Camerona

Photography is not just a word consisting of a few letters, rather it is a term full of science and math. ‘How camera lenses work’ is the most common question that arises in the mind of newbie photographers.  

A camera lens processes light rays coming from an object into a visual image. Without a lens, the camera produces insignificant white light. So, having a lens, specifically a good quality lens is important to capture great photos. 

Here is a full guide revealing the science behind the functionality of camera lenses. Additionally, this write-up contains the details of 10 different types of lenses. 

What is a camera lens?

Basically, a camera lens is a specialized tool, consisting of one or many optical lenses, to bring light to a focal point. It is mounted to a camera body, either interchangeable or permanently fixed. 

Interchangeable camera lenses deliver different focal lengths, apertures, and other visual properties. Compared to them, fixed lenses don’t perform versatilely. 

A lens can be made of plastic or glass, curved inward (concave) or outward (convex). Plastic lenses are cheaper and poor in quality, whereas glass lenses are totally opposite. 

How does it work?

• First, a lens catches straight light rays (through the frontal glass piece) coming from subjects/objects placed in front of a camera. 
• Second, it bends the light rays, converges them into a single point, and processes a focused light beam. 
• Third, the light beam reaches the light detector surface (image sensor/ film plane) and creates a sharp image. 

If the convergence fails, the image will turn out blurred or out-of-focus. The position of the frontal glass piece determines how the image will look like. 

When the glass piece is moved farther from the image sensor, the image will seem closer and sharper. Such action is needed when capturing distant objects. 

And when the glass is moved closer to the sensor, the image will turn out vague and blurry. The distance between the glass and the sensor does not affect much if the photographer captures nearer objects. 

This is a general guideline about the functionality of a camera lens. However, the science behind the functionality of convex and concave lenses is yet to be revealed.  

Convex lens 

A convex or positive lens is thick in the middle and thin in the edges. It works like human eyes. Both human eyes (front part) and convex lenses are curved outside, bend and converge the light, and create an upside-down image. Eyes do it on the retina and lenses do it on the sensor. When a convex lens flips an image, it appears smaller than the actual size. 

Concave lens 

A concave or negative lens diverges light rays, does not flip an image, keeps it upright, and makes it bigger. In a word, a concave lens produces virtual images. This lens is narrower at the center and broader at the upper and lower edge. 

Convex-concave combo 

When light rays pass through a convex lens, they make different focal points. The focal points of red light, green light, and blue light are respectively the farthest, farther, and far. 

Consequently, the light rays flowing through the convex lens are not clearly visible. To solve this problem, a concave lens must be added to the right side of a convex lens. With this combination, each ray of light can be placed together at a specific focal point. 

Such a combination allows one to clearly identify each ray of light, known as aberration correction. Again, a convex lens creates a real image by flipping it upside down. 

If a concave lens is added between two convex lenses, they will reverse the inverted image and form a real yet upright image. And such technology is used in cameras. 

Basic characteristics of a camera lens 

Focal length 

In simple words, focal length represents the area that the lens is able to capture. When focused on an image, the distance between the lens’ optical center and the camera sensor is measured in millimeters. 

And this measurement is known as focal length. The focal length focuses on a particular object of an image by isolating other elements. Also, it defines the field of view and magnification of a lens. 

Variable focal lengths result in alterable magnification and visual properties, which a fixed focal length does not provide. A longer focal length means a narrower field of view, and a shorter one provides wider capture. 

Aperture 

An aperture is basically an opening or hole that allows light to pass through the lens to the image sensor. In other words, before the processed light meets the sensor, the aperture controls it. The aperture number is measured in F-stops and T-stops. 

F-stops or Estimated Measurements are commonly used by digital photographers and independent filmmakers. And T-stops or Exact Measurements are the thing of professional filmmakers. Like focal length, lower or higher stop numbers determine the quality of an image. 

Higher stop numbers (like f/16) result in narrower openings, allowing less light on the image sensor, and creating a sharp image. Lower stop numbers (like f/2.8) mean wider opening, more light, and less focused capture, only beneficial for capturing in darker locations.

Shutter speed 

As the name depicts, the speed at which a camera shutter opens and closes. Shutter speed either freeze motion or makes it slower. 

When the speed is faster, the shutter opens quickly, the aperture allows less light to pass in the lens. The camera then records a fast moving object and the shutter closes speedily. Everything happens so fast, and the captured snapshot turns out blur-free. 

However, a slower shutter speed does exactly the opposite of what a faster speed does, consequently producing blurry snapshots. The shutter speed is measured in the fractions of a second. 

For example, the shutter count of a 500 mm lens is 1/500 seconds. It means the camera shutter will open and close within five hundredths of a second.  

Depth of field 

Depth of field refers to the area of focus of an image. In other words, it prescribes the highlighting ability of a lens. 

Different depth of fields offers both good and bad sides. Shallow depth of field on the one hand results in a blurred background, on the other hand, emphasizes a specific subject or object. 

A deeper depth of field gives equal importance to the background and other things. As a result, everything remains clear and focused. Also, viewers have to digest every imagery available. 

The depth of field varies according to lens aperture. Large apertures result in more light and shallow depth of field. And small apertures equal less light and a large depth of field. 

Types of camera lenses

1. Prime lens

• Contains a fixed focal length (24 mm, 35 mm, 50 mm).
• Provides a faster and sharper view.
• Easy to carry.
• Budget-friendly.
• Performs greatly in low light.
• Meant for interior photography, landscapes, portraits, street photography, etc. 
• Less flexible.
• Need to move to get a closer or farther view. 

2. Zoom lens 

• Contains different focal lengths with a series of lenses (17-40 mm, 24-105 mm, 70-200 mm). 
• More flexible than prime lenses. 
• No need to move physically to get a desired view.
• Great for wide range photography like wildlife, also for weddings and portraits. 
• Bigger, heavier, and slower than prime lenses.
• Costs high.
• Creating Bokeh or any less compressive mode is impossible. 

3. Macro lens 

• Provides a very close-up, accurate, detailed, sharp, and contrasting view. 
• The focal length ranges between 50 mm and 200 mm. 
• Perfect for small objects, like human eyes, dewdrops, insects, teardrops, coins, diamond rings, water droplets, etc. 
• Significant for product and fine art photography. 
• Delivers up to 5x magnification, results in high quality images. 
• Unqualified for capturing distant objects, general photography, and portraits. 
• Expensive.
• Takes a long time to focus.
• Slow shutter speed. 

4. Wide-angle lens 

• Captures a great large area into the frame. 
• Focal length commonly ranges below 35 mm. 
• Delivers a focused and vivid quality picture.
• Ideal for architecture, landscape, and street photography.
• Lightweight and mini in size. 
• Pretty affordable.
• Does not allow to create a blurry background.
• Distorts very close subjects/objects near the lens.  

5. Standard lens 

• Affords visual properties and perspective similar to human eyes.
• Snapshots look more natural and accurate.
• Valuable for documentary projects, portraits, street, and travel photography. 
• Focal length numbers are mid-range, falling between 35 mm and 55 mm. 
• User-friendly.
• Disappoints while clicking close-up sports photos and wide landscapes. 
• May deliver boring visuals. 

6. Fisheye lens 

• Best for achieving a 180° panorama view. 
• The field of view resembles fish eyes. 
• Offers an outstanding aperture to shoot easier in low light conditions.
• Focal length ranges lower than 24 mm. 
• Purposely distorts straight images to look curved or bubble, giving an artistic look. 
• Fits for abstract photography, design work, small spaces, security cameras, and wide landscapes.  
• Delivers enormous yet unnatural and annoying field of view. 
• Unversatile. 

7. Tilt-shift lens

• Manipulates perspective by making things toy-sized. 
• A wide lens with 17 mm, 24 mm, and 35 mm focal length numbers.
• Offers selective and sharp focus with fantastic saturation and contrast. 
• Minimizes lens distortion to provide quality images.  
• Meant for architecture and fine art photography.
• Heavy in weight.
• Getting auto exposure is impossible.  

8. Telephoto lens

• Captures things from farther to farthest distance. 
• Allows zooming as per demand in a static position.
• Isolates things with a great blurry background.
• A zoom lens with an 85 mm to 600 mm focal range.  
• Made for astronomy, wildlife, and sports photography. 
• Provides a narrower field of view. 
• Bigger, bulkier, and more expensive than other lenses.
• Requires monopods or tripods to handle. 

9. Kit lens 

• Captures realistic images of subjects and/or objects.
• Works as a complimentary or interchangeable lens with another lens. 
• Known as a ‘starter’ lens, also perfect for amateur photographers.
• The focal length range is 18-55 mm. 
• Ideal for general-purpose photography, including architecture, events, landscapes, and portraits. 
• Performs either as a wide-angle lens or a short telephoto lens according to perspectives. 
• Lightweight and inexpensive. 
• Moderate focal length and slower autofocus limit exploration. 

10. Infrared lens 

• Detects and captures unseen infrared energy, converts the energy into an electronic signal, and processes the signal to create a thermal image. 
• Produces unique visual effects.
• 35 mm, 50 mm, and 80 mm are focal range numbers. 
• Works finely in both darker and brighter conditions.
• Also delivers black-and-white images with B+W infrared filters. 
• No focus shift problems. 
• Only meant for IR photography.  
• Filtering out visible lights results in long exposure times. 

To conclude 

No lens is a perfect lens, and no lens is a bad one. Every lens works differently for various purposes. If the user is unaware of the functionality of each lens, it won’t make a lens faulty. 

Therefore, a photographer should have an intense knowledge of camera lenses. Before choosing a compatible lens, it is better to try each lens to know which matches best with the project’s preferences.