I think what's happening is you're placing a JPEG file with a 72 ppi image.
InDesign can not set the resolution of your image. You need to use an image editor like Photoshop to do that. In Photoshop you would do that in Image > Image Size.
It does affect performance because InDesign has to create a huge preview image.
Sounds like you are placing an image by just doing a simple click on the document where ID places the picture at actual size.
Have you tried to click-and-drag a frame first for the graphic to be placed into?
Thank you for the replies!
I know ID isn't intended to be able to edit an image's resolution, but can't it read the value? It's putting 1 dot per inch (not a common resolution). Is there somewhere I can let ID know what resolution placed images are likely to have, like 72dpi, so that it can size them accordingly? I sometimes want to arrange a dozen or more images on a page, so having to use a workaround like creating a prepared frame for each image isn't what I was hoping for (although it is good to know that such a workaround would be effective).
Regarding the effect on performance, shouldn't that issue go away once the image is resized to something smaller? Does ID just hang on to the largest version it's ever made for each image? Also, could this be influencing the size of the final ID file? The ones I make usually come out to 10-20MB, but now I've got one over 50MB, which doesn't seem attributable to normal fluctuations.
Just to make sure what the resolution is, try this: Select the image with the Selection (black arrow) tool. Choose Window > Info to open the Info panel. What does it say the Actual ppi and Effective ppi is?
I know ID isn't intended to be able to edit an image's resolution, but can't it read the value? It's putting 1 dot per inch (not a common resolution). Is there somewhere I can let ID know what resolution placed images are likely to have, like 72dpi, so that it can size them accordingly?
This typically happens with images that are placed straight from the camera without processing first in an image editor. Not all cameras record a resolution value, so ID must make an assumption. If you click and release, ID wants to place the image at 100% size, but that size has not yet been written into the image data, so ID punts. If you click and drag while placing (since CS4) ID will scale the image to the size you drag.
A lot of images are indeed listing an Actual ppi of 1 within ID. However, if I browse to the image location and right-click for the summary, a resolution of 72dpi is listed in the EXIF data. I have other images (taken with other cameras) for which ID correctly reads the dpi values. Still other images have incorrectly-read dpi values, but aren't defaulting to 1 - I'm looking at an image now with 96dpi listed in its summary, but ID reads it as 72. Is there some other location for that information that I should double-check, or a setting I have to tweak somewhere?
I tried clicking and dragging while placing those images that defaulted to 1dpi, but having several of those images on a page still causes drastic slowdown. I can put dozens of "normal"-dpi images on a page, with no noticeable difference in speed.
I've opened a few of these images in Photoshop to see if that could provide some additional information with the File Info command. Some of the problem images ("Actual ppi" of 1 in ID) have a "Resolution" of 72 for both X and Y, but their "Pixel Dimension" is 1 for X and the image's width (not height) in pixels for Y. Other problem images list a Pixel Dimension of their width in pixels for X and their height in pixels for Y. Some images, which somehow have very limited EXIF data, don't return any data whatsoever with File Info, but load fine in ID (although the Actual ppi sometimes changes from what it should be, such as from 96 to 72). Images taken with yet another camera (specifically, my own) can be placed by a single click, without dragging, at 72 Actual ppi (which is what they are) and starting at a useful 288 Effective ppi. Images from an older camera I used to use get placed at 150 Actual ppi (again, as listed in EXIF data), and 150 Effective ppi, which is another good approximation of what size I might use in an ID document. I've noticed that images which "work" in ID have some listing for "Compressed Bits per Pixel" (in Photoshop's File Info), while problem images have no value for that field. The camera I mentioned that creates images which place at 72/288 Actual/Effective has a Compressed Bits per Pixel value of 4.0, which happens to be the ratio between the Actual and Effective when default-placed into ID, although I'm not sure what significance that has, as the older 150dpi images default-place at 150/150 even with a Compressed Bits per Pixel value of 2.4.
What exactly is ID looking for when handling images? I would be more than willing to batch process images in a separate program in order to make them play nice with ID.
As far as I know, ID does not read the EXIF data.
Well, I haven't discovered exactly how this issue arises, but for now I'm just opening each affected picture in Photoshop and saving it as a new jpg, which resolves the issue enough for my purposes of one or two dozen images every month. If I were to need to resave much more than that, I would probably look into making a batch command or something.
If you are using OSX AppleScript has ImageEvents which can be very powerful for resizing and formatting images—much faster than batching in PS. If you want to give a try I can post a script