Time to be with your loved ones

Time to be with loved ones

by sat

submit your photo


Hall of Fame
View past winners from this year

Please participate in Meta
and help us grow.

Take the 2-minute tour ×
Photography Stack Exchange is a question and answer site for professional, enthusiast and amateur photographers. It's 100% free, no registration required.

Possible Duplicate:
How can I upscale a low-res image to make it appear higher-res?

I need to scale up a small photo to the 3x of the original size. What method is common to become the best possible quality?

share|improve this question
    
I wouldn't consider this a duplicate of the above mentioned question, since the linked to question is about Photoshop and this one makes no mention of such software. It is not safe to assume that all users have access to such expensive software. –  dpollitt Nov 20 '12 at 19:44
    
People use "in Photoshop" as a proxy for "with some sort of post-processing software" all the time. It happens that Photoshop doesn't do anything particularly magical in this area, so I think that one is fine as a generic question. –  mattdm Nov 20 '12 at 19:57
1  
Have a look at onOne's Perfect Resize (formerly Genuine Fractals). Great piece of software with some handy features when doing prints. I agree that it's a dupe too... –  John Cavan Nov 21 '12 at 1:10
add comment

marked as duplicate by mattdm, Itai, Imre, John Cavan, Matt Grum Nov 21 '12 at 16:36

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

4 Answers

It depends. If you have sufficient pixels for the size you need, than all you need is to change the DPI. So lets say you have a 12 megapixel image (4000 x 3000 pixels) at 300 DPI, then changing the DPI to 100 will make it 3 times bigger. This will take the 10" tall image and make it 30".

Should you judge that you do not have enough pixels, you need to interpolate the image. Most image processing software will do this and some have different algorithms, for example you will find something like Bicubic Smoother (Best for Enlargements) in Photoshop. Just enter your parameters in the Image Size dialog and let it do the work.

The number of pixels you need will depend on size and resolution. The resolution depends on viewing distance for your print. 300 DPI is common for small images which are seen closely and down to 150 DPI for poster-size is quite acceptable. In general, the larger the image, the further you look at it and the less resolution is needed.

share|improve this answer
1  
Just a small note here for users of Ps CS6 (and, I'd assume, above when there is an "above"): the resize options now include a "Bicubic Auto", which does the smoother/sharper thing automatically depending on the new resolution, and does iterative up-rezzing so you don't have to do it manually anymore. –  user2719 Nov 20 '12 at 19:58
    
Good to know. The CS6 box is still unopened here :) –  Itai Nov 20 '12 at 20:31
    
@Itai - Open the box, it's a nice upgrade to have. Still, I think I'd go with onOne's Perfect Resize over the Photoshop options if it's more than a 50% increase in image size. –  John Cavan Nov 21 '12 at 3:33
add comment

There are many different free and paid software to do this and most of them have different algorithms to do so with various qualities.

As the process have to "guess" what happens between each the true pixels (that exist in the original) the chosen "interpolation filter" will make its own "assumptions" how to deduce from the neighborhood what happens. Each filter makes its own "artifacts" in the result.

As an example, in your case you want 300% size. That means that there are two unknown pixels between each true pixel:

{-}{-}{-}

{  -  }  {  -  }  {  -  } 

This page shows examples and explains in detail what's going on:

http://www.imagemagick.org/Usage/filter/#compare

I've implemented "Box" Nearest Neighbor (useful in some research cases because it never makes a pixel value that doesn't exist already), Hermite, Gaussian and Lanczos in Image View Plus More. I pick different filters to give me the result I think looks best in the given image.

It also has the feature to automatically do it incrementally in , say, 5-20% steps, as others recommend, instead of having to do this yourself, the program does it for you.

share|improve this answer
add comment
  1. Download Xnview here: http://www.xnview.com/
  2. Open image in Xnview
  3. enter image description here
  4. enter image description here
  5. enter image description here
  6. enter image description here
  7. enter image description here
  8. Save image
share|improve this answer
    
Will this method give "the best possible quality"? –  mattdm Nov 20 '12 at 19:38
    
@mattdm - This is the quickest dirtiest way to make it happen. From reading the question I got the notion that the user might not know a whole lot about photography or image manipulation. Yes they asked for "best quality", but they also said "What method is common to become" which makes no sense at all. Sometimes we take answers waaay to far on this site when people want a simple "how do I do it the easiest/fastest way". The linked to question that you used as a possible dupe uses Photoshop, which many people don't have access to. Itai's answer is good, but goes in depth and can confuse some. –  dpollitt Nov 20 '12 at 19:43
    
Well, I have to admit, I think this is going to be fine on a billboard a hundred feet away, but not so much on a print that you'll hang on a wall. There are tools to do this at much higher quality, but they aren't free. Nevertheless, for quality, there are common options and OP didn't say it had to be cheap. –  John Cavan Nov 21 '12 at 3:31
    
Ugh whatever. You are right, lets just assume that everyone wants to spend $99 for Perfect Resize, or $699 for Photoshop, or $89 for PS Elements. Look at the wording of this question. They tagged it with "scale". The title is "How to scale up a photo?". My bet is that it someone completely unfamiliar and potentially not caring what DPI is. So explaining a verbose example of why DPI matters and what it is, etc might not help them whatsoever. They probably want to blow up a thumbnail that they have for Facebook! Not everyone is a programmer or has that mentality; or cares to be a pro photog. –  dpollitt Nov 21 '12 at 3:58
    
If you just want to blow up you dont even need xnview or any other software. MSPaint does this out of box what you have shown here. –  2-Stroker Nov 21 '12 at 9:29
show 3 more comments

This is based from some pro photogs and printer studio's that have been doing large scale billboards. What they recommend is to enlarge the image in Photoshop by 5-15% at a time. This is to avoid pixilating the image too much when Photoshop applies the enlargement to the image. The cause of this is how Photoshop enlarges the pics. They say PS makes the image bigger by creating spaces between pixels and filling those pixels up with what Photoshop assumes as the correct color for that space, based on the surrounding colors. Increasing it 5-15% at a time means that PS will only need to create and fill up a small space, making the rendition of the new colors in the space more accurate.

share|improve this answer
add comment

Not the answer you're looking for? Browse other questions tagged or ask your own question.