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Tech Corner

E-Z Guide to Digital Cameras

- by Bill Boyle - N4UMS

The following is some information and explanation of terms that I've put together to help you with your new digital camera, or possibly help you decide which model to purchase.

How many pixels? -

The number of pixels a digital camera has, ultimately determines how large a print you can make with reasonable sharpness (resolution). If you plan to make only small photographs, this is not so important. Even a critical eye has trouble determining whether a 4 by 6 inch print was shot on a 3 megapixel (Mp) camera or an 8 megapixel model. However, the 8 Mp camera will allow much larger prints, while still holding resolution. Also, the larger the Mp number, the more able you’ll be to crop an image and still have adequate detail. When taking photos with any digital camera, you can set the camera to use the maximum megapixels or several settings less than maximum. I usually use the maximum setting, or maybe one setting down from maximum. If the resulting photos are too large for emailing, etc., I can always reduce them in my graphics program. I would avoid using the smallest Mp settings on your camera. You can always downsize a photo without loss of quality; you cannot increase a photo’s size without losing quality.

Another factor to consider is that the larger the megapixel number of the photo, the fewer images can be recorded on a given memory card.

This table below shows approximately how many images you can get per memory card at a given resolution: (consult your owner’s manual for exact figures)

Quality Setting

5 Mp

3 Mp

2 Mp

.3 Mp

Number of pixels

2592 x 1944

2048 x 1536

1600 x 1200

640 x 480

16 MB Card





32 MB Card





64 MB Card





128 MB Card





256 MB Card





512 MB Card





1 GB Card





Focusing -

An automatic focusing (AF) camera doesn’t always work the way you think it should. I see a lot of photos that are out-of-focus only because of lack of understanding as to how auto-focus actually works.

AF cameras will display some type of pattern in the viewfinder/LCD that shows where the focusing is taking place. Usually, this is a small area in the center of the finder. Whatever is in this area, or in this plane, will be in focus. AF ScreenFor example, when you are photographing two persons, standing side-by-side, the AF pattern may actually be between the two persons. If you take the photo, the camera will focus on the space between them (background) and the result will be that the two persons are out of focus! When this type of situation arises, the trick is to move the camera so that the AF pattern is on one of the two persons, depress the shutter button half-way (this activates the AF function), then, while still holding the button down half-way, move the camera back to the center position to include the other person, then depress the button all the way to take the photo. This can also happen when your subject is off to one side in the photo. Holding the button half-way down will hold the focus setting until you are ready to take the photo. Most AF cameras work this way. Be sure to read the owners manual to know just how your camera handles this function. In some situations, such as trying to focus through a fence or even a window with reflections, the AF function may not work as expected. An important point to remember: if time and the size of your memory card permits, shoot several shots of each subject: the auto focus may or may not work as expected each time.

Macro Focusing -

Most digital cameras have a ‘macro’ mode. This is for extreme close-ups, much less than the normal close focusing distance. Usually, when in the macro mode, a small tulip-looking icon appears in the viewfinder/LCD. Remember to turn this feature off after taking your close-up photos. Just how close you can focus varies with different camera manufacturers. Consult your owner’s manual for detailed instructions.

Digital Zoom -

When choosing a digital camera, I pay no attention to the digital zoom specs; I just don’t plan on using digital zoom. If the camera’s Mp count is high, you probably can get by with a 2X digital zoom, but I wouldn’t consider using anything higher than 2X. All the digital zoom function is doing is enlarging the pixels you already have. You can do the same thing later in your graphics program: just enlarge the image to 200% (or 400%, or 800%). On a lower Mp camera, this is going to result in “pixelating”, or a blocking effect as you will begin to distinguish individual pixels. It may or may not be objectionable, but it will be there. Most cameras give you the option of disabling the digital zoom.

Optical zoom, on the other hand, can be an important feature in any digital camera. Optical zoom can take the place of several lenses. On a non-slr digital camera, this can be very important. By not having to change lenses, you eliminate the possibility of getting dust on the camera’s sensor, plus you don’t have to lug around other lenses (or pay for them!).

Memory Cards -

There are many (maybe too many!) types of memory cards on the market. It seems every manufacturer has their ‘favorite’. There are Memory Sticks, XD Cards, Compact Flash cards, SD (Secure Digital) cards, miniSD cards, microSD cards (also called TransFlash cards), etc. In the past, if you already had a camera that used a particular memory card, you would tend to buy a new camera that used the same type as memory cards were relatively expensive. With memory prices continuing to fall, this is no longer an issue. 

You should always have at least two memory cards for your digital camera. This way, if you were to lose or damage one, you could continue photographing. Like anything electronic, cards can go bad! Also, some types are so small that they are easily mis-placed (or lost!) Rather than buying one large (in terms of capacity) card, you may be better served to purchase two smaller ones. As an example, using a 3 Mp camera, you can get 325 full resolution photos on one 256 Mb memory card. A 5 Mp camera will get 204 images on this same card. Both of these numbers are assuming you shoot a full resolution. Using a smaller Mp setting, you’ll get many more images on each card.


When downloading your images to your computer, DO NOT immediately erase them from your memory card! You could find out, too late, that the download did not go as planned and the only backup was on your card!

What I do is:

1.       Download my images to my computer.

2.       Make sure that the download was successful (by checking each image with my viewer or graphics editing program).

3.       Then burn these same images to a CD.

4.       After checking that the CD burn went as expected, I then feel secure in erasing the images from my memory card.

With my photos, I don’t trust just one backup.

Remember, when burning to a CD, if you don’t ‘Finalize’ or ‘Close’ the disk, you can later add more images until the CD is eventually full. When the CD is full, I’ll even burn a copy of this same CD!

Flash -

Most digital cameras have a built-in flash of some type. Some are obviously more powerful than others, but no built-in flash is going to be the end-all in low light situations. A typical point and shoot camera’s flash will work up to a distance of maybe ten feet. Some less; some more. If you are attending a sporting event, a basketball game for example, you can save battery power by turning off the flash. It’s not going to help you anyway. In fact, it will probably just light up the back of the heads of the people sitting in front of you! The light from the flash will never reach the basketball floor! Also, if taking photos in a museum, theater or anywhere that flash is objectionable or prohibited, be sure to disable your flash.

On the other hand, there are times when the flash is needed, but will not operate automatically! A back-lit scene outdoors in bright light is a good example. In these instances, you can set the flash to ‘always’ work, regardless of existing light. Another instance would be photographing someone standing in the shade (under a tree, etc.), while the background is brightly lit. The flash will probably not work automatically, but can be set to always fire.

Other flash settings may be “Slow Sync”. What this does is allow the flash to fire while holding the shutter open longer, to better expose the background (in an interior room, for example). It is crucial here to hold the camera steady for the entire exposure, maybe on a tripod, unless you’re going for a special effect.

Finally, the “Red Eye” setting can be used when photographing people in a dark setting. What this setting does is ‘pre-fire’ the flash to cause the subject’s pupils (in their eyes) to close somewhat, eliminating the red-eye effect. Then the flash fires again, this time making the exposure. The problem with this setting is that in the short time between the ‘pre-flash’ and the actual exposure, someone will invariably blink, move or change their expression. I never use this setting as it is too easy to correct the red-eye effect after the fact. (The free viewer, IrfanView, does an excellent job of this.)


ISO is the sensitivity setting, similar to choosing different film speeds. The neat feature with digital cameras is that you can change the ISO setting for individual photos! This number works just like it does with film cameras: lower settings are used in bright to normal conditions and have finer detail. Higher settings are for low light conditions and will have a higher degree of ‘noise’ in the photos. Noise is similar to ‘grain’ in a film camera. With some digital cameras, the noise can be quite high. In normal use, you’ll not need these high ISO settings. Some cameras may use a high ISO setting while in the ‘Auto’ mode, but only if it is a low light condition or a high shutter speed is required. I try to use the lowest ISO setting I can, under any given condition. When I use a film camera, I do the same thing.

Exposure -

Getting the exposure correct is one of the neatest things about a digital camera! Instead of waiting to get back home and having the film processed, you get immediate feedback! If the exposure is wrong, you’ll know right away and will normally be able to make corrections and re-shoot the photo. However, if it’s a fleeting moment, such as the bouquet toss, the home run hit, etc., the ability to re-shoot may be lost. Therefore, knowing how to properly expose the image is crucial. In most situations, the “AUTO” setting will usually work just fine. But with special conditions, you should have an understanding of how exposure is obtained.

If your scene has a strong backlight, such as a sunset or early or late in the day, you may have to compensate for the lack of light on your subject. In many instances, you can use the camera’s electronic flash to ‘fill in’ or lighten the shadow areas of your subject. Some cameras have a “Backlit” setting. Others may have an “Exposure Compensation” control where you can adjust the exposure up or down from ‘normal’. Again, you can usually tell whether you need to use this feature as the results are immediate.

The Exposure Compensation feature should also be used if you are consistently getting photos that are too dark or too light. This same type of compensation can be set on some in-camera flash systems.

Shutter Speed -

The shutter speed is the fraction of a second that the aperture is open for exposure. If the shutter speed is quick, any movement in the photo will be sharp, or frozen. If the shutter speed is slow, any movement will be blurred. If your camera allows adjustment of the shutter speed, it can be a great advantage in many instances.

Panning (or moving the camera horizontally with the subject) while using slower, or longer, shutter speeds can help keep fast moving objects in focus. This gives a feeling of ‘speed’ as the background will be smeared, or blurred across the image.

Aperture -

The aperture, or f-stop, controls how much light is hitting the camera’s sensor in a given exposure. The aperture is an adjustable opening in the camera’s lens that is similar to the iris of a human’s eye. A larger aperture allows more light to hit the sensor than a smaller one.

A secondary feature of the aperture setting is depth-of-field. Depth-of-field is defined as the focused area of an image that has reasonable, or acceptable sharpness. The smaller the aperture (larger the number), the more depth-of-field you’ll have. To enhance the separation of the subject from the background, use a large aperture (lower number).

Using the common aperture numbering method, consider this to be the denominator in a fraction: i.e., f8 = 1/8, f4 = 1/4, etc. This will give you a relationship between the aperture number and the lens: example, f8 (smaller opening) allows less light than f4. The aperture and shutter speed work together to provide the proper exposure.

White Balance -

In the ‘old days’ of film photography, color balance (or white balance) was always a problem. Normally, you used either a Daylight balanced film or a Tungsten (indoor) balanced film. If you used a daylight film indoors, you would get a yellow cast to all colors (unless the indoor lighting was fluorescent, then everything would be greenish). Conversely, if you used a tungsten film outdoors, you would get a bluish cast to everything. Corrective lens filters are used to balance lighting to film.

With digital cameras, this correction is set using the white balance setting. Some manufacturers make this process easier than others. Most will have ‘pre-set’ white balances already programmed into your camera. In addition to “Auto”, some of the pre-set white balances are:

Outdoors in Shade
Daylight Fluorescent
Cool White Fluorescent
Warm White Fluorescent
Incandescent Lighting

The Custom setting is one you can set, yourself. To do this, you go to the White Balance setting and choose “Custom White Balance”. Then, while holding a white sheet of paper in front of the lens (paper must cover full frame), you depress the shutter release. This sets the White Balance for the lighting conditions at that particular location. Upon leaving that situation, be sure to reset the White Balance to “Auto” or another custom setting.

Post -

This is what I referred to earlier as “after the fact”. ‘Post’ is actually a motion picture term, but I use it here as related to still photographs. The term is short for ‘Post Production’: all the special effects, etc. that are added after original shooting. A lot can be done to improve your photograph with most any graphics programs on the market. Some common applications are: Paint Shop Pro, Corel Photo-Paint, Ulead PhotoImpact, Adobe Photoshop, Photoshop Elements, ACDSee, Paint.NET, PhotoPlus, GIMPshop, etc. (Note: the last three are free!)

I have never printed a digital image without some sort of retouching or ‘Post’. It can be as simple as cropping, increasing saturation, color correction, sharpening, straightening, or any combination of these. I’ve rarely seen an image that couldn’t be improved in ‘Post’. Of course, the object is to improve the image without it appearing obvious.


When doing any ‘Post’ work, never use your original image: always work on a duplicate or backup version. That way, you’ll always have the original to fall back on if you make a mistake, or just change your mind. If your graphics program uses ‘layers’, make a duplicate layer and use it as your basis. Also, if you backup as I mentioned earlier, you’ll have the original on a CD.