Compact Digital Cameras and Bird-photography (continued).
Focus, shutter response and other things:
Compact Digicams are, primarily, 'point-and-shoot' cameras which means that
just about everything
that can be automated is. Sometimes there are so-called 'manual' facilities
which usually turn out
to be 'manual' only in that a specific setting is selected from a number of
choices on an electronic
menu displayed on an LCD screen.
Zoom:
Most Compact Digicams have a zoom lever/rocker-switch on the body of the camera
but a small number
have a 'zoom-ring' on the lens assembly. It seems that in only a couple of
cases the zoom-ring is
actually mechanically connected to the lens while in most cases the lever or
ring controls a motor
which drives the zoom.
Don't bother asking the sales person what the set-up is for a particular
camera: you would probably
be better off searching the manufacturer's specifications for that sort of info.
The speed of the zooming action is usually variable according to the pressure
applied to the zoom
'lever'. Zoom action is not particularly fast in most cases but the recently
announced Canon
PowerShot Pro 1 is claimed to use an Ultra Sonic Motor (USM) which has a faster
action than the
'normal' type. This type of motor is more often seen in good lenses for SLR
cameras.
Focus:
The prime focusing method in all Compact Digicams is an automatic system which
seeks out points of
obvious contrast such as distinct lines or sharp changes in colours.
Focus can be gained from a large area of the viewed scene or from a spot in the
scene.
The percentage of the scene which is evaluated can be regulated in various ways.
This system is generally quite good and is mostly accurate and reliable except
when:
- There is very little contrast;
- There is low light;
- There are objects in the focus zone between the camera and the subject.
The last problem is the most common and troublesome for bird-photographers with
the second problem
not far behind.
The birds you want to photograph often seem to want to frequent bushy
environments where there is a
distinct lack of light.
To overcome these problems a manual system of focusing would be handy but, in
most cases, the system
provided is manual only in that you are able to select a setting from a list on
an electronic menu
displayed on an LCD screen (I think I said that before somewhere). Menu-driven
manual focus systems
are slow and cumbersome to use.
Some of the Minolta Di'MAGE models with high-powered zoom lenses appear to have
a truly mechanical
focus ring on the lens while the aforementioned Canon PowerShot Pro 1 has a
focus ring on the lens
but it controls the aforementioned USM motor.
Any manual focus system using menu selections is a waste of time for
bird-photographers and it would
be best for the intended user of the camera to properly test any focusing ring
to see if it was
really suitable.
I have not had 'hands-on' experience with a digicam equipped with a genuine
manual-focus ring so I
am not able to say how effective they really are...but..I would prefer to rely
on the auto-focus
system anyway.
And I would look for a camera which has true 'spot-focus'.
Spot-focus should minimise the area being used for focusing and thus help avoid
focusing on the
wrong thing in the scene.
A desirable focus feature would be 'continuous-focus' (sometimes called
'follow-focus').
This enables the lens to remain focused as the subject is 'tracked' and while
the shutter button is
half pressed. Continuous-focus may not always be available in all shooting
modes and can be a heavy
drain on battery power.
Don't expect blindingly fast focusing from any compact digicam.
And it can take a bit of practice working out all of the different focussing
methods and which is
most suitable for the occasion.
Exposure:
Once again, exposure (aperture and shutter speed) is normally expected to be
done 'automatically'
and I think this is usually the best way to do it, at least in the beginning.
However, the camera models of most interest to bird-photographers will have a
number of operating
'modes' which will allow the operator to 'manually' (a combination of those
electronic menus and
external switches) select aperture and/or shutter speed.
White-balance (the 'colour' of the ambient light: daylight, cloudy, flash etc)
can normally be set
automatically or manually; auto usually works well for most occasions but
'picky' photographers can
usually also create and store 'custom' white-balance settings.
It should be noted that cameras which record the image as a JPEG (JPG) file
usually perform some
'enhancement' of the image at the same time. This can mean that the same
'scene' taken at the same
time by two different brands and models of cameras using the same exposure
settings can result in
images with slightly different colour tones and contrast. Compact Digicams
always perform some
'sharpening' (makes the image look more crisp but is not actually anything to
do with focus) when
storing images in JPEG format.
Shutter Response:
This is probably the most important feature as far as bird-photographers are
concerned!
As birds are often quite active little blighters it is best to have a camera
which 'responds'
quickly when the shutter button is pressed.
Up until recently this was a rare thing in most Compact Digital Cameras. Most
Compact Digicams have
had a bad reputation for excessive 'shutter-lag', i.e., the time between when
the shutter button is
pressed and when the shutter actually operates.
Note: This has nothing to do with the actual shutter speed.
Shutter-lag can range from a fraction of a second to several seconds and is
caused by the camera
having to carry out a number of functions after the shutter button is pressed
and before the shutter
can be allowed to operate.
Some of these functions include:
- Checking white-balance (see above)
- Focusing
- Setting aperture and shutter speed
If the camera is being used in a full-auto mode and the light is not ideal
these functions can take
quite some time which often results in a missed shot, the bird having flown!
It is possible to reduce this time somewhat by using some 'manual' settings
(aperture and/or shutter
speed) but the real problem is usually the focusing speed.
The auto-focus works best when there is good light allowing aperture sizes
greater than approx 5.6,
so the story goes.
ISO settings:
Film has a chemical coating which reacts to light and records an image. This
coating contains
granules of different chemicals the size of which varies according to the speed
of the film. Fast
film (film which reacts to low light) has larger granules which can cause a
'grainy' appearance to
the image.
Film cameras have settings (auto or manually set) to cater for film of
different ISO values.
Digital cameras can also be adjusted for different light levels but this is
done by amplifying the
output signal of the sensor. Like any electronic device, if the signal power is
boosted above the
optimum, 'noise' (electronic static) is likely to be induced into the output
signal. This noise is
then recorded in the final image and is commonly but wrongly called 'grain'.
Digicams have user-adjustable amplification values which have been given ISO
ratings but the degree
of 'grain' observable at each setting is usually much lower than the equivalent
for film cameras.
Electronic sensors are designed for a specific 'ISO' rating which usually is
deemed to be ISO 100
or, sometimes, 200 and rarely 50.
Most digicams produce very little difference in 'grain' between ISO 100 and 400.
The factors causing 'noise' are varied and really depend on the 'quality' of
design and manufacture
but it should be noted that small sensors with very high pixel counts are more
susceptible to noise
than larger sensors with the same pixel count or the same size sensors with
less pixels. Sensor
design is very complex and good sensors with high pixel counts and low noise
are very expensive.
Most Compact Digital Cameras have small sensors and the number of pixels
(picture elements) is
increasing, i.e., the latest models have 8 Mega pixels.
Shot rate:
This is the number of shots per second which the camera is capable of.
In most cases this is determined by the rate at which each shot can be written
to the storage card.
This write-speed is, in turn, determined by the size of the image file.
The size of the image file depends on the 'quality' setting being used.
For bird-photography the quality setting should be the highest available.
Quality setting can be restricted by some shooting modes such as 'movie mode'.
It can take almost 30 seconds for a Nikon Coolpix 4500 to write a maximum
quality TIFF file to the
media storage card.
During this time the camera cannot be used to take another shot.
This time can be reduced if media cards capable of being written to faster are
used but generally
the camera limits the maximum write speed.
Most cameras have a 'burst' feature which allows a certain number of shots to
be taken and stored in
an internal memory before they are written to the media storage card. Even so
there is a limit to
the number of shots in a burst before the camera will stop and no further shots
can be taken before
room has been made in the memory.
Shots taken in burst mode may not be the maximum image quality.
Check this feature carefully before deciding on a purchase.
Sensor Resolution:
This is the number of Picture Elements (pixels) on the sensor.
These days there has to be truth in advertising so the stated pixel count is
now the number of
pixels actually used to record the picture.
For bird-photographers a sensor with at least 3 mega pixels is desirable but 4
or 5 mega pixels
would be better. The 'larger' sensors will produce a larger 'on-screen' image
which will allow
better 'cropping' of the picture. Effectively, larger sensors give an on-screen
magnification
similar to using a more powerful lens.
The new 8 mega pixel sensor should be sensational if the potential problem of
increased noise has
been overcome. A digicam with an 8 mega pixel sensor and a 7x zoom may even be
a better proposition
than a 4 or 5 mega pixel camera with a 10x zoom lens.
RAW file format:
The 'normal' file format which Compact Digital Cameras use to record images is
JPEG (or jpg/JPG).
JPEG is a 'compressed' format which introduces some loss of information but
depending on the degree
of compression this may not cause any noticeable loss of image quality...unless
there is a
requirement for maximum image quality.
Some cameras also offer the 'loss-less' TIFF format. TFF files are much larger
than JPEG but contain
much more data about the image.
However, both TIFF and JPEG are 'processed' files which contain less
information than was recorded
by the camera's sensor. Having access to this extra data can be an advantage
when the very best
quality image is required as an end product.
To provide the photographer with all of the information captured by the sensor
a file type called
RAW is also provided by some cameras.
The term 'RAW' is a generic one as there is no fixed standard for RAW files.
This means that each
camera manufacturer may use their own 'version' for creating the RAW files in
their cameras. As a
consequence, very few image-file reader programs are able to 'read' all RAW
files so cameras which
provide RAW files come with a dedicated RAW file reader usually with some
limited processing tools.
The latest version of Photoshop (CS) is equipped to read RAW files from a
number of camera models
with more being added progressively.
A 'plug-in' program for Photoshop 7 is also available for a fee.
There are a couple of stand-alone RAW processing applications available on the
WWW but I have only
had experience with the Photoshop one.
RAW files are bigger than JPEG files but smaller than TIFF files.
Bird-photographers with a serious intent would be wise to consider a camera
which can record RAW
files. The RAW file contains 'raw' data about the image and provides the
'digital-darkroom' operator
with more data to work with than either JPEG or TIFF files.
Although this will not help re-focus an out-of-focus image it does allow for
much more
precise/creative processing which should result in a better final picture.
RAW files are an ideal format for archiving the original image file.
LCD screen:
The simple story with LCD screens is that most are virtually useless to use
outdoors in strong
sunlight.
LCD screens with high zoom review capabilities can help to check if focus and
composition are
satisfactory and if that bird was actually 'captured'.
Check how effective they are by taking the camera into open sunlight before
purchase.
But remember, there aren't too many really good ones so far. New technologies
promise better
screens.
Electronic Viewfinders:
EVs are a poor substitute for either optical viewfinders or Through-The-Lens
(TTL) penta-prism
viewfinders (found on good SLR cameras). But more and more Compact Digicams are
using them.
It is more than likely that any Compact Digicam suitable for bird-photography
(other than
Digiscoping) will have an EV.
My experience of EVs has been that they can:
- Have very low resolution making it difficult to check focus;
- Show a very poor quality image;
- Have a slow 'refresh' rate which can be annoying when trying to 'track' a
moving subject;
- Be 'dark' when used in low light situations.
- Have significant 'black' or 'frozen' periods when the shutter is pressed.
In fact, the only attractive feature I can find is that they effectively give a
'Through-The- Lens'
view.
This ends the notes on Compact Digital Cameras. It may seem to be rather
detailed and long-winded
but it actually is only a small amount of what there is to know!
Next: Bird-photography with Digital SLR cameras.
Cheers
Bob Inglis
Woody Point
Queensland
Australia
http://users.tpg.com.au/inglisrc/
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