GIMP

2019년 3월 21일 (목) 07:16, Rick Strong 님이 작성:

Does anyone know of really good software for scaling up an 8x12 inch, 300 pxi photo to, say, 16x20 or 20x24 inches or larger? Will GIMP do that?

Would be displayed on a wall in a living room, lots of daylight, viewing distance: 10 to 12 feet. Any ideas appreciated.

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Gimp will do this easily. Only constraints are memory and disk.

Use Scale Image from Image menu. Options include width and height (can modify default display from pixels to inches) and you can specify dpi. If you start with 300dpi, no need to change that.

Note, however, you should confirm the quality of the image will handle this kind of scaling. An image may look fine on your monitor or tablet or smart phone but will not be fine for this kind of scaling. Jpeg artifacts are often a barrier and they can exist in a 300 dpi image as well as a 72 dpi image. Gimp can also help fix that kind of issue.

Regards.

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On Wed, Mar 20, 2019, 5:16 PM Rick Strong  wrote:

> Does anyone know of really good software for scaling up an 8x12 inch, 300
> pxi photo to, say, 16x20 or 20x24 inches or larger? Will GIMP do that?
>
> Would be displayed on a wall in a living room, lots of daylight, viewing
> distance: 10 to 12 feet. Any ideas appreciated.
>
> Rick
> _______________________________________________
> gimp-user-list mailing list
> List address:    gimp-user-list@gnome.org
> List membership: https://mail.gnome.org/mailman/listinfo/gimp-user-list
> List archives:   https://mail.gnome.org/archives/gimp-user-list
>

On Wed, 2019-03-20 at 17:57 -0400, Rick Strong wrote:

Does anyone know of really good software for scaling up an 8x12 inch, 300 pxi photo to, say, 16x20 or 20x24 inches or larger? Will GIMP do that?

At 10 to 12 feet, 144dpi will be fine. Fine Art magazines and books rarely go over 150 lines per inch in a dot screen, so although 300dpi is recommended, 150 is fine, as long as you don't have text at small sizes.

So, 8x12inch at 300dpi is 16x24inch at 150dpi.

Now, newspapers use 75 or 72dpi screens generally. So try looking at a newspaper photograph from ten feet away and see if you're OK with the quality.

If so, your image is good for 32x48inches unchanged (or just changing the image’s Print Size).

If you're sending this out to a print shop, ask what resolution they need. If they insist on 300dpi, you can use gimp to scale it up; the results will not generally be as good with Fractal, though. You might also be able to use the liquid rescale / resynthesizr plugin to get better quality, because you're asking gimp to invent detail.

Liam

Liam Quin, https://www.delightfulcomputing.com/
Available for XML/Document/Information Architecture/XSLT/
XSL/XQuery/Web/Text Processing/A11Y training, work & consulting.
Web slave for vintage clipart http://www.fromoldbooks.org/

On Thu, 21 Mar 2019 00:04:08 -0400, Liam R E Quin wrote:

On Wed, 2019-03-20 at 17:57 -0400, Rick Strong wrote:

Does anyone know of really good software for scaling up an 8x12 inch, 300 pxi photo to, say, 16x20 or 20x24 inches or larger? Will GIMP do that?

At 10 to 12 feet, 144dpi will be fine. Fine Art magazines and books rarely go over 150 lines per inch in a dot screen, so although 300dpi is recommended, 150 is fine, as long as you don't have text at small sizes.

So first off, I agree and if anything would go further and say that there's rarely going to be a problem at even 75-100 dpi.

One is often viewing a ~20" print from rather closer than 10-12'; that's not an atypical viewing distance from a much larger TV. But I don't disagree with the conclusion for a photograph, where there's not normally extremely high spatial frequency data at high contrast, even if the image is reasonably sharpened. Even highly detailed scenes, such as trees, fields of grass, and such usually in my experience don't have a lot of pixel-to-pixel detail, and if they do, it's only going to be right at the focal plane.

Text and line art (including high quality photographic reproductions of same) are another matter, but that doesn't sound like the use case here.

Just to give you an idea, [1] has long been one of my own favorites, and I've printed it at 16x24 many times. It has quite a bit of fine detail throughout. It was taken in 35mm film with an inexpensive lens (Tamron 28-200, in the late 1990's when that was an early superzoom), and might charitably have 2000 lines/inch resolution or 6 megapixels, which would work out to 125 dpi on the final print.

[1] https://rlk.smugmug.com/Other/Landscapes/i-qGZ7Jx9/A

So, 8x12inch at 300dpi is 16x24inch at 150dpi.

Now, newspapers use 75 or 72dpi screens generally. So try looking at a newspaper photograph from ten feet away and see if you're OK with the quality.

That's a bad comparison; there are other reasons why newspaper photos are poor quality (cheap paper and ink, bad channel-to-channel registration, and so on).

Which also brings up the issue of print technology -- the printer's screening, whether a fixed grid dot screen like offset printing or the much higher frequency but less regular dithering of an inkjet or laser, will usually help hide pixelation in a continuous tone image, and if not, good quality scaling as Liam suggests will hide the pixelation. Pixelation is a lot harder on the eye than a small bit of softness.

If so, your image is good for 32x48inches unchanged (or just changing the image’s Print Size).

If you're sending this out to a print shop, ask what resolution they need. If they insist on 300dpi, you can use gimp to scale it up; the results will not generally be as good with Fractal, though. You might also be able to use the liquid rescale / resynthesizr plugin to get better quality, because you're asking gimp to invent detail.

Liam

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