Who should do the interpolation?


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yanyewkay

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#1
I have to make a 6m print from my 3000x2000 pixel image with minimum viewing distance of 1.5m. From the recommended 200dpi for large prints, It'll mean I need 47000pixels on the longest edge? :bigeyes:

I've read from the net that it is recommended that the max interpolation is only up to 4 times the original picture. From my above calculation, I'll be upsizing the length by ~16 times? :confused:

The question is, do we need to upsize our pictures when we send to the printers or will they do the necessary based on my 6MP picture?
 

yanyewkay

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#3
erm.. how to quantify quality? :think:

how about "enough so that pixelation is not obvious?".. even at 100dpi it'll still be 8x upsized?
 

eikin

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#4
it's not practical. printing at that size will definitely give you visible pixelation from 1.5m away.

what's the purpose of the print? art exhibition quality? advertisement quality? or just need some general forms to be decipherable?
 

eikin

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#5
for retail print shops, the quality probably will be around 72 dpi maximum for such large prints if not the single print will jam up the queue ... and what medium are you looking at? banner canvas? paper?

i know some shops that do 150dpi for super large prints, but given the small size of the original file, pixelation is unavoidable
 

yanyewkay

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#7
eikin said:
what's the purpose of the print? art exhibition quality? advertisement quality? or just need some general forms to be decipherable?
picture for a wall in a room that spans 6m across. maybe i'll say advertisement quality? The print on the wall is part of a concept to bring "realism" into the room as if they are at a particular place.

eikin said:
for retail print shops, the quality probably will be around 72 dpi maximum for such large prints if not the single print will jam up the queue ... and what medium are you looking at? banner canvas? paper?

i know some shops that do 150dpi for super large prints, but given the small size of the original file, pixelation is unavoidable
medium will be matt non-textured paper.
 

yanyewkay

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#8
kex said:
can try to "soft proof" the upsized image by viewing it at 100% at 1.5m..
:think: does it work? I'll try that out tonight. this is something new. thanks!
 

eikin

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#9
yanyewkay said:
picture for a wall in a room that spans 6m across. maybe i'll say advertisement quality? The print on the wall is part of a concept to bring "realism" into the room as if they are at a particular place.



medium will be matt non-textured paper.
can be done, but not without pixelation. you might want to process the file into print size at 150dpi and touch up to reduce the pixelation into 'soft' effect instead. the touching up will definitely be tedious. what's the width of the print you're looking at?
 

eikin

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#11
yanyewkay said:
the width is 6 metres..

so that means I have to do the interpolation?
yes, interpolate it yourself, it's too time consuming for the print shops to do it.

length is 6m, what's the width? or the breadth of the picture?

if it's bigger than A0's length (approx. 118.8 cm) you're going to have problems looking for a print shop
 

yanyewkay

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#12
oops.. i think I made some confusion here. the longest edge which will be the width is 6meters.. the height is less 4m (about 3 or 3.5)

I took width as length - 6m.
height or breadth is ~3m (to ceiling of room from a raised platform)

So i'll have a 6m by 3m picture.

The printing won't be done by me so I wun have to worry about finding a shop to do that.
 

eikin

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#13
yanyewkay said:
oops.. i think I made some confusion here. the longest edge which will be the width is 6meters.. the height is less 4m (about 3 or 3.5)

I took width as length - 6m.
height or breadth is ~3m (to ceiling of room from a raised platform)

So i'll have a 6m by 3m picture.

The printing won't be done by me so I wun have to worry about finding a shop to do that.
i see ... it's going to cost a bomb.
 

eikin

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#14
just to show you an example of why it's almost an impossible task ...

sample picture


this is 100% crop of the result of a 16x magnification at the focussed portion
of the flower somewhere at the centre of 2 adjoining petals


paiseh forgot to time the interpolation time.
 

yanyewkay

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Sep 22, 2004
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#15
cost a bomb? :dunno: I'm not paying ;p I only give photo :bsmilie:

from your pic, i tried to use kex method, and even at 3m away i can see the pixelation.. that's bad.. :(
 

Jan 23, 2005
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#16
eikin said:
just to show you an example of why it's almost an impossible task ...
The pixelation that you're showing is due to crappy interpolation methods. Proper interpolation does not result in any pixelation at all, the resulting picture will merely look blurry. However, the starting picture must be of good quality. If it is overprocessed, the artefacts (some of which resemble pixelation) will show very clearly.
 

eikin

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#17
LittleWolf said:
The pixelation that you're showing is due to crappy interpolation methods. Proper interpolation does not result in any pixelation at all, the resulting picture will merely look blurry. However, the starting picture must be of good quality. If it is overprocessed, the artefacts (some of which resemble pixelation) will show very clearly.
try blowing up any image to 1600% and tell me if it can maintain any reasonable quality viewed at 100%
 

P

Phildate

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#18
I have Genuine Fractals and will try and interpolate for you if you like. Just email me the file and I will give it a go. Might have to send back to you some other way.
 

Jan 23, 2005
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#19
eikin said:
try blowing up any image to 1600% and tell me if it can maintain any reasonable quality viewed at 100%
I tried with the image you provided, and no problem at all. I think it would be quite acceptable for a 6 meter wide wallpaper - and keep in mind that the image, when displayed pixel-by-pixel on a computer monitor, is enlarged compared to what would actually be printed at the target resolution of 200 dpi.

The only objectionable problems are some colour fringes from the Bayer pattern interpolation and some jagginess due to sharpening the image. This, along with the blurriness, can be partially masked by adding some suitable noise. If you allow me to use your sample image, I can show what it would look like.
 

eikin

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#20
LittleWolf said:
I tried with the image you provided, and no problem at all. I think it would be quite acceptable for a 6 meter wide wallpaper - and keep in mind that the image, when displayed pixel-by-pixel on a computer monitor, is enlarged compared to what would actually be printed at the target resolution of 200 dpi.

The only objectionable problems are some colour fringes from the Bayer pattern interpolation and some jagginess due to sharpening the image. This, along with the blurriness, can be partially masked by adding some suitable noise. If you allow me to use your sample image, I can show what it would look like.
as yyk is talking about interpolating his 3000X2000 image, i've used the original file for the above enlargement, feel free to use the following, it's saved at quality '12' on PS



the main issue here is really the impracticability of blowing up a small image 16 times to fill a wall and expect to see a reasonable image when viewed from 1.5m away. so far i have not heard of any ingenious software that can perform such a task. if there is any, feel free to share it with the folks here.
 

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