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Frequently asked Questions about Digital Imaging

 

Questions

1 What is Digital Imaging?

2 Why use Digital Imaging?

3 What is the importance of resolution?

4 Why record on CD ROM?

5 What file formats do you use?

6 What are the best photo manipulation software packages?

7 What sort of printer will I need?

8 Who are www.friendlymouse.company ltd?

9 How do we contact www.friendlymouse.company ltd?

10 System Requirements

11 Small Print

 

 Answers

1 What is Digital Imaging?

 

Traditionally pictures were represented by colour on a piece of paper such as with a painted picture, photograph or printed materials. If a copy was to be made it was usually done photographically from a master - the negative. In digital imaging the master isnít a negative but a computer file from which copies can be printed. The master represents the original image by subdividing it into a matrix of cells. Each cell is given a value which represents the colour and brightness of the original image at that point. Because the human eye can see very fine detail and distinguish small changes in colour the original image has to be divided into a large number of cells each containing detailed colour information if the digital image is not to appear crude and blotchy. This leads to very large file sizes typically 100 times bigger than that required for text.  

To process such large files requires powerful computers and it is only in the last few of years that such computers have been affordable in the home market. To generate digital images directly is even more difficult because it is expensive to produce sensors which can record high quality digital images as well as the traditional film camera. So unless there are specific reasons for taking pictures digitally it is often better to take pictures with film and then convert (scan) the pictures to digital format to get the benefits of computer processing.  

Paradoxically its easier to generate moving pictures of an acceptable quality than still pictures - our brains concentrate on the movements and ignore the blemishes! As an excample look at the freeze frame on a camcorder. In spite of sophisticated techniques it doesnít give the same sharp image as the moving picture. Strictly current camcorders donít produce digital images - they are analogue - but the MPEG video cameras which are just becoming available do produce true digital video. Return to top

 

2 Why use Digital Imaging?

 

The strengths of traditional photographic and printing methods were the high quality of image which could be produced and the acceptable cost for producing copies. The image once captured was fixed. So photographs could be used in courts as evidence. Once the image is digitised however each cell can be modified individually before printing providing immense opportunity for the artist. Modern graphic arts software packages can process the millions of cells that can be involved so precisely that its impossible to tell what is photo reality and what has been created. And the software is sufficiently intuitive that high quality results can be produced by just about anyone. 

At a more prosaic level digital imaging means that your pictures can be readily incorporated into any document you care to produce and printed as you need it. Return to top

  

3 What is the importance of resolution?

 

Resolution is the term that defines how sharp an image is. In digital imaging it is measured in dots per inch (dpi) or pixels per inch . The resolution you need depends on what you are trying to do. Three factors are key:

If the resolution is too low then the picture will look blurred. Straight lines particularly diagonal ones will have jagged edges. Individual pixels may be visible rather than a smooth continuous tone. Conversely if the resolution is too high then the computer file size can become very large slowing down or even totally overloading the computer.

72dpi is often used to get a good picture on a PC monitor. The full screen may display 1024*768pixels or 800*600 A higher resolution may be needed if a proportion of the image is to be enlarged. Printing generally needs a higher resolution from 100 - 200dpi depending on the quality required. Magazines may be screened at 150dpi whilst newspapers are typically 75dpi and fine art reproductions up to 300dpi. Posters can be lower resolution because they are designed for viewing from further away. The number of pixels required is then calculated by multiplying the dpi for the apprprriate medium by the image size required.

The printer resolution is a different matter. An inkjet printer for example may have a resolution of 1200 dpi but this doesn't mean that the image size for printing has to have 1200dpi. This inconsistency is explained because printer resolution is different to display resolution. Each pixel on a monitor can be controlled with a high degree of accuracy for brightness and colour. Those in an inkjet printer are generally either present or absent so a lot more pixels are needed in the printer to build the same quality image.

Its also important to ensure that there is only one element controlling resolution in the chain from the original object to the final image. Double sampling as it is called will significantly reduce picture quality and will cause all sorts of unpleasant jagged edges to an image. Scanning screened images, rotating images or rescanning printed images are all likely to lead to significantly lower resolution final images. Take care with rotations and skew effects because depending on how clever the software package is and its anti aliasing features you may get the unwelcome effects of double sampling. If you are unsure try a practical test. If that doesnít work see if thereís another way to get the same end result.

So as a simple rule of thumb start with the final image size required. Allow 72dpi for a monitor and 150 dpi for printed material viewed close up. (Pro rata less if it will be viewed from a distance) and ensure that there is only one process in the production which limits the resolution to less than twice these values.

Our standard file sizes are 1500 by 1000 pixels on CD or high resolution photo disks to give good images on a monitor 20 by 14 inches or for a good 10 by 8 print. They are roughly the same resolution as high definition TV and have 4 times the number of pixels as broadcast TV. We use smaller file sizes when images are for web publishing or e-mail. For these applications it's essential to have smaller file sizes generally by reducing the displayed image size often substantially, using a standard 72dpi and by using compression techniques. Return to top

 

4 Why record on CD ROM?

 

With its large storage capacity CD ROM is an ideal medium for storing high quality photofiles. Floppy disks donít hold enough data for high resolution pictures although they are suited to storing compressed photofiles. Other computer storage media could be used but they arn't usable on the majority of PCís which only have cd rom and floppy disk drives. The high speed of CD ROM drives mean that it is very practical to use CD ROM instead of storing the files on your hard disk thus freeing up valuable hard disk space. Return to top

 

5 What file formats do you use?

 

We want to use file formats which are as close to universally available as possible. Just about every PC program can read BMP files opening up an enormous range of uses for your personal photofiles. The files are 24 bit colour (millions of colours). They are not compressed. This way all the information scanned from your photos is permanently retained. When a small file size is important either because its going to be stored on disk or because its going to be emailed or published on the web then we use the JPG format. We use TIF format when the file is for a (commercial) print application because its the industry standard. However if you particularly want another format then tell us what you want we can almost certainly do it without additional cost. We can provide RGB or CMYK separations or we can provide output in the native format of photo editing software e.g. Photoshop PSD format. Return to top

 

6 What are the best photo manipulation software packages?

 

The industry standard photo manipulation package is undoubtedly Adobe Photoshop. There are many plug-ins available which further extend the range of effects you can create with it. However it's designed for the full time user who is able to dedicate time to becoming skilful. The user interface is designed for speed of use and flexibility. It's priced for the professional market. 

If you canít make this commitment the alternative is to go for a more limited package which is designed for the less frequent user with a simpler and easier (less flexible) user interface. Adobe Photodeluxe and Paint Shop Pro fall into these categories as does Corel PhotoPaint. There are many others each with their advantages and disadvantages. Our advice would be to try several but once you have a favourite to stick with that to master all its features. 

Weíd like to hear about your experiences using these software packages so why not drop us a note, fax, or email us. Return to top

 

7 What sort of printer will I need?

 

Clearly the better the printer the more enjoyment you can get from your photofiles. The majority of modern "photoreal" printers will produce very good results. Price from around £100 upwards. When choosing a printer donít get swayed by claims for 1200 or 1400dpi resolution. Of course resolution is important but its only one parameter. Do the colours come out true? Will it print onto all the types of paper you want (and maybe on both sides if you need it) or just onto some specific (expensive?) ones. Try to get a test print of a natural scene with a close up of people in it. A print of a photo of you will show up the quality of the printer far better than a dramatic computer enhanced picture of Chinese dragons, fireworks, a Harley Davidson or tropical fish. Television is often assesed using 'The Colour Girl Chart' intoduced by the BBC and showing a small girl. It was an extremely skilfully produced and difficult test. Just ideal for testing printers! Return to top

  

8 Who are www.friendlymouse.company ltd?

 

9 How do we contact www.friendlymouse.company ltd?

 

10 System Requirements

 

PC or Mac Compatible. For PC: Windows 3.1, 95 or 98, 486 or Pentium

 

11 Small Print

 

We take every care with your order but in the unlikely event of your photos being damaged or lost our liability is limited to the cost of the unexposed photographic material plus postage. Special value photos can be insured by prior arrangement. Freeware & shareware are provided "as is". Software has been virus checked but please make your own checks. Statutory rights are unaffected.

Registered in England & Wales, No: 3401191, Registered Office:194 Red Lion Rd, Surbiton, Surrey, KT6 7RA

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