What if you are not making prints, maybe you are
just sharing on the web. How many pixels do you need for email or
the web?
When you are uploading JPG images to the web there are some things to take into consideration.
Format - how do you want your picture to look, crop it square or rectangle in horizontal or vertical.
Image size - pixels are information, how many pixels X pixels you have dictates your image size in
height, width and resolution. If you change the pixel ratio you may squeeze or expand the image.
File size - number of pixels dictates amount of information in megabytes (MB) or kilobytes (KB). This
affects the time it will take to download on a site. You can decrease the size of your file by compressing it.
JPG compression analyzes images in blocks of 8X8 pixels in size and selectively reduces the detail within each block.By using JPG compression, you can keep the physical size of the image the same and reduce the amount of disk space required to store it but you will be sacrificing the quality of the image.
Resolution refers to the number of pixels in an image. Resolution is sometimes identified by the width and height of the image as well as the total number of pixels in the image. For example, an image that is 2048 pixels wide and 1536 pixels high (2048X1536) contains (multiply) 3,145,728 pixels (or 3.1 Megapixels). You could call it a 2048X1536 or a 3.1 Megapixel image. As the megapixels in the pickup device in your camera increase so does the possible maximum size image you can produce.
same image blown up from 500 X 331 to 1000 X 660 it is the twice the original size but with 1/2 the information.
Notice the difference in the resolution.
to make a 11in X 14in print at 200 dots per square inch). That many pixels are not nessesary for email or websites.
In most cases 1000 X 664 pixels (6.6MP) would be sufficent (as seen in the Facebook image chart below). Large image files on a web page take longer to download so just use the right number of pixles to suite your final output device weather it be the web or printer.
For emailing or websites a much smaller image can be used. On my imac email I am offered four different sizes. Actual size 3.1MB (4288 X 2848) Large 250KB (aprox 1300 X 863), Medium 84.0KB (aprox 650 X 432) Small 34.0KB (aprox 400 X 266). These compressed images are all the same image ratio just smaller images and file sizes. Notice the actual size is larger then the page so (depending on the monitor) the receiver of the email will have to use the sliders to see the whole image. |
The larger the screen, the larger you likely have your screen resolution set. If you have a 17" monitor, likely you have it set at 800X600 pixels. If you have a 19" screen it is likely set at 1024X768. You can change the settings but these are optimum for those screen sizes.
Now, if your monitor is set to 800X600 and you open up an image that is 640X480, it will only fill up a part of your screen. If you open up an image that is 2048X1536 (3.1 megapixels) then you will find yourself moving the slider bar around to see all the different parts of the image.
For website photos it will depend on the amount of space you want the image to take up on the page or a particular size that is requested from you. Most web sites will request thumbnail or very small images that save on file size. On my imac Preview will resize and reformat images. Tools>adjust size, can lock the image format to original or custom size it. |