Image resolution

[rehana36276218]

hello my friends and adobe forum members...! nice to meet you , actually i am a graphic designer and my question means problem is that i received Photoshop file form customers psd format , the file size dimension is bigger like 250 feet x 12 feet for outdoor printing , but those who send this design they set normal resolution  according to them, but when i send this file to outdoor printer he said file is not good enough resolution to print on outdoor printer....now i have to make this artwork again, you can see attach artwork,  i want to know that is there is any formula or how do we know that if we are making design in Photoshop let say take this example 250 feet by 12 feet right when i open new page  i put these size 250feet x 120 feet in inches right , now my question is start from here that how i know the resolution i insert in new page  50 dpi , 20 dpi , 100 dpi .... ? how do i know what value should i insert  , to set correct pixels for printing large outdoor printer ... sorry for my english is poor

thanks in advance  for your precious time that you spend for my question... long live you and your family

[davescm]

Hi

The resolution required is based on the proposed viewing distance. There is a handy formula for working out ppi and it based on the resolving power of good healthy eyes.

ppi required = 2/(viewing distance in inches x 0.000291)

Any more than that is wasted as your eyes simply cannot resolve it. A banner of 250 feet x 12 feet will be viewed at a large distance. Estimate that distance, in inches,  and put it into the formula.

There is some background reading here:

What print resolution works for what viewing distance?

Dave

[rehana36276218]

technically distance is not easily measured for fixing the sign boards , there is alot of commercial signboard sites in city, how you will ask vendor that we required size , i think practically not possible. any other idea if you can share please ... any formula that required no distance

[Grant H]

50 effective ppi is more than enough. But, what resolution is your printer requesting. If for some reason it is a lot more you may have to break the image into 4 to meet the requirements...

[davescm]

Hi

No there is no formula that does not involve viewing distance as that is how our eyes work. They actually resolve a minimal viewing angle. That translates into a different physical width based on the viewing distance - the greater the viewing distance, the greater the size covered by that angle.

A poster that size is unlikely to be vewed at less than 15 feet which , using the formula makes 38 ppi. So anywhere around 40ppi is going to work.

Dave

[rehana36276218]

how this formula works ppi=2(viewing distance * 0.000291 is very much less value, and not correct formula

let calculate 250 feet x 12 feet

let say  ppi = 2 (3000 in inches x 0.000291)

ppi = 2.2909 is coming that is not possible ..?

i think its wrong..?

[jane-e]

rehana36276218  wrote

ppi = 2.2909 is coming that is not possible ..?

i think its wrong..?

Hi

I think davescm mistyped when he wrote

ppi required = 2/(viewing distance in inches x 0.000291)

Elsewhere he has written ppi = 1/((distance in inches x .000291)/2)

His theory is correct.

~ Jane

Re: Maximum Enlarging for Mural

[davescm]

Hi Jane

just for completeness

1/((d x 0.000291)/2) is the same as 2/(d x 0.000291)

Dave

[Grant H · Accepted solution]

thats right but i am sure it will be viewed closer... you are overthinking this... for this size panel its an industry standard accepted at effective 50ppi.

[davescm]

Hi

In your calculation you used 3000 inches as the viewing distance. That is 250 feet. With a height of 12 feet your poster will be viewed closer than that.

If you use 15 feet you get:

2/(((15x12) x0.000291) = 38ppi.

So anything around 40 ppi is going to be fine from that distance.

Dave

[Grant H]

for that size artwork 50 dpi for output is fine, the printer that will print it probably is a massive 5meter bed and printing at under 40 DPI, so you can work at 10% size with an output DPI equivalent to 500DPI or full size at output 50DPI.