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I have been contracted to shoot a night tim cityscape in B&W that will be printed on a wall in an office. 30 feet wide by 6 feet high. I am shooting a Canon 5D mkiii with lens options being a range L series. Whats the best tactic to get the resolution high enough for such a large print that will be viewed from a close distance?

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  • \$\begingroup\$ Related: Is there a general formula for image size vs. print size? \$\endgroup\$
    – scottbb ♦
    Commented Apr 28, 2017 at 14:25
  • \$\begingroup\$ When you say "close distance", how close are you talking about? Please be specific. Are you seeking to have "retina resolution" (i.e., typical human eye can't resolve the pixels / line pairs) at that distance? \$\endgroup\$
    – scottbb ♦
    Commented Apr 28, 2017 at 14:27
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    \$\begingroup\$ It will be above a row of cubicles in a room full of cubicles. So viewers as may be close as 2 feet, but the majority would be 6 feet to 25 feet away. Some pixel detection is acceptable, no more that "newsprint" level would be desirable. Thank you. \$\endgroup\$
    – memoryinflightphotography
    Commented Apr 28, 2017 at 15:55
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    \$\begingroup\$ How will the panorama be printed? Max. resolution may be limited by the printer for such a large poster. \$\endgroup\$
    – ths
    Commented Apr 28, 2017 at 17:10
  • \$\begingroup\$ I think the answer below is on target, but I will offer another comment: I had some regular shots, unexpected, made into large wall prints in an arena. Like 15'x20' or so. From Noisy JPG's (indoor sports). They looked awfully good, and it was clear that vendors who produce these have resizing software that smooths out noise and grain fairly well. Clearly it can't add detail back that was not there, but you may be surprised how good yours will look even if you do not try to get massive pixel density with panos (though it will be better if you do). \$\endgroup\$
    – Linwood
    Commented Apr 29, 2017 at 16:55

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I'm going to cut straight to the answer — panoramic stitching — before the analysis.

I assume that you will only want to take a single-row panorama. That is, your final image will consist only of images stitched together horizontally.

When taking a landscape panorama, turn your camera into portrait orientation. This will give you more resolution in the vertical dimension. For your camera, this means you will have at most 5784 vertical pixels on your 30' × 6'. (In reality, you will lose a few pixels due to cropping the top and bottom, even under the best panoramic technique.)

Thus, when your mural is printed, your image will have a maximum print density of 5784 px / 72 in ≈ 80 PPI.

Drfrogsplat's answer to the question, "Is there a general formula for image size vs. print size?", gives us some useful formulae to help us determine the tradeoff between viewing distance and required print resolution.

According to that answer, somewhere between 53 and 100 pixels-per-degree (PPD) is considered "retina resolution", that is, the point at which the human eye can't distinguish individual pixels.

Using the formula

d ≈ PPD / (PPI * 0.01745)

where d is in inches, PPI is 80, then your "retina viewing distance" for a single-row panorama is 38"–72" (for PPD in the range of 53—100).

Now, the single-row panorama, combined with the required print size and the viewing distance, doesn't leave you much room for cropping, possible "de-warping" in software, etc. Your choices to deal with this are:

  1. Accept a lower spatial resolution (i.e., lower PPI, meaning possibly less-than-retina viewing);
  2. "Suggest" a farther viewing distance, to maintain retina viewing);
  3. Reduce the print size;
  4. Use a camera with higher resolution;
  5. Take a multi-row panorama.

(Obviously, 3. and 4. are not an option, based on the statements in your question).

As far as taking the panorama images, if you're not familiar with that, I suggest the following questions:

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    \$\begingroup\$ Multi-Row Panorama what I had been considering, thank you very much for underpinning the explanation with the math and linking to the Pano tutorials. Your help is greatly appreciated!! \$\endgroup\$
    – memoryinflightphotography
    Commented Apr 28, 2017 at 15:58
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    \$\begingroup\$ Not much to add to @scottbb's excellent answer. When there is no moving subject you can't beat the resolution of a stitched panorama. Use a tripod, prefferably a pano head and lock your exposure and ISO. Then pray the light does not change while you are at it :) \$\endgroup\$
    – Jindra Lacko
    Commented Apr 28, 2017 at 17:01
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    \$\begingroup\$ @JindraLacko And take more than one set of the complete series just in case it does change momentarily while you are shooting. (e.g. airplanes flying through the FoV, etc.) \$\endgroup\$
    – Michael C
    Commented Apr 28, 2017 at 19:33

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