A Guide to Digital Photography

By Mike Siesel

Would you like to shoot like a pro and have your photos come out ready for print? Well I can’t promise that, but I can help you get closer to that point if you follow a few basic rules when you’re taking pictures.

First, you must know your camera. There are several websites that offer a detailed review of most of the cameras on the market today. Even if you’ve already bought a new camera, or you’re shopping for a used one, you’ll find these reviews helpful because they often describe the idiosyncrasies of the model, and provide some information on settings that will improve your ability to take a better photo.

For instance, after reading Phil Askey’s review of the Canon 10D I decided to set my exposure compensation to a negative value when shooting in bright light. This pulls the exposure back from pure white, and avoids the loss of highlight detail. I might have learned that on my own, through trial and error, but that would have meant that some of my photos would be less than optimum.

Just the same, you can increase the exposure value in low light. This is advantageous if you do not have a tripod handy, or your subject is moving. You probably know that your digital camera, like film, has an ISO rating or setting, and you can think of the EV or exposure value as an intermediate value, or a means of fine tuning the ISO.

The best way to insure that your color photos are well balanced is to manually set the white point with a gray card. Now that’s a bit confusing isn’t it? Well consider that it is very difficult to find anything that is pure white - even paper has a tint - so the standard is instead a precise level of gray. 18% gray cards have been used for over a half century, though some recommend 12% gray for digital. (Canon recommends using a white card or plain sheet of paper)

The main thing is that you have a color neutral surface so that you can register the light source. This sets the camera so that it captures the colors without the tint associated with artificial lighting. You can buy gray cards, and even lens cleaning cloths in gray, from any decent photo store. By taking this simple step you will insure that you’ll get the best color rendition that your camera offers.

To do this you’ll want to enter the menu and select Manual White Balance, and then meter the card. There is a difference between incidental light, meaning that which falls on the subject, and the reflected light coming from the subject. While the camera only meters reflected light through the lens, you’ll get your best results by placing your gray card so that you can meter the light as it falls on the subject. In some cases they’ll be the same, or very close, but it’s a good idea to understand the difference if you’re going through the trouble to set the white point or balance your color using a gray card. 

In case this has you worried, all digital cameras have a default setting that automatically sets the white point. This generally works well outdoors. There’s also specific settings for florescent lighting and incandescent lighting. Some cameras are better than others, and when shooting indoors you can use the flash, but under artificial light the only way to be certain is to use a gray card.

Another consideration is the file format. Some cameras only offer one format and that is JPEG. This is a compressed file, and in processing the compression there’s always some level of artifact and loss of information. Generally this is not a problem, but naturally as compression is increased, so are the artifacts. There are software programs that can remove most of the artifacts, but none can add in the lost detail.

That’s one reason why professionals and serious amateurs often select a raw or TIFF format instead of JPEG. The raw format stores the actual information collected by the sensor and allows the photographer to manipulate that data. TIFFs are uncompressed images with the camera settings applied, but not many cameras offer this format.

Raw files are approximately the same number of pixels as the sensor. Because the raw data is interpolated to provide red, green, and blue pixels, the file size of a TIFF will be at least three times the size of a raw file. If your camera records in more than 8 bits per color channel, typically 10 or 12 bits per channel, the TIFF file will be six times the size of the raw file.

To add some clarity to this, I’ll use my Canon 10D as an example. The raw file is 5.8 megabytes. At 8 bits per color channel the TIFF file is 18 megabytes. At 16 bits per channel the TIFF file is 36 megabytes.

The camera only records 10 bits per color channel, but the image can only be saved as either an 8-bit or 16-bit file. That’s just the convention and there’s no getting around it.

So what’s the difference? Eight bit color is sometimes described as “true” color. It’s about what we can see, or readily discriminate, basically 256 levels of intensity in all three channels — red, green, and blue. That also corresponds to the binary system that our computers use and display. In binary it takes 8 bits to count to 256.

However, in the real world there’s an infinite number of colors. And professional grade photo printers are capable of printing a wider range of color than our monitors normally display. So, relatively speaking, a camera that records 10 or 12 bits per channel provides more color information, and therefore detail, for those who are capable of printing the wider gamut or range of colors.

Photography became popular because of the 35mm format. The actual size of the frame is 36mm by 24mm so I'm not sure why it’s called 35mm. The point here is that SLR digital cameras use the same lenses that a 35mm film camera does. Consumer models use smaller lenses and quote the focal length in 35mm equivalents. Keep in mind there’s a difference between 35mm as a format, and 35mm as a focal length, which also determines the field of view.

The use of the 35mm standard made it convenient for photographers who gravitated from film to digital. However, most digital SLRs have smaller sensors, making them more affordable. However, this also causes a cropping of the image projected by the lens and results in a telephoto effect. My 10D has a crop factor of 1.6; therefore my 50 mm macro lens is equivalent to an 80mm lens on a 35mm film camera. Of course we are now seeing full frame digital SLRs meaning that the sensor is the same size as the 35mm film frame, so these cameras do not crop the image. The least expensive is the Canon 5D which as of this date sells for $3000, no lenses included.

So most digital SLRs have a crop factor, and certainly all of those within the price range of the average enthusiast do. Now there are different ways of looking at this. On one hand my 7-300mm zoom suddenly taps out 480mm. That’s a nice long shot. But the 20mm I just bought is effectively a 32mm, which drops the field of view from almost 90 degrees to maybe 60. That’s still wide angle, but it also cost me another $200 to get it.

Consumer models have fixed lenses. All that I know of have zoom lenses, some that look like an SLR and provide as much as a 12x magnification. The focal length of the lens is quoted in a 35mm equivalent, but the lens itself is actually many times smaller. The reason for this miniaturization is that the sensors are very small. My Canon G1, for instance, has a sensor that measures 7.18mm x 5.32mm, or about one-fifth the size of a 35mm film frame.

To fit the lens to the sensor, the lens had to be made smaller. So the 7mm to 21mm zoom lens is quoted as a 35mm to 105mm equivalent because the field of view is the same through the lens as those focal lengths on a 35mm film camera.

The reason for bringing this up involves the effect on depth of field. Normally when taking a photograph some consideration is given to the depth of field because you always want the entire subject in focus, and just the same there are times when you’d like the background to be out of focus (this is known as bokeh, a Japanese word). The problem that I and others had with the early digitals was that there was no bokeh even with the lens wide open. And there was a bit of wonder when at f4 we were getting sharp pictures of objects some considerable distance away.

Depth of field is controlled by the aperture, or the opening of the lens. For several decades aperture was expressed as a function of the size of the lens. So f2 is the focal length of the lens divided by two. (In other words, the lens opening is half the diameter of the lens.) Naturally this varies with the actual focal length and on a 7mm lens the actual size of the opening at f2 is 3.5mm. But the 35mm equivalent in field of view is a 35mm focal length, and f2 on a 35mm film camera lens is actually 17.5 mm.

Now the tricky part of this is that while the aperture of the lens is relative, the depth of field is determined by the actual size of the opening. If in fact you were to stop down the 35mm film lens to an opening of only 3.5mm, the aperture would be an f8. Extending this to the minimum aperture, an f8 on my G1 would be equal to f42 on the 35mm focal length film lens. That’s extraordinary, and the reason that the depth of field was significantly enlarged.

The camera manufacturers have made allowance for this phenomenon and all the newer models (from 2000 and on) offer a choice of scenarios. And if you’re a casual shooter you’ll definitely want to use the portrait mode, or macro mode, if you want the bokeh in the background; and landscape mode if you want the entire scene in focus. If however, you aspire to understand this better you can do a search on "depth of field" and the "circle of confusion" which is the zone where the image appears to be in focus.

In addition to the lens and aperture issue, consumer cameras also exhibit a higher noise level than the SLRs. Because their sensors are very small, the pixels are closer together. And the more pixels they pack into a sensor the more noise they generate. This has led to noise reduction algorithms in the camera’s firmware and essentially negates some of the advantages of the extra pixels.

So the advantage an SLR offers is that the sensor is larger, allowing more space between pixels, and therefore has less noise per pixel. In addition, some SLRs like my Canon 10D have a CMOS sensor rather than the CCD or charged coupled device used in the consumer models. It’s the primary reason that Canon is able to reduce noise and other artifacts in their digital SLRs to a level that has become the benchmark for all others.

Let me say it this way. If I am a CMOS sensor, I live in a house and I have nine neighbors surrounding my property. If I were a consumer camera I’d have nine neighbors but all in one very small apartment building. And that’s not an unfair comparison.

One of the complaints among reviewers is that manufacturers continue to engage in a pixel race, each year adding a couple of megapixels to their sensors, crowding them even further, rather than addressing the noise factor in the chips. For this reason improvements in image quality are incremental, and the impression on the consumers is somewhat misleading.

What I’m saying is that last years model shouldn’t be scorned because it has fewer pixels, and don’t be fooled into thinking that a ten megapixel sensor in a consumer model will provide an equivalent image to that from a true SLR. Ultimately it depends on how large a photo you wish to print, as well as what type of photos you like to take.

One of the best ways to learn what a particular camera will do is to join a forum based on that brand or model of camera. When you pose a question include some information about your skill level, and whether you take photos indoors or outdoors, of people of landscape or architecture, and what size prints you’d like to make, and basically what’s most important to you in a camera. That will usually generate some meaningful responses that will help you become a better photographer, and if you’re shopping, it will help you narrow your choices.

Finally, all the camera manufacturers include a software suite that’s adequate for fine tuning and printing your photos. So it’s a good idea, if you’re just starting out, to learn those programs before you go shopping for something reportedly better. And there are better or more fully featured programs, but unless you’re planning a career in photography you probably won’t need them.

That said, there are a couple of freeware programs that you may find very useful. The first is Picasa2, a beta program from Google. It requires either Windows 2000 Professional, some version of Windows XP, or Linux. What it does is index all your photos, offer some basic controls to enhance them, and makes it easy to publish them on the web. You also get 250 MB of storage (approximately 500-600 photos) for your web albums, and you can make them public or not.

The other is a lightweight image viewer that can create slide shows, play videos or music. But IrfanView is more than that. It’s what I use for batch resizing, conversion to another format, and renaming photos. In other words, if I have just taken 50 photos and I want to rename the files September xxx then I just load the photos into IrfanView, designate a folder, let it do its thing. It happens to be very popular among amateurs and even some pros, so it’s worth your time to take a look.

If you’ve read this far you’re probably interested in learning more about digital photography. The web is a great place for information, tutorials, and reviews. But I also encourage you to grab a handle and join a couple of forums where you can interact with other photographers, see what they’re doing, get some ideas of what you might do with your own camera. Above all have fun. You’ll always do better doing something you enjoy.

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