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Actual Size ignoring screen resolution

Jan 5, 2013 3:01 PM

Tags: #size #indesign #dpi #actual

Hi everyone,

 

I open an image in both Preview and InDesign.

I set the display size to 100% in both apps.

Preview displays a correct physical size on my screen for the image.

InDesign displays an incorrect physical size.

 

I read online that InDesign ignores the monitor's resolution and instead uses a hardcoded 72 DPI value. What is up with this? If i was on a retina display, this would be so wrong.

 

I can't believe i'm understanding how this works right. It seems very wrong that people need to use a JavaScript everytime they want to display images with their "real" actual size.

 

Can someone shed some light on this matter?

 

Thanks

 

Louis Pontoise

 
Replies
  • Currently Being Moderated
    Jan 5, 2013 3:24 PM   in reply to lwouis

    Hello Louis,

     

    I am not certain what you are desiring to compare.

     

    If I place an image of say 2000 px in width and it has a DPI of 300 by simply choosing the file and clicking on the page (to automatically arrive at a 100% scale), then the image on the page occupies 6.6667 inches (my current measurement units). Which is precisely correct.

     

    Mike

     
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  • Currently Being Moderated
    Jan 5, 2013 3:29 PM   in reply to lwouis

    I suspect Louis may be using a version of ID earlier than CS6....

     
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  • Currently Being Moderated
    Jan 5, 2013 3:43 PM   in reply to Peter Spier

    Sorry Louis.

     

    Perhaps earlier than CS5.5 too.

     

    CS6 and CS5.5 are the only versions I have installed. Both are identical in this regard. At least on Windows. I cannot remember what happened in the earlier versions I used when I worked for someone else. Now where is that Ginkoba...

     

    Mike

     
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  • Rob Day
    3,116 posts
    Oct 16, 2007
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    Jan 6, 2013 6:35 AM   in reply to lwouis

    The image scale percentage that shows in the Transform panel is the scale relative to the print output. Below my placed image is 400x200 pixels with an actual ppi of 100, so when it's scaled at 100% it will print at 4" x 2", which is what the Transform panel correctly shows.

     

     

    Screen shot 2013-01-06 at 9.21.12 AM.png

     

    If I change my ruler units to pixels and set the width and height of the image to 400 x 200 the scale changes to 138.8. In inches that's 5.5556" which is 138.8% of the actual 4" width

     

     

     

    Screen shot 2013-01-06 at 9.30.05 AM.png

     

     

    Screen shot 2013-01-06 at 9.30.21 AM.png

     
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  • Currently Being Moderated
    Jan 6, 2013 7:52 AM   in reply to lwouis
     
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  • Rob Day
    3,116 posts
    Oct 16, 2007
    Currently Being Moderated
    Jan 6, 2013 7:54 AM   in reply to lwouis

    I can't believe i'm understanding how this works right. It seems very wrong that people need to use a JavaScript everytime they want to display images with their "real" actual size.

    If you are designing for screens the CS6 Zoom percentage is also relative to print output—100% zoom view is the actual print size and not the 1:1 monitor to pixel ratio you get in Photoshop or Preview.

     

    On most system's if you double-click the ID magnifier tool you'll get the 1:1 ratio:

     

    Screen shot 2013-01-06 at 10.45.06 AM.png

     
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  • Rob Day
    3,116 posts
    Oct 16, 2007
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    Jan 6, 2013 10:03 AM   in reply to lwouis

    I have no interest in printing in my case, so i would like to work with actual screen sizes.

    When you are preparing your images set them to 72ppi. So if my 400x200 pixel example is saved as 5.556" x 2.778" @72ppi it will by default place with the scale as 100% at 400 x 200 pixels in ID:

     

    Screen shot 2013-01-06 at 1.02.30 PM.png

     
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  • Currently Being Moderated
    Jan 6, 2013 11:54 AM   in reply to lwouis

    Changing the resolution in Photoshop without resampling has no effect on the image quality at all. There are no changes to pixels, only inthe dimensions it will print at "100%".

     
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  • Rob Day
    3,116 posts
    Oct 16, 2007
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    Jan 6, 2013 1:07 PM   in reply to lwouis

    I mean, all the others tools (Preview, Photoshop) just show me my image without any extra step on my part. There must be a way of having InDesign behave correctly.

    In a pagelayout application there can be any number of objects at different scales, which is different than an image program where there's one object at a set resolution. So, as Peter notes, when you scale in ID the image is resized not resampled. It's the same as resizing in Photoshop—if I uncheck Resample Image the pixel dimension doesn't change when I change dimensions or res, and the image views the same at a 100% zoom level:

     

    Screen shot 2013-01-06 at 3.52.01 PM.png

     

    Screen shot 2013-01-06 at 3.51.51 PM.png

     

    InDesign is still used primarily for print and the transform scale is relative to the print output, so it makes sense for the default scale to be 100% when you place. If the default was to place at the image's pixel dimensions than a realtively high res like 2880 pixels wide would place at 40" wide in the layout.

     
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  • Rob Day
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    Jan 6, 2013 1:15 PM   in reply to lwouis

    (Preview, Photoshop) just show me my image without any extra step on my part.

    Also, Photoshop's 100% view is useful for viewing actual pixels but it doesn't help with actual print size. If your image is at a relatively high ppi and you show rulers they don't represent the output size. Here you can see 1" on the ruler is not 1" output:

     

    Screen shot 2013-01-06 at 4.10.26 PM.png

     
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  • Rob Day
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    Oct 16, 2007
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    Jan 6, 2013 1:45 PM   in reply to lwouis

    I'm using CS6 on a macbook pro 13".

    This AppleScript will place an image and set its layout dimensions to match its pixel dimensions no matter what res you are using:

     

    http://www.zenodesign.com/forum/PlaceAsPixelsDim.zip

     

     

     

    ---------------------------------

     

    tell application "Adobe InDesign CS6"

        --make sure units are pixels

        set horizontal measurement units of view preferences of active document to pixels

        set vertical measurement units of view preferences of active document to pixels

       

        --get the page and the selection

        set pageNumber to name of active page of active window as integer

        set s to selection

       

        --choose a file to place

        set myFile to (choose file with prompt "Please select a file to place") as alias

       

        --if there's no selection place on the active page else on the selection

        if s is not {} then

            try

                set myImage to place myFile on s

                my setPixelDim(myImage, false)

            end try

        else

            try

                set myPage to page pageNumber of active document

                set myImage to place myFile on myPage

                my setPixelDim(myImage, true)

               

            end try

        end if

    end tell

     

    --sizes the placed image to its actual pixel dimensions

    on setPixelDim(myImage, fitFrame)

        tell application "Adobe InDesign CS6"

            set i to item 1 of myImage

            --make sure the starting scale is 100%

            set absolute vertical scale of i to 100

            set absolute horizontal scale of i to 100

            --the image's res

            set ap to item 1 of actual ppi of i

            --image starting bounds

            set {a, b, c, d} to geometric bounds of i

            --get the pixel height

            set pct to ap / 72

            set ph to (c - a) * pct

            --get the pixel width

            set pw to (d - b) * pct

            --set image bounds to pixel width and height

            set geometric bounds of i to {a, b, a + ph, b + pw}

            --match the frame if its placed directly on the page

            if fitFrame is true then

                set geometric bounds of parent of i to {a, b, a + ph, b + pw}

            end if

        end tell

    end setPixelDim

     
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  • Rob Day
    3,116 posts
    Oct 16, 2007
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    Jan 6, 2013 2:45 PM   in reply to lwouis

    You have to double click the Magnifier tool—your zoom view is at 100%.

     

    Looks like your InDesign page is smaller than the image you are placing—look at File>Document Setup to see the page dimension. The image is 1600x1200 pixels, so it's going to be wider than your screen's 1280 width. If you want it to be 650px wide you'll have to resample it to that in PS.

     
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  • Rob Day
    3,116 posts
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    Jan 6, 2013 3:13 PM   in reply to lwouis

    Right, you're not double-clicking the Magnifier Tool. Your zoom view is 100% which shows the actual print size not actual pixel size. Note my ID Zoom percentage:

     

    Screen shot 2013-01-06 at 10.45.06 AM.png

     
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  • Rob Day
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    Jan 6, 2013 3:21 PM   in reply to Rob Day

    Also, it looks like you have the frame and not the image selected. Select the image with the white arrow tool—it's scale won't be 100%

     
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  • Rob Day
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    Jan 6, 2013 3:36 PM   in reply to lwouis

    Resolution changes with the image scale. What program let's you choose image res in the Print dialog? I thought you were designing for screen and not print?

     
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  • Rob Day
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    Jan 6, 2013 6:55 PM   in reply to lwouis

    I don't know any, but how come? Seems common sense that i chose the resolution at the last minute, depending on the medium i'm printing on.

    I think you are confusing image resolution and printer resolution. You can choose the printer res from the Printer... button of the Print dialog

     
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  • Currently Being Moderated
    Jan 7, 2013 2:41 AM   in reply to lwouis

    lwouis wrote:

     

    I'm designing for screen but if i had to print, i would find logical that ID let me decide on the resolution of my images at printing time.

    I a sense, ID does allow that.

     

    Your image is made of pixels. By themselves they have no resolution, only quantity. Resolution is introduced by making a decision on how large or small you wish to print those pixels. If you print your image large, the pixels will be large, and the resolution correspondingly low. If you print the image very small, the pixels will be very small and the resolution will be higher, but you are still printing the same pixels. The only way to change the resolution at any given size is to change the number of pixels.

     

    ID does allow you to downsample, though not perahps in the way you mean, both during print (Send Data > Optimized Subsampling) and export to PDF [Print] (where you can choose a resolution and a threshhold above which images will be downsampled to your target), but does not upsample. Upsampling in most cases will not improve image quality as you are simply creating new pixels out of thin air and any jagginess or artifacting inthe original image will remain.

     
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  • Rob Day
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    Jan 7, 2013 7:12 AM   in reply to lwouis

    but if i want to upsample, i need to re-open the image in Photoshop and set it to let's say 300 PPI.

     

    Upsampling isn't included as an option because it doesn't improve quality—just adds pixels and not meaningful image information. If upsampling worked we'd be scanning at 50 pixels per inch and using 1 megapixel cameras.

     
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  • Currently Being Moderated
    Jan 7, 2013 7:31 AM   in reply to lwouis

    lwouis wrote:

    The problem i'm seeing though is that softwares such as Photoshop embbed a resolution with the image when they export. This means that when i'm importing my picture in ID, the information about how I want it printed is already decided (let's say 72 PPI). I can then downsample like you said when exporting to PDF, but if i want to upsample, i need to re-open the image in Photoshop and set it to let's say 300 PPI.

    Not quite.

     

    For screen display in a browser, only the pixel dimensions count and there is no resolution. When you place an image on a physical page, though, you are saying that you want that image to be ooutput at some specific size relative to that page. You've added dimensions to the image, and resolution is the pixel count divided by the dimension you've selected in each direction.

     

    The resolution you save in Photoshop is entirely irrelevant. It simply sets a "default" dimension at which to output the image. The same pixels can be saved with an infinite number of different resolutions, but you don't alter the pixels in any way. If you have an image that is 300 pixles sqaure and sve it at 300 ppi, by default it will appear in ID at 1 inch by 1 inch, regardless of the size of the document.  If you scale the image inside ID to 2 inches by 2 inches, the resolution drops to 150 ppi (and you will see exactly the same thing in the Image Size dialog in Photoshop if you change the resolution or dimension values withthe resample box unchecked). You haven't changed the pixels, only the size each individual pixel will have when rendered. When the resolution is low enough, your eye is able to pick out the individual pixels, but how low this value will be is dependent on how far away the image is from your eye. You don't print billboards, or even posters meant to be viewed from across a room, at 300 ppi.

     

    ID shows you two resolution numbers. Actual PPI is just the value that is saved in Photoshop and is completely meaningless in any useful way. Relative PPI is the current resolution at the specified output size. If you want to change the resolution, you just change the scale.

     
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  • Rob Day
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    Jan 7, 2013 7:46 AM   in reply to Peter Spier

    You don't print billboards, or even posters meant to be viewed from across a room, at 300 ppi.

    Just to clarify—printer resolution and image resolution are two different resolutions and have no relationship. A billboard wouldn't need images with 300ppi resolution but they would be printed at considerably higher printer resolution—my inkjet printer's lowest res is 720dpi. Print resolution is defined at print time via the Print dialog.

     
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