Resizing Images - Basic

Transcription

1 Resizing Images - Basic

2 A few things you need to know Pixel (picture element) A pixel (px) is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of a picture that can be represented or controlled 1,000,000 pixels = 1 Megapixel (MP) (A raster graphics image, or bitmap, is a data structure representing a generally rectangular grid of pixels. Raster images are stored in image files with varying formats, i.e. JPEG, TIFF )

3 Resolution Resolution Resolution properly, refers to the pixel density. Display resolution is something else it is the digital dimensions, the actual number of distinct pixels your screen can display, from left to right and from top to bottom. Pixel density (resolution) affects only one thing - the size of the image when it's printed. By setting the resolution we tell the printer, not the screen, how many of the pixels in the image to squeeze into an inch of paper. It is noted in pixels per inch (ppi). By setting the image dimensions we set the size of the image. For web or screen, usually in pixels i.e. 1024px wide by 680px high.

4 Viewing Images on a screen The size at which an image appears on your screen depends only on two things - the pixel dimensions of the image and the display resolution of your screen. The native or display resolution of a display device is the number of distinct pixels in each dimension that can be displayed. Typical sizes are 2560 x 1440, 1920x1080, 1366x768, 1280x1024, 1280x800, 1024x768 and 800x600 Images will be displayed pixel-for-pixel. In other words, each pixel in the image will take up exactly one pixel on your screen. For example, a 640x480 pixel image would fill a 640x480 pixel area of your screen. No more, no less. No matter what you set the image's (pixel density) resolution to, whether it's 72 ppi, 300 ppi or 3000 ppi, it will have no effect at all on how large or small the image appears on the screen. For best results, set your computer's display (monitor) Properties (settings) to the native resolution of your monitor.

5 Viewer Programs When you open an image, in most cases, the program (viewer program) automatically scales the image down to fit the screen or window. As an example, 3000px by 2000px could size down to something like 800px by 530px to fit the window on the screen. The image will still look great because it is still being displayed pixel by pixel. Viewing images this way may give you the impression that the image is the correct size (pixel dimensions) for displaying on a projector or on a web page. This may not be the case.

6 Viewer Programs Default Viewer Program Windows Picture and Fax Viewer Usually, automatically fits to screen Options to; View full size Rotate Will not necessarily open RAW files Web browsers Usually displays full size MAC I Photo MAC Preview Will open just about anything Preferences will set scale to window and other options Numerous free viewers Gimp (Mac) Seashore (Mac) IfranView (PC) ViewNX2 (Nikon) RAW Viewer CR-2 (Canon) Windows RAW Viewer

7 Resizing for Digital Competition Generally You have selected an image that you want to submit. You will need at least two versions, one for screen (projector) one for print. You should process the print version first. Keep in mind that if you intend to mount it in a standard picture frame (i.e. 5x7, 8x10, 11x17) the aspect ratio (height/width) will probably change from how it came out of the camera and you may not want this same aspect ratio for the competition entry. You may need 2 or 3 versions of the same image.

8 Resizing for Digital Competition Workflow (from a copy of your original image which has been processed for print) using any program you are comfortable with. Crop for best aspect ratio (club projector has been set to a 3:2 aspect ratio this is recommended, but not mandatory) Most digital SLR cameras are a 3:2 ratio and compact cameras are 4:3. Many cameras now have the option to change the aspect ratio before shooting) Set resolution (pixel density) to 100 ppi Resize (change the pixel dimensions) to 1920px by 1080px for landscape and 1080px x 810px for portrait. Save as JPEG, if need be, compress to 1MB or less (usually one of the save options)

9 Hints & Tips Q I have an image that is 640px x 580px. How big a print can I make? A True answer, as big as you want. But, very quickly you will start to see "blocks" (pixelization) and the quality will drop off For printing you need at least 200ppi (pixel density resolution), so the best print size for this image is = 3.2inches by = 2.4 inches However, it will look great on the screen, a full 640px wide by 580px high, likely 7 inches by 4.5 inches

10 Hints & Tips Express workflow for PhotoShop Crop image to 3000px x 2000px (3:2 aspect ratio). Adjust as required, sharpen at end. Save as jpeg, set compression to give a file size of 8MB or less. Then, click Save for web and devices, select jpeg, high quality, size 1920px by 1080px, save with new file name This will give you two images, one suitable for printing (4x6, or 8x12 or 12x18) and uploading for printing, and another image suitable for digital competition submission and .

11 Hints & Tips If you want to a picture for someone to print, here is a rule of thumb for the image size Image Resolution (pixels) less than 640X X X X X1200 Maximum Print Size (inches) Wallet size only absolute largest, 4X6 By doing the math, you can see that we have a minimum of pixels per inch (300 is better as long as you don t have upsample) Note that a lot of Internet providers will bounce s with large attachments, especially 10MB or larger 4X6 5X7 8X10

12 Hints & Tips Best size for digital competitions, slide shows, websites and presentations. These images do not need the same resolution (pixel density) that is required for printing. 100ppi will suffice. Older monitors, projectors and the default for PowerPoint and ProShow etc. is usually a 4:3 aspect ratio. (i.e. 1024px by 768px) Modern screens and projectors have an aspect ratio of 12:9 (i.e. 1366px768px) The club projector has a native (display) resolution 1600px by 1200px (12:9 aspect ratio), however the aspect ratio is adjustable and is set at 3:2 (1920px by 1080px)

13 Hints & Tips Upload to Costco and the Like for Printing Costco now allows 8MB per image. Process your image normally, simply make a JPEG compression of the file to get to 8MB or less FTP Companies like PrintPartner who do things like 40 x30 prints on canvas, need lots of pixels. They provide an FTP (File Transfer Protocol) site and will take up to 40MB size files (best to use.tif or.psd). You will need an FTP program, user name and password for the site. (In essence you upload directly to their hard drive)

14 Hints & Tips Good (free) Image Sizing Software Ifranview Fastone ViewNX (Nikon) Picasa