Post Reply 

Resize Photo Without Making Blurry

Feb 7, 2012, 01:14
Post: #1
Resize Photo Without Making Blurry
Hi,

I want to know how to resize one of my photos to 190px wide by 147px high? When I do it becomes super blurry and I need it to be crystal clear...am I correct in assuming that it has to be a landscape picture? Are there special sharpening tools that I need to use, etc.?

Thanks!
Regan
Find all posts by this user
Quote this message in a reply
Feb 7, 2012, 01:36
Post: #2
RE: Resize Photo Without Making Blurry
Downscaling a picture makes it blurry. Landscape or portrait orientation is the same.

There are two things to do to mitigate the problem:

1) although it is counter- intuitive, pre-blur the picture. If you downscale 2x, use a Gaussian blur of 2px, 3px for 3x, etc... this avoids moirés and aliasing artifacts which, even if not very noticeable, are part of the blurriness.

2) after downscaling, apply some re-sharpening to restore some sharpness. The filter of choice is Filters/Enhance/Unsharp mask (which despite its name, sharpens the pictures)

But you'l never get something which is 190x147 crystal clear because people will unconsciously look it up close and see the pixels. The accepted rule in photography is that the smallest detail one can see is about 1/1800th of the picture diagonal (which is roughly one pixel for a 1500x1000 picture), and on your 190x147 picture, a pixel is 7 times bigger than the smallest detail.

[Image: 2Tvo0.png]

Find all posts by this user
Quote this message in a reply
Feb 7, 2012, 06:04
Post: #3
RE: Resize Photo Without Making Blurry
Hi there,

Thank you for your response and for your helpful advice...I am completely new to picture editing and I have no clue how to do anything, so I will probably ask for at least a billion clarifications...:-)

It does seem to make a difference when I make the landscape picture 190x147 and when I make the portrait one the same size...the portrait one comes out much more smooshed...so, I get that they will both be blurry, but I actually meant that it seems better to use the landscape to keep most of the pic in tact...

What do you mean by downscaling 2x? Do you mean if I resize the picture twice? What Gaussian blur would I use for the picture 190wide by 147 high?

I tried the unsharp mask and that did help...





(Feb 7, 2012 01:36)ofnuts Wrote:  Downscaling a picture makes it blurry. Landscape or portrait orientation is the same.

There are two things to do to mitigate the problem:

1) although it is counter- intuitive, pre-blur the picture. If you downscale 2x, use a Gaussian blur of 2px, 3px for 3x, etc... this avoids moirés and aliasing artifacts which, even if not very noticeable, are part of the blurriness.

2) after downscaling, apply some re-sharpening to restore some sharpness. The filter of choice is Filters/Enhance/Unsharp mask (which despite its name, sharpens the pictures)

But you'l never get something which is 190x147 crystal clear because people will unconsciously look it up close and see the pixels. The accepted rule in photography is that the smallest detail one can see is about 1/1800th of the picture diagonal (which is roughly one pixel for a 1500x1000 picture), and on your 190x147 picture, a pixel is 7 times bigger than the smallest detail.
Find all posts by this user
Quote this message in a reply
Feb 7, 2012, 07:48 (This post was last modified: Feb 7, 2012 07:49 by ofnuts.)
Post: #4
RE: Resize Photo Without Making Blurry
Quote:Thank you for your response and for your helpful advice...I am completely new to picture editing and I have no clue how to do anything, so I will probably ask for at least a billion clarifications...:-)
That's what these forums a made for.

Quote:It does seem to make a difference when I make the landscape picture 190x147 and when I make the portrait one the same size...the portrait one comes out much more smooshed...so, I get that they will both be blurry, but I actually meant that it seems better to use the landscape to keep most of the pic in tact...
I have a very hard time admitting this... This may come form the difference in nature of the two pics. Take the same picture, crop it to landscape and portrait formats of the same size, downscale, and compare.

Quote:What do you mean by downscaling 2x? Do you mean if I resize the picture twice? What Gaussian blur would I use for the picture 190wide by 147 high?
No, I mean dividing the size by two. From a 1000x1000 picture, a 2x downscale yields a 500x500 picture, a 4x a 250x250 and a 5x a 200x200.

Quote:I tried the unsharp mask and that did help...
It usually does.

[Image: 2Tvo0.png]

Find all posts by this user
Quote this message in a reply
Post Reply 


Possibly Related Threads...
Thread: Author Replies: Views: Last Post
  Making edges seamless rondon9897 7 117 Dec 15, 2014 10:49
Last Post: rich2005
  Making a decal user459 2 69 Dec 11, 2014 21:05
Last Post: user459
  Not allowing to move a photo penny2three 8 102 Dec 10, 2014 20:19
Last Post: penny2three
  Resize image without layer icemans 17 288 Nov 19, 2014 19:08
Last Post: icemans
  Blurry effect? tamikaflynn 11 233 Nov 19, 2014 16:03
Last Post: rich2005

Forum Jump:


GIMP ForumPortalArchiveContactTermsRSS