InDesign two-page full bleed image: Scaling in InDesign or changing the dpi
Im working on a 13×11 inch Blurb book with a lot of images. I shot the pictures with my Canon 60D in raw format, edited them in Lightroom, and color proofed in Photoshop. The dimensions of the images are 5184×3456 pixels and I save them as 300 dpi .psd files. I use InDesign to create the book.
Now I want an image to fill the entire two-page bleed. This gives an image width of 25.25 inches (there is no problem with the height of the image as it is cropped at the top and bottom). With a printing quality of 300 dpi this width requires 7575 pixels, while 200 dpi requires 5050 pixels (which is ~ the dimension of the images).
I have two questions. First, is there a difference in the print quality between:
A. Using a 300 dpi image and scale it to ~150 percent in InDesign. (This gives what InDesign calls an "effective ppi" of ~200).
B. Reducing the image to 200 dpi and keep the scale at 100 percent in InDesign. (This of course gives the same "effective ppi").
I guess that there is no difference as it is the total amount of pixels that must matter (however, I’m not sure how InDesign does the scaling), but couldn’t find much on this on the forum.
Second, is the quality of my image good enough for a two-page full bleed?
Any comments or alternative solutions are much appreciated.
The two questions posed do indeed give you the same answer and InDesign will treat the image in the same way. Blurb suggest for best results that images be kept at 300ppi but that you can go as low as 150. Your images at 200ppi will therefore still be pretty good quality over the two page spread. Hope that helps.
Thanks for your reply!
as described, there is no difference between your two methods.
Once you have placed the images in your InDesign layout, you open every single image in Photoshop and change its size to the dimension the image will have in the final album and set it to the resolution of the output device (like 300 DPI for Blurb).
If your image will be smaler afterwards, then use Bicubic sharper as a resample method.
If your image will be enlarged, then Bicubic smooth is a good way to resample (except for images with really sharp edges like architecture).