NWA-PCUG Newsletter Article
Purchasing a Digital Camera
by Larry Horn, User Group of South Jersey, September 2001
Digital cameras are the latest "Must Have" toys for gadget loving computer users and many others. The reason computer users love digital over regular film is the computer gives them the ability to make endless changes, corrections, and improvements to their pictures and use them in creative projects. (Be sure to attend this months meeting where MGI will show you some of the digital editing techniques and tricks you can do using their line of products.) This article will be my very opinionated list of what you should consider before purchasing a digital camera, or getting your new one with more features. Remember, technology in this field is advancing so fast with more resolution and features for less money on a monthly basis. Therefore any recommendation for a specific camera is obsolete before the article can be printed.
An Important point:
No consumer level digital camera of today under $3,000 will equal 35MM film for absolute image quality! The structure of film is way beyond 3 or 4 MegaPixels (MP), and film has grain which softens the edges presenting a more natural picture to your eyes. Additionally, film cameras can be purchased, at a very reasonable cost, with interchangeable lenses which greatly increase the flexibility of the camera use. Yes, you can fake a telephoto lens in the camera but that kills your resolution. (I will get into that below.) You can also scan a photo, but that will also reduce the resolution and ultimate image quality. When you get your film developed and placed on a CD by the camera store, they actually scan the film (with a very good film scanner) and save the file to a disk.
First, why do you want to purchase a digital camera?
Because they are fun to use and can actually save you a lot of money over time. It takes the Polaroid ®® concept of a picture in a minute and speeds that up. You take the picture, preview it on the LCD screen and delete it if you don't like it or save if for future posterity - all at no additional cost for film or developing. Print out the pictures you like (paper quality does matter) or send them as e-mail attachments to friends and relatives.
Let's get down to the actual items to consider when buying a camera. These items are in my order of importance although many of the items are actually of equal ranking and personal preference has influenced it.:
Resolution and Sensor Size:
The heart of all digital cameras is the light sensitive electronic chip called a sensor. It takes incoming light and converts it to a digital file. This chip determines the maximum resolution and, ultimately, image quality. This sensor is made up of a number of individual photo-receptors corresponding to pixels. When a digital camera says it has 1MP resolution, the sensor actually has that number of photo-receptors The density of the sensor determines a camera's overall picture quality.
Using a lose analogy to relate it to your computer screen's resolution, the original default VGA resolution of Windows on a computer monitor was 640x480 which means it has 640 dots or pixels across by 480 down or .3 million pixels making up the screen image. A digital camera with this same resolution would have .3 million image sensors each representing a pixel or .3 MegaPixels (MP). Cameras in the mid-price range ($150-300) now have 1MP, or 2MP. In the $400-$1,000 price range you will get 3MP or 4 MP. This directly impact the size of a picture you can print as more pixels translate into a larger picture that still looks good. The camera has captured more detail and doesn't have to "guess" or interpolate at the missing dots or expand the existing ones causing a blotchy print.
I have seen two kind of sensors:
A charge coupled device (CCD) which is usually found in high-quality cameras and a complementary metal-oxide semiconductor (CMOS) which is more common in the low-cost "entry-level" cameras. Most of the reviews I have seen favor CCD chips.
What resolution do you need?
That depends on how you will be using the final output. Yes, more is always better, but as a rule of thumb related to final use:
o .3MP (640x480) = On screen viewing, Web Sites, sending as e-mail attachments, prints up to 3"x5"
o .8MP (1024x768) above and prints of 3"x5" to 4"x6"
o 1MP (1152x864) = 3"x5" to 5"x7"
o 1.3MP (1280x1024) = 4"x6" to 5"x7"
o 2MP (1600x1200) = 5"x7" to 6"x9"
o 3 MP prints up 8"x10" to 11"x14"
o 4Mp 9"x12"
The above listing was the consensus of several sources but was plagiarized from the April 2001 issue of PC Photo, an excellent magazine for anyone starting out with digital photography. PC Photo generally used the more conservative - smaller sizes.
One last point on resolution:
Many people will want to eventually crop their pictures for a better composition. When you crop it down, you effectively throw out the resolution in the area you delete. A 3MP image could quickly reduce to a 1MP with cropping, so if you like to work on your images and make relatively large prints, start with and shoot at the highest resolution you can afford.
There are two main points to consider here, lens material and zoom capability. Lenses can be made of glass or plastic. Glass is the hands down winner for quality.
The stated Zoom range is a bit more complex. You can have Optical Zoom and Digital Zoom. Optical Zoom uses the actual optics of the lens to magnify or zoom in on the image. There is no loss of resolution/quality, but it is more expensive to manufacture. Digital Zooms take the original image from only the center part (how much depends on the degree of magnification) of the sensor and use the camera's internal computer to interpolate or guess at the "missing" pixels between the real ones. It is like cropping the picture and then stretching the image back up and filling in the blank spaces. Image quality is degraded and the greater the magnification, the more you lose. A 3MP sensor might actually be using only 1MP at the center and "filling in" the other 2MP. Don't get me wrong, I have seen cameras guess very well and produce good quality images at high digital zoom magnifications but optical is always better than digital. The most common range I have seen in optical zooms is 3X or three times magnification.
Also, be aware that the sensor is not the same size as a piece of 35MM film, so when you see the focal length stated in mm like 38-115mm (3X) this is actually a more telephoto angle lens than you would get in a 35MM camera. PC Photo Magazine list the conversion at approximately 5X. My Olympus camera has a lens of 5.4mm - 16.2mm which they state is equivalent to 35mm-105mm on a 35MM camera which equals slightly wide angle to short (Portrait) telephoto for those not familiar with 35MM cameras.
Framing the Picture:
You can frame the picture in either an optical, ideally through the lens, viewfinder or with an LCD display panel on the back of the camera. I feel a digital camera should have both! Being a long-time photo enthusiast I am accustomed to an optical viewfinder. LCDs also have the bad tendency to "wash out" or become too light to be viewable. I also find it awkward to hold a camera away from my face while trying to frame the image. Another disadvantage is LCDs consume a lot of battery power. You can shoot all day on one set of batteries with an optical viewfinder, but you had better have extras if you use an LCD. I would not purchase a camera without an optical viewfinder. (Our VP, Elliot Glantz, feels just the opposite, and although his camera has both, he always uses the LCD over the optical viewfinder.) I will also admit an LCD is more accurate in framing the subject, especially close-ups, unless your optical viewfinder is "through the lens," something generally found only on top-of-the-line digital cameras.
If I am so partial to an optical viewfinder, why do I want a digital camera to have an LCD panel? Because it is invaluable for previewing your pictures to make sure you really got a good shot. If it didn't turn out, you know it instantly and can reshoot it. The bad picture is simply deleted, making room for another shot and with no waste of film. It is also great being able to show off your pictures while still at the party, etc. and see the reaction. One neat feature I saw on a Sony camera was an LCD panel which swivelled so you could still see it if you put the camera over your head or were using the self-timer to take your own picture.
Simple, inexpensive, digital and film cameras have a single fixed, or two zone, focus. It is a compromise or zone guess. This is OK as a quick point-and-shoot camera but will not give you the best shots. Most better ($250+) digital cameras have autofocus lenses. This will give you far better, sharper images. An added feature is a focus lock. This feature allows you to lock the focus on the main subject and then re-frame the picture to a more pleasing composition. When you get up to the professional level ($2,000+) cameras, you can even get optional full manual focus for real creative effects.
Memory - Storage Cards:
Digital cameras store their images in non-volatile memory cards; they save the memory even when the camera is off. Some very inexpensive have only internal memory which will hold 25-30 pictures before you have to get to a computer to download them. This is OK around the house but would require you to lug a laptop with you on a trip if you wanted to take any additional pictures. A better solution is removable memory cards so you can take several with you and when one is full, just change it like you would film, and keep shooting. There are several, unfortunately non-compatible, options available. These are Smart Media (SM), Compact Flash (CF), Sony's Memory Sticks, Multimedia Cards, Click Disk, the new IBM MicroDrive, and just released CD-R. The 2000 Fall Comdex in Las Vegas also saw the introduction of additional formats but these are not yet available. SM and CF are the most popular at this time. They are all small cards, about the size of a matchbook, which slide into the camera. You purchase them by memory size, in Megabytes, which range from 4Mb to 64Mb with the MicroDrive going up to 340Mb. These capacities are increasing as I write this. Some Sony cameras still use a standard 3 ˝˝" floppy disk. These are cheap but are limited to 1.4Mb so they can't hold many pictures as the resolution increases. The number of images you can save per Megabyte is directly related to the resolution and the amount of image compression you use.
Image Compression - File type:
A non-compressed high resolution picture would take up multiple megabytes of storage space so most cameras store the images in a compressed format. The most common formats are TIFF and JPEG. TIFF uses minimal compression and produces the largest file sizes but also the best pictures. JPEG is a "Lossy" compression algorithm. This means that some information is thrown away forever when the file is compressed——so if you compared the "uncompressed" image with the original, you would find some differences. You can, on some cameras, set the amount of compression so you can determine the amount of data you are willing to lose (and reduce file size) before the image becomes pixilated and looks unacceptable. Setting the camera to Fine, Normal or Basic determines the amount of compression. Some brands use different terms but the concept is the same. I discourage the use of the Basic - highest compression - setting as it gives the lowest quality. A good quality camera will give you a choice of file type as well as degree of compression.
So how many pictures do I get on a memory card?
A basic camera my neighbor has includes only 2Mb of memory and at 640x480 resolution with what it calls fine compression they can take 16 pictures or 32 pictures at the basic setting. The average camera with removable memory comes with a 8Mb card. Using that as a guide I will reproduce part of a table (with their terms) from the camera I own:
Resolution Compression # of pictures
1600x1200 TIFF - Minimum 1
1600x1200 JPEG - Minimum 5
1600x1200 JPEG - Std 16 *
640x480 JPEG - Fine 32
640x480 JPEG - Normal 82
* This is the setting I use most often but I have to go back and Save-As with a higher level of compression if I am sending the files over e-mail to keep the size at a reasonable level for a dial-up download.
The Feel of the Camera
Even with the best specs in the world, if a camera does not "feel right" you will not use it. This is very subjective but also very important. Getting the size, weight, design, location and operation of the controls, and the general Ergonomic Fit comfortable to you are important. There are some necessary compromises in size and weight if you want every bell & whistle. You might be carrying the camera all day on vacation so don't overbuy on size just to get a feature you may never use. The box of my still camera says it will take video clips also. But when you look at the spec sheet you find out the video is low resolution and limited to only several seconds, even with a relatively large media card. My camera only gives you 96 seconds with a 32Mb memory card at 320X240 resolution. No very practical
Viewing and getting the pictures out of the camera.
I consider it important, but not critical, to have a TV out on the camera. The small LCD screen on the back of the camera makes a poor screen you several people to view the pictures. Being able to plug the camera into the TV, especially if the camera has a slide show feature, is very nice.
There are several way you can get the pictures into your computer. The oldest and slowest is with a serial connection. All PCs have a serial port so you "guaranteed" a connection. The preferred way is with USB. It is many times faster, almost every computer now supports USB, and you can "hot-sinc" with USB, you don't have reboot to connect the camera as you probably do with a serial connection. Even if your camera only has a direct serial connection, you can still use USB by purchasing a media card reader. Plug the reader into a USB port, remove the memory card from the camera, place it in the reader and your computer now has an additional drive letter, making it fast and easy to copy your pictures. They even make adapters that look like 3 1/2" floppies that you can put the memory card into.
This article is brought to you by the Editorial Committee of the Association of Personal Computer User Groups (APCUG), an International organization to which this user group belongs.Click here to return to top