Canon A40

Mode: AUTO / P / M
Resolution / Compression
AiAF and focusing
Focus Lock and Metering
White Balance
Macro / Snapshot / Infinity
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Canon A40. Lenses/Filters. Equipment. General Information. Useful Software. Troubleshooting



The camera usually selects a wide aperture to give the fastest shutter, and so avoid camera-shake. (There's no way to tell it, "it's OK, take as long as you like, I'm using a tripod").

However, if the the conditions are very bright, it will switch to a narrow aperture.

I use Auto very little. I take most shots in P mode these days, without the AiAF, and where I know I'll get the white balance and ISO that I select.

Program Mode

In Program mode, exposure compensation and light metering modes are there to give quick but minimal control over an otherwise automatic exposure.

I started out using Manual mode, and only after a time gradually began using Program mode more often. Now I mostly use Program mode, and only slip into Manual mode for the odd, unusual, tricky, or extreme shots.

Manual Mode

I switch to Manual for longer exposures, perhaps at night, or for a shorter exposure perhaps with flash to freeze motion, or to select a narrow shutter for increased DOF for close-ups.

The shutter can be varied between 1/1500 second to 15 seconds.

In general, 'F-stop' is used to refer to the setting of the aperture, and the higher the number, the smaller the aperture. The usual sequence of F-stops is 1.8, 2.8, 3.5, 5.6, 8, 11, 16 and 22, and each increase in F-stop lets in half as much light as the previous one.

For each zoom setting on the A40, there is a choice of two aperture settings, as shown in the following table:

Focal length
35mm equivalent
5.4mm 35mm f/2.8 f/8
6.6mm 43mm f/3.2 f/9
7.8mm 51mm f/3.5 f/10
9.4mm 61mm f/3.5 f/10
11.3mm 73mm f/4 f/11
13.4mm 87mm f/4.5 f/13
16.2mm 105mm f/4.8 f/14
(Data complied by IanJ of the 'Canon PowerShot A-Series Users Group')

Notice that there's roughly three full F-stops between the two apertures available.

What settings to use will vary depending on how much light is available. The only rule of thumb that I know of for calculating exposure is for objects lit by bright sun ... i.e. the 'sunny 16 rule' (see").

In other conditions, and without a light meter, it's very much a case of trial and error. However, for faster exposures (less than 1sec) the LCD is quite good at showing beforehand how the picture will look. For longer exposures, take a few practise shots first, adjusting the shutter and/or aperture until it looks about right.. (In reviewing shots on the LCD, I find I need to hold the LCD almost horizontal to see how the picture really looks ... if I hold it too vertical, it looks lighter in the LCD than it actually is ... I've underexposed many shots that way, because I thought the test shots looked OK in the LCD.)

If the exposure is too long, e.g. for a moving subject, the shutter time can be decreased by using flash or increasing ISO, but both of these have drawbacks.

At shutter speeds of 1.3 seconds or more, the camera will perform internal noise reduction. This may take a few seconds.
  1. I just tried a couple of low-light photos indoors - it's late morning on a very dull day with two puny 60 watt bulbs - and had to use 0.5sec at f/2.8, and as much as 2.5sec at f/8, to get a decent exposure.
  2. For longer night time exposures - trails of car lights, etc - I've used something like 3.2 sec at f/8 (with ISO 50) ... as long as there was something on which to rest the camera.

Aperture and DOF

To make a subject stand out from the background, the usual method is to reduce the depth of field, so while the subject is in focus the background blurs.

I understand achieving a shallow DOF is difficult with most digital cameras. The reason appears to be very short lenses, and small CCDs (compared to the size of film) giving less magnification.

Depth of Field Calculator for Canon A40
Lens focal length . . . zoom setting
Selected aperture
Subject distance (Meters)

Hyperfocal distance for this lens/aperture combination.
Near limit of acceptable sharpness.
Far limit of acceptable sharpness.
Total depth of field.

Free JavaScript provided by The JavaScript Source

At wide angle (5.4mm), with the wide aperture of f/2.8, for a subject distance of 4 meters, you'll see that 'Far limit of acceptable sharpness' is actually infinity. So the background will always be in focus.

However, if you try it with full zoom (16.2mm), with a wide aperture of f/4.8, you'll see the 'Far limit of acceptable sharpness' is now something just over 7 meters. So the background will begin to blur if one can place the subject far enough away from it.

Not enough depth of field is not normally a problem, but this can happen when taking close-up or macro photos. For the greatest DOF, one needs the widest setting (no zoom)  with the narrowest aperture (f/8).

However, with or without close-up lenses, one gets closer to the subject by zooming in. So it's more a matter of what one is going for, and balancing close-up ability with DOF. Either way, use the narrowest aperture.

Adding a wide-angle lens should increase the DOF even more. 

  1. The A40 has a circle of confusion of 0.006mm
  2. There's a more comprehensive DOF calculator at
  3. See also <>, and particularly the following section on limiting DOF - <>


  1. I always shoot photos at highest resolution and lowest compression. One can always reduce resolution or increase compression afterwards, but you can't get it back if it's not there to start with. The price of cards is coming down, so lack of space shouldn't be too much of an issue.


  1. If the subject is not moving - or if a little motion blur would enhance the photo - I'd rather leave ISO on 50 or 100, brace the camera somehow, and take a longer exposure. I generally have ISO set to 50 for P and M. But of course, if one needs the fastest exposure possible in low light conditions, and if using flash, which can be a bit harsh and flattening, is out of the question, then increasing the ISO becomes a useful option. But it's not something I change very often.
  2. Although it only goes up to ISO 150 with ISO set to AUTO for P mode (see bottom of p.79), I got the impression that one or two of my low light photos in Program mode turned out a bit grainier than I would have expected, so I've tended to set it explicitly, rather than use the AUTO setting.

AiAF and focusing

The AiAF system uses three focusing points, and normal AF uses just one.

The A40 AF system focuses by detecting vertical lines of contrast. This is why sometimes, if there are more horizontal lines of contrast, you might find it focuses easier if you turn the camera through 90 degrees.
  1. I have AiAF turned off. Of course it still uses the three AiAF boxes in Auto mode, and that's fine, but in Program and Manual mode I prefer to have more control over focusing.

Focusing - low light

The camera requires contrast, and the sharper the better, to focus. So in low light conditions it's become second nature for me to line up an edge of some sort in the focus box.

The camera also finds it more difficult to focus when zoomed, so try taking it out of zoom.

Finally, try turning the camera sideways - it will often find more definition on which to focus when oriented vertically.

Don't forget that you can also try focusing on something else at the right distance, and then use 'focus lock' and recompose to get the picture you want.

Focusing - low contrast

Trying to get close-up shots of something uniformly coloured or furry like a cat, what I'd do is:
Once (if) I'd managed to focus, I'd use focus lock if necessary to recompose the picture - but I still find that a bit fiddly, so I'd rather not .

Focus Assist Light

This is not as helpful as one might have hoped. It doesn't have much reach, and is not particularly bright.

It only really works if the subject reflects back enough light (gloss finish, glass, metal), and creates enough of a contrast within the focus square, for the camera to focus. However, I found that a tiny glint on the edge of a picture frame was enough to focus in almost complete dark conditions.


The camera will set the exposure according to the metering (see p.74) - this happens when you half press the shutter.

What this means generally is that if you point at a dark object, the camera will increase the exposure and give a lighter picture, and if you point at a light object, the camera will decrease the exposure and give a darker picture.

So if your pictures are coming out too dark, try metering on dark areas rather than light ones.

In Evaluative metering mode, the camera does some complex calculations that take into account not only the subject but also the lighting round about, so you get an average sort of exposure that will hopefully not be too under- or over-exposed anywhere.

In Spot metering mode, the camera will meter on just the center spot. This will give you more precise control over the metering.
  1. Metering is generally set to Evaluative. I only use Spot metering in more complicated circumstances, where the right exposure is difficlt to achieve otherwise. I've experimented with metering, but I admit it's something I tend to forget about when taking the 'real' pictures. This is perhaps one of those things I'll get around to using more effectively when I'm not having to think consciously about all the other more obvious things.
  2. In Program mode the exposure can also be adjusted using EV compensation (see p.75)

Focus Lock and Metering

Half pressing the shutter locks both focus and exposure, so you can recompose the scene if necessary.

But the camera is even more versatile, in that one can use focus lock 'Method 2' (p.72) to lock the focus, then recompose and half press the shutter to lock exposure, and then recompose again if so desired.

So focus and exposure can be locked independently.

To see how this works, try the following:

In Program mode, first switch to spot metering just so you can see the effects more easily ... this works with evaluative metering as well, but the effects are not so extreme.

  1. Looking at the LCD screen, point the camera at, for example, a light bulb and then away, and then back again - and you will see the brightness of the whole image alter as the camera meters on the subject and adjusts the exposure.
  2. Now point away from the light bulb, and half press the shutter. Still holding the shutter half pressed, point at the light bulb. Notice that the image stays bright, and the light bulb looks over-exposed.

    Alternatively, point at the light, half press the shutter, and point away from the light - the image is now too dark because metering, and therefore exposure, has been been fixed on the light.

    - this is how one normally locks the focus, but it locks metering/exposure as well.
  3. Now point away from the light bulb, half press the shutter, and use focus lock 'Method 2' by pressing the macro/snapshot/infinity button. Release the shutter. 'AFL' should appear on the LCD to show this has been done.

    Now if you point at the light, though focus has been locked, you will see that metering is still taking place - the image on the LCD alters as you move towards and away from the light.

    - so the 'AFL' method locks the focus, but releases the metering.
  4. Still with that same 'AFL' on (locked on the dark subject), point at the light and half press the shutter. Now still holding the shutter half-pressed, point the camera away from and towards the light, and notice that metering has become fixed again.

    - so now we have focus fixed (using 'AFL') on a dark subject, and metering fixed (half-pressed shutter) on a light subject.
  5. At this point we can now aim the camera wherever we wish for the actual composition of the photo.


Your subject is in front of and to one side of a computer screen, which is on and very bright.

  1. Point the camera at the subject and lock focus using 'AFL'.
  2. Tilt or swivel the camera towards the computer screen until the exposure looks about right in the LCD, and half press the shutter.
  3. Holding the shutter half-pressed, tilt or swivel the camera back until you have the composition you desire, and fully press the shutter.

The result should be that the computer screen in the background is not over-exposed, while the subject (not necessarily in the centre of the photo) is the thing which is in focus.

Evaluative metering tries to get the best exposure for the subject, taking into account the surrounding conditions, and this by itself is probably sufficient a lot of the time.

But it's nice to know that other options are available when required.

White Balance

  1. I do pay attention to white balance ... setting to tungsten, cloudy or sunny in the right circumstances makes a big difference to the colour balance.
  2. For night shots, I'm finding that AUTO, Tungsten or Fluorescent (the first one, and not Fluorescent H) usually works best ... Cloudy seems the worst setting for night shots.
  3. High pressure sodium street lights are a problem - 'Fluorescent' looked OK in the LCD, but when I got them home there seemed to be quite a yellow cast to some of them, which I reduced somewhat in PhotoShop.



You can take close-ups in whatever shot mode you like ... the AUTO, Program or Manual modes all have the Macro Mode setting (p.55 of the manual).

The spec for the A40 says that in Macro mode, the minimum focusing range is 16cm at wide angle and 26cm at full optical zoom, though I find the borderlines are more like 11.5cm and 20cm, as measured from the front of the lens.

Note, however, that one can get more of a close-up with 3x magnification at 26cm than with no magnification at 16cm, so it's more effective to zoom when shooting macros. So whatever shot mode you're in, switch to Macro, and zoom in fully.

(As well as magnifying, close-up lenses/filters allow you to get closer to the subject - with a +10 diopter close-up filter I find the minimum distances are about 5.5cm and 7.5cm.)

Snapshot / Infinity

My best understanding of these modes is that Snapshot restricts the focus to a certain range, but that they both provide a default focus distance if the camera doesn't manage to focus.

There are a couple of threads in the Canon PowerShot A-Series Users Group that investigate this at:

Chuck Martin finds that:

"The A40 restricts focus distance when in Snapshot mode. At 5.4 mm f 2.8, this range appears to be 5 ft to 10 ft. At 16.2 mm f 4.8, the range is around 8 ft to 16 ft. If no focus indication is given (no double beep) the A40 seems to default to the closest allowed distance, i.e. 5 ft or 8 ft.

"What Snapshot mode does not do:
It does not force focus on a near object. For instance with the zoom at 16.2 mm, if a subject at 8 ft is placed in front of a distant background, and the focusing square is positioned on the background, the A40 may succesfully focus on the background (double beep), leaving the subject out of focus.

"What Snapshot mode does do:
It will give a predictable focusing distance when the A40 is unable to focus, as in dim lighting. This could be very useful indoors. At 5.4 mm f 2.8, the depth of field when in Snapshot mode and focus is not successful (no double beep and camera therefore focused at 5 ft) is from 2.5 ft to 100 ft. At 16.2 mm and f 4.8, the equivalent range is from 6 ft to 12 ft. So indoors under dim light, put the camera in Snapshot mode, set the zoom from wide to medium and fire away. If the A40 focuses, great. If it doesn't, objects from a few feet away to 20 ft or so should still be in focus.

"I also have data for Landscape mode at 5.4 mm and 16.2 mm. Landscape appears to set the A40 to the hyperfocal distance. At 5.4 mm f 2.8, the A40 uses 6 ft as the hyperfocal distance. At 16.2 mm, it uses 25 ft. The corresponding closest in-focus distances are 3 ft and 12 ft. For those interested in depth of field tables and such, these data best match predicted hyperfocal and closest focus distances when a Circle of Confusion of 7 microns is assumed. Apparently, the A40 was programmed around the 7 micron CoC ...

"... when in Landscape even if the camera does not double beep you can go ahead and take your shot and be assured that everything within the depth of field range shown in the hyperfocal distance column of the depth of field table I published will be in focus. At full zoom of 16.2 mm and f 4.8 that range is from around 12 ft to infinity."


Digital Zoom

Digital zoom only works if the LCD display is fully on and not simply displaying settings.
  1. I usually have digital zoom turned off, so I can't go there accidentally when optically zooming.


Contrary to the chart on p.82 of the manual, in AUTO mode both 'Red eye reduction' and 'Auto' will be retained after power off. But in any case, in AUTO mode, the flash will always be on when you power on the camera. In Program and Manual modes, all available flash settings are retained, including OFF.

Flash Intensity

The intensity of the flash is determined by the feedback from the pre-flash, so that the flash is reduced if there is much ambiant or reflected light ...  for example, shooting against a light background.

In general, using Macro mode may reduce the intensity of the flash, but it's hard to find any consistent behaviour: different shooting modes have different effects, and if the flash is already reduced a lot, then it might even be fractionally brighter in macro mode.


In the sample shots below, I chose a darkish background so that the normal flash wouldn't be reduced by the camera too much (- shots were taken using ISO50 and auto WB).

The first examples are taken using AUTO mode, and the first one shows the object without any flash - i.e. quite low-light conditions.

The third shot, with Macro set, shows a very slight reduction in flash, but in brighter conditions it may even seem to be increased.
auto - no flash
auto + auto-flash
auto - flash
auto + auto-flash
auto - flash - macro
The next examples were taken in Program mode, using the auto flash setting. (The shutter turned out to be 1/60 seconds)

In Program mode, the exposure can also be varied using the +/- ev Exposure Compensation settings.
P + auto-flash
P + auto-flash
P + auto-flash
P+ -1ev
P + auto-flash
-4/3ev + macro
P+ -1ev+macr
The next examples are using Program mode and the Slow Sync flash.

The Slow Sync flash in Program mode seems to have a bigger reach, by combining flash with a slower shutter to take in more ambiant light. It also seems to produce less of a yellow colour cast than normal flash.

One can get a more interesting, less over-exposed, and perhaps less flattened, look when using flash by combining 'slow-synchro' with some negative exposure compensation.

The following shots turned out to have a shutter of 1 second, which is perhaps not so handy for moving subjects.

Note that just switching to Macro in the second photo seems to have little effect, but in other test shots I've seen a significant reduction in flash in similar circumstances ... it's not easy to pin down the exact circumstances.
P + slow-sync
-4/3ev + macro
In Manual mode with flash, even if you set it to less, the minimum shutter speed will be 1/500 sec, which is what I used for the following examples. The only way to reduce the exposure further is to select the narrow aperture setting.

In Manual mode with the macro setting, the flash is consistently throttled down significantly.
M + forced flash
M + forced flash + wide
M + forced flash
M + forced flash +narrow
M + forced flash
wide + macro
M + forced flash +wide + macro
M + forced flash
narrow + macro
M + forced flash +narrow+ macro
The exposure can be increased using the shutter setting, but in very low light conditions the exposure needs to be relatively long to make a difference ...
M + forced flash
narrow + macro (shutter 2sec)
  1. If the flash is still too strong, one might try using a translucent screen of some sort to cover the flash - this might give a softer effect.


The A40 has an internal memory of 4MB, and this is why movies are limited to 16 and 32 seconds.


The A40 AVI uses the common PCM 'Codec' (compressor/decompressor) for audio, so the sound should be fine in most players.

However, it uses Motion-JPEG (MJPEG) compression rather than the more common MPEG compression for video, which will only play in the Quicktime player unless an MJPEG codec is installed.

Note that Windows XP includes a form of MJPEG codec, and so the movies can be played in Windows Media Player under that system.

But for other operating systems, any players other than Quicktime will need an MJPEG Codec to be installed on the computer - i.e. a key for decompressing the MJPEG.

The currently available MJPEG codecs are Morgan-Multimedia, MainConcept, PicVideo, and the Lead Video Codec. (They are not freeware, but in some instances the decompressor may remain free when the compressor trial expires.) See 'Useful Software' page for further information.

But you won't be able to share your movies unless other users use Quicktime, or also have Windows XP or an MJPEG codec installed.

Therefore, the best method for sharing a movie is to convert it from an MJPEG AVI to an MPG.

Simplest solution - MJPEG to MPG

The most straightforward method I have found is to install an MJPEG codec, and use TMPGEnc to convert to an MPG. I find this his works with the Morgan-Multimedia codec, but not the LeadTools codec.

MovieMaker on Windows XP

Windows XP also has a small application called 'MovieMaker', which can be used to convert MJPEG AVIs to WMVs, and I believe from there one can convert to any other format..

To convert to AVI of another format

There are AVI editors and converters which can convert between different AVI formats, as long as the relevant codecs are installed. One might therefore convert the MJPEG to a DivX AVI (- DivX4 codec free, and DivX5 codec currently free for private use) or Xvid AVI (- Xvid codec free and open source).

From there one can then use a package such as TMPGEnc to convert the DivX AVI to an MPG.

Problems that may be encountered when converting from AVI to MPG

The camera appears to use a frame rate of 20 fps, and an audio frequency of 11.024 Hz. These are not standard, and some software may object to these.

For example, AVI2MPG1 is a command line based program (a GUI wrapper is also available from, and will object to the original 20 fps and 11.024 Hz.

Standard frame rates include 10, 12, 15, 24, and 25 fps. Depending up what software you use, you may need to interpolate a few frames to convert to e.g. 24 fps, before converting to MPG.

The standard frequencies are 11.025, 22.05, and 44.1 Hz. If you encounter a problem because of this, then you may need to strip out the sound and save it separately, before converting the video part to MPG, and then add the sound back afterwards.

  1. For information about A40 MJPEGs under Linux, see Ben Edgington's page at