What DPI is okay for large scale printing?
I have recently displayed some of my photography in a gallery for the first time. I only printed relatively small prints at 300dpi which with my 18mp camera was around A3 size. I know the best resolution for print is 300dpi but many other exhibitors images were huge A2+ sized. With my 18MP camera or in fact even a very high end Canon/Nikon SLR that has a similar number of MP it would mean printing at around 200dpi or lower for A2+ sized images.
My question is how low can I go with the dpi? I understand in a gallery you are viewing them from a distance but even so these huge images were still quite sharp close up. I guess they may have been shot with a film camera. I would experiment with sizes if I had a large scale printer myself however it costs a lot to get a large print done so I can't afford to experiment, it would be nice to have some opinions from fellow photographers.
It is possible that some print are from Film cameras, that may change the quality in prints as well,
18 MP camera
http://www.hugge.netg.se/java/MegaPixels.html
5016 x 3762 ~ 69 by 52" ~ 177 by 133 cm
A2 ~ 42 by 59 cm
http://www.theinternetprinter.com.au/info/A4_A3_A2_A1_A0_Size_Explained.aspx
42 by 59 cm as 5016 x 3762 is 220 ppi / dpi value as is,
for 300 value increment maintain A2 cm Value
and raise pixel count 8989 by 5225 ~ish
or what ever ratio is per image captured from camera to fit page,
Perfect Resize 8
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Alien Skin Software: Blow Up 3
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BenVista Photozoom Pro
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_________
Qimage Professional Quality Photo Printing Software
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PrinTao 8
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X-Rite: i1Basic Pro 2
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SpyderSTUDIO
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http://www.northlight-images.co.uk/article_pages/print_viewing_distance.html
Contrary to popular belief, the bigger you print something the less DPI you need.
That's because as you increase the size of a print, the natural viewing distance increases, and despite the fact the pixels get bigger, your eye will not notice the difference because you are further away from the pixels, so the image looks the same quality. For example, to admire an A4 print you need to stand much closer than you do to admire an A0 poster - you need to step back to take the whole poster in.
An 18 megapixel image is good enough to reproduce any size you want. In fact 12 Megapixels is more than enough to print something the size of a billboard.
As an example, billboards typically 48ft across are often printed at 6dpi
An A4 print is printed typically at 300dpi, same as smaller prints.
An A3 could be printed at 200dpi
For your A2 poster, 150 dpi
For an A1, 100 dpi
For an A0, 75 dpi
Take a smaller slice of one of your images that has good detail. Print that at lower dpi. An alternative is to upload the file to http://mpix.com. The site will tell you how large you can reasonably go. I've had 10mp shots blown up to 20x30 inches with good detail. As you know, the 300dpi figure really only applies to prints that you hold in your hand. Billboards, which are meant to be viewed from a distance, are often around 75dpi or less.
Here this is a really great resource for calculating view distances based on DPI and other factors.
http://www.photokaboom.com/photography/learn/printing/resolution/1_which_resolution_print_size_viewing_distance.htm