Everything about digital cameras

Digital cameras were the subject of a fine presentation by Roberto Segura of MicroCenter, May 3rd, at 'Coffee and Computers.' Interestingly, less than half of the 60 attendees owned a digital camera, myself included.

As we discussed what kind of digital camera to buy, one topic of considerable confusion appeared to be "how many megapixels should the camera have?" Pixels, or picture elements, represent how detailed an image the camera can take. Modern digital cameras have many millions of pixels in their internal sensors, thus cameras are rated in "megapixels." There is a saying, "you can't be too rich, to thin or have too many megapixels."

There are some practical and technical constraints on this, however. More pixels increase the cost of the camera. In addition, if you take advantage of a larger number of pixels, the size of the digital files that contain the images increases also. You would expect this: more pixels, greater possible detail in the image, larger computer file to hold the image.

After you click the shutter, you must transfer the images to the computer. Doing this also can be confusing. Most cameras give us a large selection of formats in which to capture the image. The choice of format determines the size of the image file that must be stored in the camera and then transferred to the computer.

One choice you can make in the camera is "resolution." This is a misnomer since the number of pixels in the sensor determines the actual resolution of the image. For instance, a 3 megapixel camera is capable of taking a picture of 2048 pixels wide by 1536 pixels in height. But if you took all your pictures with this maximum resolution, each picture may take a file size of around 9 megabytes. This may be more than some camera memory cards can hold. The pictures might be crystal clear, but you would have to carry a bag full of expensive memory cards or other storage devices for your camera.

Therefore most cameras give a choice of "resolutions" down to 640 by 480 pixels. This is the size of most 15 inch computer screens and is perfectly adequate for images that are going to end up in emails or small size paper prints.

The next confusing choice in the camera is whether to save the image in a "native" format like BMP (bitmap), TIFF (tag-based image file format) or in a compressed format like JPG (Joint Photographic Experts Group).

Native formats are used when you plan to do sophisticated image manipulation in your computer. These formats contain all the information in the original picture and make it easy to make large paper prints or artistic changes to the picture. However, pictures saved in native formats have large file sizes and take a lot of camera and computer storage space.

Compressed formats like JPG change some of the original picture information but result in small file sizes and thus more pictures stored in the camera. JPG pictures are great for minor image manipulation in the computer and then sending to family or friends via email or making small paper prints.

Most digital cameras allow you to make all these choices directly within the camera. Less expensive cameras may limit your choices. Of course you can save the pictures in native format and change them to JPG using image manipulation computer programs.

We've just scratched the surface of the questions that came up about digital photography in Roberto's presentation. In the future we will explore how to manipulate the image once it gets transferred to the computer. There we can fix image brightness or contrast, remove "redeye" and put in special effects.

If you would like to hear more about digital photography, or other computer topics, visit 'Coffee and Computers' at the Tustin Area Senior Center, 200 S. 'C' Street, any Friday morning from 9 a.m. until noon. Bring your questions or just come in and visit.

In the meantime, keep the neurons happy, synapses snapping and enjoy computing.


Dr. Art Holub is a long time resident of Tustin and teaches computer and Internet courses at the Tustin Area Senior Center and the Tustin Adult School. Visit his web site at: This column is written to address the computer adventures and concerns of older adults. If you have comments, questions or suggestions for future columns, Email HIM at:

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