newbie question

how resolution affects size of images in importing indesign

resolution meaningless in image until image given physical size (on web, images measured in pixels , size of pixel on monitor depends on physical size , resolution of monitor). when save image in editing program photoshop assign physical size , resolution, physical size choose divided number of pixels in dimension. can cange either physical size, or resolution, without resampling, , other value changes in inverse proportion, actual pixesl in image not affected (and appearance in photoshop willnot change @ all).

 

indesign reads the physical size , resolution information saved file when place it, , reports resoution under link info "actual ppi." if click , release place image, unless extremely large @ low saved resolution, id use physical dimension saved in file place @ "100%." id scale image on placing way becasue physical dimensions large, or no information recorded in image -- typically happens images straight camera.

 

the actual ppi figure of no importance. remember, scaling image in id not alter pixel count, changes realtive size of how pixels rendered on page, inflating or deflating printed balloon. resolution of image scaled in id callled effective resolution , listed in link info "effective ppi." number 1 need watch.

 

different output methods , viewing distances require different effective resolutions. 300 ppi image on book page viewed 100 yards wouldn't single dot, can read billboard resolution below 1 ppi because far away.  there's pretty discussion of @ distance-resolution formula.

 

presuming, though, making layouts viewing @ aor around arm's length, there "rules of thumb" can use determine if image output in satisfactory way. first resolution should 2 x lpi in half-tone screen. since commercial printing @ 150 lpi when rule evolved, give standard 300 ppi value see used in many places. can, in fact use lower resolution, down 1.4 x lpi, without degradion images, , images without lot of detail, on uncoated paper, can go lower in pinch. desktop printers typically output in range of 100 lpi, it's safe stay in range of 180 - 200 ppi effective resolution if paln print @ home.

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