View Full Version : Size V resolution v ppi confusion :)
May 31st, 2006, 08:28 PM
Hey all :)
I have been pondering this for a few days now and am still confiused so I thought best to ask you guys :)
Ok here goes..
Using Photoshop CS 2
You create a new document of size width-794 pixels / height-1123 pixels and you use 96 ppi for resolution.
That creates an innitial document of 2.55m
NOW we again create the exact same document but this time we use 300 ppi for resolution, this creates a document of 24.9m
Now I can understand why the 300 ppi resolution document is greater in m or mb because it has more pixels, but WHAT I CANT figure out is WHY the document is bigger in SIZE inside PS CS2.
See I thought that when you added more pixels to a document all that happens is the pixels are divided more times so as create more of them for depth or detail whatever.
As in you have a square and divide by four, then you divide again, and again and again, all the time the square is getting more segments but IT ISNT getting bigger in actual size.
So why does a document inside ps cs get bigger in actual size inside PS CS 2 instead of just geting it's pixels divided to create more of them in the same space?
I just thought all that would happen would be that pixels got divided to create more of themselves in the same amount of space or document.
Anyone lol ?
June 2nd, 2006, 08:21 PM
It is geting bigger by having more information to save for each pixel, is that not obvious?
June 2nd, 2006, 08:51 PM
well it should go like this
I just tried... if you do a 1 inch by 1 inch with a rez of 300 it should be the same format size as a 2 inch by 2 inch with a rez of 150... which is 264 mb...
June 3rd, 2006, 02:39 PM
a pixel is the smallest it can be, you can't divide it down any smaller, so the higher the resolution, the larger the canvas.
June 3rd, 2006, 10:05 PM
nii NO its not obvious because thats not what I meant at all.
I know its getting bigger in the amount of information it has, which translates to it getting bigger in MB size because its getting more pixels, so yes I do know that.
So dont get all high and mighty with me, because it just makes you look small isntead of you trying to make others look small.
Besides if you could read english properly you would understand that wasnt what I meant AT ALL.
What I am confused with [but I think I might understand now, not too sure] is when you create a document at 96ppi then another at 300ppi the one at 300ppi usually comes out at 16% so if you put it up to 100% the thing is MASSIVE and 4 times the size of what should be the original documents true size.
So that confused me, HOWEVER after reading some txts and posts in other forums, I think the whole % number and bringing it up to 50% or 100% etc is just zooming in and not a true reflection of the documents size at all.
I hope I have it right with that now lol.
So at 0% the document is at its true size and not zoomed in, but if I put it to 50% its zoomed in to 50% yes?
but even now that still doesnt ring right in my head... or look right on screen.
I guess I am still confused after-all.
Thats were my confusion lies, I dont think I understand the % percentage number thing at bottom left of documents, is it a zooming number? or actual size of document number?
If I make a documet of 1024/768 at 96ppi, it comes out in ps cs 2 at 16.68% were as a document with the same size but at 300 ppi comes out at 6% but is the same size inside ps cs 2 on the screen.
You see what im getting at?
Im not talking about actual size in mb or kilobytes or even gigabytes, im talking width and height sizes and their relevance to the % percentage number at bottom right of documents.
Simplejack -- yeah I know that bud :) what I meant by dividing is dividing the document up even more to fit more pixels within it, which is what is done to create more detail.
June 3rd, 2006, 11:47 PM
Hah! Where did you get the impression I was being high and mighty mate. And I definitely wasn't trying to make you look or feel small.Its just I didnt really understand where exactly you were begetting confused with. Anyway your confusion seems to lie in the ppi part and the difference between print and screen resolution. In units like cm and inches it seems that pixels are being divided but when you set height and width to pixels you'll just get pixels added on so it's ralletive to how many inches (if you set res to ppi)the height and width make up. And nothing is being divided pixels are added within the square inches or cm etc so you can have more detail mainly in print. Screens usually display 72 dpi when you zoom in 100% I'll say it again 100% your seeing the pixels displayed at their true size, on the screen that is. So higher res images or more pixels per inch are going to appear larger on screen when you start zooming in on the actual pixels at 100%. Now I'm confused as to whether any of this made sense and I think your query seems a bit confusing too. Just don't think about pixels being divided I guess and more like theyre being added.
June 3rd, 2006, 11:59 PM
If I make a documet of 1024/768 at 96ppi comes out in ps cs 2 at 16.68% were as a document with the same size but at 300 ppi comes out at 6% but is the same size inside ps cs 2 on the screen.
Actually I m having a hard time following you...
I just tried a 1024/768 at 96 ppi (pixel per inch) and a 1024/768 at 300 ppi and comes out the same size both a 66%
the thing is about the ppi is that it doesnt matter if you are doing an image to post on the internet cause no matter what the ppi will be, it will always display itself by the number of pixel... if you are running the resolution of your screen at 1024/768, an image you will create with a res of 1024/768 will always take up all the screen when 100% in photoshop
at 100% a pixel will be at his original size... create a new image that is 500 pixels x 500 pixels... now it will come out at 100% cause for sure you cant run a screen under 800/600 now change the resolution of your screen from 800/600 to the max you can you will see the image is smaller but it is still at 100%
I dont even know if what I m saying is what you want to know
but ppi is when you want to print something on paper print to small image of about 800/800 pixel... they both have to be 5 inches x 5 inches... one with 72 ppi for resolution and the other one at 300... now you ll see a diference
June 5th, 2006, 08:38 AM
Hmmm I also have a problem in following you...
The size of an image lies in the ampunt of pixels.
And with the word size I mean the data-size.
The image size you see is always relative to the matrix (resolution) your are watching it.
If you have an image of 1000 x 1000 pixels the data-size keeps always the same, wether it is set to 72, 96, or 300 dpi.
You can check this, if you zoom to 100% this showas you always ALL pixels of your image, whatever the selected resolution is, cause the data-size the image has keeps the same.
The selected size of resolution affects, when you are exporting, or printing the image. then the selected resolution will affect the output size of the image.
So if you change the resolution of an image inbetween PS, with uncheck the calculate image new box then just your point of view will change, the data-size keeps the same.
But if you change the resolution with "calculate image new" then PS will add new pixels to the image, untill it reches the relative amount needed to get the desired reslution.
June 5th, 2006, 09:24 AM
ok clarifying explanations all round I think heh.
Firstly nii, if I was mistaken in reading your, "is that not obvious?" statement as being offensive one directed at myself, then I appologise, but it certainly seemed that way to me at the time.
Anyways explanation time, and I will try and put as much detail in as I can.
My monitor has a DPI setting of 96.
My monitors resolution is at 1280/1024
When I create a new document in PS CS 2 my settings are set at thus..
Width = mm / Height = mm
Resolution = pixels/inch and usually I do a standard of 300
Right onto document creation.
Lets say I want to create an A4 sized documet using the A4 template in "preset"
Using that A4 preset template I get the following document.
Width = 210mm / Height = 297mm
Resolution 300 pixel/inch
I click ok and the documnt is created and we are now looking at that document having NOT touched anything so far but simply creating the document.
The document details in its title bar are thus...
Untilted-1 @ 16.7% ( RGB/8 )
If I take the 16.7% number and change it to 100 I get a document that I cannnot pan out so I can see the ENTIRE document on my screen all at same time - simply because it way way to big for my screens current resolution of 1280/1024.
If I do the exact same steps as above during the document creation side of things, EXCEPT this time I have 96 pixel/inch, I get a document inside PS CS 2 that comes out at 66.67%
Its details on its title abr are thus...
Untitle-1 @ 66.7% ( RGB/8 )
And this document having not touched anything is already bigger in size inside ps cs 2 as I am looking at it now.
If I again crank its percentage number up to 100% THIS TIME I can indeed more or less see the entire document, apart from some of its height - within my screen.
SO I guess what I am trying to say is I am confused as to why the 300 pixel/inch document is bigger in over actual SIZE on screen than the 96 pixel/inch version is.
After having read some of your replies though I think what I have mistaken was that pixels were not being divided as such but were simply being added.
It's all a little confusing still, but I think I have thye basic idea, I was just confused as to why the 300ppi doc was bigegr ina ctual size than the 96ppi doc as I was thinking that the size wouldn't change for the 300ppi doc but all that would change was it would have MORE PIXELS within it as they were divided :)
Anyways I THINK I have it right now heh, thansk for replies all :)
June 7th, 2006, 03:02 PM
Sounds like you are getting to it... the relationship between onscreen pixels and real-world measurements is pretty tricky.
So, first you are correct about the % measure in the image titlebar... it represents zoom settings. If the titlebar says 100% you are looking at the image's actual on-screen size. % under 100 is zoomed out and % over 100 is zoomed in.
The thing about pixels is they are indivisible. No matter what your screen resolution, 300 pixels is 300 pixels. However when you are printing something out, you can squish more information into the same area depending on your printer settings.
The bottom line is if you create a document say, 4 inches square at 96ppi you will end up with a PS file that is 4x96= 384 pixels square. Create the same 4 inch document at 300ppi and you will get a file that is 4x300 = 1200 pixels square.
Now, even though one appears bigger than the other on screen, if you print both of those documents out, they will both print at 4 inches square. Of course the 300ppi document will look better because it has more information in it.
Them's the basics anyway.
June 7th, 2006, 08:11 PM
yeah cheers :) I totaly got it at last heh.
It was the whole dividing pixels thing that had me stumped, don't know were I got that from but I had it in my mind that they were being divided to create more information not added :)
Anyways all is good now heh
Powered by vBulletin® Version 4.2.1 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.