Problem with pixelation of ONE image on an exported PDF

[AJ12170409]

Hey everyone,

I am not a total expert when it comes to InDesign, so I'm sure there's just something I'm missing. I've been in charge of formatting lesson plans for work and haven't had this problem until now. I've got several hi-res graphics on all the pages of the document. When I first open the doc in InDesign, the image shows up pixelated, then I change the display setting to hi-res and get it fixed. But when I export, it slightly pixelates instead of remaining hi-res. None of the other images are doing it. You can see how the white figures are pixely while the green plankton and shrimp antennae are not. And the words on the speech bubbles also pixelate. This image is from Preview:

In InDesign, it looks like this:

And in Acrobat, it looks like this:

Any ideas on why this would happen? Should I just scrap the image entirely and try something else?

[Eugene Tyson]

It's likely the image is not high enough resolution - so you could try something else - or reduce the size of the image in inDesign would increase the effective resolution.

I wrote on an article on this

https://creativepro.com/high-res-image-look-low-res/

[AJ12170409]

I think you're right. Thanks for the help! I will replace the image with something better.

[Robert at ID-Tasker]

@AJ12170409 

To be honest - BOTH of your images are pixelated in Acrobat - more than in the InDesign...

Left is InDesign - right Acrobat:

What are your PDF Export settings?

[AJ12170409]

I'm not sure I've ever messed with the export settings in some time. I don't know what everything means, but I'm assuming you're talking specifically about compression? At least, that's the only place I found that might be affecting the export quality. (Again, I don't understand everything.) It's just weird that it only just happened to this one image. 

[Brad @ Roaring Mouse]

Your compression settings are "normal" for most purposes, so if your image is above 450 ppi effective resolution (you can check this in your Links panel), it will be downsampled, so that would definitely look worse if you zoom in on it on the screen, but it's perfectly fine for print prodiction.

As a test, change yor export setting from Bicubic Downsampling to Do Not Downsample. This shouldn't change the appearance of your images at all. The downside of this is a larger PDF file size, as the whole purpose of compression is to make a PDF as compact as possible for the intended use.

[AJ12170409]

Thanks so much Brad! That helps loads 🙂

[Robert at ID-Tasker]

@AJ12170409 

But BOTH of your images are affected - the "legs" and the "antennae".

[Peter Spier]

which tends to support Brad's downsampling theory, I think...

[AJ12170409]

Yeah, I agree. You go in far enough, and that is definitely the case. That won't be a problem, though. It was definitely obvious on those legs. So thank you all 🙂

[Willi Adelberger]

What file types are the images?

[Robert at ID-Tasker]

which tends to support Brad's downsampling theory, I think...

By @Peter Spier

Not arguing with that - but @AJ12170409 thought that only one image has been affected.

[AJ12170409]

I believe those were jpgs

[Brad @ Roaring Mouse]

If the other image was below 450 ppi, it wouldn't be downsampled, so it would not change.