jpeg - What is the relation between image file size and image quality? - Photography Stack Exchange
Because of the aforementioned correlation between size and resolution, a lot of people think that How to choose and control image size and file size?. as files on computer disks and the dots are called pixels. A digital So there is a fixed relationship between file size, physical size and resolution. For a given. In this lesson we look at issues of resolution and file size. Understanding this is very important if you are going to consistently deliver the right image size to.
So while both 'image sizes' may be the same, the resolution of each is clearly different. The aim is to have enough pixels, which when resized to fit the image size, are smaller than the monitor or printer dots. The image above has a pixel size smaller than the monitor dots and so looks good. The picture below has too few pixels and so have resized to the point where the pixels are larger than the monitor dots and the image looks either bad, or even useless as in the 12 x 8 pixels image.
Since the pixels are now set to the same resolution, it is the image, or document size, that shrinks or expands to fit. Both images now have the same resolution, it is now the image size of each that is clearly different.
Image size and resolution
While both look good now, what differs is the size at which the image is displayed. The smaller image only has enough pixels to display well at that size. This means that when talking about the working file size of an image it is not enough to just state the resolution or image size by itself.
- How to Understand Pixels, Resolution, and Resize Your Images in Photoshop Correctly
- Resolution and File Size
Both resolution and image size need to be used together. Resolution So often people speak about a dpi image as being a quality image. But what do they mean by a ' dpi' image? This is rather like someone asking you how far is it from Abuja to Lagos and you answer '70 kilometers per hour'. They would look at you funny. That is because you only told them half of the answer.
Yes it may be 70 kilometers per hour, but you need to tell them for how many hours. This is the same as someone saying, 'Oh, just give me a dpi image'.
How to Understand Pixels, Resolution, and Resize Your Images in Photoshop Correctly
What they have told you is that they want each inch of your image to have dots, but they haven't told you how many inches they want the image to be. It is the number of pixels in an image that determine file size; resolution by itself is not enough. DPI means 'dots per inch' but you need to know how many inches to know the file size of an image. Just giving the resolution is not good enough. The image is clearly more than just one inch square. So to understand the file size you need to know both the resolution dpi and the reproduction size 8 inches high by 12 inches wide, for example.
So when an editor or a designer is asking you for an image and they say, "just send me a dpi image", you need to ask, " dpi at what dimensions? File Size There is actually an easier way to ask the editor what he really wants and that has to do with file size. This is much the same way that if someone asked you the distance between Abuja and Lagos it would be easier to answer, ' kilometers'.
In reality it is closer to 8. To see how the file size is calculated, take the image above as an example and assume that it is A4 at dpi. To simplify it let's assume that is 8 inches x 12 inches. File size is determined by the number of pixels so the aim is to find out how many pixels the image contains.
Since the resolution is dpi, it means that each inch is pixels across. As the image is 8 inches wide that means there are 2, pixels in width 8 x Likewise, as the image is 12 inches long, the image is 3, pixels in length 12 x To get the total we multiply the breadth by the length and the answer is 8, pixels x Very fine screen typically used for annual reports and images in art books Determine a suggested resolution for an image If you plan to print your image using a halftone screen, the range of suitable image resolutions depends on the screen frequency of your output device.
Photoshop can determine a recommended image resolution based on the screen frequency of your output device. If your image resolution is more than 2. Save a copy of the file, and then reduce the resolution. For Screen, enter the screen frequency for the output device. If necessary, choose a different unit of measurement. Note that the screen value is used only to calculate the image resolution, not to set the screen for printing.
For Quality, select an option: Draft Produces a resolution that is the same as the screen frequency no lower than 72 pixels per inch. Good Produces a resolution 1. Best Produces a resolution 2 times the screen frequency.
View the print size onscreen Do one of the following: Select the Hand tool or Zoom tool, and click Print Size in the options bar. The image is redisplayed in its approximate printed size, as specified in the Document Size area of the Image Size dialog box.
The Print Size command is not available in the Creative Cloud version. Resampling Resampling is changing the amount of image data as you change either the pixel dimensions or the resolution of an image.
When you downsample decrease the number of pixelsinformation is deleted from the image. When you resample up increase the number of pixels, or upsamplenew pixels are added. Resampled up selected pixels displayed for each set of images Keep in mind that resampling can result in poorer image quality.How to reduce picture file size (jpg)
For example, when you resample an image to larger pixel dimensions, the image loses some detail and sharpness. Applying the Unsharp Mask filter to a resampled image can help refocus the image details. You can avoid the need for resampling by scanning or creating the image at a sufficiently high resolution.
Photoshop resamples images using an interpolation method to assign color values to any new pixels based on the color values of existing pixels. You can choose which method to use in the Image Size dialog box. Nearest Neighbor A fast but less precise method that replicates the pixels in an image.
This method is for use with illustrations containing edges that are not anti-aliased, to preserve hard edges and produce a smaller file. However, this method can produce jagged effects, which become apparent when you distort or scale an image or perform multiple manipulations on a selection.
Bilinear A method that adds pixels by averaging the color values of surrounding pixels. It produces medium-quality results.
Bicubic A slower but more precise method based on an examination of the values of surrounding pixels. Using more complex calculations, Bicubic produces smoother tonal gradations than Nearest Neighbor or Bilinear. Bicubic Smoother A good method for enlarging images based on Bicubic interpolation but designed to produce smoother results. In other words it is the number of colors per pixel.
For example, a 2-bit depth can store only black, white and two shades of grey, but the more common value is 8-bit. This is already more that the eye can distinguish which means that bit or bit will look relatively similar to us. Of course, this means that your image will be heavier even of the size is the same, because there is more information contained in each pixel.
This is also why quality and quantity are not necessarily the same. Therefore quantity helps, but also the size and depth of each pixel determine the quality. This is why you should look all the specs of the camera and its sensor and not just the amount of Megapixels.
How to choose and control image size and file size?
Resolution and File Size | Shutha
First of all, you need to choose the outlet for your photo, there is a maximum density that you need. If you are going to post your image online you can do great with only 72 dpi, but that is too little for printing a photo. If you are going to print it you need between and dpi. Of course, we are talking about generalizations because each monitor and each printer will have slightly different resolutions as well. Anything bigger than that will only be taking up space on your hard drive.
How to resize in Photoshop Open the menu for the image size and in the popup window, you need to tick the Resample Image box. You can also choose to tick the Constrain Proportion if you want the measure to adjust according to the changes you make.
So the width adjusts when you change the height and vice versa. Notice the pixel size is x This is web resolution and is the exact size of all the images in this article.