Basics

Camera Basics

Several years ago, digital cameras were largely seen as either totally exorbitant and used only by professionals in a few specialized applications, or as very expensive toys, with limited resolution and capabilities. Currently, many excellent cameras are available at a range of prices below $1000. For a quick overview of theory and background of digital photography read on.

What is digital photography?

Strictly speaking, digital photography is defined as the use of a digital camera to capture images. However, this site encompasses the broader meaning, referred to as digital imaging, which includes any means of transferring pictures from the analog to digital world. It includes the use of regular film and slide cameras, with subsequent digitization, most commonly through scanning. It also includes the use of digital cameras, which allow pictures to be taken digitally directly, via media such as compact and smart flash, or digital film backs to conventional SLR cameras.

What are the advantages of digital photography?

Everyone has different reasons for choosing digital photography. I will mention here a few of the reasons I made the transition to digital cameras completely several years ago. After losing several rolls of slide film back to back- to different processors, I became wary of losing precious images. I had lost a roll en route to or from the processor on nearly every trip I've taken over the past 25 years, since shooting seriously, and digital provided a way for me to take control of the processing. When finished shooting, I immediately transfer the cartridge to my computer, and on a weekly basis back it up to compact disc to archive off-site.

Another big plus is, once you make the initial investment in a digital camera (which averages under $1000 currently for top of the line prosumer models, with prices steadily dropping) the cost of shooting is essentially free. On some days in the field, I shoot the equivalent of ten or more rolls of film, and don't pay a thing for film or developing. Because of this, I shoot more freely than I used to, when calculating the cost each time I pressed the shutter. Now, I experiment more with exposure, metering, and even choice of subjects. Where in the past I might have shot one or two individuals of a plant or animal, now I'll shoot a dozen, to make sure I get just the right one, from just the right angle.

Still another advantage is the instant feedback in the field. Using the LCD screen, you can compose the shot visually in the field, and with playback mode can review the shot instantly for sharpness, exposure, and even on some of the newer models (like the Nikon 990 I'm currently using) get a histogram display of the image. Combining this with review after every field session on the computer, and it provides enough feedback right away to determine if the shot needs to be redone. With film, many times by the time I got the developed film back, it was too late to try shooting my subjects again.

Basics of Digital Cameras

What is a digital camera? Traditional film cameras have been in use for over a century - they use chemicals to store images, first on glass, then later on paper and plastic. The chemicals are light-sensitive - they change chemically in very predictable ways when exposed to light. That is the essence of any camera - the ability to record differences in light very precisely. A digital camera, instead of using direct chemical reactions to store variations in color, uses an integrated circuit that is light sensitive. As different wavelengths and intensities of light strike the light sensitive integrated circuit in the camera they create very small electrical charges. These electrical charges are recorded as binary (zero and one) values in a digital format and stored. A digital camera is actually a small specialized computer with a light sensitive chip to record images. Most modern digital cameras store the pictures taken in the same format used to store pictures on the Internet. The pictures are stored as computer files on CompactFlash(CF) cards, or other small memory devices. IBM even makes a small hard disk that is used in some of the more expensive digital cameras.

Why use a light sensitive computer to record images instead of a traditional film camera? There are several reasons:

1) Digital "film" can be re-used - with traditional film cameras, film can be used only once. With a digital camera, the CF card or other electronic component used to store the images can be erased and used over and over again. You can usually erase pictures while the camera is in use, giving you the alternative to shoot an unlimited number of pictures if required.

2) Most publishing is computerized. In addition to the Internet, which is only computers, newspapers and magazines have for decades been computerized. Images and text are stored on computers during the composing stage. Traditional film pictures have to be converted to digital form via a scanner before they can be printed. Using a digital camera saves this scanning step - the second the picture is taken it is stored in the same format it will be published in.

3) No developing is necessary. It usually takes a few seconds to complete the digital conversion and storage steps on a digital camera. No chemical developing step is necessary to take the original film and convert it to prints or slides as is done with traditional film cameras. This means you can get instant input on how your pictures look. You can hook the camera up to a computer or a TV and look at your pictures within minutes after taking them.

4) Digital cameras have fewer moving parts than film cameras, and generally are less prone to outright mechanical failure. Exposing the "film" to light in a digital camera causes no harm, and since pictures do not have to be sent to a lab to be developed, there is no chance of pictures being lost at or in transit to a remote lab.

If digital cameras are so nifty, then why do film cameras still exist? There are several disadvantages to the current generation of digital cameras:

1) Digital cameras are more expensive to purchase than conventional film cameras. Digital cameras, however, are less expensive to operate, since you do not have to buy film or pay for developing.

2) You need a computer to get real use of a digital camera. Many inexpensive inkjet printers now print out very nice photographic quality prints.

3) Picture quality in digital cameras is not as good as high end 35 mm cameras. The gap is narrowing, but 35mm slide and print film still get better quality if you actually look at the prints or slides. If you are planning to use the pictures electronically (on web sites, etc.) then this difference disappears, since it takes a very expensive scanner to get a digital image as good as one produced by a good quality digital camera.

Each month brings new digital cameras, and cheaper prices on older digital cameras. While a computer will remain a critical accessory for a digital photographer for years to come, picture quality is improving rapidly, and price is dropping every bit as fast.

Let's say that, like me, you shot for many years in the analog world of film and slides, before digital cameras ever entered the scene. Obviously, you don't want to throw out all those images and start over. What to do? There are many options, but the two that are probably most appropriate for photos intended ultimately for digital consumption are:

1- have your images scanned to a disk or, preferably, a CD- Kodak photo CD provides several resolutions per image, generally at sufficient quality for most purposes

2- buy a film/slide scanner- although these can be costly, depending on quality, if you have lots of pictures you want to digitize, it will pay for itself quickly

In a digital camera, as mentioned above, a picture that has been taken is stored as a series of electrical charges on a silicon chip in a compact flash card. These are interpreted as binary (zero-one) values to display the image. How do zero-one values translate to the shot of Aunt Maude with Mickey at Disney World? Imagine that you could take that picture and play a very complex game of tic-tac-toe with it. You draw vertical and horizontal lines crisscrossing the picture. Since you like challenges, however, you make the tic-tac-toe grid more than 3x3. Let's say you make the tic-tac-toe graph 1536 rows high and 2048 columns wide. At this point you should probably forget about winning this game, and call each cell a pixel. If you make this tic-tac-toe board large enough, you could take a paint brush, and by putting appropriate colors in each pixel, you could wind up with a pretty good likeness of both Aunt Maude and Mickey. This is what a digital camera, like a Nikon Coolpix 990 does. It creates a very large grid with 3,145,728 (1536 x 2048 = 3,145,728) individual pixels or cells, each of which is assigned a color. The color in each cell is represented by a binary number (I bet you thought I had forgotten about the binary part) which ranges between 0 and 16,777,216. This is called a 24 bit RGB color value. It is called RGB because it is a mixture of Red, Green, and Blue values. The value for each color ranges between 0 and 255 (255 x 255 x 255 = 16,777,216).

This combination of very large numbers is what the camera generates when you press the shutter. So while you are admiring the way the sun shines on Aunt Maude's bleached hair, the camera is chugging away figuring which of 16,777,216 possible numbers should be assigned to each of the 3,145,728 pixels. When it gets finished with this bit of computation, there is even more work to be done. With 24 bits (or 3 bytes, 16,777,216 possible values) of data per pixel, the original image for a Nikon Coolpix 990 is 9,437,184 bytes in size. The problem is that a Coolpix 990 comes with a 16 MB Compact Flash card, and this one image is 9.4 MB in size. Nikon sales would suffer if folks spent $1,000 on this digital camera and could only take one picture with it before having to find a computer to save the image. In order to help out Nikon stockholders (and parenthetically their users) the camera usually does another step, called compressing the image. The compression used by the camera is the same one commonly used on the Internet, one developed by the Joint Photography Experts Group (JPEG) Not surprisingly, these images are called JPEG images. JPEG is called "lossy" compression because some image quality is lost during the compression process. JPEG is modifiable, it lets you trade off between an image very close to the original and a much smaller one. The Nikon 990 (and a number of other digital cameras) give you four options: uncompressed (the 9.4 MB image in TIFF format), fine, normal, and small. A fine image is very close to the original in quality, and is usually about 1.1 MB in size. This JPEG compression is a fairly sophisticated computation, so a digital camera does a lot of work to save that memory of Aunt Maude and Mickey.

Digital cameras are computers, and a number of standards exist for computer images in addition to JPEG. So why do digital cameras use JPEG? Is it the only image format I need to use? If the answer to the second question was yes, I would not be writing this paragraph. JPEG is a very good compression format for representing complex images, such as photographs, because it retains 24 bit color resolution (the 16,777,216 colors I talked about earlier), and a lot of the complexity of the original image. Unless you really know what to look for, it would be very hard to tell the difference between a high quality JPEG image and an uncompressed image. There are two factors that determine the quality of a digital photograph: resolution and color. The two are equally important, although resolution is mentioned much more in advertisements(3.4 MegaPixels!!!) than color. An 800x600 image with 24 bit color looks much more realistic than a 1024x768 image with 256 colors.

The sole problem with JPEG is that the compressed image is not quite as good as the original image. In order to make the image smaller, some detail is lost forever. There are compression techniques that do not lose anything ("lossless" compression) in the original image. They are used widely on the Internet for computer graphics in the GIF file format. Techniques like GIF achieve their savings in size through identifying clusters of pixels at the same location that have the same color value. The reason why GIF is not good for digital photographs is that the sun gleaming on Aunt Maude's bleached hair is slightly different in color than neighboring pixels. In order to get a GIF image of reasonable size of this photograph you have to reduce the number of colors. in the Aunt Maude case, it means taking a bunch of pixels depicting her hair and making them the same color. This color reduction is frequently done to a digital palette of 256 colors. Detail is also irretrievably lost with the color reduction. JPEG looks better, so it is used in digital cameras because flash cards are expensive and the pictures look pretty good.

If you are editing your pictures in a program like Photoshop, however, JPEG is not such a good option as your sole format. If you are editing your images on a computer, it is better to store your pictures in an uncompressed format such as TIFF than JPEG. This is because every image editing expands the compressed file to make it uncompressed every time it is opened. When the picture is changed and saved, it goes through the compression process again, irretrievably losing a little detail. After you are done with your final edits, you can save it again as JPEG. In summary:

JPEG -> Good for storage

TIFF -> Good for editing

I think the best thing about digital photography is the freedom to experiment. With rechargeable batteries you can shoot a lot of pictures, and not feel guilty about it. Push those boundaries!

Step by Step Guide to Digital Photography

This section is for folks who have their hands wrapped around a digital camera and are trying to figure out what to do next.

Getting Pictures Into the Camera

This is the easiest one - point the camera at a subject of interest, take the lens cap off, and press the shutter. For more information on how the camera takes the picture, and what form it is in, check our pages on Resolution, Image Compression, and Digital Colors provide additional insights on factors that affect the quality of pictures taken by your camera.

Getting Pictures out of the Camera

There are basically two options in these cases: paper and electronically. If you are interested in only printing your pictures, and not storing them electronically, check out our printing page. There are printers on the market that will print directly from a digital camera memory card. If this is your only use of a digital camera, however, you lose a lot of the advantages. In almost all cases, it is better to move your photos to a computer for editing, sending to friends via email, printing it out, and posting to the Internet. In order to manage this simple and natural migration, however, you have to swim through a veritable sea of acronyms and technical terms: USB, RS-232, 1394, PCMCIA, CF, FireWire, Parallel, Memory Sticks, Type I, Type II, Serial, and so forth. Not all computers support all these ways of talking digitally, in fact almost none support all of these. Here is a quick decoding of the alphabet soup, arranged in order from slowest to fastest (speed is important with modern digital cameras because multi-megapixel digital images are large):

Serial (RS-232, usually a 9 pin connector on most modern computers)

Parallel (20 pins, also referred to as the printer port)

USB (Universal Serial Bus, a single flat plug with a slot in the middle - don't confuse this one with RS-232, even though they both use the word serial, they are very different)

1394 (FireWire - this is usually a little square plug with a hole in it - this option is not present on most current computers)

PCMCIA, PC-Card, Cardbus, CF, ATA - these refer to slightly different protocols that generally work the same on almost all modern notebook or laptop computers. These are the flat sockets on the side of a notebook computer into which you can plug a modem or a network card. A CF (CompactFlash) card is much smaller than the card that most notebook computers will use, but there are readily available adapters that fit around a CF card and fit in a notebook computer slot.

Which of these options is available for your digital camera depends to some extent on the camera. For example, my Agfa ePhoto Smile camera, does not use removable memory, so it only comes with a serial cable. That is the only way to get pictures out of the camera. This camera retails for less than $100, and most more expensive digital cameras often provide several options for getting the pictures from your camera to your computer. Let's run through the options for four digital cameras I am fairly familiar with:

Agfa ePhoto Smile - This 0.3 megapixel camera uses a serial (RS-232) cable and Agfa software to pull the pictures from the camera. No other option.

Hewlett Packard PhotoSmart C30 - This one megapixel camera uses CompactFlash cards, and comes with a serial (RS-232) cable. You can transfer pictures from the camera using the serial cable and some HP software. Alternatively you can copy the pictures directly from the CompactFlash card to a notebook computer through a PC Card slot, or through a CompactFlash adapter. CF adapters come in two different flavors: parallel and USB. USB is the more recent and faster of the two. When you plug the CF card into a PC Card adapter and a notebook, or into a CF adapter connected to your PC, the card from the camera looks just like a disk drive to your computer. You can use Windows Explorer to copy the pictures to your computer for editing, printing, and posting to the Internet. You just pop the CF card out of the camera, put it a slot in the PC Card adapter or CF adapter and copy the files to your computer. On a PC, at least, the pictures are already in the JPEG computer image file format.

Nikon Coolpix 950 - This 2 megapixel camera also comes with a serial cable, and Nikon software called NikonView. You can transfer pictures from the camera to your computer by hooking up the serial cable and using the Nikon software. This camera comes with a CompactFlash card, and a faster alternative is to use a CF adapter or notebook PC Card slot, just as mentioned above for the HP C30.

Nikon Coolpix 990 - This 3 megapixel camera knocks out large images - an uncompressed 990 image runs about 9 megabytes - it would take a long time to transfer over a serial cable. For this reason, the 990 comes with a USB cable and NikonView. This speeds up the transfer, but this camera also uses Compact Flash memory, and using a CF adapter or a notebook computer with PC Card slot is still faster, as described for the HP C30.

Where do I put them?

This may sound like a silly question, but after decades of using computers on a daily basis, I still occasionally lose files on my hard disk. Oh, they are there somewhere, but I am not sure where. The thing is not to lose important files. Digital photos fall into this category. Photography is something you do over a long period of time, and you want to be able to find the pictures you took several years from now. Putting a little time and thought into how and where on your computer's hard disk you are going to put your pictures is a really good investment. One key component is to make use of folders (or directories) on your computer hard disk. Putting all your pictures in a single folder or directory makes it very hard to find pictures after you have accumulated several years worth. In addition, cameras like the Nikon 950 and 990 only have 10,000 possible picture file names. Picture 10,001 has the same number as picture 1. If you put them all in the same directory or folder, the new one overwrites the old (probably not what you want). Here is one possible scheme:

Pictures2000
July
1
2
3

The scheme I use is much geekier, but presents the same information in a single level:

Pictures
   2005
        11
          14
            Nikon D2x

The final value is the camera model. You would probably do best to develop your own system that matches the volume of pictures you take, and your personal preferences.

BACK UP YOUR PICTURES

Whatever you do, do not leave the only copy of your important pictures on your hard disk. You run the risk of losing them. Make copies of the pictures you want to keep. There are a number of options here, depending on what kind of computer you have: floppy disks, zip drives, CD-Recordable (CD-R), CD-ReadWrite (CD-RW), and Internet storage. This service is free, and is a good form of backup, in addition to other methods. For more information on storage alternatives see our page on Image Storage. It is impossible to have too many copies of your good pictures.

What about my old film pictures? Are they left in the bit-bucket of the digital age?

No. Any photograph, in negative, slide or print, can be converted to digital form through the use of a scanner. A scanner is a very specialized form of digital camera that comes in several sizes, shapes, and prices. The largest are flat-bed scanners that look like a copying machine, with a glass plate that you can place pictures on. There are also slide and negative scanners that take very high density images the size of a 35mm slide or negative. If you have expensive 35mm camera equipment, buying a scanner can be the most inexpensive way to enter the world of digital photography. We used scanners for years before there were cost-effective digital cameras, and have gotten excellent results from 35mm film. We currently use scanners for converting our existing film library to digital form, and pictures will be posted on this web site in coming months that have been scanned from 35mm. If we have scanners, why did we spend the money to buy a digital camera? There are two reasons why we generally prefer digital cameras to scanners:

1) With a scanner you take each picture twice - once with the camera, and once with the scanner. This increases the amount of time spent on each picture. In both cases there are losses that are unrecoverable and subject to possible error (the latter is particularly true in my case).

2) If you already have expensive camera equipment, then buying a scanner is the cheapest way to enter the world of high quality digital photography in terms of initial cost. In the long term, if you take very many pictures, then the digital camera comes out much cheaper, no matter what the initial cost, because there is no film or battery cost if you use rechargeable batteries. None of the 35 mm SLRs we own (Pentax, Nikon, and Canon) use rechargeable batteries, and those batteries are expensive.

The work flow with a scanner is very different from a digital camera, because you when are scanning a film photograph you are actually taking a digital photograph with a very large and unwieldy camera. Scanners usually come with scanning software, that lets you monitor the exposure and frame the shot, the same way a view finder does in a digital camera. You can modify a lot of parameters on a scanner, change the image a lot, all the while looking at a good-sized view of the image on a computer screen. For a lot of people this is all the image editing they plan to do, so scanning works out pretty well. With a digital camera, these steps occur when you focus and adjust the settings on the camera. If the camera and you have done a good job of taking the picture, you should have equivalent quality when you transfer the pictures from the camera to the computer.