The series of resolution columns that have been published in the Northern Star Newspaper over the past month (you will find 3 column postings on this) have discussed generally three themes:
- Monitor display resolution
- Image resolution
- Printing resolution
Some examples
Check out how resolution effects the following image:
| This is the original image -
width 212 pixels, height 242 pixels,
resolution 72 ppi
with a printing size of 7.46 cm x 8.54 cm
jpeg compression level 12 - high |
 |
 |
Now the resolution has been upped to 300 ppi
the screen dimensions are the same bu the printing size has changed to
1.79 cm x 2.05 cm
see what differences you can or can’t notice in the image |
| Back to the 72 ppi image but changing the pixel dimensions to
500 width but cropping it down to save space here to
width 431 x 496
jpeg crompession level is still 12 - high |
 |
 |
Finally saving the same image with a low resolution |
In fact it is impossible to give any detailed analysis of these topics in 300 word columns, but then of course the purpose of the column is to get you started in thinking about a concept and hope that you then go on a journey to find out all that pertains to your own needs or situation.
I’ve collected a large volume of research in order to write those columns and below am providing you with a listing of online articles to take you further in understanding resolution.
Enjoy your journey!
Monitor Resolution stuff
Image Resolution stuff
Printing Resolution stuff
I have been discussing resolutions over the past few weeks and have covered how your computer monitor addresses and uses resolution, and how it affects images on your screen.
There is yet another side however to resolution when it comes to images and that is the print resolution.
The software used by your printer translates pixels into ink dots and are expressed as dots per inch. Printers have different capabilities as to how many dots per inch they can produce, and in general the more dpi, the smoother the tones in the printed image and the wider the colour gamut produced.
The minimum resolution for magazine-quality printing is 300 ppi but there is a surprising effect on the size of your image.
An image that is 640 x 480 pixel dimension, printed at 300 dpi will only print at 3.2 x 1.6 inches.
So our monitor resolution and print resolution are 2 different environments. This becomes particularly important for images that are designed to be viewed for instance on a web page.
This can actually be good news!
If you are displaying copyrighted material on your web page of your own images and are concerned that someone may take your images and reproduce them illegally then you can take advantage of these resolution issues.
Using bitmap images such as jpegs, set with a low resolution suitable for screen of 72 dpi will produce great screen viewing images to showcase your products, whilst ensuring that any attempts to enlarge or print as high quality cannot be achieved.
The fine balancing acts that I have been describing may well be the reason that you obtain professional advice on images for your web site and printed brochures.
Resolution is a complex subject in some ways, even though most people using a computer may not think about it often.
I wrote about display resolution last column, but that is not the entire story! The resolution used to show you the contents of your computer only shows you what you have in your image, but image resolution determines the quality of the image.
Image resolution describes the detail that an image holds. It can be measured by quantifying how close lines can be to each other and still be visible. Line pairs are often used instead of lines – a pair of adjacent dark and light lines. A resolution of 10 lines per millimetre means 5 dark lines alternating with 5 light lines. Photographic lens and film resolution are most often quoted in line pairs per millimetre.
Most commonly image resolution is described as a pixel count in digital imaging.
It is generally measured as pixels per inch (ppi), and the higher the number, the clearer and higher the quality of the image. This is not to be confused with dots per inch (dpi) that describes the way an image will be printed or displayed, though there is a direct relationship between the ppi and the print size of the image. I will discuss resolution in relation to printing next week.
Some image file formats allow you also to ‘compress’ the image. JPG compression analyses blocks of 8×8 pixels and selectively reduces the detail within each block. At higher compressions, the actual block pattern becomes visible and the loss of detail is noticeable.
Vector images however are not made up of a series of dots but the objects and shapes are defined mathematically and therefore are independent of resolution, meaning they can be enlarged without pixilation and cannot be compressed.
Display resolution in computer terms refers to the number of pixels that can be displayed on the dimensions of your monitor.
When we talk ‘display resolution’ we are talking about the number of actual pixels in columns and rows that fill up your monitor display.
For example, a resolution of 1280 x 1024 means you are displaying 1280 pixels across the screen and 1024 pixels down the screen.
This is different to talking about the resolution of the display, which is given typically as the number of pixels per inch, which will indicate the quality of the image, say in a photograph.
This makes understanding resolution quite difficult at first as the term ‘resolution’ is used interchangeably but has quite different meanings.
The eye’s perception of the ‘display resolution’ can be affected by a number of factors such as the rectangular shape of the screen known as the ‘aspect ratio’. A display with a ratio of 1280 x 720 on a 16:9 display will have square pixels, whilst 1024 x 780 on the same display will have rectangular pixels.
This will affect the perceived sharpness – displaying more information in a smaller area results in a higher resolution, and makes the image clearer.
Basically the importance of this for the computer user is how your display resolution settings will affect how things look on your screen.
The higher the numbers on your display resolution will result in smaller individual pixel sizes being displayed. The smaller the size of the pixels on your screen will result in everything looking smaller. This is great if you want to fit more on your screen, but not so great if you find text difficult to read.
There is no ‘right’ resolution, as everyone is comfortable with a different setting, which is why all computers allow you to adjust your resolution to suit your own needs.
