Enlarging an image

[sylux92]

How do professional printers blow up images to a big poster with no loss of quality? I have searched around for software, but it all makes the quality deteriorate. Anyone know a good program?

 

[Killermech]

You don't. They are already big sized or professionally remade. They could originally be vector images as well (rarely), then you can resize it to any size
without losing quality.

You could naturally try and do it manually with a combination of 'cheap' tricks, like sharpen filters etc. But it will never look as good as the original.

 

[Rowan]

for some reason photoshop 7 made my images blowup with no reduction in quality i dont know why though doesnt work on cs3

 

[Akoji]

Haha, Well what you are asking, is exactly my job, so yeah, there's no magic around it.
The first poster size that we make is the bigger one, and then we resize to smaller size, so yeah... we really work sometimes on images that weight 1gig and that's measured by meters

And he's right about vectors, but yeah, you can't vector photo's since it give an illustration look to everything that's made of vectors.

 

[sylux92]

Haha, Well what you are asking, is exactly my job, so yeah, there's no magic around it.
The first poster size that we make is the bigger one, and then we resize to smaller size, so yeah... we really work sometimes on images that weight 1gig and that's measured by meters

And he's right about vectors, but yeah, you can't vector photo's since it give an illustration look to everything that's made of vectors.

So how do you make theses posters bigger? (Sorry, im new to photo editing)

 

[jumpman17]

Haha, Well what you are asking, is exactly my job, so yeah, there's no magic around it.
The first poster size that we make is the bigger one, and then we resize to smaller size, so yeah... we really work sometimes on images that weight 1gig and that's measured by meters

And he's right about vectors, but yeah, you can't vector photo's since it give an illustration look to everything that's made of vectors.

So how do you make theses posters bigger? (Sorry, im new to photo editing)

Well, if your image is tiny, then your only options are to not blow it up, or blow it up and lose quality.

 

[ScuberSteve]

He just said that you DON'T make photos bigger. They take large images and make them smaller.

 

[Akoji]

Yeah we never blow up small images to make big poster, it looks like shit.
But yeah, like I said, we start with huge images and make them smaller.

 

[Panzer Tacticer]

Yep, what he is missing, is you don't make small images bigger, you make big images smaller.

If the image started small, it's likely going to stay that way too.

If you were to take a scanner, and scan an image at a massive data size with considerable detail level, it can be enlarged a long way before it hurts the image. But a small lousy image is likely doomed to remain that way.

Although you can get interesting images with 2 foot wide pixels I suppose

 

[Akoji]

Well sometime you can use the pixelated effect for some stylish thing... but yeah most of the time it's just plain ugly.

Yeah for making photo's high resolution, you need a GOOD scanner. And some photoshop.

 

[FAST6191]

I do this for video (a little thread I did a few months back: http://gbatemp.net/index.php?showtopic=739...t=0&start=0 ) rather than still images (they bore me for some reason) but the principle is the same (although video has the luxury of several hundred near identical images you can use to fix errors which is a bit of a double edged sword as quality does not necessarily have to be as high when there are 20 odd frames per second). The maths behind all this gets horrific (it takes matrices about 60 levels further).
Avisynth (a scripting language that forms one of the most power editors going) has image processing capabilities too (see the producing/source filter " ImageReader / ImageSource ") and has a hell of a lot of very high end/experimental grade filters (normally quite slow but when it is but a single image it does not matter so much).

Everyone so far has said what I would have (half decent chemical/film photos have an effective resolution far higher than most digital cameras this side of "how much???") but still you sometimes have to blow up small images.
Digital images are almost always pixel based (I am ignoring vector based images and wave compression right now) and part of that is a good deal of the time the pixel adjacent to another is going to be very similar to it. This means you can guess what a pixel would have been if the resolution was higher. Enter numerous algorithms to do the deed.
The simplest (in general use anyhow) is nearest neighbour (called PointResize in avisynth) and is very rarely used for upscaling by itself if quality is your aim (examination, quick and (very) dirty and "special effects" only).
After this Avisynth has BicubicResize, BilinearResize, GaussResize, LanczosResize, Lanczos4Resize, Spline16Resize, Spline36Resize. For serious upscaling (up to around double size) Lanczos works for me.
More advanced ones can be found here:
http://forum.doom9.org/forumdisplay.php?s=...mp;daysprune=-1
One to look at:
http://forum.doom9.org/showthread.php?t=129953

For some really nice tests (albeit slightly outdated now):
http://www.general-cathexis.com/interpolation/index.html

Sidenote the principle behind mipsmooth (a fairly nice filter for noise reduction) is that of mip map, it works by assuming noise is small and will disappear when the image is shrunk and then not be there when it is blown back up. Knowing this you do not need to find a filter for your app of choice.

Secondly deinterlacing filters (especially of the bob variety) are quite useful as resize tools and more than that the inpainting algorithms are even better so as was hinted at with the "use sharpen afterwards" posts above you can chain filters to improve the result.

 

[Prime]

FAST has to go one step above everyone else even when the question has been answered.

 

[sylux92]

I understand now. Thanks for your help, everybody!

 

[matriculated]

Also, with posters you tend to look at them from a few feet away so they don't need as much dpi as, say, a magazine which you read up close.