michael przewrocki
Posts: 734
Location: basel, Switzerland
Registered: 19 Nov 2004
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sharpness-imagesize-pixels-dpi
Posted: 20 Nov 2008 at 10:44 GMT
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as a digital-newbie but panorama-analogue-pro(2009=30 years) i would like to know the relations of pixel-imagesize and printsize. with noritsus new qss-37hd-640dpi-printer 30x90cm and epsons 160cm-posterprinter and 80/130cm LEDprinters there are a lot of option. i have a lot of quality-questions. i could not go to photokina and check the vr-prints. i have seem too much unsharp posters-some scanned from film to be satisfied. its the same like with circle of confusion(coc), sharpness is in direct relation to it. if the lens us supersharp then grain of high-iso is not a big problem anymore.
you can show me a forumula telling me that image 1a can be enlarge to size A bit it will cannot tell me how sharp it will be.
i have seen an aerofoto-book about switzerland by white-star.de fully digital. schweiz von oben- 82 chf. beautiful shots(except form my town) but these 35cm-prints were terribly grainy and some unsharp. certainly high-iso used. i would have used an analogue camerasystem 70mm with gyroscope.
michael przewrocki-basel-switzerland
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rudders
Posts: 390
Location: North Yorkshire & Northern England, United Kingdom
Registered: 21 Aug 2005
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Re: sharpness-imagesize-pixels-dpi
Posted: 20 Nov 2008 at 20:48 GMT
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As a 'print' pro, well 10 yrs anyway.. printer resolution isn't directly affected by the image resolution.. Generally the best size - quality for printing is 300dpi. An image seen on screen needs to be approx '16 times' as larger in print. ie 4 times longer and 4 times taller. (approx 72dpi - 300dpi ratio)
Example print we would typically do for a panorama would be 30 x 10 inch. You would need an image an image 9000 x 3000. So basically just multiply your print size by 300 to get the required 'raw' resolution of the image required.
Of course though print quality can vary massively depending on printer / media used, but have the correct size image and your half way there...
hope this helps a bit?
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ebig
Posts: 169
Location: Haiku, Maui, Hawaii, United States
Registered: 21 May 2007
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Re: sharpness-imagesize-pixels-dpi
Posted: 21 Nov 2008 at 6:11 GMT
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My take on it - hope it's not too redundant:
For a printer think DPI. Many Epsons use 1440 or 2880 depending on speed needed and paper surface used. The glossier the paper and more complex gradients (16-bit) the higher the resolution needed to avoid banding.
For a source file, think PPI, a minimum for matte paper (with "normal" viewing distance) is probably around 140 PPI, and for glossy at least >200 PPI, and for half-tone on coated book or magazine stock, >300 PPI.
For a camera think PPD (pixels per degree FOV.) The wider the lens, the fewer PPD (less resolution per degree.) At some size source file (under 3000h x 6000h?) the benefit of longer lenses and more exposures is minimal.
Here's a calculator:
www.worldserver.com/turk/quicktimevr/panores.html
Regards,
Ed
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michael medina
Posts: 310
Location: portland, oregon, United States
Registered: 27 Jan 2008
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Re: sharpness-imagesize-pixels-dpi
Posted: 21 Nov 2008 at 7:17 GMT
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the epson rep told me that 240 and 360 work better, i print almost everything at 360
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John Houghton
Posts: 2335
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
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Re: sharpness-imagesize-pixels-dpi
Posted: 21 Nov 2008 at 8:27 GMT
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The native resolution of several high end Epson desktop printers is 720ppi, which is what Qimage will use for those printers. It's instructive to make some small sample prints at various resolutions and then after shuffling them into random order, attempt to sort them into order of quality with the unaided eye. You will then get a more realistic idea of what works and what doesn't, for different paper surfaces.
John
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michael medina
Posts: 310
Location: portland, oregon, United States
Registered: 27 Jan 2008
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Re: sharpness-imagesize-pixels-dpi
Posted: 21 Nov 2008 at 9:29 GMT
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keep in mind though that your image dpi has no need to be anywhere near as high as 720. in your printer settings however, it would be best to print at 1440 or 2880 even, 720 is often too low a setting.
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John Houghton
Posts: 2335
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
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Re: sharpness-imagesize-pixels-dpi
Posted: 21 Nov 2008 at 13:47 GMT
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Michael, If you supply an image of less than 720ppi to the Epson printer, then the image will be resized upwards to 720ppi. You may be able to make a better quality 720ppi image from your 140ppi (or whatever) original image than the printer does. That is the claim to fame of Qimage, which many people swear by.
John
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ebig
Posts: 169
Location: Haiku, Maui, Hawaii, United States
Registered: 21 May 2007
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