of the features as
described above!
The lens:
Most Compact Digicams come with a 'zoom' lens.
[Important: Digital cameras are usually described as having 'optical zoom' as
well as 'digital zoom'
. Optical zoom is obtained from the design of the lens while digital zoom is
obtained using software
which selects part of the sensor and magnifies the part of the image recorded
by that section of the
sensor (CCD/CMOS/etc). It is my opinion that, due to the degradation of image
quality caused by
digital zoom, no self respecting bird-photographer would entertain the thought
of using it!
If you feel you have to enlarge the original image then do it using the image
software program in
your computer.]
A zoom lens is one which has a variable focal-length. The focal-length of a
modern lens is a
somewhat theoretical measurement which determines the magnification power of
the lens. The generally
accepted 'normal' lens (for 35 mm cameras) is about 50 mm so a 200 mm telephoto
lens has a
magnification factor of 4.
The zoom lenses fitted to Compact Cameras are usually referred to by a
multiplication factor such
as: 3x (3 times) or 6x (6 times), etc. This can be confusing because this is a
multiplication of the
minimum focal length of the lens which is usually around the equivalent of 35
mm or even around 28
mm!
Most Compact Cameras have zoom lenses of 3x giving a focal-length range of
approx 35 mm to approx
105 mm in 35 mm camera terms.
Note: The lenses fitted to Compact Cameras are not designed to a single
'format' as are the lenses
for 35 mm cameras. The actual focal lengths of Compact Digicam lenses for a
given magnification are
much smaller than the equivalent 35 mm lens.
For example, the minimum focal length of an Olympus Camedia C-700 Ultra Zoom
lens is 5.9 mm while
the minimum focal length of a Nikon Coolpix 4500 lens is 7.85 mm.
However, both lenses have a minimum focal-length equivalent to 38 mm in 35 mm
camera terms in spite
of the differences in the two digicam lens 'formats'.
To make it easier for 'consumers' to imagine the 'power' of a digicam lens it
has become common
practice to quote 35 mm equivalents. These figures can usually be found in the
manufacture's
specifications for the particular digicam model.
No Compact Digital Camera is fitted with a 600 mm (35 mm equiv) lens let alone
an 800 mm one.
The most 'powerful' Compact Digicam lens which I am aware of is fitted to the
Panasonic models:
DMC-FZ10, DMC-F22 & DMC-FZ1.
Not all of these models may be currently in production.
This lens has a zoom ratio of 12x giving an equivalent of 35 mm to 420 mm.
Several other manufactures have digicams with zoom ratios of 6x, 7x and 10x
giving equivalents of
more than 200 mm and less than 400 mm.
These telephoto 'powers' are well short of my absolute minimum requirement of
600 mm but some of
these cameras can be fitted with Teleconverters to increase the magnification
power.
Teleconverters are supplementary lenses which can be added to the front of a
fixed-lens camera
usually by means of an adapter tube which screws into the camera body and over
the standard lens.
The teleconverter is not normally fitted directly to the camera lens in modern
digital cameras.
Teleconverter lenses will tend to degrade the quality of the recorded image
depending on the quality
of the lens used. To limit the amount of degradation the magnification power of
the teleconverter
recommended by a manufacturer for a particular camera is usually limited to
1.4x or 1.7x. Thus a
focal length (equivalent) of 350 mm becomes 490 mm or 596 mm which is now
approaching the minimum
focal-length required for effective bird-photography.
Some people have even used zoom type teleconverters with up to 8X magnification
on some digital
compact cameras with a certain amount of success but I would suggest 2x would
be a more practical
limit. I use a 2x teleconverter on an Olympus Camedia C-700 Ultra Zoom (10x
zoom) which gives an
equivalent maximum focal length of approx 780 mm.
(The Panasonic DMC-FZ10 fitted with the approved 1.7x Teleconverter (Tcon)
would have maximum focal
length of 714 mm.)
If greater magnification than that is required from a Compact Digital Camera I
would suggest that
the system of Digiscoping be employed.
(For more information on Digiscoping see that section on my web-site at:
http://users.tpg.com.au/inglisrc click on the Digiscoping link.)
A problem which can rear its ugly head when using high-powered lenses and
especially when
supplementing those lenses with teleconverters is 'Chromatic Aberration' (CA).
CA is often referred to as 'purple fringing' because of the purple edges to
bright parts of the
image although there can also be 'green fringing'. The problem is caused by the
lens 'splitting' the
primary colours of the light entering the lens and not 'recombining' the same
colours accurately
when they leave the rear-end of the lens. This is a design problem requiring
special lens materials
and construction techniques to overcome. Lenses designed to minimise this
problem are referred to as
'Apo-chromatic' lenses (APO for short) and are expensive so only the better
quality (and higher
priced) Compact Digital Cameras are likely to have such lenses. You will need
to read the camera's
specifications very carefully to determine if it has an APO lens. It probably
will not but there are
some models with this type of lens. Look for a reference to 'ultra-low
dispersion lens' (UD) or
fluorite glass (note the spelling, not 'flourite'; there are no lenses made
from flour that I am
aware of). If a particular model is using high-grade lenses I am sure the
manufacturer will want you
to know about it.
The recently announced Canon PowerShot Pro 1 (7x zoom, 8 Mega pixel CCD sensor)
has a UD fluorite
lens and I believe some of the later models of the Olympus Camedia C-7xx Ultra
Zoom range also have
some UD glass elements.
Image Stabilising:
There is a great desire amongst many new bird-photographers to want to take
photos with the camera
'hand-held'. The problem is to hold the camera steady. Because of the
relatively small apertures
that these zoom lenses are capable of at the high end of their range it is
difficult to get enough
light through the lens to allow for high enough shutter speeds to overcome
'camera shake'. To
overcome this problem a few consumer Digicams have employed an 'Image
Stabiliser' (IS) mechanism.
Usually this mechanism is built into the lens but, rarely, it can be built into
camera body.
Image Stabilisers are intended to counter the movement of the camera and not
the movement of the
subject!
Some manufacturers that have employed IS in past camera models have deleted it
from later models.
This could be because it can cause problems when trying to photograph moving
subjects by 'panning'
the camera (the stabiliser tends to go crazy trying to correct for the movement
of the camera) or it
could be to cut cost and to reduce the size of the lens.
The recently announced Canon PowerShot S1 IS (10x zoom, 3.2 Mega Pixel CCD
sensor) has an Image
Stabiliser (or Stabilizer as they call it).
The Panasonic DMC-FZ10 (12x zoom, 4 Mega Pixels CCD sensor) also has an Image
Stabiliser.
The general 'rule' for shutter speeds when 'hand-holding' is to place a 1 over
the focal length
being used thus the shutter speed for a 300 mm lens would be 1/300 sec. Image
Stabilisers are said
to allow a shutter speed a couple of 'steps' below that theoretical figure.
I have not had personal experience with a Compact Digicam fitted with an Image
Stabiliser but the
results I have seen seem to show it works well for stationary subjects.
Fortunately, the IS can usually be switched off for those times when it is not
desirable.
To attempt to overcome camera shake I often mount my digicam (and D-SLR) on a
custom-made shoulder
stock.
To be continued.....
Cheers
Bob Inglis
Woody Point
Queensland
Australia
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