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illustrator-photoshop pixel scale integration

Forum|Forum|15 years ago
September 6, 2010
4 replies
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If I export to a jpg file an Illustrator created object that measures via the ruler 5 pixels (appx.) length and then open that file in Photoshop, the object is 50 pixels (appx.) in length. Then if I try to compensate by reducing the scale of the Photoshop object by 1/10, the object fuzzes out and loses its features. Anyone know how to sustain the scale of an Illustrator created object opened in Photoshop? I'm not interested in the kluge solution of beginning with an Illustrator object 50 pixels in length.

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Correct answer JETalmage

Scott has answered your question. I'll give this all-too-frequent confusion another shot:

First, think Photoshop:

All Photoshop does is arrange a bunch of color values in rows and columns. Each "cell" in this array is a color value; nothing more.

A pixel is NOT a measure. It's just a color value. It has no intrinsic size. A pixel can be scaled to any measure you want it to be. That's what you are doing when you resize (not resample) an image in Photoshop; you are telling Photoshop to scale each pixel in the image to a new size, in the form of so-many-pixels-per-actual-unit-of-measure (most commonly, PPI; Pixels Per Inch).

Do you see that?

Pixels per Inch.

Pixels per Inch.

"Pixel" is just a color square. "Inch" is an actual measure. A pixel has no measure whatsoever until you scale it to an actual unit of measure. Without the "per whatever" the pixels in your image have no size.

When it all comes down, a Photoshop file contains one raster image. All the pixels in that image are scaled to the same measure. You can't grab a subset of the pixels and scale them to a different measure. Hold on...yes, I know Photoshop's interface lets you pretend to do that, but trust me, you can't. When you select a bunch of pixels and "scale" them, as soon as you commit the change, the actual pixels in the image are just recolored.

Because all the pixels in a Photoshop document are scaled the same, when the ruler is set to "Pixels," the ruler can be thought of as counting pixels.

Now, think Illustrator:

Illustrator individually arranges, scales, rotates, and distorts any number of entirely separate objects. Those individual objects can be text objects, path objects, or raster objects. Again, they can be individually scaled. So you can place a raster image in Illustrator and scale it so that its pixels measure 1/100th of an inch (100 PPI). You can place that same raster image again in the same Illustrator file and scale it so that its pixels measure 1/300th of an inch (300 PPI). Both instances of that image still have the same number of pixels. But they will not "measure" the same, even if you set Illustrator's rulers to "Pixels."

Because each raster image in an Illustrator file can be independently scaled to any size, when the ruler is set to "Pixels," the ruler cannot legitimately be thought of as counting pixels.

The rulers in Illustrator always represent real-world, physical measure for whatever eventual output method/environment the file is intended. Because "pixel" is not an actual measure, the use of "Pixels" as a supposed "unit of measure" is completely bogus. It's just an ill-conceived "convenience" for those who want the rulers to represent how many pixels the file will be rasterized to, if and when the whole thing is exported as a single raster image.

All too often--especially in Illustrator--supposed "convenience" features become time-wasting "confusion" features. The assumption of this particular "convenience" is that the user already understands all of the above. As is painfully evidenced by the frequency of recurrance of this very same topic in this forum, that assumption is as bogus as pretending that "pixel" is a unit of measure.

In other words, the people who are the target of this "intuitive convenience" (newcomers to vector programs dragging along some comfort-level in raster programs) are the very ones most likely to be confused by it, and the net result is anything but intuitive.

Since "pixel" is absolutely not a unit of measure, and since Illustrator's rulers always represent an actual measure, what is the actual measure being represented when one sets Illustrator's rulers to "Pixels"? The actual unit of measure is the typographer's point. A [modern] point measures 1/72 of an inch. When you set Illustrator's rulers to "Pixels," you are really setting them to Points.

I don't know which program actually started this particular interface idiocy, but Illustrator is far from the only vector drawing program that commits it. They should all be burned at the stake.

JET

U

ugotbawlz

Participating Frequently

@JETalmage... no need to come off as a p-r-i-c-k about a simple repost to help others. a forum is just that...an INFORMAL place to post info...some helpful, some not so helpful. geez...come off your high horse. dude can re-post it wherever he wants...although he should give you credit when he does it. when you come off the way you did...you are most definitely not helping the greater good. you sound like some aristocratic academic freak. not cool and absolutely no need to be like that...he wasn't stealing your artwork. nuff said.

A

Anonymous

Hello All,

Brilliant answers to everyone and much, much appreciated. I am super newb-tube to this and am self-teaching so forgive me if I stumble with lingo and whatnot; I'm still learning the concepts.

With an object(s) open in Illustrator (CS5 in my case), how can I answer the below request?

"Can you send me the [logo] in a jpeg format, not longer than 944 pixels or taller than 250 pixels, and 300-350 d.p.i clarity?"

I will let the brains answer this, but from what I understand the requested output is an image with specific dimensions and high density. I could (I think) easily perform this request from PS, but directly from AI, how (rather, can) I output the requested JPEG?

Thanks in advance, you're all super smart.

Postscript - Should I make this a new thread or is it OK to keep it within this one?

JETalmageCorrect answer

Inspiring

Scott has answered your question. I'll give this all-too-frequent confusion another shot:

First, think Photoshop:

All Photoshop does is arrange a bunch of color values in rows and columns. Each "cell" in this array is a color value; nothing more.

A pixel is NOT a measure. It's just a color value. It has no intrinsic size. A pixel can be scaled to any measure you want it to be. That's what you are doing when you resize (not resample) an image in Photoshop; you are telling Photoshop to scale each pixel in the image to a new size, in the form of so-many-pixels-per-actual-unit-of-measure (most commonly, PPI; Pixels Per Inch).

Do you see that?

Pixels per Inch.

Pixels per Inch.

"Pixel" is just a color square. "Inch" is an actual measure. A pixel has no measure whatsoever until you scale it to an actual unit of measure. Without the "per whatever" the pixels in your image have no size.

When it all comes down, a Photoshop file contains one raster image. All the pixels in that image are scaled to the same measure. You can't grab a subset of the pixels and scale them to a different measure. Hold on...yes, I know Photoshop's interface lets you pretend to do that, but trust me, you can't. When you select a bunch of pixels and "scale" them, as soon as you commit the change, the actual pixels in the image are just recolored.

Because all the pixels in a Photoshop document are scaled the same, when the ruler is set to "Pixels," the ruler can be thought of as counting pixels.

Now, think Illustrator:

Illustrator individually arranges, scales, rotates, and distorts any number of entirely separate objects. Those individual objects can be text objects, path objects, or raster objects. Again, they can be individually scaled. So you can place a raster image in Illustrator and scale it so that its pixels measure 1/100th of an inch (100 PPI). You can place that same raster image again in the same Illustrator file and scale it so that its pixels measure 1/300th of an inch (300 PPI). Both instances of that image still have the same number of pixels. But they will not "measure" the same, even if you set Illustrator's rulers to "Pixels."

Because each raster image in an Illustrator file can be independently scaled to any size, when the ruler is set to "Pixels," the ruler cannot legitimately be thought of as counting pixels.

The rulers in Illustrator always represent real-world, physical measure for whatever eventual output method/environment the file is intended. Because "pixel" is not an actual measure, the use of "Pixels" as a supposed "unit of measure" is completely bogus. It's just an ill-conceived "convenience" for those who want the rulers to represent how many pixels the file will be rasterized to, if and when the whole thing is exported as a single raster image.

All too often--especially in Illustrator--supposed "convenience" features become time-wasting "confusion" features. The assumption of this particular "convenience" is that the user already understands all of the above. As is painfully evidenced by the frequency of recurrance of this very same topic in this forum, that assumption is as bogus as pretending that "pixel" is a unit of measure.

In other words, the people who are the target of this "intuitive convenience" (newcomers to vector programs dragging along some comfort-level in raster programs) are the very ones most likely to be confused by it, and the net result is anything but intuitive.

Since "pixel" is absolutely not a unit of measure, and since Illustrator's rulers always represent an actual measure, what is the actual measure being represented when one sets Illustrator's rulers to "Pixels"? The actual unit of measure is the typographer's point. A [modern] point measures 1/72 of an inch. When you set Illustrator's rulers to "Pixels," you are really setting them to Points.

I don't know which program actually started this particular interface idiocy, but Illustrator is far from the only vector drawing program that commits it. They should all be burned at the stake.

JET

C

cyberbaffledAuthor

Participating Frequently

I'm catching up on my correspondence. I didn't check the forum after my reply to Scott's second post so I'm just today finding yours. Never-the-less, it provides an immense amount of critically useful information and I'm copying it -along with Scott's- to an informal Illustrator-Photoshop user guide. I've toggled your reply a useful or helpful answer, I forget Adobe's precise term, and I would have toggled it a "correct" solution if the system gave me that option.

Scott Falkner

Community Expert

There is no such measure in Illustrator as pixels. Yes, I know you can select “Pixels” on the ruler, but the units used are not true pixels. They are points, or 1/72 of an inch. Illustrator assumes that you will export your artwork as rasters at 72 ppi (pixels per inch), which you will is you use Save for Web and Devices. But if you use File > Export you can select a different output resolution, which will scale your artwork and ignore your use of pixels as a unit of measure.

So tell us how you are exporting your artwork to Photoshop. Tell us the versioonns of Illusrator and Photoshop you are using. When you open the JPG file in Photoshop and go to Image > Image Size, what is the file’s resolution in pixels per inch? While we’re at it, why are you exporting JPG files if you intend to further edit them in another program? You should use a lossless format such as PSD, TIF, or PNG.

C

cyberbaffledAuthor

Participating Frequently

Scott,

I'm using Illustrator CS4 and Photoshop CS4. In Illustrator, in EDIT>PREFERENCES I've selected pixels for "general" and "stroke". After exporting the image as .jpg (because I'm using it in Dreamweaver) and opening it in Photoshop the IMAGE>IMAGE SIZE is set to pixels. Nevertheless, despite the fact that pixels are chosen in both Illustrator and Photoshop, the exported .jpg file opens ten times larger in the latter. To reiterate, I'm rastorizing a file and exporting it to .jpg because that's the format that works in Dreamweaver.

Scott Falkner

Community Expert

cyberbaffled wrote:
Scott,
I'm using Illustrator CS4 and Photoshop CS4. In Illustrator, in EDIT>PREFERENCES I've selected pixels for "general" and "stroke". After exporting the image as .jpg (because I'm using it in Dreamweaver) and opening it in Photoshop the IMAGE>IMAGE SIZE is set to pixels. Nevertheless, despite the fact that pixels are chosen in both Illustrator and Photoshop, the exported .jpg file opens ten times larger in the latter.

You still have not explained how you are exporting your artwork. Are you using File > Export? Are you using Save for Web and Devices? Are you copying and pasting to Photoshop? Are you opening the Illustrator .ai file in Photoshop and letting Photoshop rasterize? Whichever you are using, what settings are you using?

Once again: There is no such unit as pixels in Illustrator. Adobe does not want you to know this, but it is a fact. Pixels, when properly used as a unit of measure for an image, have no physical size. But Illustrator was build to be used for creating vector drawings for print, and that will always be in every Illustrator file’s DNA. Every object and every artboard in an Illustrator file has a physical size, which tells Illustrator how large things will be when they print. That guarantees that pixels cannot ever be used as a unit to define sizes, since pixels have no physical size.

Try this: Open an image in Photoshop and look at the size in Image > Image Size. Let’s use a 72 pixels by 72 pixels file that is 72 pixels per inch. It’s easy to see that, when printed, the image should be a square, one inch wide and one inch tall. Place that image in Illustrator and that’s what you’ll get. Save a copy, but with one change: change the resolution to 144 pixels per inch (Resample set to None). Now import that image into Illustrator. You will get the same image, but only one half inch wide and tall. Switch units to pixels, and your 72 pixels by 72 pixel image will be reported as being 36 pixels by 36 pixels. How can that be? It can’t. Illustrator is assuming you will export your file as a raster image at 72 pixels per inch, so the half-inch image will end up being 36 pixels wide.

Photoshop and Illustrator are very different programs, for good reason. Photoshop is a pixel based graphics program. Everything in Photoshop is pixels, so it’s a simple idea to keep the pixel size (defined under Image > Image Size) consistent throughout one file. But Illustrator is object oriented, and some of those object can be pixel-based, such as the appearance of a drop shadow effect, artwork rasterized within Illustrator, or artwork imported into Illustrator. Each of these types of object can have its own defined pixel size. Each of these objects can be further enlarged or reduced in Illustrator, further varying the pixel size for each object. How can one entire document use pixels as a unit of measure when there are several objects built out of pixels that all use different sized pixels? Answer: it can’t because it is impossible.

When you use pixels, Illustrator is assuming you are preparing artwork for screen, like a presentation or a web page. So Illustrator decides that each point (1/72 inch) will correspond to one pixel. If you export your file at 72 pixels per inch (which is what you do when you use Save for Web and Devices) you end up with what you expect, since a one inch line in Illustrator is 72 points (also called pixels in Illustrator). But if you export at any other resolution, you end up with a different sized line.

Adobe had made several mistakes with Illustrator, going back decades. They show no sign of caring that Illustrator is a dog’s breakfast of poorly thought out features, awful interfaces, overall unintuitiveness, and just all around USDA choice fuçk-up. Using pixels as a unit of measure has been, in hindsight, one of their biggest mistakes. Someone should have been fired for adding it but, knowing Adobe, they probably got a promotion and a great parking spot.

To reiterate, I'm rastorizing a file and exporting it to .jpg because that's the format that works in Dreamweaver.

If you plan to open the image in Photoshop to edit it, then DO NOT use JPG as the format for export from Illustrator. Use a lossless format. Once the image is as you want it in Photoshop you should save it as a TIF or PSD (especially if using adjustments or layers) as well as a JPG for Dreamweaver.

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