transferring images into different documents 1

[wildmouse35]

i have images scanned at 200dpi that i am pasting into a 300dpi document. the image size of the 200 dpi images become smaller when pasted into the 300dpi canvas. what is the best way to address this? should i change the image size of the 200dpi scan to 300 dpi and then paste it into the same dpi document? or, make the second document 200 dpi as well? i need maximum clarity and don't want the images to be smaller than original size.

secondly, if i have a low resolution document (say 72 dpi) what is the best way to make it higher resolution?

thanks.

 

[apepp]

...200dpi will indeed be smaller as you have lesser pixel dimensions in the 200dpi images, however if your 300dpi image is in fact the same "physical" dimensions than the 200dpi image (e.g. both are 100mm x 100mm) then the only difference is how many dots get printed in the inch, they still both print the same "physical" size, just not quite the same quality...

...the best way to address this is to re-scan your images to 300dpi if you want absolute results, but you might not be able to do that or unwilling for whatever reason...

...whether you upsample the 200 images to 300 is in effect the same as placing the 200 in a 300 and physically re-sizing manually in the 300 document, re-sampling takes place which ever route you take, as photoshop has to make pixels that don't exist based upon the surrounding ones that do (bicubic algorithm is the best)...

...if these files are for high end printing then the ideal is to have them scanned correctly from the start, and scanning to a "worst case" scenario, which in most cases might be targeting 1.5 to 2 times the required output resolution...

...with scanning, more pixels is better than not enough but of course this means larger sized files to store, and with todays affordable large storage devices and quicker computers it has been much less an issue than it used to be...

...depending on the subject matter of the images you probably won't notice much difference between re-sampling 200 to 300 than if you were to scan it at 300 to begin with, but this can be subject to how physically big these images are as well from viewing distance...

...a 72dpi image doesn't always mean you can't get high res prints, if you turn off resampling and type in anywhere between 260 and 300 in the dpi field, that will tell you the physical size you can get optimum quality...

...optimum quality is pretty much determined by the linescreen an output device is capable of reproducing at, and the paper your printing on...

...the rule of thumb is 1.5 to 2 times a given linescreen in litho printing, so for magazine work typical screens are 150, 175 or 200, newspapers are around 133 or 150 linescreen, and for more challenging printing uch as fine art printing linescreens can be 250, 300 and I have known some to go as high as 400 line screen, but that is pushing it beyond what would suffice...

...for massive upsampling of low res images (for poster work) then your better off using Genuine Fractals (not free) to re-sample images up, as this plugin program is better than photoshop, however photoshop is perfectly adequate for upsampling images, you need to be careful about how far you go with it...

Andrew

 

[apepp]

...and to add, if these images are destined for screen use (RGB) such as the web, then dpi has no effect on how big or small an image is viewed at, what matters is the actual pixel dimensions...

...pixels determine the size an image is viewed, which is then dependant on the monitor you are using...

...so on a higher resolution monitor images will look smaller than on a lower resolution monitor...

Andrew

 

[wildmouse35]

thanks, andrew. the images are fine lined drawings in b&w and cannot be scanned at a higher rez as the writing on the other side of the documents shows through. the details are important and the drawings will be printed on material...tshirts/etc.
so what is the best way not to make them smaller or lose clarity? should we paste them into a 200dpi document so we are even? or, can we just open the drawing and change the image size to 300dpi and then paste it?
basically, i need to know if i can scan at one rez and change the image size and rez when i open the document and if i can, what that does to the clarity...i can't lose that. also, is there a way to sharpen the little lines and details? thanks so much

 

[apepp]

...line drawings have to be treated differently to full color images when scanned, you need to scan those between 600dpi and 1400dpi (at actual final output size)...

...best to scan in greyscale for those and then convert to 1 bit in photoshop using a thresholds adjustment layer, so you can tweak the levels better visually, convert to 1 bit with 50% threshold as the method setting (image > mode > bitmap)...

...with "show through" you can remove that by using the curves in greyscale to get the background to near white as possbile, or just painting with a white brush for any stubborn areas, when converting to 1 bit bitmap though, any areas below 50% turn to white, any above 50% turn to black...

...if the paper is so thin that the light picks up "show through" then one method is to place more white paper or a thicker piece of white card on top of the original, then scan to limit the amount of "show through" the scanner might pick up...

...now that you have mentioned these are line drawings 200dpi is not enough res, nor is 300dpi as you will get jagged edges and the thin lines will become broken up...

...personally i would advise you re-scan to at least 1200dpi in greyscale and then convert to 1 bit in photoshop after tweaking the image with a thresholds adjustment layer...

...you can in some situations re-sample your existing scans in photoshop, blur the edges with gaussian blur to smooth, and then convert to 1 bit after tweaking with a thresholds adjustment layer...

Andrew