Megapixels and Digital Images

A few years ago when we were still using film cameras, the quality of a photo was based on several factors. The speed and size of the film, camera lens quality, type or grade of photo-paper, the chemical processing of both the film and paper, not to mention the aperture setting and the shutter speed.

Throughout this article I will be making the comparison between film photography and digital. Most of us were raised with film, so the comparison perhaps gives us a better understanding and frame of reference.

Excluding camera movement by the operator, the appearance of the photo was referred to as either high or low resolution. This term came about because a piece of film is plastic covered with a chemical layer (emulsion) containing light-sensitive silver halide crystals. I mention this because these crystals can loosely be compared to digital pixels in the cameras of today.

A digital pixel is a small miniature square that records light. The more pixels that are contained within the recording area, renders an image that has a better resolution. The higher the resolution means that the image will be more clear and sharp to the eye. In general, this resolution value is referred to as megapixels, where "mega" means million.

If a photographer using a film camera wants to gain the maximum light that was recorded on a piece of film, the film would be over developed which is referred to as "pushing" the image. What happens is that the silver crystals become enlarged from over-development, giving greater surface area, which in turn provides an image in dark situations. The problem is that even though the photographer obtained the image, the enlarged crystals become more visible, rendering a noticeable lack of resolution. These images are usually referred to as "grainy".

"Grainy" images can happen in digital photography as well. However what makes a "grainy" image in a dark situation is usually caused by the smaller number of pixels. If two people are shooting the same low-light image, one using a 2.1 mega pixel camera and the other using a 5 megapixels, the larger number will usually render the acceptable image.

The next consideration in digital photographs is the final size of the image. You will rarely see an advertising photographer or portrait photographer use a 35mm film camera. To make a final photograph 16 X 20 or greater, a 35mm image is simply too small, and the results would not look good. Usually they will use a 2 x 2 inch image (roughly twice the size of a 35mm image), and many times a 4 X 5 inch or larger film plate. The reason is simply there are more crystal grains of silver that contains the image than if a 35mm were used. Incidentally, before you go off on a tangent that you have seen or heard of a large photo in New York City's Times Square, which was taken from a 35mm negative,

let me quickly explain that this image was manipulated to render that photo. In other words, most of us could not afford what it took to obtain that final display.

How the previous example applies to digital photography, is that the higher the pixel rate of the camera, determines the maximum final photograph. For example, the maximum a 2.1 mega pixel image could safely be printed is approximately 11 X 14. If there was strong light and no camera shake, one could possibly get an acceptable larger print. However, the general rule is that the more megapixels contained in the image, the larger the final print potential.

One major advantage of digital cameras is the storage of the images. With minor exceptions, a film camera is limited to taking a maximum of 36 images before changing rolls - not to mention that each roll is a one-time use.

Digital cameras store images on small "flash" memory cards, which can be downloaded to a computer, then to a CD or DVD for permanent storage. The card is then wiped clean ready to store a new batch of images. Using approximate values, one could expect the following.

2.1 megapixel camera"

128mb (megabyte) card = 144 images = 4 rolls of 36 images

256mb (megabyte) card = 288 images = 8 rolls of 36 images

512mb (megabyte) card = 576 images = 16 rolls of 36 images

4 megapixel camera (or more):

128mb (megabyte) card = 47 images = 1 1/4 rolls of 36 images

256mb (megabyte) card = 95 images = 2 1/2 rolls of 36 images

512mb (megabyte) card = 191 images = 5 1/3 rolls of 36 images

Given the size of the "flash" card, one could record their whole vacation, sports or performing event on a single card, rather than the distraction of changing film spools all the time.

Although I did not include them in this example, "flash" cards are available in higher storage capacities - typically from 1 to 4gb (gigabyte) and in some cases higher.

A few years ago when digital cameras become more affordable, these cameras were usually a maximum of 3 megapixels. Cameras that had 5 megapixels or more were typically priced around a thousand dollars or more, and were generally out of reach for the average household.

It wasn't too long ago that a camera with 6 megapixels could cost $10,000 or more. Today, one can obtain a camera with 5 or 6 megapixels for under $200. If one wants a camera with interchangeable lenses, the price is closer to a thousand dollars or more.

The future is bright for digital photography, Not only will we see the digital camera increase in technology and decrease in price, but camera's built into other electronic devices such as cell phones are getting easier to use with better quality.