Question about canvas size so that file size is not huge

[Jacob_W]

I have a school project where the dimensions are 13 feet by 89 feet. What would i set my canvas size to get a small enough file size that will take a long time to load for the client to see?

[melissapiccone]

That is a crazy size. I'm assuming if a school project you have to do it in Photoshop? Illustrator would be better. I would do it in a few files - 13 x 30 and not a smaller size - 1/2 or 1/4 size. Is this something that will be output and printed that size?

[Jacob_W]

yes the wall that they are going to put it on is 13 feet high and 89 feet wide. it is going to be a mural showcasing the history of tallahassee florida from 1920-today

[Derek Cross · Accepted solution]

If you set the resolution to 10PPI or maybe 15PPI you might manage it!

Why this huge size?

[Jacob_W]

It is for a mural for a bus depot in tallahassee named after C.K. Steele. it is to showcase the history of the city and that is how big the wall is that they are wanting to put it on.

[Terri_Stevens]

Oh I don't know, this seems doable to me. I created a new file at 156"x1068" at 100pixels/inch and put in a few high definition Adobe stock images and the memory usage was 1.25GB and it saved to disk as a *.psb file at 908MB and still had 100% efficiency on the scratch disks. You do see the computer slow down though and I wasn't applying filters or doing anything creativity as I suspect that would be slow. Seems strange for a school project though. It would probably be broken into smaller sections for printing, but 100ppi would look fine.

[Jacob_W]

yes, i am just trying to get it to a smaller file size so that it can be loaded by my teacher to show to client cause she is quite strict that if the file size is too large she will not open it.  It is also being done in sections, just trying to figure out a good canvas size so that i keep the file size from going to gb.  This is a school project yes, but the city came to our class specifically for this project to be done, whomever's design is selected is forever immortalized on the wall that it is going on. It is a mural showcasing history of the city that I live in, for when people ride the city transit from in town and out of town.

[Terri_Stevens]

try doing the actual design work at 100ppi and save as *.psb file, but to show your teacher a preview resample the image down to 72ppi and save it as a Tiff file with LZW compression. When I tried that I got a 200MB file which would easily fit on a memory stick. An image that size will be sluggish on even a well specified computer, but your teacher should know that.

[Jacob_W]

Thank you very much, i didnt even think of that.

[Terri_Stevens]

Ok Jacob with your full sized design try this

1) Go to the image size dialog

2) It should look like this

3) Resample the image by changing the resolution value to 72ppi, making sure the resample box is checked

4) Now save the file in a more efficient format

5) Just give it a name

6) Set the Tiff file options like below and press OK. That should give you a much smaller file. Incidentally Byte Order doesn't matter even if you are on a Mac.

[Terri_Stevens]

Forgot to say flatten the file before saving as a Tiff

[Jacob_W]

Thank you again.

[davescm]

Jacob

Think of the viewing distance. Our eyes can only resolve so much detail and therefore the pixels per inch that we are able to resolve drops dramatically the further away we stand from the image.

There is a formula for working out the ppi required. It is ppi = 2/(distance x .000291) where distance is in inches.

Anything higher than given by the formula is wasted - our eyes just cannot resolve it.

You mention viewing the mural from the city transit. That would suggest a viewing distance of some 25 feet ? if that is the case then you only need 23ppi.

That gives 13ft x 89 ft image a pixel size of 3588 x 24564. Which would give an image size of 264MB at 3 bytes per pixel. That is easily handled on most systems.

In short look at the spec and decide the viewing distance - then work from there.

Dave

[D Fosse]

I always try to memorize that formula, and then promptly forget it every time

Anyway, I have a rule of thumb: Anything that requires more than 20 000 pixels is probably wasted. That's experience, not theory.

[richardplondon]

It is usual at these large sizes, to work in a scaled manner rather than defining your canvas to the full physical dimensions.

This avoids exceeding sheet size limits (such as PDF) as well as fitting better into the usual print and marketing etc etc workflows.

People tend to be better reassured by a 300ppi image which is at 1/10th scale, so 106.8 inches long, than they would be by seeing a 30ppi image, even if that 30ppi was happening  at full final scale of 98 feet. That is not always a reasoned or rational reaction; since the image content will be identical at 35,000 pixels wide, either way - which is in my opinion plenty for the case in question.

But the former kind of file is, simply, easier for people to deal with.

Provided that the image file clearly communicates what physical scaling has been employed, e.g. in its file naming or accompanying info.

[D Fosse]

It's true that InDesign and Illustrator both have a physical size limit of about 5.5 meters, so there you have to work at scaled sizes above that.

I find it creates confusion no end every time, and it was with great relief I learned that they are now discussing removing that limit.

No printer I ever worked with had any problem with real sizes instead of imaginary ones.

[Terri_Stevens]

Thanks for the formula Dave, must admit I didn't know that one-comes from only doing screen work and not pre-press, but very useful none the less. When I tried my suggestion on an i7 with loads of memory at 100ppi it was sluggish and I thought to myself I wouldn't want to do anything elaborate at this resolution, so if Jacob can get away with 25ppi that's the way to go.

[davescm]

Hi Terri

The formula came from the link below , which I came across years ago.  I've had book-marked for years and still find it useful to refer to  :

What print resolution works for what viewing distance?

Dave

[D Fosse]

Here's the relationship between ppi and viewing distance: