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Digital Cameras

by David Hunt
December, 2001

Introduction

The use of digital cameras in KAP is slowly increasing in popularity, paralleling the popularity of digital cameras in the general public. The biggest concern expressed in the past about digital cameras was the poor resolution offered by consumer grade cameras. This is changing at a rapid pace. 2+ megapixel cameras came on the market during 1999 and the pixel resolution more than doubled in the following two years.

New models are introduced at an astonishing rate. Because of this, I will not recommend specific camera models.



Two excellent resources for digital camera information are, the Digital Photography Review web site, and the Imaging Resource web site. A great feature offered by both sites is the ability to select several models and then view a side-by-side comparison of the different features of each model. The Imaging Resource web site offers side-by-side comparisons of test images. Both sites offer excellent information and guides for the digital newcomer. Each camera review has Un-retouched images taken with the camera. Viewing these images is critical to making a good choice. More about this later.


What To Look For In A Digital Camera For KAP
(In order of importance)

  1. Determine Your Use. If you will only view your pictures on a computer screen, then cameras in the 1 megapixel range or lower are more than adequate. If you plan to print some of your pictures use the guide below.
    4 X 6 prints 1.0 megapixel
    5 X 7 prints 1.3 - 2.0 megapixels
    8 X 10 prints 2.0 megapixels & up
    Resolutions above 3 megapixels will created sharper looking 8 X 10 prints or allow for cropping.
  2. Image Quality. Go to the two web sites mentioned in the Introduction and look at the sample images. The first test that I look at is the "Far Field" test found on the Imaging Resources site. It gives a good idea of how the camera handles detail in grass and vegetation. Often you can reject a camera based on this one image. If the detail looks good investigate further.
  3. Weight. This is always a prime consideration. Don't let it be the only determining factor.
  4. Power Consumption. Digital cameras are big power users, some are worse than others. Look for a camera that will operate continuously for at least an hour. Two factors are important to power consumption, the number and resolution of the pictures taken, and the use of the LCD screen. Larger resolution images use more power during the storage phase; so fewer large image files can be stored per charge cycle. LCD screens are the biggest power user on a digital camera, make sure that the camera you choose has the ability to turn the screen off. You will not need it when your camera is a couple hundred feet in the air (I have a Fujifilm digital that requires that the LCD screen be turned on if I wish to connect to a video sender). If information about a camera's power usage cannot be found in the manufacturers specifications or on a review site, visit a user forum. You can bet that someone on the forum will bring the subject up if a camera uses more power than is typical. Both sites mentioned earlier have links to digital camera user forums.
  5. User Activated Auto Shut Off. Most digital cameras have an auto-shutoff feature to help save battery power. Make sure that the camera has the option of disabling the auto-shutoff.
  6. Lens. You don't need a zoom lens for KAP but you may not have a choice. Over the last couple of years there have been fewer fixed focal length lenses offered. Make sure that the widest angle is equivalent to a 35mm camera lens of 35mm or less (see focal length, in next section). You might go with 38mm, but I wouldn't go any higher. Some cameras have threads on the front of the lens that allows the user to attach filters or lens converters. Lens converters make the camera's lens more telephoto or more wide-angle. Lens converters may be available for Cameras without threads, but you will need to check availability on a model-by-model basis. (The two camera review sites mentioned in the Introduction present focal length information differently. The Digital Photography Review site only lists the 35mm equivalent of the lens' focal length. The Imaging Resource site lists the actual focal length and the 35mm equivalent. The Digital Photography Review has the best presentation. Allowing you to see lens sizes for each manufacture's complete line on a single page.)
  1. Battery Type. Since digital cameras are big power users, you will want to make an informed decision about the battery system that the camera uses. Look for three battery arraignments in digital cameras. (a) Some cameras will use standard battery sizes (AA or AAA) and a battery charger will not be supplied. If you plan to recharge your batteries then you will want to invest in rechargeable batteries and a battery charger. Use Nickel Metal Hydroxide rechargeable batteries (NiMH). Other cameras will use a proprietary rechargeable battery. There are two variations of this type camera. (b) One type recharges the battery in the camera; (c) the other type recharges the battery in a unit away from the camera. Most of the batteries in these two groups will be Lithium-Ion batteries (Li-ion). There are pros and cons to the three systems. Charging in the camera means one less piece of equipment to keep up with, but it also means your camera will be bound to a wall outlet while charging the batteries. Using standard battery sizes means that you can use alkaline batteries if you get in a pinch, but alkalines weigh more than NiMH batteries and NiMH batteries weigh more per unit of power than Li-ion batteries. Since most digital cameras have a DC input jack, you could power the camera with an external battery pack. (The battery industry refers to the power per unit mass of a battery as its power density. Alkaline batteries are heaviest, or lowest power density, NiCd are next, then NiMH, and the lightest are the Li-ion with the largest power density. The weight savings can be significant. A NiMH battery with the same milliamp hour rating-mAh- as a NiCd battery will weigh about 1/3 less.)
  2. Storage Media. If you already own memory cards from another camera you may wish to stay with a camera that uses the same type card. SmartMedia cards are cheaper than Compact Flash cards, because Compact Flash has the controller built into the card. SmartMedia requires that the controller be located in the camera, so your camera may not support the largest SmartMedia cards on the market. Some cameras support the Microdrive cards, which come with up to 1GB of storage and fit in a Compact Flash type II slot. I would discourage the use of Microdirve cards for KAP because they are sensitive to shock.
  3. External Control. Somewhere in the future digital cameras will start offering external control features. Digital cameras are basically little computers. Every operation of the camera could potentially be controlled from a remote location using a serial or USB port. The software that comes with the camera, that allows you to download images to a computer, is in effect remotely controlling the camera. Camera manufacturers do not publish the control commands that are specific to their cameras, but some hobbyists have deciphered the codes for a few of the many cameras on the market. Much of the code deals with image file maintenance, but most cameras have a code that trips the shutter. Someone who knows how to program PIC mircrocontrollers could easily trip the shutter using the camera's serial port. Keep an eye out, in the future, for cameras that will allow you to control operations through a computer interface. Some of the very heavy, very expensive, professional digital cameras have started offering these capabilities.

Understanding Camera Specifications and Terminology
Picture Resolution -
This subject can be confusing to someone not familiar with digital imagery. When speaking of resolution, there are two factors that will affect the quality of the final product.

1. CCD Resolution
The CCD (charged coupled device) is the electronic component on which the light from the lens is focused. Digital pictures are made up of tiny "squares", each of a single color, called pixels. Each CCD has a maximum number of pixels that it uses to generate the image. Camera specifications will list the Max Resolution and the Minimum Resolution. The user selects these values before the picture is taken. The more squares you fit into a given space the better the resolution. If you multiply the number of horizontal pixels by the number of vertical pixels you will get the total number of pixels in the image.

You may notice that a camera's maximum setting does not quite add up to the camera's advertised size. An example of this is my Fujiflim MX-2700, which claims to be a 2.3 megapixel camera. Its Max Resolution is 1800 X 1200; this means that when the camera is set for Max Resolution each picture will be 1800 pixels wide and 1200 pixels high. 1800 times 1200 equal 2.16 million pixels in the whole picture. The 2.3 megapixel claim is for the total CCD pixel size. The missing pixels are used in system housekeeping duties and cannot be used for picture taking. This is true of all digital cameras.

2. File Compression
File compression is the other variable that needs to be considered when looking at a camera's ability to produce a good image or print. Some cameras have the option of storing an image in an uncompressed file format (.TIF). An uncompressed file means that every pixel that the CCD records is stored with its original color information. Uncompressed picture files are very large. One picture will almost fill an 8 Meg memory card.

To save space on the memory card, digital cameras make the file smaller by using JPEG compression. When the compressed file is redisplayed or printed the picture will contain the same total number of pixels and most of these pixels, but not all, will have their original color information. Some pixels will have slightly different color information and are called "compression artifacts".

Example of Compression Artifacts

Enlargement Showing
Compression Artifacts

Most digital cameras offer 3 levels of compression which are usually referred to as quality levels; the "Fine" quality level has the largest file size and the best picture quality, the "Normal" quality level will have smaller file sizes and a little less quality, and the "Basic" quality level has the smallest file size and the lowest quality. Raising the amount of file compression, introduces more "compression artifacts", and lowers the picture quality. "Compression artifacts" along with the pixel resolution will limit how much you can enlarge a picture before the "compression artifacts", and or pixels become noticeable. The combination of CCD resolution and file compression that you chose is determined by the size of the final picture that you need.

ISO Rating-
This is the same rating used on photographic film. The cameras that offer variable ISO settings do so by amplifying the signal from the CCD, this will also amplify the background noise in the picture. Camera reviews should compare side-by-side enlarged pictures taken with different ISO settings. Most of the noise will appear in the darker portions of the image, and the noise will be similar to the graininess seen on high-speed film.

USB connection-
Universal Serial Bus is a relatively new type serial connection that is faster than the old serial connection, It is "Hot Swapable", meaning you can plug and unplug a USB device while your computer is running and the computer will recognize that the device is connected without having to reboot the computer. Almost any new computer you buy today will have a couple of USB ports. USB is supported by Windows 98, XP, 2000, and ME but not by Windows 95 or Windows NT. If your camera has the slower serial output in place of a USB output, purchase a memory card reader that will connect to your computer using USB. Large picture files transferred over a standard serial connection can take longer than a minute to complete. With a USB connection the transfer takes place in the blink of an eye.

Shutter / Aperture Priority-
Shutter priority means that the photographer sets the desired shutter speed and the camera determines the proper f-stop for a correct exposure. Aperture priority lets the photographer set the f-stop and the camera determines the shutter speed. Some digital cameras that offer shutter and or aperture priority, only offer it over a limited range of settings.

Focal Length-
Because the imaging chip on a digital camera is smaller than the image size of a 35mm negative, the focal length needed to create wide-angle views is shorter. On a 35mm camera a 35mm lens is considered the upper limit of the wide-angle range and a 14mm lens would be a fish-eye lens, taking in a view of 180 degrees. The 35mm equivalent of a 35mm lens on a digital camera can be somewhere between 4mm and 8mm depending on the size of the camera's CCD chip.

Digital Zoom-
If you purchase a digital camera with a zoom lens make sure that it is an optical zoom and not a digital zoom. An optical zoom uses the lens elements to project an enlarged image on the full CCD chip, so an image will be made up of all the pixels available to the camera. A digital zoom selects a smaller area of the CCD chip and electronically converts it to an image with the same number of pixels as the camera's current resolution setting. The camera will have to create the extra pixels it needs using some type of algorithm. The more "zoom" used, the blockier the image becomes. Digital zoom is trying to create an image using fewer pixels, so expect the image quality to suffer. The same effect can be achieved with software on your computer after the image is taken. Digital zoom is just a gimmick. Some cameras may offer a combination of optical and digital. The low end of the zoom will be optical and the upper end will be digital.

SuperCCD or Image Interpolation-
Some of the Fujifilm digitals use a special CCD chip called SuperCCD. The individual pixels are arraigned in a honeycomb pattern instead of the typical straight rows and columns. To create a rectangular image it interpolates the data between pixels. The Fujifilm MX-4700 has a SuperCCD imaging chip. The chip has 2.4 megapixels, but it creates an image with 4.3 megapixels. The camera is advertised as a 4.3-megapixel camera but when you compare images with other 4-megapixel cameras (and some 3 megapixel cameras) you will be disappointed. Your liable to see image interpolation used in other cameras from time to time, Stay Away From It!