About Digital Cameras

About Digital Cameras

Rev. 1

 

Digital photography and video are increasingly popular. The user has more satisfaction and motivation when he or she gets better pictures and videos. We believe that the best way to improve users’ skill is through better understanding of how digital camera works. This article reveals some basic aspects of digital cameras and has suggestions how to use them better. The references about the digital cameras are abundant containing also schematics and various graphs. Anybody can go to Internet and make a search on digital cameras using various search engines. The outcome will be several hundred thousands if not millions of results covering a multitude of direct and related aspects.

This article summarizes the main functions and features of digital cameras, either point-and-shoot – PS, or single lens reflex – SLR. We do not claim complete coverage of the subject. We only highlight key features of digital cameras. It will be a great reward for us if this article can trigger further investigations for those interested to find more information. The reader is strongly encouraged to post comments in this site about this article and also to tell us what particular topics we should comment in the future. Thank you in advance for your help.

 

Digital PS is the modern version of popular viewfinder cameras for films. In digital PS, the lens permanently attached to camera makes the image of the scene on the image sensor built either in CCD technology, or in CMOS technology. Some recent PS camera models such as Canon PowerShot A1300 16.0MP Digital Camera with 5x Digital Image Stabilized Zoom 28mm Wide-Angle Lens and 720p HD Video Recording still have an optical view finder matching the viewing angle of the lens, like its film ancestors. Optical viewfinder is very good when framing the scene in the sunlight. Obviously, this camera has also rear LCD for viewing the scene, as most of digital PS cameras have. We recommend too, this camera to our readers.



Digital Cameras Schematic shows on the right hand side the main elements of typical digital PS cameras. Vast majority of the digital PS cameras, such as Canon PowerShot S100 12.1MP Digital Camera with 5x Wide-Angle Optical Image Stabilized Zoom use only rear LCD for displaying the scene aimed by the lens, at the expense of battery drain. We recommend also this camera, which is pocket-friendly and has the most advanced DIGIC 5 Image Processor. Keep in mind that there are always problems watching the picture on rear LCD in bright ambient light.

Do not forget: rear LCD drains significant power from the battery in any digital camera. For preserving battery life, it is better to turn ON the rear LCD only when you need it. All digital cameras keep ON rear LCD for a limited time selected by the user. We suggest to keep LCD active for 1s.

AUTO Shooting mode gives reasonable quality pictures for most situations. This article summarizes some aspects to consider when shooting to get consistently good quality pictures.

All digital PS cameras have optical zoom lens, but there is also electronic zoom. For good quality picture, our suggestion is for using mostly the optical zoom. When enlarging the image beyond the boundary of the optical zoom, the camera goes into the electronic zoom mode, which may blur the image significantly if enlarging too much. Higher electronic zoom gives more blur. When shopping for a digital PS, look at the minimum focal length and also at the optical zoom factor. Lenses with short focal length have wide viewing angle and vice-versa. Be aware that short focal length may distort the image toward its sides. Optical zoom inherently decreases the picture sharpness toward longer focal length, but the picture has less distortions toward the sides. There are no ways to change this: it is a matter of physics.

When shooting, press the shutter button half way gently and wait one or two seconds to allow the lens to focus the image and also to allow the camera to set properly the ISO_speed, the exposure f/number and shutter speed. You feel half-way position of the shutter as slight resistance at your finger. When you shoot static scenes, several half-way trials give even better ISO_speed, f/number and exposure. Keep in mind that image focusing requires mechanical movement of some elements of the lens; therefore, it requires some time to settle. Do not push the shutter button too fast; you might get blurred pictures. Eventually, the camera “tells” you “when” to press further the shutter button. Check your camera manual for details.

For shutter speed slower than 1/60, we recommend using a stable tripod and camera timer for delayed shooting. In this way, good quality pictures is almost guaranteed. Very few people have “stable” hands for not moving the camera during exposure times longer than 1/60.

In Manual mode, set sensitivity at ISO100, or ISO200 in bright light. For dim light such as candlelight, select ISO3200, ISO6400 or higher, if the camera allows this. There is very little noise in the image when shooting with ISO100. In dim light, you must increase ISO_speed to be able to shoot, but do not be surprised to see speckles or noise in the image. Currently available cameras have some noise at high ISO_speed beyond ISO1600, which is normal. However, camera manufacturers are continuously striving to reduce this noise.

We suggest to select a reasonable picture size of 3072x2040pixels or 2400x1600pixels, or medium-size option. This gives good picture quality on 1900x1024pixels computer screen and also on 4x6inches paper. Digital SLRs offer more choices for picture size, better sensitivity and less speckles when shooting in low light.

If the picture is clear, do not be deceived if it is a little bit either darker or lighter. Anybody can fix this easily by computer, using one of the image viewing applications built in the modern operating systems, either Windows or MAC OS. Rear camera LCD gives you a rough idea about picture quality. For more information on picture, look at its histogram. In Exposure Cases schematic, top row shows a correct exposed picture and its histogram with its maximum roughly in mid tonal range.


Portability and good image quality made today’s digital PS increasingly popular among the amateurs and professionals alike. The continuing progress in electronic technology made digital PS better at affordable prices, with increasingly better image quality.

We recommend several cameras from the Top 100 Best Sellers in digital PS:


Compact System Cameras released recently on the market by several companies such as Nikon, Olympus and Sony are digital PS cameras with lens-changing capabilities. We recommend Nikon 1 V1 10.1MP HD Digital Camera System with 10-30mm VR 1 NIKKOR Lens.

We recommend several cameras from the Top 100 Best Sellers in Compact System cameras:



 

Digital SLR camera as you see in the left hand side of Digital Cameras Schematic, is a modern version of the film SLR camera. A reflex mirror and a pentaprism directs the image from the lens toward the viewfinder. Digital SLR Cutaway schematic gives you 3D perspective of digital SLR camera. Digital SLR camera has two main advantages over digital PS camera: (i) the lens can be changed and (ii) you always see in the viewfinder the image made by the lens regardless of the lens type.

You see below Canon EOS Rebel T3i 18MP CMOS Digital SLR Camera and DIGIC 4 Imaging with EF-S 18-55mm f/3.5-5.6 IS Lens, one of the most popular digital SLR cameras on the market. We also recommend this camera to our visitors.

A digital SLR camera schematic is shown in Digital Cameras Schematic at left hand side and also in Digital SLR Cutaway schematic. In the pointing position, the reflex mirror directs the image upwards to a pentaprism and further to the viewfinder. A smaller secondary mirror, solidly attached to the reflex mirror and behind it, reflects the rays going through the main mirror toward the auto focus sensor located on the bottom side of the camera. Before pressing the shutter button, the operator defines the shooting area by looking through the viewfinder. When the operator presses the shutter button half way, the camera microcontroller adjusts the lens for the best sharpness using signals from auto focus sensor. Digital SLR allows the operator to focus the image either in center or off center in one of the focusing points selected by photographer. The number of image focusing points depend on camera manufacturer. Read carefully your camera manual for details. The same microcontroller adjusts also f/number and eventually the shutter speed for the best exposure for selected ISO_number.

Shutter speed is computed by the microcontroller using the information from the light metering system measuring the luminous flux across the image in up to 252 points. Pressing the shutter button further for shooting, the main mirror flips upwards for covering the pentaprism, thus preventing the ambient light from outside the camera to penetrate into the mirror box area. Now, the light from the lens hits the image sensor and the microcontroller opens the shutter during the shutter speed time. The computation is based on selected ISO_number and other shooting options for obtaining the best light exposure of the image sensor, according to camera firmware. For selecting ISO_speed, follow the same hints as mentioned in digital PS. Digital SLRs have more choices for ISO_speed selection either in bright light, or in dim light. Select ISO100 or less in bright light. For dim light such as from candle, you can select ISO6400 or more, with some loss in image details. If you shoot a static scene in dim light, use a tripod and select ISO100 for preserving image details and for minimum noise. The pictures taken in bright light are practically free of speckles or noise. Camera manufacturers are constantly striving to reduce image noise, which is not an easy task at all.

For shutter speed longer than 1/60, we recommend to use a stable tripod for obtaining consistently good quality pictures. Very few people have “stable” hands to not move the camera during longer exposure times. Make sure that you do not move the camera when you press the shutter button, even if the camera is locked on tripod.

We strongly suggest you to use also a tripod when you you use telephoto lenses with focal length longer than 85mm, even in bright light and when the exposure time is as short as 1/250. The natural move of the hands is heavily amplified by the lens and can blur the image.

Digital Cameras Block Diagram shows the main elements of digital cameras and the functional links between them. The image sensor is a two-dimensional pattern of photosensitive elements or pixels for converting the image in electrical signal. Each pixel is converting the image across its area. More pixels across the image reveal more details of the image. An image sensor with a special color filter on top of it is used for color images. Today, all digital cameras have color image sensors containing between 6M pixels such as Nikon 1J1 and 36.3M pixels such as Nikon D800. The pixel count is very important, but is not the only parameter defining the image quality. Noise level of the image sensor and the Imaging Core have also important contribution to the quality of image conversion.

The Imaging Core process the signal from the image sensor. For clarity purposes, in Digital Cameras Block Diagram we show only Digital Image Processor and the Microcontroller as main components of the Imaging Core. In reality, the imaging core is very complex. Every digital camera manufacturer has its own Imaging Core, such as DIGIC of Canon and Expeed of Nikon. Briefly, the Imaging Core makes image processing, video processing and camera control. Image and video processing are strongly related to the characteristics of the image sensor. The Microcontroller performs multiple tasks, such as reading ISO_number, exposure time and aperture eventually provided by the operator through the user buttons. In automatic mode, the Microcontroller sets all exposure parameters. It performs also the best focus on the image sensor, triggers the flash unit, opens the shutter, saves the picture to the flash card and sends the picture to rear LCD.

Most of SLR cameras have also manual focus option. For best picture quality, we strongly suggest to use by default auto focus, which gives by far sharper images, works faster and gives more reliable results than manual focus. There are also rare situations, such as shooting through chain-link fence, when auto focus will will focus on fence, which is closer to the camera than the targeted subject.

We recommend several Digital SLR cameras from the Top 100 Best Sellers in Digital SLR cameras:


There are several types of flash memory cards for storing pictures of digital cameras, such as secure digital (SD, SDHC, SDXC), memory stick and Multi Media Card (MMC). Always you need one to three spare flash memory cards for your camera. Three elements are important for flash memory cards: (i) mechanical compatibility, (ii) capacity expressed in GB, and (iii) speed. With so many flash card options available on the market, the best advice is to look at the camera manual to see the suggested flash memory cards for your camera. We recommend to choose the largest capacity supported by your camera, and fast enough to accommodate the camera transfer rate. Below are our recommended flash memory cards. For more options, follow the links.


Flash card management is totally at user’s choice. The user can select the picture size saved by the camera, ranging from 720x480pixels, up to 6144x4912pixels. Obviously, larger image size gives more details, but less pictures can be stored on the flash memory card. It is always a tradeoff between the picture details and the number of stored pictures on the flash memory card. This tradeoff is totally the operator’s choice. We suggest a reasonable image size of 3072x2040pixels or 2400x1600pixels, giving good picture quality on 1900x1024pixels computer screen and also on 4x6inches paper. Typically, the digital cameras store the picture in compressed .jpg format, widely accepted by most computers and Internet applications. All digital SLRs can store pictures in RAW image format, to avoid compression artifacts associated with .jpg compression. Be sure that your camera was set to store the pictures in .jpg format, for efficient use of your flash memory card, for easy transfer to your computer and for easy reading using the image readers available in major operating systems of computers and smartphones. Picture files in RAW format are used at professional level. They are very big, take a lot of space on your flash card, and need camera manufacturer software for transferring them to your computer.

All digital cameras are provided with USB connection for transferring the pictures either to a computer, or to an iPad. Be aware that USB transfer from camera consumes a significant amount of power from camera battery. Our suggestion is for using a flash memory card reader connected to a computer, which does not affect at all camera battery life.

When the scene is not sufficiently lit for taking a good picture, use either the built-in flash unit, or external flash unit.

By default, the digital cameras keep ON the rear LCD for a limited time, for preserving the battery life. The ON time is set to default value in factory before shipping the camera, but it can be changed anytime by the user within large limits. We suggest 1s display time.

Many digital photo cameras have output for video signal, which allows you to see the pictures on TV. Be aware that the available TV signal at the camera output must match the TV standards of your geographic region, such as NTSC for North-America, PAL and SECAM for Europe.

The high speed connection according to IEEE1394 standard is optional for some digital photo cameras, but is always present in camcorders.

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