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CAMERA FACTS
DIGITAL STORAGE

DIGITAL IMAGE STORAGE

In digital cameras as we've seen the light falls not on film but onto a photosensitive sensor called a CCD (Charge Coupled Device). This digitally converts light and colour into a digital information.

The CCD is the heart of any digital camera and usually the most expensive component. The price of CCD's vary by their image and colour resolutions.

We've looked at resolution in films above but here it is of so much more importance. Even the best consumer CCD at 5 megapixels (~Jan 2002) are a long way off of matching the resolution of a ASA/ISO 100 to 200 film at the moment. Cameras usually express their image resolution in pixel form as either "2 megapixels" or "640 x 480"

Does the last figure seem familiar?

It should do.


It's a monitor resolution (actually the highest possible on the old basic VGA monitors without a graphic card).

Essentially the CCD converts the image into pixels.

On a computer monitor each pixel is the smallest dot your monitor can produce at a given setting (on most if set on it intended settings usually each pixel is 1/72nd of an inch tall and wide (3)).

A good way of getting your head round this is to think of text font sizes. This text you're looking at is 12 point (or pixels) tall.

The higher the resolution of the image the less grainy it is as you blow up the image

Lets look at an extreme example.
This thumbnail pic looks okay when in its natural size of 90 by 58 pixels

Loch Lomond thumbnail. Copyright A.Duncan

When blown up to 3 times it size it's low resolution becomes apparent

 

Loch Lomond thumbnail blown up. Copyright A.Duncan

 

Where as this is the same picture but in slightly higher res (resolution) format at 300 by 192 pixels.

Loch Lomond. Copyright A.Duncan

 

Now as I've mentioned the resolution of the best digital camera is still less at the moment than film. This can be a problem if you're blowing up an image from a low res camera and printing it out, but for most users adequate results can be achieved.

The newest printers will print 1440 dots per inch (dpi) along the horizontal plane (effectively 20 times the resolution of most cameras). A megapixel image printed on a full A4 page will still look pretty good provided specialist paper is used. (3)

If your using them for web uses or sending by email this is less critical as they'll be viewed on a monitor which will have limited resolution

 

In this example we use one low resolution thumbnail and a higher resolution image but set <img ....width=90 height=58>

Loch Lomond thumbnail. Copyright A.DuncanLoch Lomond. Copyright A.Duncan
Original thumbnail image
ochthumb.jpg 2Kb
90 x 58
Original image
lochlomond.jpg 9Kb
300 x 192

It doesn't matter if you compress the picture from the original using the width and height tags of the <img> tag. It just appears the same as the output monitor will still render the image in pixel as described. And as you can see no real difference except image memory size.

Most digital cameras take pics in the 8 X 6 format that monitors resolutions are in. This can give you an idea of how detailed they are

MONITOR SIZE

PIXEL RES

Mega-
- pixel Res

Size On A 800 X 600 Monitor

Size On a 1280 X 960 Monitor

320 X 24076,800<0.1 megapixel<1/5 of screen1/16 of screen
640 X 480307,200>0.3 megapixel3/5 of screen1/4 of screen
800 X 600 480,000<0.5 megapixelFull Screen2/5 of screen
1024 X 768786,432>0.75 megapixelsCan See 3/5 of picture2/3 of screen
1280 X 9601,228,800>1.2 megapixelsCan see 2/5 of pictureFull Screen
1600 X 12001,920,000<2 megapixelsCan see 1/4 of pictureCan see 2/3 of picture

 

Once the image is digitally converted it is store in the camera's memory in some image file format (this varies from camera to camera but .jpeg with or without compression options is a common standard)

Most cameras will have some form of internal memory. Many modern ones have removable memory in addition. There are 3 systems offered (all prices listed are at the time of writing on 2nd January 2002 (4)). Most camera use either smartmedia (Jessop 16 MB card £14.99 GBP) or compact flash cards (£19.99 GBP for Jessop 16 Mb card). Most modern Sony cameras use the Sony's Smartstick form of removable storage (16Mb Sony smartstick £29.90 GBP).(4)

There is little between all 3 technologies for most home PC users. They're all reusable and although initially are expensive you can use them time and time again.

Once you've take a pic many camera offer the chance for you review it on their LCD screen and delete it if you wish.

The beauty of digital camera is that thereis no need to develop and print the image (unless you want). You can hook up your camera or storage media to your computer and within minutes edit your pics, print em out yourself, send them round the world as email attachments or add 'em to your website (remember to convert them to .jpeg files if your doing that).

If you want pics several photographic stores offer a specialist dedicated service where you can take your camera in and get actual pics printed out on very high res photo printer (in the UK Fuji film is one supplier of equipment - visit it's website to find out more and where your nearest store is)

(4) Prices quoted from Jessop's online site on 2nd January 2002. http://www.jessops.com/


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page 1 Introduction
page 2 Lenses
page 3 Shutter & Aperture
page 4 Viewfinder
page 5 Film
page 6 Digital storage

This article was written by A.Duncan from BWRS in Jan 2002. © 2002

 

REFERENCES TO WHOLE ARTICLE

(1) Figures From
Michael Freeman
The 35mm Handbook
revised 1st edition, 1989,
Publisher New Burlington Books
ISBN 0 906286 21 2

(2) Images courtesy of Canon UK image use scheme via their website at http://www.canon.co.uk/

(3) Figures from Digitalcamera guide.com's site at http://www.digitalcamera-guide.com

(4) Prices quoted from Jessop's online site on 2nd January 2002. http://www.jessops.com/