Quick question : how to you tackle image size regarding printing projects (distance, dpi…)

[Loic.Aigon]

Hi everyone,

More than ten years ago, I wrote this little utility (likely circa PS CS5.5) that would help users to identify the maximum printable size regarding viewer distance. It was yet a bit empiric.

PrintableSizes extension Oldie

I am tempted to recreate this tool in the new UXP Plugin ecosystem but would enjoy your testimonials. Eventually, the new version would better fit your actual needs. And possibly lay on more scientific rules.

If anyone is interested in sharing his/her thoughts on this, it would be greatly appreciated (features expected…)

TIA

Loic

[War Unicorn]

I haven't done this kind of work, but the obvious one is: Whatever you can get away with. A lower DPI means more distance (needed) and less processing in Photoshop.

[Loic.Aigon]

thanks for the input

[TheDigitalDog]

Old Bruce Fraser quote that sums this up for some:

”The distance a photographer views a print is based on the length of his nose”.

[Loic.Aigon]

Thanks @TheDigitalDog for the laugh 🙂

[TheDigitalDog]

Thanks @TheDigitalDog for the laugh 🙂

By @Loic.Aigon

Bruce wasn't joking. This was at a gallery opening of photography I attended. 

[Loic.Aigon]

Understood 😉

[davescm · Accepted solution]

There is a formula you can use which is ppi required = 6878/Viewing distance in inches

It is not just plucked out of the air, but is based on the resolving power of our eyes. Using anything above that is a waste.

A good human eye can resolve 60 line pairs per degree i.e. pairs of black and white lines.  So in half a degree we would have 60 single lines.

Simple trigonometry means that the width containing those 60 lines can be calculated by:
               Width of 60 lines = Viewing distance x tan(0.5°)

Once we know the width for 60 lines (or pixels) we can calculate how many lines per inch can be seen by using 60/Width of 60 lines.

So putting those together gives:
60/(Viewing distance x tan(0.5°)) = 60/(Viewing distance x 0.0087269) = 2/(Viewing distance x 0.000291)    

Or

1/(Viewing distance x .0001454)

Or

6878/Viewing distance

Dave

[Loic.Aigon]

Hi Dave,

Thanks a lot for this valuable input 🙂

Loic

[Leslie Moak Murray]

"Simple trigonometry" hahahahahahaha I see you have not met me, a non-STEM person

[Rob_Cullen]

This link may also be of interest-

PPI PRINTS -OMNI CALCULATOR -PIXELS PPI etc

[Loic.Aigon]

Thanks @Rob_Cullen , actually it's funny because i did a few researches before I post here and I spotted this website. I wasn't sure how trustworthy it was.

[D Fosse]

If you want solid numbers, Dave's formula is the way to go.

Simply put: a good high resolution file from a current camera will work equally well at any reproduction size. Magazine spread, exhibition print, wall size banner, roadside billboard, whatever.

There's no real reason to worry about ppi. If the file is good, it'll work. By good I mean in focus, quality optics, no camera shake, a decent sensor resolution of 6000 pixels long side and upwards. You're good to go.

The reason is that you will automatically take a position where you see the image at a comfortable size, filling a pretty standard angle in your field of view. If it's big, you go back. You can't really stop yourself. You don't want to get up close, it's uncomfortable.

[Loic.Aigon]

Thanks for the great feedback!

[NB, colourmanagement net]

It might work to have a guideline and for sure it would help some and it's definitely true that viewing distance affects file resolution requirements. But, I fear that eyesight and personal perception will affect the viewers opinion. Plus as DigitalDog showed, some folk will walk right up to even a massive print. 

I hope this helps
neil barstow, colourmanagement net :: adobe forum volunteer:: co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management

[gener7]

I agree that not everyone's visual acuity is the same. You can however go for the best case planning your calculator as in 60 line pairs per degree, or Dave's 6878/Viewing Distance in inches. From there others can move closer, move back or get new glasses. 🙂