Digital Is Different: Part II

Continued from Digital Is Different: Part I

No Film to Carry

A 256MB memory card will typically hold over a hundred high-quality JPEG images from an 8-megapixel camera and several hundred with a smaller resolution, such as 3 mega pixels. That’s equivalent to three to six (or more) rolls of 36-exposure film — all in a card smaller than a matchbook.

Think about how people shoot film. Most folks take many extra photos just to be certain they got the shot they wanted. Photographers will often shoot 3 or 4 extra photos of each subject, especially when using slide film. So now we are looking at 19-24 rolls of film compared to one little memory card. Think of the space all that film takes up.

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Carrying enough film can really be a problem when traveling, especially with today’s tight airport security. Photographers who always packed lots of film on trips now find they have extra space in their bags—sometimes a lot of space. They can take smaller bags with them, which are easier to put in the overhead compartment of a commercial jet. IN addition, they have fewer security problems. Photographers could not keep film in checked baggage because of threats of damage from the scanners. While carry-on film, multiple scans may result in fogging, especially with high-speed films. In other countries, the effect can be worse. Film and security can be an annoyance or a disaster.

With digital cameras, this all changes dramatically, making travel and photography mix just like they should. Each small memory card has the same image capacity as many rolls of film, takes up very little space and is easily tucked into your carry-on bag. Gate security machines have no affect on memory cards. The cards are small and cause no security problems, so keep them with you to ensure your photos are not lost in transit.

White Balance Control

White balance is probably the biggest departure from film of anything digital. It represents a totally different way of dealing with the color of light and the benefits of this feature are great. We’ll examine how to best use with balance later in the book. In this chapter, we’re going to look at how white balance changes the photo experience compared to film. It really does, and this is very important to understand.

First, though, you need to know that different types of light have inherently different colors. Our eyes and brain interpret these changes and compensate for the way we see colors whether the light is fluorescent, incandescent or daylight. On film, these conditions appear as extremely different colors of light. If you’ve ever shot film under fluorescents, the results were probably photos with an overall green cast.

Film can only be balanced for a single type of light, and any other light will give the scene a color cast. Use a daylight-balanced film indoors, for example, and it looks like you dipped the resulting picture in orange soda. Pros who shoot in business or industrial situations always carry an extensive set of color correction filters to deal with the varying lighting conditions. Print film handles different types of lighting better, but often requires major color corrections in the printing.

A digital camera adjusts its sensitivity to the color of light so that the camera responds more like our eyes. White balance refers to the way videographers would use a white card to actually balance their cameras to the color of light. The purpose of white balance is to make neutral colors neutral and the rest of the colors more natural. The camera isn’t quite as tolerant as our eyes, so slight variations in a scene’s light can affect it even with white balance tricks. Still, it does work quite well.

White balance is a common feature on all digital cameras. The digital camera today can examine a scene, automatically check the light for “proper” white balance, and select a setting for those conditions. More importantly, white balance presets can be chosen to match specific light conditions, or, in some cases, the camera can be custom balanced to match the light. In any case, no filters are needed, no light is lost due to filtration, and you can see through the lens with no darkening of the viewfinder from filters. All huge advantages!

Flexible ISO’s

Film speed, measured with an IS number, tells you how sensitive a film is to light. This is predetermined by the manufacturing of the emulsion, although it can be altered in special circumstances by the exposure and processing. This sensitivity rating was established by the International Organization for Standardization. It is a standard agreed to by countries throughout the world, and is used universally by manufacturers.

The important thing about ISO and film is how varied films with different ISO’s relate to each other. Low numbers—50 or 100—represent less sensitivity. High numbers—400 or 800—show that a film is more light sensitive. The numbers are mathematically proportional so that, when two films are compared, doubling or having a number represents twice, or half, the sensitivity, or speed, of the film. Once you choose a particular film, you must use the whole roll at that film’s specific ISO setting.

This does not apply to digital cameras. Technically, they do not even have true ISO numbers because they do not have the same standards as film, and because their sensitivity changes based on processing circuits in the camera. They have what are called ISO equivalents, though most cameras do abbreviate this to ISO. The equivalents are pretty close to true ISO’s in film, but if you use multiple digital cameras, you may discover exposures are slightly different even at the “same” ISO. This discrepancy is because manufacturers do their own bit of interpretation on the numbers since there is no central testing standard.

What actually happens with a digital camera when the ISO setting is changed is that you modify the sensitivity of the sensor’s circuits. Using a higher ISO setting is like turning up the volume on the radio when a station’s signal is weak. This can result in static, or in the case of a digital camera, noise. But the really great thing is that you can now change film speed at the touch of a button. You can be indoors, photographing your child’s party with an electronically chosen ISO setting of 400—and you don’t need to use the flash! Then, you follow the kids outside to play and change to ISO 100. This is a huge benefit! Since one camera can handle the multiple situations, you don’t need to carry along a ton of extra film in case you need the speed of different emulsions. And you don’t need to load a new roll of film or switch camera bodies.

There is one very big difference in film and digital cameras as to how ISO is set by the camera. In most automatic film cameras made in the past 20 years, ISO is set automatically when you put the film into the camera. The DX code—the silver and black checkerboard pattern on the side of the film canister — tells the camera what ISO speed to set. This means that you don’t have to think about ISO once you load the film, unless you want to manually override the film speed.

Digital cameras don’t work like that at all. You never use film or anything else that has a specific sensitivity to light. With a digital camera, you may have to choose the ISO. (Some automatic picture control modes on certain digital cameras will automatically set the ISO.) For standard auto and manual exposure settings on digital cameras, you must deliberately choose and adjust ISO settings.

Since digital camera and it’s sensor do not have a true ISA that matches film, manufacturers have developed ways to make the sensor respond similarly to a film’s sensitivity. Practically speaking, if you set a digital camera to ISO 400, it will respond to light in a way that is very close to that of ISO 400 film in a traditional camera.