Að stækka ljósmyndir – Gimp vs. Photoshop vs. Qimage – (á ensku)

Hér er ein grein sem ég skrifaði á gamla bloggið mitt, reyndar á ensku en læt flakka hér.

One thing I have to do more often then not is enlarge my digital prints for printing. Unlike with traditional film which you can scan on a flatbed scanner and get incredible resolution for printing, I have to use Gimp or Photoshop to enlarge my prints for the final print size. Most of the time I am not enlarging my prints by that much but since I am using the Sigma Sd-14 Digital camera with the Foveon censor and it only has 4.6MP I have to enlarge most of my prints by some degree for printing. The Sigma Foveon digital files do enlarge extremely well and outperform other cameras with higher Megapixels count. But what if I wanted to make a print 63x42cm? Enlarging a digital SD-14 file from 2640×1760 pixels (4.6mp) to 7500×5000 pixels (36mp) is no problem for Foveon but I need a program to enlarge the print. How well will the open source Gimp performe up against Photoshop CS2 and Qimage (version. 2010.210)? Well lets find out.

I started out with the native resolution Sigma file and enlarged them in Gimp, Photoshop and Qimage. Lets see the results, you are looking at a small area in the print at 200% resolution or zoom in Gimp.

SDIM2463-Gimp-enlarge
Enlarged with Gimp
SDIM2463-PS-enlarg-sharpen
Enlarged with Photoshop – Bicubic sharper
SDIM2463-Qimage-enlarge
Qimage – Hybrid enlarged

 My conclusions
Qimage creates the best version with a cleaner, sharper and less pixalated image. Gimp comes second and then Photoshop. But have in mind when I enlarged the file in Photoshop I used Bicubic sharper setting instead of Bicubic smoother. When I enlarged the file in CS2 via bicubic Smoother it created a better photo than Gimp. But not by much. Does this mean Gimp is crap? No not at all, the difference was minor and hardly visable. When I printed these files on photographic paper via Epson 1270 printer and from a normal viewing distance it was hard to tell them apart but there is a small difference. The Gimp and Photoshop image look the same while the Qimage program clearly does a better job.

If you want to make your own print and download my A4 test print which I used for evaluation. The test print show the three version at print resolution of 7500×5000 but only the area I was looking at. Also if you want to redo this test you can download the original Sigma file in it’s native resolution.

Now I only need to get Qimage to work on Ubuntu via Wine.

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Update 9. maí  2013

I have decided to revisit my old post about enlarging photos with Gimp vs. Photoshop and Qimage since I found out there is a better way to enlarge photos, albeit more CPU heavy, in Gimp. In my old post I enlarged photos in Gimp using Cubic interpolation but after some reserch I have found out that Sinc (Lanczos3) does a far better job when enlarging. To check this out I decided to revisit the old test and enlarge the photo once more but this time with Sinc interpolation.

As before I started out with the native resolution Sigma file and enlarged them in Gimp, Photoshop and Qimage. Lets see the results, you are looking at a small area in the print at 200% resolution or zoom in Gimp. The first photo is the one enlarged with Gimp using Sinc (Laczos3), then the Cubic in Gimp, then Photoshop and finally Qimage.

Gimp enlarged with Sinc (Laczos3) interpolation.
Gimp enlarged with Sinc (Laczos3) interpolation.
SDIM2463-Gimp-enlarge
Enlarged with Gimp
SDIM2463-PS-enlarg-sharpen
Enlarged with Photoshop – Bicubic sharper
SDIM2463-Qimage-enlarge
Qimage – Hybrid enlarged

 My conclusions again
Qimage still creates the best version with a cleaner, sharper and less pixalated image. But Gimp using Sinc (Laczos3) interpolation is pretty darn close. Qimage still has the edge but by so little. The final output from Gimp using Sinc looks almost identical to the Photoshop version using Bicubic smoother. Have in mind I am using PS cs2 which is a rather old program and the new Photoshop version probably has something new when it comes to enlarging. But why bother when Gimp can produce excellent result with Sinc interpolation almost rivaling the result from Qimage.

I also did a print test on photographic paper via Epson 1270 printer and from a normal viewing distance it was hard to tell them apart but there is a small difference. The Gimp and Qimage prints are very close and I see no need to use Qimage over Gimp for enlarging photos.

If you want to redo this test you can download the original Sigma file in it’s native resolution.

Now I have no longer a need to get Qimage to work on Ubuntu via Wine. It just no longer is an issue.

Creative Commons License
Enlarging photos with GIMP is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
Permissions beyond the scope of this license may be available at birgir.org.