Welcome to TalkGraphics.com
Page 3 of 8 FirstFirst 12345 ... LastLast
Results 21 to 30 of 80
  1. #21
    Join Date
    Aug 2000
    Location
    Harwich, Essex, England
    Posts
    21,895

    Default

    Great thread! Try this linkThe Mad, Mad World of Pixels Per Inch

    Another point worth mentioning is the difference between CRT monitors and TFT monitors. I don't pretend to understand the difference but I believe a TFT monitor is set a particular resolution, and whilst it can copy other resolutions it does it differently and far worse than a CRT screen
    Egg
    Egg

    Intel i7 - 4790K Quad Core + 16 GB Ram + NVIDIA Geforce GTX 1660 Graphics Card + MSI Optix Mag321 Curv monitor
    + Samsung 970 EVO Plus 500GB SSD + 232 GB SSD + 250 GB SSD portable drive + ISP = BT + Web Hosting = TSO Host

  2. #22
    Join Date
    Oct 2000
    Location
    Essex, UK
    Posts
    223

    Default

    Klaus/Marcus

    I would have thought that the lower figures are purely for the purpose of keeping file sizes down. After all, we all know that the higher the dpi the larger the file and the larger the file the longer the download time. For the web therefore, the lower the file size the better and hence the lower dpi for web graphics.

    Apart from this, I'm fairly sure that whenever I've tried saving a GIF it doesn't matter what the dpi of the source file, whether 3000dpi or 150 dpi, it is always saved at 72 dpi. As far as I am aware this does not apply to JPG or PNG.

    .....or have I got it wrong - again.

    Tracey

  3. #23
    User Guest

    Default

    Hi,

    Just thought I'd add my bit.

    You can find the resolution of your screen quite easily. Try this:

    Create a new image, draw a square at say, 100x100 pixels to start with. Now resize it so that when you hold a ruler up to your screen, it measures 1 inch by 1 inch.

    Now count the pixels - on my screen I have a 95x95 square. So the 'dots/pixels per inch' of my screen is 95.

    Of course this is only approximate as it's not easy to accurately measrure an object on a screen.

    You can do another test. Open/create a small picture, set it's resolution to your screen resolution (in my case - 95 - found using the method above) and print it at that resolution. Hold the print up to your screen image - they should be pretty similar in size.

    Obviously, if you change your screen settings from say, 800x600 to 1024x768, then you'll get a different result.

    -Richard

  4. #24
    Join Date
    Aug 2000
    Location
    Norway & Sweden & USA
    Posts
    1,233

    Default

    Tracey: "I would have thought that the lower figures are purely for the purpose of keeping file sizes down. After all, we all know that the higher the dpi the larger the file and the larger the file the longer the download time. For the web therefore, the lower the file size the better and hence the lower dpi for web graphics."

    NO! NO! NO! You stilll don't get it. There is no "DPI" for screen/web images - there are ONLY the actual pixel dimensions: 300x300, 600x600, etc.

    For anyone who finds this resolution-topic even slightly confusing, I repeat this simple - but totally correct - advice: WHEN IT COMES TO SCREEN/WEB IMAGES, FORGET YOU EVER HEARD ABOUT DPI. IT ONLY PERTAINS TO PRINTING.

    Exasperatedly,

    K
    www.klausnordby.com/xara
    K
    www.klausnordby.com/xara (big how-to article)
    www.xaraxone.com/FeaturedArt/kn/ (I was the first-ever featured artist in the Xone)
    www.graphics.com (occasional columnist, "The I of The Perceiver")



  5. #25
    Join Date
    Aug 2000
    Location
    Norway & Sweden & USA
    Posts
    1,233

    Default

    Richard, what you're saying is of course mathematically correct. :-) But it's also TOTALLY useless - and only further serves to spread the confusion that screen/web images "really have" a DPI. If people think that your ruler-idea is relevant, then they will start to creat screen/web graphics with 92 and 98 and 88 and 101 DPI - ALL OF WHICH IS SENSELESS AND A COMPLETE WASTE OF TIME.


    K
    www.klausnordby.com/xara
    K
    www.klausnordby.com/xara (big how-to article)
    www.xaraxone.com/FeaturedArt/kn/ (I was the first-ever featured artist in the Xone)
    www.graphics.com (occasional columnist, "The I of The Perceiver")



  6. #26
    Join Date
    Aug 2000
    Location
    New York, NY, USA
    Posts
    171

    Default

    Thanks Klaus & company!

    Anyone here can also "get it." Just perform this simple test using Photoshop (or some other application that lets you choose image width & height in inches AND pixels and also image resolution in pixels per inch):

    Create a new image (File > New). In the new image dialogue box, enter the following settings:

    WIDTH: 100 pixels (NOT inches)
    HEIGHT: 100 pixels (NOT inches)
    RESOLUTION: 72 pixels per inch

    DON'T click the OK button. Instead, look at the top of the dialogue box. Photoshop tells you how big this image will be: 30K

    Now click the OK button and look at the physical dimensions of the graphic: it's 100pix by 100pix (as you specified), so it's a small square.

    OK, now create ANOTHER new image. Use the following settings:

    WIDTH: 100 pixels (NOT inches)
    HEIGHT: 100 pixels (NOT inches)
    RESOLUTION: 300 pixels per inch

    NOTE: these are the same settings as in our first test, except here we're using 300 pixels per inch instead of 72 pixels per inch.

    DON'T click the OK button. Instead, look at the top of the dialogue box. Photoshop tells you how big this image will be: 30K

    Click OK and now compare the physical dimenstions of the two images. The are EXACTLY the same size -- same width and height. Which shouldn't be surprising, because they are both 100px by 100px. The resolution had NO effect at all! (Of course, it would have a MAJOR effect if we printed these graphics).

    Also, note the filesizes are also the same 30K and 30K. They are the same, because BOTH images contain 10000pixels (100pix by 100pix). Filesize is determined by number of pixels -- NOT by dpi. So there will be no difference in download time either. Resolution is MEANINGLESS on the web.

    Now, here's ANOTHER experiment:

    Create ANOTHER new image using the following settings:

    WIDTH: 1 inch
    HEIGHT: 1 inch
    RESOLUTION: 72 pixels per inch

    This image is 16K in filesize and looks quite small on my screen.

    Create a final image using the following settings:

    WIDTH: 1 inch
    HEIGHT: 1 inch
    RESOLUTION: 300 pixels per inch

    This image is 264K and looks much larger on my screen!

    Both images are 1 square inch (in print), but whereas we've only packed 5184 pixels into the first one (72pix * 72pix = 5184pix), we've packed 90000 pixels into the second one (300pix * 300pix = 90000pix). More pixels = a bigger file = longer download time. Also a 300 pixel by 300 pixel image appears larger -- on the screen -- than a 100 pixel by 100 pixel image.

    Bottom line: all that matters online is the number of pixels in the width and the number of pixels in the height. The resolution (dpi/ppi) doesn't do anything for you, good or bad.

    Marcus Geduld
    { email me } { visit me }
    Marcus Geduld
    { email me } { visit me }

  7. #27
    Join Date
    Aug 2000
    Location
    New York, NY, USA
    Posts
    171

    Default

    Figure 1:
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	dpi72px.gif 
Views:	357 
Size:	6.1 KB 
ID:	5552  
    Marcus Geduld
    { email me } { visit me }

  8. #28
    Join Date
    Aug 2000
    Location
    New York, NY, USA
    Posts
    171

    Default

    Figure 2:
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	dpi300px.gif 
Views:	356 
Size:	10.5 KB 
ID:	18578  
    Marcus Geduld
    { email me } { visit me }

  9. #29
    Join Date
    Aug 2000
    Location
    New York, NY, USA
    Posts
    171

    Default

    Figure 3:
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	dpi72in.gif 
Views:	356 
Size:	5.9 KB 
ID:	18440  
    Marcus Geduld
    { email me } { visit me }

  10. #30
    Join Date
    Aug 2000
    Location
    New York, NY, USA
    Posts
    171

    Default

    Figure 4:
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	dpi300in.gif 
Views:	368 
Size:	5.9 KB 
ID:	15788  
    Marcus Geduld
    { email me } { visit me }

 

 

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •