why does a 1024x1024 pixel image when placed in a 1024x1024 InDesign document need resizing?

It is also important to point out that InDesign has no issues with 1024px square JPG files that either embed the PPI using Xmp meta data properties or no meta data at all.

Only with Photoshop's Exif Save As-->JPG.

When I remove Photoshop's meta data and the Exif meta data and generate Xmp meta data to embed the 72PPI x and y resolution property via PhotoLine: InDesign places the file correctly.

Apropos of nothing at all, I've been skimming this thread and one thing jumped out at me -- the 1024 multiple and I'm thinking this is a common multiple for actual monitor screens. I wonder if there is any connection.

Did some quick testing:

• any file without transparency (either a loaded file or a new file) saved from Photoshop via File-->Save As-->JPG and 72ppi will be placed at 144ppi (instead of the expected 72ppi and in a 1024x1024px Web intent InDesign document.
• No other FIle-->Save As format that I tested causes the same issue in InDesign. Only the classic JPG.
• I created the same image in PhotoLine (alternative image editor), saved as JPG and no issues in InDesign.
• Exporting JPGs from Photoshop using the new Export As does not trigger this issue in InDesign.
• The Export As option does save the PPI parameter. But using a different meta data format and parameter compared to either the Save As JPG option or legacy Save For Web with all metadata activated during export.
• The legacy Save For Web export also triggers this issue in InDesign when all metadata is activated. If no meta data is embedded, no PPI info is embedded and InDesign treats the resolution "as-is" at 72ppi and correctly places the file.
• I checked the meta data (using ExifToolGui) that Photoshop's classic Save As --> JPG and SFW-->JPG generates, and compared with the newer Export As and PhotoLine's JPG export, as well as Irfanview's JPG output.
  Classic PS JPG export and SFW both use the old Exif IFD0 format to express XResolution and Yresolution (set to 72). Classic PS JPG export does also include a second set of Photoshop specific meta data parameters for the x and y resolution (in addition to the EXIF ones). This older meta data format does not include standard Xmp values for resolution. Newer software avoids Exif and uses Xmp and a different parameter format altogether.
• If both the Exif and Photoshop specific meta data is removed, the file no longer contains any PPI information.
• When Exif IFD0 res meta data is missing, software tends to fall back to the xml values. If these are also missing, no PPI parameter is set, and (for example) IrfanView leaves the PPI empty. Software like InDesign and OSs fill in the blanks for x and y PPI resolution with default 72 PPI.
• If a JPG (or other images in different file formats) lacks a PPI parameter InDesign just places that file at 72ppi.
• InDesign has no issues reading xml meta data. If it finds the resolution in the xml data/jfif/ whatnot, it will happily use that PPI parameter.
• If InDesign encounters a classic Photoshop JPG file generated with File-->Save As or the legacy SFW with full meta embedding active, AND a resolution of 72PPI (in classic Exif format), InDesign somehow decides to place the file at 144PPI instead of the original and correct 72PPI.
• I compared the CS6 file with the CC2024 JPG file that I generated, and there is NO difference in meta data structure. Therefore, it seems that the Save As-->JPG code hasn't seen an update since at least CS6 times.
• InDesign can deal with more up-to-date meta data structures in JPG files (XML based) just fine.
• When I delete all Exif info from the original PS file, and open it in PhotoLine, and define a PPI, the file no longer acts problematic in InDesign (as expected). A new xml meta data entry for x and y resolution is then set that InDesign reads properly. This also works with the new Export As option in Photoshop.

All of which means that:

• Photoshop's classic Save As-->JPG is in dire need of an update how it embeds meta data.
• InDesign needs a fix to identify these type of JPG files and avoid importing 72PPI files as 144PPI.
• To avoid this from happening in the current version: use the newer Export As export. It embeds the resolution data in a modern meta data format. (This may not be a good solution depending on the context that the jpg is prepared for, however)
• If working in an older version such as PS CS6: you are out of luck. The trick with setting a slightly higher or lower PPI will work, but is an ugly work-around. Or use the SFW to output JPG images without any resolution set.
  If the 72ppi parameter is important, prepare your work either as PNG files and export from InDesign with JPG set for images, or switch to another image editor or image conversion tool to create 72PPI JPG images that are compatible with InDesign.

...It's a really odd bug, though. I have no clue yet why InDesign decides to place 72 PPI images using the Exif PPI parameters as 144PPI while any other PPI rez seems to bypass that behaviour. Must be a rounding errror in the code, or intended, or something else. And with JPG files using a different meta data format it's not an issue. Weird.

It almost seems intentional.

Holy cow pies, he said, looking over the longest, most churned thread in years.

Is it possible that "placement" is not the precise mathematical operation that some assumptions are trying to make it, and more a case of InDesign using a process or algorithm to make an imported image with no defined boundaries a "useful starting size" instead?

That is, instead of placing an image of which you see a 5% corner, making it nearly impossible to work with until several positioning and scaling steps are executed, is it more likely that ID applies some machine judgement and makes it a roughly page-fitting size the wetware component can then see, grab, resize and place as esthetics guide? And that this placement might seem "erratic" since it doesn't follow simple rules?

@Ian D361303828pe2 

I think I know WHAT the problem is ...

When you do SAVE AS - looks like Photoshop is saving JPEG with a Scale = 50%??

And when you place your file:

If you do SAVE FOR WEB - your JPEG will be saved with Scale =  100% - and after placing in InDesign - no "Scale" at all:

Anyway, first issue (of many) is I want to create a PDF booklet for the web using images that are sized 1024 pixels by 1024 pixels. In Photoshop these have been created at 96ppi.

Hi @Ian D361303828pe2 , An InDesign page has no resolution—it is a vector object. There is a static measurement unit (Pixels), but it has nothing to do with output resolution, and is defined as 1/72". So if you want an image Placed at 100% to match a page set to 1024 x 1024 Pixel Ruler Units, save it from Photoshop at 1024 x 1024 px at 72ppi.

There is absolutely no such thing as resolution on the web; only pixel measurements. InDesign will fake it by assuming your images are 72 ppi no matter what you specify them as.

That said, if you're exporting to PDF, why does it even matter? Make sure the images have enough data to look good and you're done. In short, you are overthinking this.

First, I can't reproduce the discrepancy between pixel sizes in Photoshop and InDesign you describe: for example, a 200x200 pixels Photoshop image is also measured 200x200 in InDesign when InDesign rulers are set to pixels. (Although I think there are also legitimate reasons for the discrepancy you experience, which other users may explain.)

Second, pixels don't have any meaning in the context of PDF (as you're creating a PDF booklet). Acrobat doesn't even have pixel rulers. PDF objects are only measured in physical ("print") dimensions. (Once again, a deeper explanation may be offered by other users.)

How do you save your file in Photoshop - PSD / TIFF / JPG / GIF / PNG ?