Need Help Do you loose quality when scaling raster image in Illustrator

If by "quality" you mean "image resolution", then only if you output in a lower (than the image's native pixel size) bitmap format.

 

Any raster image will loose quality when you expand it...

 

If you’re exporting it at 1/20 then scaling in your rip, then it will likely look horrible.

 

No, you will not lose resolution. Check linked or embedded images with the Document Info palette to become clear.

 

If you're saving as a pdf, go to compression tab, then select do not downsample on all 3. This will keep the images at full resolution.

 

If you take 100dpi image in Illustrator and scale it down by 20x, the image is now 2000dpi. Now if you take that 2000dpi and print it while scaling it 20x, it will most likely look worse than if you scaled everything back up to 20x and then printed.

 

Scaling it 20x in your RIP will change the resolution from 2000ppi back to 100ppi. It should be no different from scaling back up 20x before loading into your RIP, unless the people who designed your RIP software are complete idiots.

 

Correct me if I'm wrong.. But illustrator doesn't alter the image at all. It embeds the original image... Or links to the original image if your not embedding. So resizing won't affect it at all.

IE: if you have a 500mb 10 ft image... Then shrink that image to 1".... Illustrator doesn't actually change the image, and when you save the file it'll still be a 500mb file.. So long as you don't use compression or tell illustrator to downsize the file.

Now if you have a 10" file and want to make it a 50" file... You'll get better quality using photoshop / on1 resize due to its "smart pixel adding" Alligrotham.

But in your case, your image quality will be the exact same as your original image.

 

The problem with scaling down in Illustrator is it has to re-render the preview between each step. For some stuff this is not an issue...but if you have a bunch of images that are scaled or rotated (in Illustrator), Illy will hit a wall. Also, if you "embed" the image, it takes on Illustrator's working color space. This can be an issue if a designer uses less conventional icc profiles. Using linked files leave the images untouched.
This is how Illustrator will "alter" your image if you embed.

It's always more efficient to size and crop your file in Photoshop (at quarter scale 288ppi, place as a link at 100%).
We see the laziest crap, it used to be the norm as a professional to build a lean production file...

 

I just wish people knew the difference between LOOSE and LOSE.

 

Is suggest anyone try placing as many scaled and rotated tiff or PDF files as they care to in order to learn how their copy of Illustrator reacts. Then try placing EPS image files. Then, if the display redraw is slow for the EPS images, simply go to Preferences and find something like “Use Low Resolution Proxy for Linked EPS” to see if it's the instant remedy for speed of display.

After that simple test, maybe let's learn about the remainder of statements in the post if there is any interest.

 

EPS drops color profiles. Is there really ANY use for eps anymore?

 

Are you saying you're experiencing slow re-render previews with other than EPS file types?

 

Yes. When an image is placed in Illustrator and scaled or rotated, in Illustrator, it must render the previews between each step. If the image is pre rotated and placed at 100% it doesn’t have to reprocess each “transformed” instance.

The other mess we hate cleaning up is when people crop to 2% of an image with a clipping mask, 30 times in one file. It’s lazy, and perpetuates the inefficiency all the way through the pipeline.

 

Not my experience at all nor anyone I've asked or observed. That's why I suggested anyone here test on their end and, hopefully, post what they find.

 

How exactly are you determining this to the case? I ask because I don't experience this.

 

We hit Illustrator’s memory ceiling quite often. The re render issue is minimal if you’re working with poster size layouts.

We will get 2 gig .ai files with 6 gigs of links sometimes, it taxes our 8 core trash can Mac pretty heavy. Typically after we optimize all of the art and remove extraneous crap our production files are about a third the size or smaller.