Re: dpi

[Keith Davison <Keith.Davison@xxxxxxxxxxxxxxx>]

The optimum file dpi required for best quality will depend upon the 
output resolution of your printer and its dithering/screening method 
(if it is not a contone device).   I have read a lot of confusing 
discussion about this subject and finally decided that the only way 
to be sure  was to test it for myself.
I use an Epson Photo Stylus EX and a Photo stylus 700, and was 
interested in in finding the otpimum "on the paper" file dpi for 
these printers in top quality photo mode (photo paper 
S041140, 1440dpi, super microweave, driver version 4.11).
I printed a series of the same test image (a large 24bit colour 
TIFF),  adjusted to give the same printed size and with resolutions 
in the range 1000-100 dpi.  
Examining the output shows that pixelation artefacts are visible at 
300dpi and below,  best quality was reached at 400dpi, there is no 
increase in printed quality with dpi's higher than 400 with these 
particular printers
I was pleased to discover this, because the optical resolution of my 
slide scanner is 3175dpi, giving about 4500 pixels along a 35mm 
frame, corresponding to about 11 inches on my printers at 400 dpi.
As my panoramas are stitched in portrait mode, this means I can get 
optimum resolution  across the width of the Stylus EX output, and up 
to 44 inches long!  Of course, this optimum dpi figure will only 
apply to the above mentioned printers, but they are among the most 
popular models used for photo work. 
Hope this helps,

Keith



> I am planning to get into digital manipulation and improvement of my old and
> new photos.  Before I buy a scanner (probably a negative scanner) and upgrade
> my printer, I need to know more about what the acceptable dpi is for prints to
> look like good quality photographs.  
> 
> Can anyone give me advice on this?  
> 
> Gary