Upscaling and Processing LARGE canvas print

Some help will be appreciated here.

I am busy preparing a massive panoramic canvas print for a client.
I have upscaled photos for canvas printing successfully in the past, but most times it was upscaled by a factor of 0.5 to 1.5 - this time I need to upscale about 3x the resolution.

The native high res image is a panoramic stitch of 3 images from a Canon 7D.
10182 x 3388 pixels...measuring 86x21 cm

Now I need to print it at 3mx1m for a hallway.
This means upscaling it to 35433x11790.

I am familiar with the need to heavily oversharpen to make up for the loss of detail when printing on canvas.
Question is - how much do I need to sharpen this upscaled image to print acceptably for normal viewing (ie nobody will be standing a few inches from a canvas like this, you'll view it from a distance)??

Thanks in advance!

Hello Morkel,

For my own work I sharpen less for canvas than for paper prints. For me, the reason for printing on Canvas is that the print look more like a painting than a photograph. Even regular sharpening can make it look odd. For some images I even soften not sharpen.

The person who does my prints over 17" of my 3880 says the same thing. He does fine art prints for artists of many mediums and thinks that prints on canvas should not be sharpened too much if at all.

I am sure others have other ideas about their own work and I look forward to reading them.

I think you also need to take into consideration the canvas you are printing on. For example, Breathing Color Lyve holds detail very well and it's very easy to over-sharpen. The first print I did on Lyve canvas using my usual sharpening amounts for canvas was badly over-sharpened. Also the subject matter should greatly influence whether you sharpen and by how much.
Eleanor has a very good point about the look of canvas and whether or not you prefer to sharpen.

Right, Randy, and I do use Breathing Color Lyve.

Morkel,

Like the others I use Breathing Color Lyve as well and I sharpen just enough so that the image looks sharp on screen when viewed at 50%. I don't want it oversharpened but to just look crisp at 50%. I don't like the look of oversharpened canvas prints and when done properly they look good at a normal viewing distance and as you get closer you actually begin to see the texture of the canvas which also hides supposed lack of sharpness. So, in a nutshell I would sharpen at 50% just until thr image loosk nice and crisp and no further. Have fun and let us know how it comes out. I am working on a canvas print for a clinet right now which will be 36 x 72. Big prints ROCK!

Hi Morkel,
I agree with the good advice from Les, Randy, and ebkw. The canvas itself can be a significant factor. I also use BC Lyve which holds detail quite well, and doesn't usually require much, if any additional sharpening just because it is canvas.

That being said, I treat every image differntly with regard to sharpening, and size. I think it is very helpful to print a few full size/res portions of your image on say a 17 x 25 inch canvas of your choice. It will give you a feel for how the image will look in detail and overall density from the anticipated viewing distance.

Hi Morkel

I do many large prints on canvas. It really depends on the canvas used. You do not say whether you are using a matte canvas or a more glossy one. The matte needs slightly more sharpening than gloss. The up-res process also has some effect, especially if you have done some selective creative sharpening whilst processing the image. Perfect Resize 7.0 (used to be called Genuine Fractals) is great.A 3m wide print needs to be ideally viewed from a little over 3m away. Canvas tends to show sharpening halos quite easily especially if you are doing a landscape with a very definitive sky/mountain outline. Have just completed a pano of 14 images (1Dm4) shot in vertical format of the Ngorongoro crater and found it worked better on a slightly glossy canvas rather than my normally used matte canvas.

John Bryant
www.photoimagesofafrica.com

Thanks for the great feedback, folks. Will consult with my printer and make a final call on how to approach this.

Text deleted. Please see following.

Morkel, according to your figures, you plan to print at a res of 300 ppi - like standard press. At this res, the minimum viewing distance where you can just begin to discern individual pixels is about 12 inches (30 cm). But, except for pixel peepers, the viewing distance for your panorama will normally be 3 m or more and you can employ a much lower res without any discernible loss of detail. For a THX-preferred viewing angle of 38 degrees, the proper viewing distance for your 3 m print would be 4.35 m (171 in). And require a wide hallway. A museum? A palace?

If you use 180 ppi to print this large picture (as per Fraser, Schewe et al), you will not need to upres nearly as much and can avoid artifacts caused by pixel manufacturing. And you will have a smaller file size. At this res the 'minimum viewing distance' is about 20 inches (51 cm).

Worth a try. Good luck and please let us know your results. Can we see the pic?

Thanks folks. Should have given feedback here already. My printer suggested upres'ing at 150dpi. It worked a charm and the print came out beautifully.

Thanks for all the advice!