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Canon Powershot A640 Digital Camera Review
by AKAJohnDoe -  12/6/2006

The Canon PowerShot A640 is a 10MP digital camera with a 2.5” LCD, a 4x optical zoom lens (35-140 mm equivalent), with an additional 4x digital zoom for 16X overall. It uses 4 AA batteries and stores images as JPGs on SD/MMS/SDHC memory cards in several selectable compression and recording modes.

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The Canon PowerShot A640 is a first in an A-Series camera, breaking into 10MP resolution. And if that were not enough, there is the 16X digital zoom, the 21 shooting modes, and the swivel-mounted 2.5 inch LCD monitor.

As you can no doubt tell, I like this camera. Let me tell you more.

Handling and Controls

The A640 is pocketable; however, it is not an ultra-compact model, so choose your pocket with some forethought. This is mostly due to the 4 AA batteries that power it. I found the camera easy to hold and to use and was immediately comfortable with the feel and control layout. The battery chamber creates a natural handgrip and virtually eliminated the concern of accidentally pressing buttons common on smaller cameras.

The controls are logically laid out. Across the top there are the shooting modes wheel - common to many Canon cameras, shutter release, zoom controls, and power button. The LCD screen and menu controls are on the back, and the battery chamber and memory card slot (which is inside the battery chamber) are on the bottom.

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Settings

I am consistently impressed and amazed by how much function Canon squeezes into such small packages and how each successive generation builds upon the previous generation with even more function. The PowerShot A640 is no exception. While it can be used right out of the box, taking some time to familiarize oneself with the extensive feature set is time well spent.

Shooting Modes

In addition to the now traditional shooting modes such as auto, program, aperture priority, and shutter priority there is a very welcome and fully functional manual mode and a very cool custom mode. Custom mode allows you to define and store a set of your own personal settings for immediate recall. Additionally, there are several pre-set modes. Portrait, for example, is pre-programmed to keep the subject in sharp focus and blur out the background, making your subject stand out better. Landscape mode is designed to achieve the greatest depth-of-field to make near and far objects equally in focus. Night Scene exposes for the background and utilizes fill-flash for the foreground. This is useful for those vacation or travel pictures. There is also a built-in Stitch Assist mode for alignment of panoramics and a Movie mode that works in VGA/QVGA at 30/15 frames per second (fps) for up to 1 hour or 1GB or in QQVGA at 15 fps for up to 3 minutes. The dimensions of each format are: VGA is 640x480; QVGA is 320x240; and QQVGA is 160x120.

Finally, there are 8 special scene modes and 2 other modes. The special scene modes are essentially pre-programmed solutions to some of photography’s trickier situations, automatically setting the camera for optimum exposure. There are Special Scene solutions for the following subjects and situations: Foliage; Snow; Beach; Fireworks; Underwater (better purchase the optional waterproof case); Indoor; Kids and Pets; Night Snapshot. The remaining two modes are Color Accent, which allows a single color to be retained while the remainder of the image is made monochrome (B&W), and Color Swap, which switches two colors in the image.

Under the options menus, there are additional photo effects that may be selected. These are called My Colors in the menu and include such choices as: Vivid; Blue; Vivid Green; Vivid Red; Neutral; Sepia; B&W; Positive Film; Lighter Skin Tone; Darker Skin Tone; and Custom Color. While each of these could of course be done in post-processing on a computer via software, it is again a technological achievement by Canon to have this capability in-camera. I was particularly fond of the Vivid and Positive Film settings, using them in my Custom mode to simulate the punch of color of slide film. I have always liked the way those Kodachrome and Velvia transparencies jumped out at me!

White Balance

The white balance may be set to automatic, several different presets, or a custom setting. I found the presets that I tested to be quite reliable. The daylight, cloudy, and tungsten were dead-on. As there are so many different fluorescent light sources, often intermixed, it is best to take a sample image to ensure that the results are as expected. The A640 takes this into account by providing two such settings: Fluorescent and Fluorescent H. There is also an underwater setting that I was unable to test. I will revisit white balance later in the review in the "Real World Use" section.

Sensitivity

The Canon PowerShot A640 sports a Hi-ISO equivalent to ISO 800 for fast action or low light situations. The sensitivity may be set to Auto, High ISO Auto, or manually to 80/100/200/400/800. For general use in normal light with expected print size being usual photo size, I found both the 200 and 400 to be good; not so slow as to affect image quality due to blur from camera shake and not so fast as to introduce noticeable noise (grain in film terms). There will be more on this topic later in the review as well.

Metering

A feature found on the A640 that is not commonly found is a spot meter setting. The spot meter can be fixed to the center AF frame, linked to the active AF frame, or manually selected. Other metering options include evaluative and center-weighted average.

The A640 allows for exposure compensation in 1/3 stop increments over +/- 2 stops for those of you so inclined.

Compression and Recording

Image compression in the A640 may be set to Normal, Fine, or Superfine. This, in conjunction with the setting for the number of recordable pixels, yields 16 possibilities, plus the movie settings. The trade-off being between file size and image quality. While it is convenient to have all these choices, particularly when taking picture for a specific purpose (web publishing or email are good examples of when to use a smaller resolution), I find that for me the answer is always to get a bigger memory card. I can always downsize later in the computer, but can never add information that was not initially captured. Therefore, taking images at the highest settings (Superfine/Large) provides me with the greatest flexibility.

Real World Use

I unpacked the camera, attached the wrist strap, inserted the batteries and memory card, and sat down with the manuals for a quick once over of the controls, functions, and features.

The manual comes in two volumes, a Basic and an Advanced booklet. The Basic manual is intended to get you up and running and the Advanced is supposed to have more detail. It seems to work that way. However, I would have liked it had the Advanced manual also included the information contained in the Basic manual. It was inconvenient to have to flip back and forth.

I carried the camera with me and had the opportunity to use it in a variety of lighting. Autumn in the Northwest provides changes at least daily, if not hourly.

The initial shots were in and around my yard of the changing foliage. The Special Scene setting was ideal for this. It was here when I discovered that this effect could be further enhanced, in camera, by applying the photo effects of Vivid and Positive Film under the My Colors menu item. The images made using these settings really do look like slide film.

canon powershot A640 sample image
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canon powershot A640 sample image
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I also picked a cloudy day (that became quite dark and rainy) to walk around a university campus. The long rows of trees, gothic architecture of the Quad (seems every university has a Quad, doesn’t it?), and atmosphere of the campus are a challenge for any camera and a cornucopia for the photographer.

canon powershot A640 sample image
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canon powershot A640 sample image
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canon powershot a640 sample image
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The light was constantly changing, so at first I set the white balance on auto to let the camera determine the optimal setting. The A640 performed quite well in this mode. However, as the day progressed I began to utilize the specific settings appropriate to daylight or cloudy. I believe that I prefer these later images. When the light is obviously one or the other, and not changing rapidly, selecting the specific appropriate white balance seemed to yield better results.

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To further evaluate white balance I took pictures of highlighting markers against both a white and a black background. While this is a subjective test, and difficult to accurately interpret without a calibrated monitor or printer, I feel that it still has merit since most folks likely do not calibrate their printers nor their monitors. They simply expect colors to closely resemble what was really there. This Canon PowerShot A640 performed admirably. Having the actual markers, I can see that the green marker is not quite true to color, but consistent.

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On a bright, sunny day, I walked around a local wetlands park to check out the autofocus on the turtles and cattails. This is where selectable AF points come in very handy.

canon powershot a640 sample image
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canon powershot a640 sample image
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canon powershot a640 sample image
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In taking pictures at different sensitivities (ISO, or “film speeds”), I found that without flash or a bright ambient light source I had difficulty with camera shake at the low end speeds of 80 and 100. I could often overcome this by choosing the Tv setting and a shutter speed of 1/250th second or faster or by using the Kids and Pets mode. In the Auto or P modes this was not the case. This seems to be due to two factors: Slower shutter speed and shutter delay. The shutter of the A640 does in fact respond quicker than other point & shoot cameras I have used, but it is not instantaneous.

At the high end (ISO 800) some digital noise (“grain”) is apparent. However, this is still a very welcome feature as there are many low light situations when flash is not appropriate or fast action subjects where the extra speed is necessary. Just don’t expect to make poster sized prints.

In the sensitivity middle ground (ISO 200, ISO 400) is where the A640 really shines. No photographer shake, all the settings and features are available, and 10MP of capture. I found the A640 to be a delight to use in this way.

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canon powershot a640 sample image
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One thing I did notice is that I could not locate the ISO at which the image was taken in the recorded data associated with the picture. Puzzling.

I generally prefer using an optical finder, which the A640 does provide, but the A640 also has a 2.5 inch Vari-Angle LCD monitor. This makes grab shots or quick snapshots easy, and also simplifies close-ups and self-portraits. The LCD can be turned back to face the subject and show a non-reversed image and the self timer set. No more shots of the photographer not quite making it into the family picture!

The flash is built-in, with no hot shoe for an external flash. Nevertheless, it is sufficient to overcome the effects of light coming in through a window to fill in and provide definition for this Dale Chihuly glass sculpture in a downtown Seattle building.

canon powershot a640 sample image
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canon powershot a640 sample image
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Specifications

For the full specifictions, see this page at Canon's site.

Pros

Cons