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Common SLR Features Explained

Choose the feature you want to see from the list below or read through the descriptions of the most common SLR features.  This is not a comprehensive list of every feature available on every camera, but rather a list of common features that are likely to be of interest to the first time SLR buyer.
Advanced Flash Control Flash Bracketing

Aperture Priority

Focus Tracking

Bracketing ISO Compensation
Built in Flash

Multi-Segment or Matrix Metering

Center Weighted Metering Program Mode

Custom Modes

Reset Button

Diopter Adjustment Shutter Priority

DX Range

Shutter Speed
Depth of Field Preview

Spot Meter

Exposure Compensation

TTL Metering
Film Advance

Variable Focus Points

Flash Compensation

Program mode - This allows you to use your SLR like a very high quality point and shoot.  It lets the camera make all the decisions for you.  In most situations the camera will be able to choose the settings to give you a picture that is technically "good";  in focus and properly exposed.  But program mode will rarely give you "great" photos.  Great photos still require the photographer to make creative decisions.

Aperture/Shutter priority modes - These modes allow you to take more control over the image without worrying about exposure.  Changing the shutter speed determines whether that soccer goalie is frozen in mid air or if her hands and feet are blurred.  Which is more desirable depends on whether you're trying to show critical detail or convey a sense of motion.  Lens aperture determines depth of field in an image.  

People get confused about this but it's a simple concept.  Think of that soccer goalie.  If that image was taken by a pro the goalie is probably very sharp and the background is blurred.  This makes the player stand out against the background.  Now think of a beautiful landscape.  That image is tack sharp from the foreground all the way into the picture.  You can control how much, or how little, of the image is in focus by how you set the lens aperture.

Custom modes/Vari Programs - Most consumer cameras and some advanced amateur cameras have custom modes.  Custom modes are variations of program mode that allow you to say "freeze action", or "I'm taking portraits" and the camera will adjust itself to expose for those situations automatically - with varying degrees of success.

Reset button - With so many features on new cameras it's not unusual for people to get confused about what they've set and what they haven't. Most cameras give you a way to get back to the original factory settings.  The only question is how easy is it to get there?  The XTsi we reviewed last month had a reset button right on top.  Great for beginners, but we thought it was kind of a pain for advanced users since it was so easy to hit.  When all else fails, take the batteries out for 10 minutes. This will usually reset the camera.

Built in Flash - Most consumer and advanced amateur cameras have a built in flash. These small flash units aren't particularly strong, they throw just enough light for fill flash at parties or for impromptu portraits.  These cameras also offer varying degrees of support for more powerful add-on flash units. The assumption with pro cameras is that a pro wouldn't deign to use the feeble flash power of a built in flash and that a pro will have invested in a more powerful unit.  Frankly, even though I have a top of the line flash, I like the convenience of a built-in flash for those candid moments.

TTL Metering - Virtually all cameras today have TTL metering, which means that the camera measures the amount of light that is coming Through The Lens (TTL) or in some cases the amount of light that is actually reaching the film.  Despite all the claims and counter claims you'll find that all cameras can and will give you accurate exposure under most conditions.  The difference comes under demanding conditions such as very low light or situations with great variations in the amount of light in different parts of the scene.  As a general rule, advanced amateur and pro cameras will handle difficult lighting conditions better than consumer cameras.  However, the casual photographer isn't as likely to put great demands on the camera's metering system.

Multi-Segment or Matrix Metering - Every manufacturer offers multi-segment metering on all of their current autofocus SLRs (all current manual focus SLRs offer center weighted metering). Nikon refers to their multi-segment metering as matrix metering.  Multi-segment metering breaks the image up into sections and determines correct exposure by comparing readings from each section of the matrix against a stored database of images to determine the correct exposure.  This is a VERY simplified explanation and the details differ with each camera model.  The important thing to note is that modern multi-segment metering is very accurate - even on entry level models.

Spot/Center Weighted Metering - Spot metering allows you to pick a small part of the scene and tell the camera to only take a meter reading from that spot.  Imagine a person in a dark room with a single ray of light falling on their face.  Spot metering allows you to tell the camera to only consider their face when metering.  Center weighted metering draws a big circle in the center of the image and primarily considers that area for exposure.  Center weighted metering has really become superfluous with today's multi-segment meters but it is still preferred by some folks who've used it extensively in the past.

Focus Tracking - Every manufacturer has a version of focus tracking.  It allows the camera to maintain focus while you follow a moving object.  Some systems are even able to maintain lock if the subject moves behind a stationary object - picking the subject up again on the other side.

Exposure compensation & bracketing - Exposure compensation allows you to choose to over or under expose a single shot.  Bracketing allows you to automatically shoot above and below the camera's suggested exposure by a set value.  Some pro cameras allow you to shoot more than one frame above, and more than one frame below the suggested reading.  Bracketing is particularly useful in low light shooting.

Flash compensation & bracketing - the same as compensation & bracketing but applied to the strength of the flash's output. Allows you to experiment with what levels of flash look most natural.

Advanced Flash control - Only an issue with advanced and pro cameras.  Today's external flash units are very sophisticated.  They can be used alone, with other flashes, or in concert with studio flash and lighting.  The best cameras allow you to control all aspects of your flash setup from the camera.  Those that don't, require you to set each individual flash by hand for these types of setups.

Viewfinder coverage and diopter adjustment - tells you if you see everything that is going onto the film.  Most consumer and amateur cameras only show you about 90% of what actually goes onto the film.  This makes up for the part of the image that is hidden behind the matting if you're framing the picture.  Pro cameras typically show 100% of what is going onto the film to give the pro complete control with no guesswork. Diopter adjustment allows you to compensate in the viewfinder if your eyes are less than perfect so  the image will always appear sharp in the viewfinder - even if your eyes aren't.

Shutter speed - What is the fastest shutter speed your camera is capable of?  Manual student cameras and consumer cameras usually have a top speed of 1/1000th to 1/2000th of a second.  Advanced amateur cameras usually top out at around 1/4000th.  Pro cameras are currently in the 1/8000th to 1/10,000th of a second range.  Frankly unless you're doing a lot of high speed work you'll rarely (if ever) shoot above 1/2000th of a second.  If you need really fast shutter speeds you'll know it. At the other end of the spectrum it's nice to have a camera that can do long exposures for nightscapes.  Many cameras will support shutter speeds longer than their slowest marked speed if left in program or night scene modes. Virtually all cameras have a "bulb" setting which allows you to keep the shutter open as long as the shutter button (or cable release is pressed).

Film advance - How many pictures per second can your camera take? Fast frame rates are especially useful for sporting events. For example; we've all seen series of images of a batter's swing as he contacts the ball.  Fast frame rates allow you to take similar images.  Expect a rate in the one frame per second range for consumer cameras, 2.5 to 4 frames per second for amateur cameras, and 8 frames per second and up for pro cameras. 

DX Range and ISO compensation - Don't worry about DX range.  Today's SLRs will handle pretty much any film speed you want to throw at them unless you're getting into something really exotic.  More useful is ISO compensation.  It's not unusual for experienced photographers to set the film speed for slides 1/3rd of a stop under it's rated speed (i.e.. setting the camera for ISO 80, when the film's rated speed is ISO 64).  This gives more saturated colors in the final image.  The same effect can be achieved by rating negative film 1/3rd to 1/2 stop faster than it's rated speed. Not all cameras offer this option, particularly consumer cameras.  This is because consumer shooters aren't likely to want to use this feature as their primary concern is usually ease of use.

Depth of field preview - A rare function these days but a great learning tool.  Depth of field preview allows you to preview what parts of the image will be sharp before you press the shutter.

Variable focus points - Many advanced and pro cameras, and even some consumer cameras allow you to pick a spot other than the center of the image as the point of focus.  The spot that you've picked usually glows in the viewfinder to let you know what spot you're using. Canon has a unique system that watches your eye to determine what part of the viewfinder you're looking at, and automatically sets the focus there.

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