How to specify the desired size of an image.
We need to know what size image do You need. If possible, specify the size in pixels.
We also need to know which image format do You need. The most requested format is 100% jpg
Is resolution adjustable?
Definitely. Resolution is a freely adjustable property of an image. (You can set the resolution according to Your needs in any better bitmap software, such as Photoshop).
Are there more kinds of resolution?
Yes. There is ppi and dpi. The first being "pixels per inch" and the second "dots per inch". Dpi and ppi often get confused. Ppi refers to a file and dpi refers to a printout.
Does ppi equal ppi?
No. Ppi is often 4 times smaller than dpi.
Pixels are the smallest units of every raster (bitmap) image. If You magnify an image, You will see them as small squares of uniform color. In CMYK color space, each square has a specified amount of cyan, magenta, yellow and black color. Therefore, printer can use several dots of hue to render one pixel. For instance, it can print a blue dot and a yellow dot next to each other to form a green color. That means that dpi and ppi are correlated, but not the same.
Each type of printer uses different method and patterns to print dots, so there is no universal coeficient, but here are some simple rules: Laser printers print generally with 300 or 600 dpi resolution, and need the ppi resolution of the source file 72 or 150 ppi.
High-end, professional devices can (but hi-res is not always needed) print with 1200 dpi or more, and need source files with 200 to 300 ppi. Please check Your print shop assistant, or a manual to Your printer. Monitors are commonly set to 72 ppi.
Can you give me an example? How many pixels do I need to print a letter size picture on my laser printer?
You want to print one of our posters on a laser printer. Your printer can be set to print at higher quality, 600dpi. Therefore, You need a file with 150 ppi. The maximum paper size Your printer can print on is the Letter size (A4), 8 1/2" x 11". 8 1/2" x 150 ppi = 1275 pixels, 11 x 150 = 1650 pixels. You need a file that is 1275 x 1650 pixels big. Since the printer has to use some paper for margins, 1200 x 1600 should do. If You want to be on a safe side, order 2400 x 3200 pix - You will give Your printer a bit more than it needs, but that will not hurt anything.
The maximum size of our scans is around 4096 x 6144 pixels [depending on poster shape] at 48 bits color depth (16 bits per channel).
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