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PostPosted: Sat Jun 09, 2007 7:12 pm 
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My last prints on DIN A3 revealed some interesting observations:
- Din A3 is almost the same size as a 20" screen
- The 10MPs almost fit 1:1 on A3 (at 300dpi?!?)

So my question comes from the last statement: Is this correct, that you can almost fill Din A3 with 10MP at 300dpi?
Because I'm not quite sure!
And does it make (visible) sense to increase the density in print above 300dpi??
So this might also signal the end of the megapixel-madness race!!

B.t.w.: on a HD-Monitor you get 1920*1200 pixels, that's only a quarter of the resolution of a 10MP pic

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Last edited by Thomas on Sun Jun 10, 2007 8:57 am, edited 1 time in total.

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PostPosted: Sat Jun 09, 2007 11:04 pm 
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Hi Thomas, your D80 produces images with 3872 x 2592 pixels, so simply dividing them by 300 would give you a 12.9 x 8.64 inch print, if you printed at 300 colour pixels per inch.

A3 is clearly a bit bigger, so your printing resolution would be below 300 ppi, but the printer software performs some interpolation to match its capabilities. There's always some calculations here as modern inkjets have multiple inks and some very fine dots.

The question really then is whether to let the printer do the interpolation or if there's any benefit doing it in Photoshop first and feeding the printer, say, a 20 Mpixel file...

Sounds like you're happy with the results though, so I wouldn't lose too much sleep over it!

Congrats on making your booklet! It's still really nice to do stuff like this rather than always viewing on-screen...

Gordon


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PostPosted: Sun Jun 10, 2007 9:15 am 
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Ah, ok! So printing 10MP on DIN A3 is more like 200 dpi.
But even on a 24" High Definition (HD) screen you only get around 100 dpi.
That means that you get double the resolution in print than on a HD-screen :idea:
What I don't get is that todays printers are quoted having "9600x2400dpi". So even in the worst case you have a 8 times higher resolution than 300dpi!
Who is ever going to see this?
What is the resolution of the human eye at normal reading distances of around 30cm?

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PostPosted: Sun Jun 10, 2007 10:43 pm 
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Hi Thomas, the thing to remember is when a printer says 9600 dpi, it's referring to dots of ink which are of a single colour. It needs to place lots of these dots in order to give the impression of a single, full colour pixel.

It's a more sophisticated version of the halftoning you see in magazines and newspapers. These are just using four inks: cyan, magenta, yello and black to produce a full colour image, so need to place lots of little dots close together.

It's interesting to compare these printing technologies against things like dye sublimation, which can actually generate dots of any colour and generally work at 300dpi. These 'continuous tone' processes are used for the photo prints you get from labs and have a quite different look to what you get with inkjets. They're smoother but look a lot less sharp than an inkjet print - an optical side-effect enjoyed by the many tiny dots of an inket. A modern inkjet with multiple colours also has the possibility of a wider gamut.

Swings and roundabouts really, but yes, the bottom line is when printing a 10mpixel image at A3, you're working with about 200 pixels per inch of genuine information. So if the printer is outputting at, say 300 full colour dots per inch, then yes, it will be making up 33% of them. So the question is whether the printer driver or Photoshop will do a better job at generating these extra pixels?

Try opening an image in Photoshop, change the dimensions to match the A3 paper, then increase the resolution to 300 dpi. The file will become much bigger. Then print that and see if it looks any better than the one the printer scaled...

The bottom line though is 10mpixel images can and DO look great printed at A3! You've got me wanting to print a load of my favourite images now!

Gordon


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PostPosted: Mon Jun 25, 2007 9:10 pm 
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Yes, Gordon, you should print a selection of your photos!
In my opinion printing gives the picture a more art(ifical)/abstract substance. It lets people relate to qualities of a picture that they don't see/realize on the monitor/TV. E.g. a very small depth of field is more appreciated on paper than on the monitor, or some abstract pattern.

But still my question "What is the resolution of the human eye at normal reading distances of around 30cm?" is left unanswered :(

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Last edited by Thomas on Sun Jul 08, 2007 9:11 pm, edited 1 time in total.

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PostPosted: Mon Jun 25, 2007 9:15 pm 
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I think that depends on the eye in question! Maybe we should go to an optician and benchmark our own optics!

I do however find that while people's eyesight obviously varies, it really helps to train yourself to look for certain types of detail. Many people with fantastic eyesight won't see as much simply because they're not looking carefully or not knowing what to look for. This really applies when looking through a telescope...

Gordon


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PostPosted: Sun Jul 08, 2007 9:19 pm 
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After searching around a bit I think the central sharp point of the human eye has a resolution equivalent to 1MP(1000x1000). That should cover a field of 10x10cm at good reading distance. That gives us 100 dots per cm or 250dpi. Well that means resolutions beyond 300dpi are mostly lost to the unaided human eye.

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