Upsampling Fine Art images

[Sanpanza]

I have some landscape images that I would like to upsample from 8200 (27") pixels to at least 7200 pixels (30") and hopefully 9600 pixels (40").

At one point does the image become too degraded for fine art printing? The images were shot on a Nikon 850 at ISO 64. You can see them in the link attached.

Any thoughts on upsampling images would be helpful. Thanks for your time and attention.

Landscapes by Ed Carreon

[Nancy OShea]

Upsizing is apt to introduce artifacts.  And the more you do it, the more artifacts are introduced.  That said, artificial intelligence and improved  interpolation methods are making strides.  See this article.

https://petapixel.com/2016/10/14/free-software-can-upscale-enlarge-photos-better-photoshop/

[davescm · Accepted solution]

Hi

As Nancy says interpolation always introduces artifacts. The question is, are those artifacts prefereable to just printing with larger pixels? In most cases the answer is no. The reason is that as we print larger, we naturally view the resulting print from a greater distance, and so from that greater distance the larger pixels are no more visible than the smaller pixels were on a smaller print viewed close up.

There is some good advice at the link below regarding the resolution required for printing. As stated above , it all depends on viewing distance :

What print resolution works for what viewing distance?

Dave

[D Fosse]

There is no earthly reason to upsample at all. A D850 file can be reproduced at any size, for any purpose.

Carefully shot, and at low ISO, that's a state of the art image file. Upsampling will only degrade it.

[Sanpanza]

So if I uderstand correctly, if I have a native file size at 8200 and I want to make a print at 9600 pixels, I DO NOT HAVE TO EXTRAPOLATE? What that just produce a an image with less pixels perh inch and this lower resolution?

[davescm]

Yes just use Image >Image size and uncheck Resample. You will retain the same number of pixels over the larger area.

Dave

[Sanpanza]

But won't I loose resolution on the image? Won't there be some degradationof the image?

[davescm]

The resolution, as in detail of the image, will be the same as it was earlier. You have not lost any pixels.

That detail will be spread over a bigger area - but you will view that larger area from a greater distance - so to your eye , it will look the same.
Interpolation just adds additional pixels in between those that exist based on the pixels around those new pixels (using the algorithm chosen when resampling). It cannot, and does not, add any extra detail to your image. The only thing it does is makes sure that no pixels are visible when viewed close up - because of teh extra pixels it drops in. The downside is that it can introduce unwanted artifacts.

Dave

[davescm]

If you doubt any of the above make a test.

Crop a small section of your image and enlarge it to the equivalent % increase that you were proposing in your first post (Approx 150%). The reason for the small crop is so that you can enlarge and still have a small print so you don't waste paper.

First use resampling to add the extra pixels - so you still have 240ppi

Second do the same but this time uncheck resampling - so the second print has less ppi than the first (it will have approx 160ppi)

Print both.

Now pin them on the wall and step back to view at the distance you will view a large 40" print (around 6 feet). Can you see a difference?  If you can, you have incredible eyes, as good eyes can only resolve around 95ppi at 6 feet.

Dave

[Sanpanza]

Thanks Dave for adding to my understanding of this process. I will run some test prints.