THE LENS
Long before photography was invented, the Camera Obscura was used as a drawing aid. It literally means darkened room. No lens, but a small hole projected an upside down image across the darkened room. Its history goes back to around the 5th century. Eventually a lens was added and the diameter of the hole became adjustable. If you ever want to view a solar eclipse, using a camera obscura is the safest way. Today we have people who use pin-hole cameras that have no lens or adjustable iris. Exposure requires much more time because the hole is small and admits limited light. You could use your camera without a lens but that’s another story on how to do it.
Your camera came with at least one lens, most likely a zoom lens. Let’s say your lens is a ƒ2.8, 24-70mm lens. This means that the widest aperture is ƒ2.8, or 2.8 diameters from the lens axis to the cameras sensitive plane. The zoom range is 24mm(wide) to 70mm(telephoto). With a full frame camera, normal is +/- 50mm. Because there are different sensor sizes, please check with your camera manual. With a point and shoot camera, normal will be half way between wide and telephoto. Point & Shoot cameras do not offer a removable lens but will have a zoom lens already attached.
DSLR (digital single lens reflex) and Digital Mirrorless cameras offer a wide variety of lenses in both zoom or prime. We know that a zoom lens has a range of focal lengths. A prime lens is only one focal length, and smaller in size and weight. A wide angle is good for interiors, vistas, getting close to your subject, and it lives on the edge of distortion. A telephoto brings your subject closer and flattens the depth. Most new cameras come as a camera/zoom lens combo with a battery and camera strap. It’s a good start and it will do well for your needs. You can add a new lens to your camera case when or if you feel the need.
Zoom lenses are available in a range of sizes from very wide to extra long telephotos. There are also different types of prime lenses. Of course there are many wide angles and many telephotos to choose from. There are also lenses made for special applications. One of the most common is the macro lens for photographing smaller things like bugs or flowers. If your lens is not a macro lens, you can buy diopters to screw into the front of your lens to allow closeups. See the man at the camera store. Lens construction is a combination of several pieces of polished glass inside your lens. The glass inside your lens moves, for focusing and works like a magnifier as in the zoom lenses. The lens should be protected and cleaned sparingly. You should have a lens shade and use it. It will help protect the lens from light flare and from things you may bump into. It is not hard to spend more on your lenses than you did on the camera.
So let’s talk about ƒ-stops. When we talk about an ƒ-stop we are talking about the diameter of the iris. The iris is adjustable from the largest diameter such as ƒ2.8 to the smallest diameter such as ƒ16. The smallest diameter will give you the most depth of field with your lens, and a large diameter (ƒ2.8) will have a shallow depth. Why not alway shoot at ƒ16 you say? Let’s say you have a subject as your primary focus but the background is busy and distracting. If you shoot at ƒ2.8 your background will be out of focus and may not even be recognizable. Different ƒ-stops will have different degrees of depth.
Depth of field is different than focus. Focus is what you decide to be the sharpest part of the image. Depth of field is the amount of recognized foreground or background. Depth of field is generally greater with wide angle vs. a telephoto with a shallow depth of field. You can hold the background or let it go soft by choosing your ƒ-stop. Aperture priority is the mode you should choose when deciding on how much depth of field you want. Wide angle offers you a wider view and telephoto gives you a closer view. Wide angle offers a greater depth of field while telephoto is just the opposite and allows the background or foreground to soften. A wide angle tells a story. It shows what and where you are. A telephoto is great for portraits and separates the subject from the background.
Focus your camera with auto-focus or manually by turning the focusing ring on the lens. Successful auto focusing depends upon where you place the sensor that you see in the viewfinder or rear screen. When shooting portraits, focus on the eyes. I quite often turn off the auto focus because it is not fast enough and I miss shots. If you are shooting vistas that are over fifty feet away it really doesn’t make a difference. If however you are shooting a portrait and want a shallow depth of field, at the perfect moment then use manual focusing. Having the auto focus hunt for your subject gets old real quick. There is an AF/MF button on the lens or camera to turn auto focus off.
