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Rasterize/Flatten Image

Nov 9, 2010 5:55 AM

Hey guys, I have a couple of questions wanted to know if you could help me out. I know these are probably geared more toward photoshop but I was just curious. Under the Layer menu there is a function called 'Rasterize', what does this do and what is it for?

 

Second one, let's say I wanted to send a file to the printer from photoshop. Would I want to flatten the image (also under the Layer menu at the bottom) to send a smaller file size or send the file as separate layers? What is the better of the two?

 

Lastly, if you have a vector image in illustrator or photoshop is it preferrable to keep it vector rather than raster for any reason(s)?

 
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  • Currently Being Moderated
    Nov 9, 2010 6:07 AM   in reply to jiyasa

    Firstly this is the InDesign forum - you could navigate back to the main forum pages and select the Photoshop forums for photoshop queries.

     

    Rasterize in the Layers Panel will convert any vector object in Photoshop, vector shapes, vector masks or text to Pixels. Meaning they will lose their scalability as increasing raster physical dimensions causes interpolation (jaggy edges)

     

    Sending a file from Photoshop to the printers is precarious depending on file format

     

    TIFF and PSD can both retain layers, including vector layers, type layers, vector shapes and vector masks - BUT they both output the data as Raster

     

    EPS can retain the vector information only for PRINTING - if you open an EPS in photoshop again it is completely flattened and rasterised - http://livedocs.adobe.com/en_US/Photoshop/10.0/help.html?content=WSfd1 234e1c4b69f30ea53e41001031ab64-78f7.html

    EPS also does not retain layers, and it can be problematic http://www.prepressure.com/library/file-formats/eps

     

     

    The IDEAL format then is to use the PDF option when saving a file from Photoshop. The PDF can retain layers, vector information for editing later and also outputs the vector and raster data - it's fully retains the objects as it wraps them in a PDF wrapper ensuring they output correctly.

     

    Lastly-

    It is preferable to keep it vector and sometimes it is prefereable to rasterise it.

     

    Vectors are sometimes best left as VECTORs as they can be increased or decreased to any size without losing sharpness.

     

    But some Vector objects from Illustrator are very complex and yield massive file sizes. If you had a 10 x 100 mb vector images in a document, that would be a 1gb of information for just those vectors. It may be best to rasterise these vectors at 300 ppi at actual print size, which could reduce the file size significantly - you may or may not notice quality issues with it - depends on the content of the image, something with sharp edges, like buildings may be more noticeable, but an illustration of a painting with soft edges may not be so noticeable.

     

     

    Hope that helps.


     
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  • Currently Being Moderated
    Nov 9, 2010 7:31 AM   in reply to jiyasa

    jiyasa wrote:

     

    So basically the answer to my first question sort of goes hand in hand with the third question I asked, if the file is too big as vector then I should rasterize it? It was meant to shrink file size?

     

    You do not have to rasterise the file if the file size is too big. I know printing companies that RIP 10gb of information for print jobs. BUT if you needed to get the file size down for whatever reason - then you can rasterise the vector, but you will lose some quality and sharpness - it may or may not be noticeable in print. But this rasterised version should only be used to get the file size down - you should always keep the vector as the master file.

     

    jiyasa wrote:

     

    To what you're saying about the PDF wrapper, does it really make any difference whether the original file has separate layers or one flattened single layer when in print?

     

    If you make an EPS - be sure to save another version as an editable PDF/TIFF/PSD file in photoshop - that way you can edit the text or other vectors again. If you save a file as an eps and open that again, everything is rasterised and flattened to a single layer. So why bother saving as an eps in the first place (Placing to Quark is one example of why you'd need an EPS file - as it will retain the vectors for outputting). But you should always always always have an editable version of the file to make changes.

     

    If you have  TIFF or PSD with text layers, you can open that in Photoshop and adjust the text. Then when you print it the text is rasterised, it's not vector, so it loses it's sharpeness.

     

    If you make a PDF from photoshop - it will retain the text layers for altering at a different date, plus it retains the Sharpness of the vector in print.

     

     

    So just save it as aPDF to start with - and you won't clutter up your system with different versions of the file.

     

     

    jiyasa wrote:

     

    dumb question: if I open a vector (.ai file) in photoshop as a vector file and then save it as TIFF or PSD it now becomes raster?

     

    Yes - when you open or place an Illustrator file in Photoshop it becomes a Smart Object. Smart Objects are denoted in the Layers Panel. A smart object is a vector object that can be scaled in Photoshop without losing resolution. BUT it is converted to RASTER on output at the native resolution of the document.

     

     

    SO:

     

    If you start a new document and choose 300 ppi (or any res)

     

    Then place an AI file it becomes a smart object

     

    You can now scale that within Photoshop to ANY size you want and it retains it's vector sharpness

     

    BUT when you output (even to PDF) the image gets' rasterised to 300 ppi (or whatever resolution you choose)

     

     

     

    THE only thing that PDF can out put as vector from Photoshop are Text Layers, Vector Masks and Vector shapes created within Photoshop.

     
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  • Currently Being Moderated
    Nov 9, 2010 7:42 AM   in reply to jiyasa

    Yes smart object will be better.

     

    BUT keep in mind that when you output it - no matter what file type you choose - it will rasterise to that PPI>

     

    If you have a 72 ppi image and you insert the AI file it will be converted to 72 ppi and rasterised for output - but inside photoshop it will look sharp no matter what size you set it.

     
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  • Currently Being Moderated
    Nov 9, 2010 7:43 AM   in reply to jiyasa

    Why are you placing it into photoshop anyway?

     

    You'd be better off putting the Photo into Illustrator.

     
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  • Currently Being Moderated
    Nov 9, 2010 8:23 AM   in reply to jiyasa

    Where are you setting 300 ppi in Illustrator? Illustrator only has Raster EFFECT settings, and these are what things like drop shadows and bevels use from the FILTER menu (not the ffects menu), and the 300 dpi becomes the resolution of the EFFECT - it has nothing to do with the vector elements. And, if you scale an image that is using effects the resolution is lessened.

     

    And if you have a vector image why would you want to convert it to pixels by placing in Photoshop? It loses it's sharpness on output.

     

    If you have Illustrator and an illustration in there, the place the photo in there and do the composition in Illustrator.

     

    Or you could place the photo and the illustration into a program like InDesign (which is ideal for page layout especially multipage documents like brochures, booklets, books etc.)

     
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  • Currently Being Moderated
    Nov 9, 2010 8:47 AM   in reply to jiyasa

    Illustrator doesn't have a setting for PPI when starting a document. It's a vector based program, meaning the objects are drawn using mathematical formuals, there is no resolution.

     

    Photoshop has a resolution as it stores each bit of information in a pixel. The more pixels you have per inch the higher the resolution.

     

     

    Yes you should import AI files and photoshop files directly to InDesign. Don't forget, don't just use PSD files for the sake of it. If you have text layers in photoshop then save as PDF from Photoshop and place that, then your text layers (vector masks and vector shapes) are retained for output.

     

    And no you didn't understand me at all - I probably made it far more complex.

     

    Photoshop rasterises illustrator files. So don't put illustrator files in photoshop.

     

    However, if you have to combine an image with the vector, then you can import the photoshop image to Illustrator, that way your vector won't be rasterised.

     
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  • Currently Being Moderated
    Nov 11, 2010 6:56 AM   in reply to jiyasa

    Sorry, don't have time to go into detail today unfortunately.

     

    These are very basic questions though.I suggest you buy a book on photoshop, like Real World Photoshop or similar.

     
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  • Currently Being Moderated
    Nov 11, 2010 1:38 PM   in reply to jiyasa

    It's easy enough.

     

    In Photoshop, the top two dimensions are for the current picture size. Now that size in mm or picas or points or (Jedediah Buxton style) hair's breadths does not mean a thing. It's the actual number of pixels that count (or are counted), and their "physical" measure is determined purely by the image resolution -- the number of pixels per fixed (real) distance, or, in reverse, how big the sizes are in our physical dimension, given a certain number of pixels.

     

    (Read the above again, please.)

     

    (Done that? Understood it? No? Read it again. If you understand it correctly, you'll agree "it's easy enough".)

     

    Now what happens when you don't change the pixel dimensions but do type in another number for the resolution?

     

    As per this explanatory paragraph, the 'image' will appear to shrink or grow, but only when viewed in real dimensions. The number of pixels stays the same.

     

    What does this have to do with viewing the image on a web page? Well, web pages are famous (notoriously so) for not actually having physical dimensions. Oh sure, you can define type in "10p" or "5mm" (I think CSS allows that), but actually, those are usually just shortcuts for a fixed calculation into the number of pixels the type should be. And that's what you are viewing, on a web page: pixels.

     

    Given an 96 x 96 pixel image, would it matter if you saved it with a 300 dpi resolution instead of 96? At 96 dpi, the image would be around 1 inch square, because -- by convention -- current screens are around 96 dpi. (That Is A Lie. But read on -- it's just a minor one.) So on your screen, hypothetically 96 pixels per inch, displaying a 96 x 96 pixel image comes to about 1 inch. What if you change the dpi to 300? Well, the screen is still only 96 dpi, and web browsers don't adjust image size for dpi, so it would still display exactly 96 x 96 pixels -- the same size as before.

     

    So ... how would you make an image appear larger or smaller on a web page? You have to change the number of pixels.

     


     

    Given that this is, for now and the foreseeable future, still the InDesign forum: resolution is of paramount importance to accurately print images. InDesign reads the dpi settings of images when you place them into a document, and that document size is a physical dimension. "But in CS5 you can define stuff in pixels!" you might complain. Well, that is a lie, straight and true, outrageous as it may seem. Personally, I consider allowing pixels as a "valid measurement" one of Adobe's gravest errors -- your post is by far the only one of someone utterly and completely getting confused by this.

     

    If you have saved the same image as above twice, once with a 96 dpi setting, and once with a 300 dpi setting, and you place both of them into InDesign at their default size, the first one will come in as a perfect 1 inch square. The second one will come in at a square of 96/300 = 0.32 inch, and if you think "oh boy, that's a bit too small -- I'd better scale it a bit up", you are making a classical mistake . Scaling that image up to, oh say, 1 inch again, will not change the image pixels, but it will change the resolution -- to be precise, back to that ol' 96 dpi again.

     
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  • Currently Being Moderated
    Nov 12, 2010 4:26 AM   in reply to jiyasa

    I see Jongware covered it there

     

     

    seriously - having books around you is the most help I can give you. You should see my bookshelf at work. Everything from Real World books to Typography, to graphic design, to books about font choices, to XML to whatever you can think of. I mostly use them for reference, but over the years I've had to use them less and less

     
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  • Currently Being Moderated
    Nov 12, 2010 4:42 AM   in reply to jiyasa

    Imagine this is one inch wide


    It has 96 pixels across and 96 pixels down

     

    Now - if you made this two inches wide - how many pixels would you have?

     

    Well you have two answers

     

    1.Same amount of pixels - but the the pixels will be larger

     

    Or

     

    2. Or you can doulbe the double the amount of pixels to - 192

     

     
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  • Currently Being Moderated
    Nov 12, 2010 4:56 AM   in reply to jiyasa

    You don't...you can't just invent data. You need a better image.

     

    Bob

     
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  • Currently Being Moderated
    Nov 12, 2010 5:22 AM   in reply to jiyasa

    It's not really a good idea try to upsample an image - as you know it becomes blurry when you do.

     

    I'm just trying to give you a visual representation of what's going on.

     

    If you doulbe the amount of pixels - then photoshop trys to guess what colour the new pixels are by sampling other pixels around it, and it's not very accurate.

     
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  • Currently Being Moderated
    Nov 12, 2010 5:31 AM   in reply to jiyasa

    Ideally you don't want to try make an image bigger - if you can avoid it.

     

    http://www.cambridgeincolour.com/tutorials/image-interpolation.htm

     
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  • Currently Being Moderated
    Nov 12, 2010 5:35 AM   in reply to Eugene Tyson
     
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  • Currently Being Moderated
    Nov 12, 2010 6:56 AM   in reply to jiyasa

    That depends entirely on the starting resolution of the image and the finished placed size.

     

    If it's 24 inches and 1ppi res then then it's pixel width is only 24 pixels (it has 1 pixel per inch)

     

    If it's 24 inches and has 72 ppi res then it's pixel width is 1728 pixels (it has 72 pixels per inch (72*24 = 1728))

     

    If it's 24 inches and has 300 ppi res then it's pixel width is 7,200

     

    and so on

     

     

    So if you have a 24 inch image that is 72 pixels per inch - it needs to be scaled 24 % to make it 300 ppi

     

    That means at 300 ppi the image will be 5.76 inches wide.

     

     

    But of course if it's only 36 ppi to start with, then it will only be 2.88 inches wide @ 300 ppi.

     
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  • Currently Being Moderated
    Nov 12, 2010 7:30 AM   in reply to jiyasa

    Quite the oppostie. The registration colour should only be used for Crop Marks and Fold marks and page information that reside in the slug area (outside the bleed area) of the document.

     

    Regristation is what it is, used for aligning (registering) inks on top of each other at print stage. So they appear on all plates.

     

    Where did you hear it didn't print?

     

    http://indesignsecrets.com/indesigns-paper-and-registration-colors.php

     
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  • Currently Being Moderated
    Nov 12, 2010 7:47 AM   in reply to jiyasa

    Was a printer from 1998 - 2001 and graphic designer from 2001 to present.

     

     

    If you want quality online tutorials check out www.lynda.com - it's not free but it's worth it.

     
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  • Currently Being Moderated
    Nov 12, 2010 8:02 AM   in reply to jiyasa

    Every job is different. Your job is outlined at interview stage, along with expectations, and these change/evolve over time.

     

    As for images, make sure you read the license that comes with them, some are free to use, some are commercial licenses and some can be used for other things. Costs vary depending on where you purchase the image. If you don't want to get sued don't do anything that you may think could get you sued.

     

    Consult a solicitor for any matters pertaining to image rights that you are unsure of.

     
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