34 Replies Latest reply: Nov 12, 2010 8:31 AM by jiyasa RSS

    Rasterize/Flatten Image

    jiyasa Community Member

      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)?

        • 1. Re: Rasterize/Flatten Image
          Eugene Tyson ACP/MVP

          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=WSfd1234e1c4b69f30ea53e41 001031ab64-78f7.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.



          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.

          • 2. Re: Rasterize/Flatten Image
            jiyasa Community Member

            Okay, only reason I asked on here is because anytime I've asked advice on the photoshop wing of the forum I seldom got a response and when I did it wasn't very helpful but ok.


            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?


            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?


            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?

            • 3. Re: Rasterize/Flatten Image
              Eugene Tyson ACP/MVP

              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.





              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.

              • 4. Re: Rasterize/Flatten Image
                jiyasa Community Member

                Okay, so when in Photoshop if I go to File>Place and then pick an .ai file to place, when it prompts me for smart object, shape layer, pixels, etc. always pick smart object to retain it's sharpness? I think I understand.


                Thank you very much for your help Eugene, always appreciated.

                • 5. Re: Rasterize/Flatten Image
                  Eugene Tyson ACP/MVP

                  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.

                  • 6. Re: Rasterize/Flatten Image
                    Eugene Tyson ACP/MVP

                    Why are you placing it into photoshop anyway?


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

                    • 7. Re: Rasterize/Flatten Image
                      jiyasa Community Member

                      Well, these are hypothetical questions. I mean, I have tried to import an .ai file into photoshop before and wasn't sure how to go about it. And when I set up the .ai file from the beginning before I even started drawing I always set the ppi to 300 and then when I open a new photoshop blank document I set it up as 300 too so it's good, it's rare that I do that but I have tried it before.


                      How would placing a photo into illustrator be better? Please explain.

                      • 8. Re: Rasterize/Flatten Image
                        Eugene Tyson ACP/MVP

                        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.)

                        • 9. Re: Rasterize/Flatten Image
                          jiyasa Community Member

                          I just meant that when I launch illustrator I can choose between different document profiles on the opening screen like "CMYK document" and "Print document" and what I was saying was I always choose Print document because I am assuming that by default it is set to 300 ppi. But I didn't know that the raster effects alone were raster, I guess from now on I will make sure that I only add them after I have done my scaling since you said that.


                          I think just to cut out the middleman that from here on out I will just stick to importing everything from their native programs/file formats directly to InDesign because it's too much work. .AI and .TIFF or .PSD to InDesign, just so much easier than all this unneccessary navigating. I trust your judgement better than my own.


                          Just to make sure I understand you correctly, when you say:

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


                          are you saying that I should place a raster photo (image, not a drawing or illustration) an image into illustrator for editing or am I misunderstanding you?

                          • 10. Re: Rasterize/Flatten Image
                            Eugene Tyson ACP/MVP

                            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.

                            • 11. Re: Rasterize/Flatten Image
                              jiyasa Community Member

                              Hi Eugene, sorry it's taken me a bit to respond to you. I've always been sort of confused as to when and how a vector becomes as raster. Opening a vector in photoshop by itself doesn't make it raster, saving it as another file format is what converts it (aside from the rasterize function I asked about earlier) am I right?


                              While we're on the topic of resolution, I know Peter glossed over this in an earlier thread I started but I'm still a tiny bit confused about that subject. Maybe you can make sense of this for me?


                              What I have been doing when working with images on the web I download them as JPEG and open them in photoshop. I go to Image>Image Size and the dialog box comes up. I don't mess with the pixel dimensions at the top of that box, don't even really know what those are for to tell you the truth. In the document size area I more than half most images in size because I remember you guys saying that shrinking a size of an image increases the true resolution but here's where I am confused... at near the bottom is resolution field, I punch in 300 but I'm guessing doing so doesn't literally and so easily change the true resolution of the image, so why even have that field in the first place if it doesn't really affect the resolution?? What's it for?


                              And to wrap it up at the very bottom of the image size pop up box I click the drag down menu and select bicubic sharper (best for reduction) and then I'm done. Am I doing this right?


                              At this point in time I'm just trying to learn enough to get my portfolio finished and resolution is something I think I really need to understand enough of to finish this up. Thanks Eugene

                              • 12. Re: Rasterize/Flatten Image
                                Eugene Tyson ACP/MVP

                                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.

                                • 13. Re: Rasterize/Flatten Image
                                  [Jongware] MVP

                                  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.

                                  • 14. Re: Rasterize/Flatten Image
                                    jiyasa Community Member

                                    It's okay, thank you again for all your help Eugene, always appreciated.

                                    • 15. Re: Rasterize/Flatten Image
                                      Eugene Tyson ACP/MVP

                                      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

                                      • 16. Re: Rasterize/Flatten Image
                                        jiyasa Community Member

                                        Jongware, if I understand you correctly this is what I sort of got out of it:


                                        In photoshop the image size dialog box, the two top fields of pixel dimensions are actually the measurements of the document and there is where I was making the mistake of thinking that altering this will increase the pixels/resolution which really only increases/decreases the size of the image. Messing with the pixel dimensions and/or image size measurements are one and the same, they do the same thing am I right? There are a set number of pixels within every inch of an image/document, you can never create pixels out of thin air so they will always be there it's just a matter of how I concentrate them (with JPEGs).


                                        So I guess, if you're saying that 96 x 96 dpi comes to one inch that 96 dpi is a set number of pixels within that one inch and will only appear to be of a higher resolution if the image is shrunk down smaller (like you were saying punching in 300 dpi will make the image much much smaller in InDesign) when in fact it is still 96 dpi just in a smaller, concentrated area. I'm at a gross disadvantage because I'm working with JPEGs and doesn't allow for much other than to shrink them down to hide the flaws. I just need to find some treasure trove of high resolution, non-lossy format images to work with because it stinks trying to work with these watered-down JPEGs I'm finding on google.


                                        If I have in any way misunderstood you or are wrong about anything please feel free to let me know?


                                        Since I don't get to say it much, Eugene, Jongware, Peter, Bob, everyone thank you very very much for your help. I know there is a lot of specialization in this field, you guys really know your stuff and I really appreciate your patience and willingness to help. I really admire you guys (a bit intimidated at times lol) but I really value your time and effort, thank you guys so so much. You guys are the coolest and it makes me feel a lot better to know that I have this kind of help on my side.

                                        • 17. Re: Rasterize/Flatten Image
                                          jiyasa Community Member

                                          That's cause you know your stuff Eugene!


                                          As of right now I am starting with the first of three spokes, I am reading up on the illustrator cs4 bible to understand that then onto photoshop. I'm working on it, how long did it take you to learn this stuff?

                                          • 18. Re: Rasterize/Flatten Image
                                            Eugene Tyson ACP/MVP

                                            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




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


                                            • 19. Re: Rasterize/Flatten Image
                                              jiyasa Community Member

                                              How would I go about doubling the amount of pixels to 192 and is that ideal or would this give interpolation? If possible, heck yeah I would like to increase the resolution but from what I've read that isn't possible without actually capturing/creating the image in another non-lossy format.

                                              • 20. Re: Rasterize/Flatten Image
                                                BobLevine UGM

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



                                                • 21. Re: Rasterize/Flatten Image
                                                  jiyasa Community Member

                                                  Maybe I'm confused as to what Eugene is saying in the number 2 option, I know the first one will give the jaggy edges and make the pixels bigger. What would the second option do? Going to refer to my photoshop book too...

                                                  • 22. Re: Rasterize/Flatten Image
                                                    Eugene Tyson ACP/MVP

                                                    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.

                                                    • 23. Re: Rasterize/Flatten Image
                                                      jiyasa Community Member

                                                      Upsampling is when you just expand the image to a bigger size am I right? If not, how do I do that should I ever need it?

                                                      • 24. Re: Rasterize/Flatten Image
                                                        Eugene Tyson ACP/MVP

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



                                                        • 26. Re: Rasterize/Flatten Image
                                                          jiyasa Community Member

                                                          Thanks Eugene, at this point I guess I can do one of two things...figure out how to do an optical zoom on my digital camera like mentioned in that tutorial or find a place that has high resolution images.


                                                          So, do you think if I find a big enough an image (say 24 inches or so) and shrink it down will it be acceptable enough for print?

                                                          • 27. Re: Rasterize/Flatten Image
                                                            Eugene Tyson ACP/MVP

                                                            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.

                                                            • 28. Re: Rasterize/Flatten Image
                                                              jiyasa Community Member

                                                              I see what you mean, I just found a website freedigitalphotos.net so that will help to some extent. The problem is that with some of these photos they are of local places I took years back and not altogether sure how to make a digital camera take a high res picture. BTW, in InDesign is it true that the swatch "registration" will not print?

                                                              • 29. Re: Rasterize/Flatten Image
                                                                Eugene Tyson ACP/MVP

                                                                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?



                                                                • 30. Re: Rasterize/Flatten Image
                                                                  jiyasa Community Member

                                                                  I think it was some amateur tutorial I heard awhile back on youtube.


                                                                  So are you a graphic designer or a printer?

                                                                  • 31. Re: Rasterize/Flatten Image
                                                                    Eugene Tyson ACP/MVP

                                                                    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.

                                                                    • 32. Re: Rasterize/Flatten Image
                                                                      jiyasa Community Member

                                                                      Yeah, I got 30 free days of lynda.com cause I bought the cs4 software earlier this year, I especially like Deke McClelland's stuff.


                                                                      Tell me if I have a decent/rational idea of graphic design here...


                                                                      From everyone I've talked to who is a graphic designer, they like using the phrase "threw me to the lions" to describe their first day on the job. I kinda imagine they're getting calls left and right "where's my product?" and constant multitasking. For awhile I was concerned that I might use an image or something that was someone else's property and likely get sued or fined then eventually fired. I guess all in all, is this a hard job? When they hire are they looking for more creativity or technical expertise? Tell me more about your job and what it's like?

                                                                      • 33. Re: Rasterize/Flatten Image
                                                                        Eugene Tyson ACP/MVP

                                                                        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.

                                                                        • 34. Re: Rasterize/Flatten Image
                                                                          jiyasa Community Member

                                                                          As always, thank you for your help.