2 Correct answers
Community Expert
,
Feb 12, 2024
Putting that formula into a basic script:
/*
Print Resolution Calculator Viewing Distance - Feet.jsx
Formula from @davescm
v1.0 - 13th February 2024, Stephen Marsh
v1.1 - 14th February 2024, Added canvas size to the alert
https://community.adobe.com/t5/photoshop-ecosystem-discussions/photo-blow-up-question/td-p/14416674
https://community.adobe.com/t5/photoshop-ecosystem-discussions/quick-question-how-to-you-tackle-image-size-regarding-printing-projects-distance-dpi/m-p/1327375
Community Expert
,
May 05, 2025
A new version, combining the separate metric and imperial scripts into one script with a GUI, adding a scale factor field.
P.S. Just in case I broke something, I welcome testing and feedback, thanks.
EDIT: v1.3 Update, 21st August 2025
/*
Poster Viewing Distance Resolution Calculator v1-3.jsx
Stephen Marsh
v1.0 - 13th February 2024: Initial release
v1.1 - 14th February 2024: Added canvas size to the alert
v1.2 - 6th May 2025: Combined the separate metric and imperial scripts into a sin
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Community Expert
,
The above is entirely right. You do not need 300 ppi for large format printing. The bigger it is, the farther away it will be seen from, so the optical resolution stays the same. The eye wants to take in the whole image. You won't stick your nose into it.
Just for demonstration, look at a traditional monitor at 95-120 ppi. How close do you need to go before you see pixels? That's right, very close. For a wall-sized banner, as low as 15 - 20 ppi may be good enough.
300 ppi is for books and magazines to be seen at arm's length or less. Even so, there's nothing magical about the 300 number. It's not even a sharpness limit - it's a smoothness limit. With a standard halftone screen at 150 lines per inch, 300 pixels per inch is the theoretical upper limit beyond which no individual pixels can be detected. But it can still be eminently sharp at lower ppi.
All that said. 2250 x 1650 pixels is a small file to begin with. That sets limits to reproduction size under any circumstances. At 30", you will end at 75 ppi. While not disastrously low, it's still not very good.
Generally, all resampling disrupts the pixel structure and degrades the image. This is especially true for jpegs, which will never look good upsampled. In most normal circumstances, the image will look best as-is, without any upsampling. But sometimes you have to, to avoid visible pixels.
Community Expert
,
Putting that formula into a basic script:
/*
Print Resolution Calculator Viewing Distance - Feet.jsx
Formula from @davescm
v1.0 - 13th February 2024, Stephen Marsh
v1.1 - 14th February 2024, Added canvas size to the alert
https://community.adobe.com/t5/photoshop-ecosystem-discussions/photo-blow-up-question/td-p/14416674
https://community.adobe.com/t5/photoshop-ecosystem-discussions/quick-question-how-to-you-tackle-image-size-regarding-printing-projects-distance-dpi/m-p/13273751
NOTE: This script assumes that the correct print size is set in the Image Size window
*/
#target photoshop
if (app.documents.length) {
var theViewingDistance = prompt("Enter the viewing distance in feet:", "1");
if (theViewingDistance < 1) {
theViewingDistance = 1;
}
var feetToInch = (theViewingDistance * 12);
var theResult = Math.round(6878 / feetToInch);
alert("Poster Size Print Resolution Calculator: " + "\r" + "Viewing Distance : " + theViewingDistance + " Feet" + "\r" + "Calculated PPI Value: " + theResult + " PPI" + "\r" + "Document Resolution: " + Math.round(app.activeDocument.resolution) + " PPI" + "\r" + "Canvas Size: " + activeDocument.width.as('in') + " x " + activeDocument.height.as('in') + " Inches" + "\r\r" + "(Based on the viewing distance, the ability to resolve 60 line pairs per degree and current document print dimensions)");
} else {
alert("A document must be open!");
}
Or for those of us who use the metric system:
/*
Print Resolution Calculator Viewing Distance - Metres.jsx
Formula from @davescm
v1.0 - 13th February 2024, Stephen Marsh
v1.1 - 14th February 2024, Added canvas size to the alert
https://community.adobe.com/t5/photoshop-ecosystem-discussions/photo-blow-up-question/td-p/14416674
https://community.adobe.com/t5/photoshop-ecosystem-discussions/quick-question-how-to-you-tackle-image-size-regarding-printing-projects-distance-dpi/m-p/13273751
NOTE: This script assumes that the correct print size is set in the Image Size window
*/
#target photoshop
if (app.documents.length) {
var theViewingDistance = prompt("Enter the viewing distance in metres:", "1");
// Metres to feet
theViewingDistance = (theViewingDistance * 3.281);
if (theViewingDistance < 3.281) {
theViewingDistance = 3.281;
}
var feetToInch = (theViewingDistance * 12);
var theResult = Math.round(6878 / feetToInch);
alert("Poster Size Print Resolution Calculator: " + "\r" + "Viewing Distance : " + (theViewingDistance / 3.281) + " Metres" + "\r" + "Calculated PPI Value: " + theResult + " PPI" + "\r" + "Document Resolution: " + Math.round(app.activeDocument.resolution) + " PPI" + "\r" + "Canvas Size: " + (Math.round(activeDocument.width.as('cm') * 100) / 100 + ' x ' + Math.round(activeDocument.height.as('cm') * 100) / 100 + ' CM') + "\r\r" + "(Based on the viewing distance, the ability to resolve 60 line pairs per degree and current document print dimensions)");
} else {
alert("A document must be open!");
}
https://prepression.blogspot.com/2017/11/downloading-and-installing-adobe-scripts.html
A new version, combining the separate metric and imperial scripts into one script with a GUI, adding a scale factor field.
P.S. Just in case I broke something, I welcome testing and feedback, thanks.
EDIT: v1.3 Update, 21st August 2025
/*
Poster Viewing Distance Resolution Calculator v1-3.jsx
Stephen Marsh
v1.0 - 13th February 2024: Initial release
v1.1 - 14th February 2024: Added canvas size to the alert
v1.2 - 6th May 2025: Combined the separate metric and imperial scripts into a single script with a GUI, including a scale factor
v1.3 - 21st August 2025: Scale factor and minimum calculated PPI formula corrected
https://community.adobe.com/t5/photoshop-ecosystem-discussions/photo-blow-up-question/td-p/14416674#U15306592
https://community.adobe.com/t5/photoshop-ecosystem-discussions/photo-blow-up-question/td-p/14416674#U14419023
https://community.adobe.com/t5/photoshop-ecosystem-discussions/quick-question-how-to-you-tackle-image-size-regarding-printing-projects-distance-dpi/m-p/13273751
Related resources:
https://www.omnicalculator.com/other/pixels-to-print-size
https://www.insights4print.ceo/2025/04/stop-asking-for-300-ppi-or-dpi-images/
https://www.linkedin.com/pulse/300-ppp-le-culte-des-pixels-inutiles-branislav-mili%25C4%2587-1qx6f/?trackingId=OGo70EImQ5cm9d3Sqe4q5w%3D%3D
*/
#target photoshop
(function () {
// Check if a document is open
if (!app.documents.length) {
alert("A document must be open to use this script!");
return;
}
// Create the input dialog window
var dialog = new Window("dialog", "Poster Viewing Distance Resolution Calculator (v1.3)");
dialog.preferredSize.width = 380;
// Create the panel for dropdown and input field
var inputPanel = dialog.add("panel", undefined, "Input Parameters");
inputPanel.alignChildren = "left";
inputPanel.orientation = "column";
inputPanel.margins = 15;
inputPanel.preferredSize.width = 350;
// Dropdown for unit selection
var unitDropdown = inputPanel.add("dropdownlist", undefined, ["Metres", "Feet"]);
unitDropdown.selection = 0; // Default selection: Metres
// Input field for viewing distance
var distanceGroup = inputPanel.add("group");
distanceGroup.orientation = "row";
distanceGroup.add("statictext", undefined, "Viewing Distance:");
var distanceInput = distanceGroup.add("editnumber", undefined, "1");
distanceInput.characters = 8;
// Input field for scale factor
var scaleGroup = inputPanel.add("group");
scaleGroup.orientation = "row";
scaleGroup.add("statictext", undefined, "Scale Factor:");
var scaleInput = scaleGroup.add("editnumber", undefined, "1");
scaleInput.characters = 8;
// Add help text for scale factor
var helpText = inputPanel.add("statictext", undefined, "Scale Factor: 1 = 100%, 2 = 200%, 0.5 = 50% etc.");
helpText.preferredSize.width = 320;
// Event listener to change the editnumber field based on dropdown selection
unitDropdown.onChange = function () {
if (unitDropdown.selection.text === "Feet") {
distanceInput.text = "3"; // Set to 3 for Feet
} else if (unitDropdown.selection.text === "Metres") {
distanceInput.text = "1"; // Set to 1 for Metres
}
};
// Cancel and OK buttons
var buttonGroup = dialog.add("group");
buttonGroup.alignment = "right";
var cancelButton = buttonGroup.add("button", undefined, "Cancel");
var okButton = buttonGroup.add("button", undefined, "OK");
// Define OK button action
okButton.onClick = function () {
var unit = unitDropdown.selection.text; // Get selected unit
var viewingDistance = parseFloat(distanceInput.text); // Get entered distance
var scaleFactor = parseFloat(scaleInput.text); // Get scale factor
if (isNaN(viewingDistance)) {
alert("Please enter a valid number for the viewing distance.");
return;
}
if (isNaN(scaleFactor) || scaleFactor <= 0) {
alert("Please enter a valid positive number for the scale factor.");
return;
}
// Validate minimum viewing distance based on the selected unit
if (unit === "Metres" && viewingDistance < 1) {
alert("For Metres, the minimum viewing distance is 1.");
return;
} else if (unit === "Feet" && viewingDistance < 3) {
alert("For Feet, the minimum viewing distance is 3.");
return;
}
// Convert to feet if necessary
if (unit === "Metres") {
viewingDistance = viewingDistance * 3.281; // Metres → Feet
}
var inches = viewingDistance * 12;
////////////////////////////////////////////////////////////////////
// A "minimal" constant of 3438 PPI (or x2 of 6878 PPI for "optimal
// smoothness") is derived from the relationship between human visual
// acuity and the resolution needed for a print.
////////////////////////////////////////////////////////////////////
var minPPI = Number(3438);
var optPPI = Number(6878);
// ✅ Required PPI depends ONLY on viewing distance
var requiredPPI = Math.ceil(optPPI / inches);
// Document properties
var doc = app.activeDocument;
var docRes = Math.round(doc.resolution);
// Original dimensions (px)
var origWidthPx = Math.round(doc.width.as('px'));
var origHeightPx = Math.round(doc.height.as('px'));
// Scaled dimensions (px)
var scaledWidthPx = Math.round(origWidthPx * scaleFactor);
var scaledHeightPx = Math.round(origHeightPx * scaleFactor);
// Original print dimensions (inches or cm)
var origWidth = unit === "Metres" ?
(Math.round(doc.width.as('cm') * 100) / 100) :
(Math.round(doc.width.as('in') * 100) / 100).toFixed(2);
var origHeight = unit === "Metres" ?
(Math.round(doc.height.as('cm') * 100) / 100) :
(Math.round(doc.height.as('in') * 100) / 100).toFixed(2);
// Scaled print dimensions
var scaledWidth = unit === "Metres" ?
(Math.round((doc.width.as('cm') * scaleFactor) * 100) / 100) :
(Math.round((doc.width.as('in') * scaleFactor) * 100) / 100).toFixed(2);
var scaledHeight = unit === "Metres" ?
(Math.round((doc.height.as('cm') * scaleFactor) * 100) / 100) :
(Math.round((doc.height.as('in') * scaleFactor) * 100) / 100).toFixed(2);
// ✅ Effective resolution after scaling
var actualPPI = docRes / scaleFactor;
// Format display strings
var origSizeUnit = unit === "Metres" ? " CM" : " Inches";
var origCanvasSize = origWidth + " x " + origHeight + origSizeUnit;
var scaledCanvasSize = scaledWidth + " x " + scaledHeight + origSizeUnit;
var origCanvasSizePx = origWidthPx + " x " + origHeightPx + " PX";
var scaledCanvasSizePx = scaledWidthPx + " x " + scaledHeightPx + " PX";
// Show the result in a new window
var resultWindow = new Window("dialog", "Poster Viewing Distance Calculation Results");
resultWindow.preferredSize.width = 400;
resultWindow.orientation = "column";
resultWindow.alignChildren = "left";
resultWindow.spacing = 10;
var resultGroup = resultWindow.add("group");
resultGroup.orientation = "column";
resultGroup.alignChildren = "left";
resultGroup.spacing = 10;
resultGroup.add("statictext", undefined, "Viewing Distance: " +
(unit === "Metres" ? (viewingDistance / 3.281).toFixed(2) + " Metres" : viewingDistance + " Feet"));
resultGroup.add("statictext", undefined, "Scale Factor: " + scaleFactor);
var requiredText = resultGroup.add("statictext", undefined, "Required Minimum PPI: " + requiredPPI + " PPI");
var actualText = resultGroup.add("statictext", undefined, "Actual Effective PPI: " + actualPPI.toFixed(0) + " PPI");
var infoText = resultGroup.add("statictext", undefined,
actualPPI >= requiredPPI ?
"Note: There appears to be sufficient pixels for output at this print size." :
"Note: There may be insufficient pixels for output at this print size.",
{ multiline: true });
infoText.preferredSize.width = 365;
// Original size
resultGroup.add("statictext", undefined, "Original Print / Image Size:", { multiline: true });
resultGroup.add("statictext", undefined, origCanvasSize + " (" + origCanvasSizePx + ") ");
// Scaled size - only show if scale factor is not 1
if (scaleFactor !== 1) {
resultGroup.add("statictext", undefined, "Scaled Print Size:", { multiline: true });
resultGroup.add("statictext", undefined, scaledCanvasSize + " (" + scaledCanvasSizePx + ")", { multiline: true });
}
// Disclaimer text
var explanationText = resultGroup.add("statictext", undefined,
'\nDisclaimer: Calculations are based on the viewing distance and visual acuity assumptions. The results are intended for informational purposes only and should not be considered as definitive guidelines for print quality. Upscaling to achieve higher PPI is rarely recommended. This script is provided "as is".',
{ multiline: true });
explanationText.preferredSize.width = 365;
// ✅ Color code pass/fail based on comparison
if (actualPPI >= requiredPPI) {
requiredText.graphics.foregroundColor = actualText.graphics.newPen(actualText.graphics.PenType.SOLID_COLOR, [0, 1, 0, 1], 1);
} else {
requiredText.graphics.foregroundColor = actualText.graphics.newPen(actualText.graphics.PenType.SOLID_COLOR, [1, 0, 0, 1], 1);
}
// Add Close button
var buttonGroup = resultWindow.add("group");
buttonGroup.alignment = "right";
var closeButton = buttonGroup.add("button", undefined, "Close");
closeButton.onClick = function () { resultWindow.close(); };
resultWindow.layout.layout(true);
resultWindow.layout.resize();
resultWindow.center();
resultWindow.show();
dialog.close();
};
// Define Cancel button action
cancelButton.onClick = function () {
dialog.close();
};
// Show the input dialog
dialog.center();
dialog.show();
})();
- Copy the code text to the clipboard
- Open a new blank file in a plain-text editor (not in a word processor)
- Paste the code in
- Save as a plain text format file – .txt
- Rename the saved file extension from .txt to .jsx
- Install or browse to the .jsx file to run (see below)
https://prepression.blogspot.com/2017/11/downloading-and-installing-adobe-scripts.html
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