Pixels, Image Size and Resolution – Basix
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Pixels, Image Size and Resolution – Basix

on Dec 15th 2010 with 56 comments
Tutorial Details
  • Program: Adobe Photoshop CS5
  • Difficulty: Beginner
  • Estimated Completion Time: 7 Minutes

Final Product What You'll Be Creating

This entry is part 3 of 29 in the Photoshop Basix Session
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Are you new to Photoshop? Have you been trying to teach yourself the basics of Photoshop but have found the amount of educational material available on the net a bit overwhelming? As the world’s #1 Photoshop site, we’ve published a lot of tutorials. So many, in fact, that we understand how overwhelming our site may be to those of you who may be brand new to Photoshop. This tutorial is part of a 25-part video series demonstrating everything you will need to know to start working in Photoshop.

Photoshop Basix, by Adobe Certified Expert and Instructor, Martin Perhiniak includes 25 short video tutorials, around 5 – 10 minutes in length that will teach you all the fundamentals of working with Photoshop. Today’s tutorial, Part 3: Pixels, Image Size and Resolution will explain the theory behind how pixel images work. It will also explain a bit about the crop tool, image size and resolution. Let’s get started!

 
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Martin is a Hungarian graphic designer, digital artist and an Adobe Certified Expert and Instructor (Design Master). He is currently teaching and working in London but usually travels around the UK and share his love for Adobe products and graphic design. You can follow him on his blog or on Twitter.  

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  • Daniel B

    “This entry is part 4 of 3 in the series Photoshop Basix” – you shell fix this :D

    • http://psd.tutsplus.com/ Grant Friedman

      Oops, thanks for the heads up. This has been fixed.

  • 7

    Decent info here. However, don’t go assuming that 300ppi is the only way to get a good quality print. Quality is a perceptual thing, dependent on viewing distance. 300ppi makes perfect sense for most hand-held printed items, or smaller items up to about half-poster size. Magazines, photos on your wall at home, etc.

    However, I don’t think you’ll ever see anybody printing billboard panels from a 300ppi image. The resolution is wasted, & since the viewer will typically be at a comfortable viewing distance based on the size of the print, a 72ppi image might do very well for a very LARGE print. Next time you’re at the movies, walk right up to the movie posters and look reeeaaallly close. They aren’t likely to be tack-sharp prints at usual hand-held sort of viewing distance (or at least aren’t meant to be scrutinized from that distance), since they aren’t meant to be viewed that close. take a few steps back, view from a meter or two away, and suddenly they look just fine.

    Start out considering usage. That’ll tell you what resolution you need to be at. Or, check the print specifications from the printer. If they didn’t send any, call them. It’s cheaper to get it right the first time. ;)

    • Darin

      Sorry,but 72ppi is not for print.
      If you want a good result print upon 225ppi,even if the people looking it from a comfortable distance.

      • 7

        I think you may be confusing PPI and DPI, or you didn’t fully understand my post.

        Thought experiment:
        You’re given an assignment, client needs a design for a billboard ad that’s to go on the side of a major highway. Do you still set this up at 200-300ppi? I’m stating that you only need to set it up for what looks good based on the audience’s anticipated optimum viewing distance.

        A billboard seen for a few seconds from a long ways away (approximating the perceived size of a business card or so held at half-arms length or so) dosn’t need a 300DPI print from a 300PPI file. It’s wasted. Lets assume your billboard is 18ft long by 9ft tall, at 300PPI that equates to 64,800 pixels wide. Quite a bit of overkill for the viewing time and distance, I’d say.

        If you took that same setup, but setup your file for 72PPI, it’s still 15,552 pixels wide. Somebody driving by on the highway would never, ever see the pixels. It’d look just fine. But, if you were standing directly infront of it from a few feet away, sure.. you’d see the pixels. But the purpose of that particular print isn’t to be scrutinized from 3 feet away. It’s to deliver its message quickly from a long distance in a short period of time. I think it would do that just fine, and at a much smaller and more manageable file size.

        I am completely in agreement with you on smaller items though. You’d never ever EVER want to print something at 72ppi in a magazine. Talk about ugly. Unless the pixels are an artistic endeavor, in which case, have at it.

      • http://www.shaneparkerphoto.com Shane Parker

        7 is exactly correct. I have printed MANY post-size prints at around 144ppi. Final medium often determines where you should be starting, this is common practice in photography/printing industries.

      • http://www.shaneparkerphoto.com Shane Parker

        …that should have been; “poster-sized prints”.

  • Printgestalt

    1 Information is wrong .. if u multiply .. 3579 (x) * 2396 (y) = 8575284… and NOT 24.5Mio
    because u have to multiply the 8575284 * 3 (RGB) = 25.725.852

    Well just for the ones that want to know this. :)

    • rome

      now i get it,, thanks a lot^^

  • http://www.ulisesart.com ulises

    ineteresante

  • http://www.designtank.ws Chris Raymond

    Print does not use ppi. It uses dpi (dots per inch, ink dots)

    • Printgestalt

      actually isnt ppi and dpi the same value? …

      • 7

        DPI is dots per inch (printed)
        PPI is pixels per inch (this can refer to a number of different things)

        When you consider the optimal printed resolution of 300DPI, a 300PPI image makes sense. The printer resolution and the image resolution do not strictly have to match, but it’s usually best practice to match your image resolution to the print resolution, which effectively gives you 1 pixel per inch being equal to 1 printed dot per inch.

      • 7

        A caveat to my previous post: alot of printing presses can and will operate at a much higher DPI than 300. The higher the resolution of your printer (say, 1200DPI) the smoother and nicer the color, tonality, and transitions will be in your printed 300PPI image.

    • Anthony

      Actually most print methods that use halftones (which is most of them) use lpi or Lines per Inch. Generally you want your image to have around 2x whatever lpi your printing method uses in ppi. A lot of offset presses print at about 150 lpi so you would want your image to be around 300 ppi in resolution. Of course you should always check with your printer they usually know best.

      • 7

        The way I’ve always understood it, LPI is usually determined by your substrate, what you’re printing on, and as an extension of that, the desired print quality. Newspresses generally tend to run lower LPI since the quality isn’t required or needed. But you’re very right. LPI is where it all starts, if you want to get technical.

      • Anthony

        You’re right. It all depends on multiple things image quality, the paper your using, and the press you’re printing on. Like I said if in doubt ask your printer, they know more about what makes a good print than anybody.

  • Chris Gosling

    For commercial offset printing the “optimal” resolution is dependent on the line screen of the printing plate.

    To find out what dpi your images should be, you need to know what halftone screen (how many lines per inch) your final product will be printed with.

    Most common offset jobs are printed between 120-150 lines per inch. The resolution of your images at 100% should be between 1.5 and 2 times the halftone screen. Therefore your image resolution for a 150 halftone screen printing plate, should be between 225 dpi and 300 dpi. For most cases 225 is good enough, it’s only in pictures with a lot of straight lines (ex. architecture) that you would need to go up to 300 dpi.

    Art books that are printed at a greater halftone screen – 200 lines per inch and greater – will need better pictures. Where as newspaper (90-100 lines per inch), billboards and other large halftone screen processes need less information. BUT when it comes to billboards – 10 meters x 5 meters at 36 dpi still gives you a 290 mb RGB image.

    Chris

  • http://www.antsmagazine.com Nahid

    I agree with printgestalt.

    • Printgestalt

      At least one dude that agree with me. :) thx.

  • Aaron Martone

    One of the common misconceptions people get with resolution is that they think that “All graphics for online use are developed for 72ppi”

    Thing is, most monitors DON’T use that PPI. For example, if a 24″ TV is displaying 1920×1200, it’s horizontal distance is about 20″. That’s 96PPI. If you go into Photoshop under EDIT > PREFERENCES > UNITS & RULERS, there is an area you can type in your resolution, so that VIEW > ACTUAL SIZE will be a more accurate representation of the object’s true size.

    I’m using a 32″ TV, which sounds great and all, except when you factor that for 1920 pixels wide, the width is 28″, and 1920/28 = 68ppi. (This is one of the reasons why a 32″ TV as a monitor is cheaper than a 32″ monitor)

  • Erika

    do you have any idea how long I’ve been trying to figure out how I could enlarge a photo without distorting the quality? So many google searches! and it was just one check away. Thank you SO much! You have no idea!!

    • 7

      You’re not enlarging so much as you are telling the software how many pixels exist in one inch of printed media. Give it a small enough number (like, 40PPI), and your perceived quality will still be “bad”, depending on physical size of the image and viewing distance, since you’ll clearly be able to see each pixel in any given square inch of your print.

      Changing your PPI setting without re-sampling dosn’t add any data. That’s impossible (well, nearly impossible) to do well without really fancy algorithms. There are plugins for photoshop that will do this (the Genuine Fractals plugin comes to mind) but they can be pricey.

      There’s truly no substitute for a proper sized image from the beginning. People will pontificate on and on about how ‘megapixels don’t really matter anymore’ when in fact they do… especially if you want nice, large prints.

  • http://www.idesignit.co.il/ Elron

    Thats great, thanks so much!
    cant wait till next video :D

  • http://www.yesimadesigner.com Martin Perhiniak
    Author

    Look at these amazing comments! I’m so glad to read some professional comments helping and teaching each other. I didn’t want to get too technical with my video, but it is great that some of you put some really detailed instructional comments here. Really appreciate it. Keep up the good work guys!

  • http://e786.wordpress mehedi

    I am glad to watch such as very nice content .

  • http://www.paradoxite.com Paw

    Learnt a lot today :) From the video and from the comments… Thanks

  • godbout

    Hi!
    A question here. I’m a total noob and I’m wondering how Martin has setup his workspace to have the photoshop windows act like the way they do. I’m gonna try to explain.
    At 5.00 it seems that the document is fullscreen and by pressing tab, the tools appear and the document’s window gets resized accordingly. For me if the document is fullscreen, pressing the tab make the tools appear but the documents are not getting resized and I don’t get the scrolling bars.
    I’ve noticed than my window mac icons (red, green and orange) are not set for the whole photoshop workspace, but only for the current opened window. Not sure it does have a link though.

    Anyone to explain?
    Thx!

    • http://www.yesimadesigner.com Martin Perhiniak
      Author

      Try using the Window/Application Frame option. Hope that helps!

      • godbout

        oh god this is fantastic!
        Thx a lot!!!

  • http://psd.tutsplus.com/tutorials/tools-tips/pixels-image-size-resolution-photoshop/ Josue R

    Im a beginner, these comments are intersting but i have a question!
    Lets say that you need to work something small, you dont need to work in 300pixel per inch
    And if your working something big and you need it fast and in a good resolution like in a scale of 20x10meters can I work in 150ppi?

    Im saying this because some computers are not so good as others right?

    • http://www.yesimadesigner.com Martin Perhiniak
      Author

      You don’t need to use 300 ppi on large format prints. The larger your print is the smaller resolution you can use because the viewing distance will be larger as well. With a 20×10 meters print even a 50 ppi print would be enough (or even smaller).

  • josel

    Very interesting subject.

  • Rando

    I have a doubt about the Resolution but then I found out that the Image you put or edited will also depends on the Resolution you made…….

  • just0408

    I am so happy with this series.
    It really helps me a lot as a beginner motivated to become better with Photoshop.
    Keep up the good work!

  • pauch

    thank you so much.. ^_^

  • Marcus

    Is it just me or everyone’s not seeing the HD option?

    • Cal

      HD is for Screen and Monitor, not for Print Use. All and HD camera will give you is more pixels to work with, when it goes to print, it will still be up to the PPI and DPI with the Linescreen as a Base of Quality.

  • Sergio

    Thanks for such great tutorials!

  • Gabby

    thank you

  • http://www.freebiejeebies-free-gifts.com klaudio

    nicely explained. thanks ;)

  • rk

    Nice video with some simple explanation on pixels/resolution. They are often confused for each other I think, by newbies atleast. Thanks for the great tutorial!

  • Victor

    Hi,
    What is the right resolution and pixels to work on with a document size of 850cm x 900cm and achieve the best

  • R

    Once again, a wonderful tut for us newbies. Thanks so much.

    Avery simple question form a very simple person:

    After you cropped your Stonehenge image, you said:you could accept it by either clicking on the icon at the top or hitting return or enter. Try as i might, I wasn’t able to follow your pointer to the icon you clicked. Which one was it and where was it?

    Rx

    • R

      Oops!:
      “A very simple question FROM a very simple person”

    • Débora

      After you draw the crop, i.e., you release the mouse click, two simbols appear at the right end of the tool bar: a kind of a stop sign next to a check sign. The first one cancels the crop operation you’re doing and the last one accepts your crop.

      I’m sorry, I don’t really memorize the interface areas names, so let me explain that by ‘tool bar’ I mean that bar which presents different setups according to each tool you choose.

  • Jess

    Question: if i want to print a 6 X 4 print: how should i set the resolution: like for example with this example it would print a 30cm or so print: if i was then to take this to a photo printing place: should i resize it then to print or should i re-size the photo to the exact size i want to print with in photoshop before i go??

  • Jess

    and also im getting some 30 X 45cm canvas prints done: what should i set resolution to for that size image: and if i want to spread one image across all three: do i then make it a 90 X 135cm print and what resolution would i set it to then??? AMAZING tutorial just has me asking lots of questions!!

    • http://www.yesimadesigner.com Martin Perhiniak
      Author

      Hi Jess,

      I’m glad you found the tutorial useful and interesting.

      For a 6x4inch print you will need to have an image with 1800×1200 pixels or more to be able to print it with 300 ppi resolution. What you should do before you take it to the print house is to turn off the Resample option in the Image size dialog box and then type in the preferred print size in inches. Photoshop will calculate the resolution from this and if it is above 240ppi than you will get a good quality print. If it is way below it than you will need to find a higher resolution image. If it is way above 300ppi than you can turn off the Resample option and type in 300ppi for the resolution. It will downsample the image so you should also choose at the bottom of the dialog box the Bicubic Sharper option. That is the best for reduction.

      When you are ready accept the change and save your file as TIFF or high quality JPEG and you are done.

      Hope that helps,
      Martin

      • Cal

        Can I just point out, that this also depends on the Grain of Canvas you are printing on. If a rougher finish rather than the smother canvases you can get away with a lesser quality image. Also treat Canvases as painting that will be viewed from a bit of distance away, rather than as a Photo Frame image. When we print canvases, you have to try and forget your printing a photo, and treat it as a wall hanging print. It took me a while to realize this myself, but we now print loads of Canvasses’ and have never had a complaint about quality.
        Cal.

  • Aditya

    Dear martin,
    Ur tutorials have been really helpful….when i began with photoshop i ws really facing problems in understanding the basics…thanks to u…ur videos really are very very helpful for the beginners..thanks..

  • sandeep

    first of all thanks a lot for the video. Makes a lot of things clear but I still have a couple of questions.
    From what i understand the ppi value is of relevance only when it comes to printing. Say for example i am going to use the image i created as a wallpaper and create it with a width and height of 1280 px * 800 px. supposing i have two copies of it copy ‘a’ is created with 72ppi and copy ‘b’ is created with 300ppi. Is it correct to say that these two images would look exactly identical to each other (of course they would both be a bit stretched but they would be identical to each other) when viewed on say a computer of resolution 1600 * 900 ? So would it mean to increase the clarity of the image the only option would be to increase the number of pixels from 1280*800 to a higher value. Changing the ppi would not help.

    Now when printing the document what determines the physical size of the printed image? Like if i save the document and print it from a photostore on a 5*7 photo paper would that mean for copy ‘a’ only 360*504 of the pixels get actually printed (so would the image be cropped with only part of it appearing in the photo or would it fit everything inside the photo and make it blurry?)while for copy ‘b’ 1500*2100 (since these values are higher than the original pixels of 1280*800 we would have some empty white space around the image?) of the pixels actually get printed.

  • TechKid

    Sorry im a beginner… I just wanted to know that what is “Rule of Thirds” ???

  • manish

    thats fantastic.. i have learnt my doubts, great job.

  • Marc Holman

    Excellent and helpful series of videos but where are the sample images? It would be nice to have them and be able to follow along. I’m very surprised in fact to find them missing — especially here.

  • http://www.facebook.com/bpenkov Бо Би

    Martin what you`ve said about the width x height that is 24.5MP is not true at all. Your photo is 8.575284 or 8.5MP and the 24.5M that you see in the panel tells you that 24.5mB of memory is the uncompressed data for the photo. That much RAM it would use for it. Its 8.5×3 because every pixel has 3bits size.