10 Replies Latest reply on Oct 11, 2009 9:07 AM by Wade_Zimmerman

    Scaling and sharpening photos in Illustrator

    John Stanowski Level 1

      What actually happens to a photo when it's scaled in Illustrator? Does it get resampled?

      I'm asking because in Photoshop you need to have an image which will be printed to be the actual size it will print before applying an Unsharp Mask.

      Scaling it afterwards will affect the sharpening.

       

      So, what happens when a larger photo is scaled down in Illustrator? Does that photo get resampled? Does it remember its original size?

      Is it safe to apply Unsharp Mask to a photo in Illustrator after it's been scaled down? Would the sharpening be applied to the photo at its new, smaller size or would the calculations be applied as if the photo were still larger?

        • 1. Re: Scaling and sharpening photos in Illustrator
          Wade_Zimmerman Level 6

          It does not get resampled it remains the same pixel count either way.

           

          You do not want to scale an image in Illustrator except under unusual circumstances where it does not matter or the effect is desired both of those cases are very rare.

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          • 3. Re: Scaling and sharpening photos in Illustrator
            D. Fraser-1eqWmH Level 2

            Wade is right about Illy not scaling the pixel density of an image. That is not to say that it can't be done. If the image file is embedded (or linked, I think it will embed the resulting image in the file and not destroy your original, linked file,) you can 're-rasterize' the down-scaled image in Illy and then apply your unsharp mask. Down-scaling is useful in certain situation but Up-scaling should not be done unless the pixel density will remain high (~300ppi.) Just make sure your 'Document Raster Effects' are set to 300ppi before you use the Rasterize menu item.

             

            D.

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            • 4. Re: Scaling and sharpening photos in Illustrator
              John Stanowski Level 1

              That's an interesting idea but it's left me a little confused when I tried it.

              I placed a large photo into AI, scaled it down, then duplicated it. I then Rasterized the second copy.

              Then I applied an Unsharp Mask to both.

              The unrasterized copy looks waay sharper than the rasterized one.

              I would have thought it would have been the opposite.

              I'll have to experiment more.

              • 5. Re: Scaling and sharpening photos in Illustrator
                D. Fraser-1eqWmH Level 2

                Of course the larger, scaled down image is going to look sharper, it has a lot more pixels to play with. A 500ppi image will always look sharper on the screen than a 300ppi image. You don't mention what the final 'product' is going to be used for, so I can't say what the best way would be. For printing to a commercial press (4-color process with a line-screen of 150-175,) the difference in the final product will be negligeable between a 300ppi image and a 500ppi image. The general rule here is the optimum resolution of an image at 100% scale should be 2x the output printer/press' line-screen. The only real difference is going to be the file size. If it is going to be used for only a monitor, as of right now, everything gets rendered at 72-96ppi anyway so the only real effect is when viewing at larger scales >100%.

                 

                D.

                • 6. Re: Scaling and sharpening photos in Illustrator
                  John Stanowski Level 1

                  I was confused because the Unsharp Mask I applied to both versions of the photo were at the same settings.

                  If the un-rasterized photo was not resampled when it was scaled down, then the fine settings in the Unsharp Mask would be applied to pixels that for all intents and purposes are now "sub-pixels" and thus wouldn't show any change. The un-rasterized photo behaved more like it had been resampled because the effects from the Unsharp were very obvious. Is there possibly a sort of limbo version of the photo which was resampled? Or did AI take into account that the photo had been scaled down and altered my settings in the Unsharp Mask filter to mimic them being applied to a smaller photo?

                  Just FYI, this is all for newspaper ads. I do all manner of work from web to tv commercials to print, but these newspaper ads I'm doing are quite a regular thing and I do a lot of them. I was looking for ways to streamline the process and that's why I'm asking about the sharpening and what really happens when you scale a photo in AI.

                  • 7. Re: Scaling and sharpening photos in Illustrator
                    D. Fraser-1eqWmH Level 2

                    John Stanowski wrote:


                    ...The un-rasterized photo behaved more like it had been resampled because the effects from the Unsharp were very obvious. Is there possibly a sort of limbo version of the photo which was resampled? Or did AI take into account that the photo had been scaled down and altered my settings in the Unsharp Mask filter to mimic them being applied to a smaller photo?...

                     

                    I just tried this, and you are right, it does seem to mimic the effect no matter what the pixel density is. The original does look sharper but in reality, it isn't going print any differently. I think this is because the filter is a live effect, meaning that it is non-destructive. On a side note, I always apply an Unsharp Mask on the highest resolution image that I have before I scale the image down. This helps eliminate the 'halo effect' of the Unsharp Mask filter.

                     

                    Just FYI, this is all for newspaper ads. I do all manner of work from web to tv commercials to print, but these newspaper ads I'm doing are quite a regular thing and I do a lot of them. I was looking for ways to streamline the process and that's why I'm asking about the sharpening and what really happens when you scale a photo in AI.

                     

                    Typically, a newspaper's line-screen, (web-press) is lower than an offset press. You can get away with a smaller image, in terms of pixel density, when designing stuff for newspapers. If I were doing this, I would place (linked) the original file, apply the unsharp mask, scale the image down to the size it needs to be and then rasterize the image at the appropriate resolution. This will embed the rasterized version in the file at 100% at the correct resolution without needlessly increasing the file size. I would do the rasterization after you have finished editing the file (being that the Unsharp Mask is a live filter) and it has been finalized. You can avoid using the rasterize menu option by using 'save as pdf', instead of an illy native file, without keeping illy's editing capability, and changing the compression settings to rasterize and flatten any transparency. I don't like to do this, because I'm never quite sure what the final output would be. If I am working on a single file that needs some flattening, I like to manually rasterize and flatten the transparency to see the results before I save the final file (always a new file.) Anyway, I hope this helps.

                    • 8. Re: Scaling and sharpening photos in Illustrator
                      Wade_Zimmerman Level 6

                      Really not a good idea. It is a work around if you want to do this 

                      link the images and edit and scale the images in Photoshop no matter 

                      how you look at it you are not saving steps and you still have to go

                      from one dialog to another.

                       

                      Also in Photoshop you have other options for sharpening that are much 

                      more helpful like using the high Pass method and Smart Sharpening.

                      • 9. Re: Scaling and sharpening photos in Illustrator
                        JETalmage Level 6

                        I'm asking because in Photoshop you need to have an image which will be printed to be the actual size it will print before applying an Unsharp Mask.

                        Scaling it afterwards will affect the sharpening.

                        Not exactly.

                         

                        Scaling a raster image that has been sharpened does not affect the sharpening. Resampling the image, of course, will.

                         

                        The distinction is important. The printing process itself effectively "resamples" a raster image to create a new one (actually several new ones; one for each color separation plate) that matches the printer-spot grid of the output device. (That's what's meant when you hear people say that eventually, everything gets rasterized.)

                         

                        That's why oversampled images tend to somewhat negate carefully-applied sharpening. The "resampling" that is inherent in the printing process imposes a certain amount of "blurring" as the too-many pixels are averaged together to make a single tone dot and those in turn are resampled into individual printer spots. For an over-simplified conceptual example, consider:

                         

                        1. An image has a light pink pixel, next to another light pink pixel, next to a bright red pixel.
                        2. Sharpening the image results in a pink pixel next to a white pixel, next to a bright red pixel.
                        3. The image is scaled to too-high a ppi for the printing method being used.
                        4. The printing method effectively results in a light pink halftone dot next to a darker pink halftone dot. The white sharpened edge is lost, as is the brilliant solid red--you've effectively averaged-away your carefully-applied sharpening.

                         

                        So the bottom line is, whether you do the sharpening in Photoshop (as I would) or elsewhere, there is no "quick and easy" avoidance of performing the sampling on an image that has a pixel count appropriate to the intended reproduction method. This is one of the reasons why I maintain that the conventional-wisdom "one-size-fits-all" admonition to make all printed images 300ppi is a corruption and misunderstanding of the original and legitimate rule-of-thumb, which is "one-to-two times the halftone ruling."

                         

                        So...

                         

                        After doing all your color correction and converting the image to CMYK:

                        1. Resample to a PPI appropriate for the intended printing process.
                        2. Then sharpen. When sharpening, do so while VIEWING the image at at least a 1:1 monitor-pixel-to-image-pixel zoom. That way, you are at least viewing your monitor's rendition of all the pixels in the image, not just a temporary on-screen downsampled image (therefore, pixels averaged together).

                         

                        Thereafter, merely scaling the image does not resample the sharpening--unless, of course, you scale the image such that its ppi exceeds the rule-of-thumb of "one-to-two-times the halftone ruling."

                         

                        (That's why, for the typical 150lpi sheetfed halftone ruling, I use 225ppi as my default "ideal"; not the oft-cited 300ppi-fits-all. But I size/rotate/sample/sharpen images before placing on the page, and don't do on-page transformations thereafter.)


                        JET

                        • 10. Re: Scaling and sharpening photos in Illustrator
                          Wade_Zimmerman Level 6

                          It is best to sharpen at the dimensions and resolution that you are going to print,that is a very wise approach for a number of reasons.

                           

                          However if you are very prudent about how you sharpen you can easily get away with it and no one will know except someone with knowledge and a very very sharp eye.