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Image too small, how to make it bigger - DPI help, please?

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Post Fri Feb 20, 2015 5:16 pm

Image too small, how to make it bigger - DPI help, please?

Hi All I have an image that we have to print large 8m long approx, but the image is only 600mm long at 300dpi so it will be scaled at 1350% is there away to know what the dpi will be at that size or is it still at 300dpi at full size ? I was alway told if its at 200dpi at 100% and you doubled the size it would half the dpi not sure if thats correct, if it is, is there anyway of keeping it at 300dpi at full size the image is going to be seen from about 2ft away so I would like it high quality, the image will be purchased of a royalty free site like shutter stock but you can't get them big enough.

Thanks Gary
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Post Fri Feb 20, 2015 6:20 pm

Re: Image size to small, how to make it bigger

I use Photozoom, I'm on V4 but V2 comes with the Corel Draw Suite. http://www.benvista.com/photozoompro. As good as it is - and it is good there is only so much you can do
Alan D
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Post Sat Feb 21, 2015 4:52 pm

Re: Image size to small, how to make it bigger

Hi

300dpi at 600mm width is equivalent to around 22.86 dpi at 8m width, which is very low for 2ft viewing - it could be OK for a billboard viewed from 10m's away though - these can be printed as low as 18dpi for really long range viewing. 72dpi at actual size would look fine, and any more than 150dpi (some might say 100dpi) would be unnecessary.

The software tools that help when enlarging images sort of fill in the blanks and add extra pixels between those in the original small image - they take an average of adjacent original pixels, also they round off the hard square pixels as they enlarge - this has the effect of softening the focus and causing image grain. Some do better than others but the magnitude of enlargement you are wanting is going to give poor results - the tools can't make up image data that doesn't exist.

Can't you use a montage of several images blended together to achieve the overall 8m image width?

Cheers
Macky
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Post Sun Feb 22, 2015 2:19 pm

Re: Image size to small, how to make it bigger

As has been said you can't put information where there is none. You are right about Dpi or it really is pixels per inch not dots. As yo double the size you half the amount of pixels.
You are defeating the object of having an 8 metre wide print to be viewed at 2 foot. You can't see it at that distance. You have to stand back to look at it like a billboard which is designed to be viewed from a distance. You can't read the billboard if you are only looking at two letters.
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Post Tue Feb 24, 2015 10:08 am

Re: Image size to small, how to make it bigger

the job is for a roof print to go inside a bus, thats why it can be seen so close, we are now going to put joining strips in so the prints are now 3m 2 qty and a 2m panel so the print will now be scaled up 500% that means the dpi will drop to 120dpi which is still low but ill print a section first to see whats its like thanks for the help..

Gary
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Post Tue Feb 24, 2015 10:45 am

Re: Image size to small, how to make it bigger

Any image more than 160dpi will not make any difference, I use 150dpi most of the time but tell customers to supply artwork at 160dpi.

There is a roland guide somewhere that gives viewing distance dpi recommendations and I seem to remember them saying 180dpi max

Steve

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