What is the best dpi I should use for my images in InDesign for best results

Thank you for all three replies. Really helpful and I'm clear about the dpi issue.

However, I'm still not clear if I should scale images down directly in InDesign to the desired output size or resize them in Photoshop beforhand? I'm asking because lwhen reading some old forum threads a user mentioned Photoshop has better tools than InDesign for resizing images at the higest quality.

I agree with @17352643 .  It is always best to ask the provider directly.  Chances are that 300dpi is standard for a print provider.

From my experience, don't be too critical of the actual number "300dpi",  I've had images that were 50dpi that looked execellent.  I have also been supplied with images at 1200dpi that looked awful.  If the image looks good at 100% final print size (on screen),  it will most likely look the same printed.

However, some on-line "upload and go" print providers don't have actual humans that look at your files, thus no one to make any judgement calls about anything that looks wrong (or right). If you do not follow their strict guidelines, your files get rejected outright, and you are forced to revise and resubmit.

Hi @Augusto24716166az1l , When you place a linked image, the Link Info panel will show you the image’s Actual Resolution and the scaled resolution, which is listed as Effective Resolution—a 300ppi image placed and scaled to 50% will have an Effective Resolution of 600ppi. It is the Effective Resolution (the output resolution that matters).

On a PDF Export you can choose whether to leave the output resolution unchanged or downsample to a specified resolution—see the Compression tab. The needed resolution is image dependant, but as a general rule of thumb 300ppi is adequate for most images output for commercial offset printing.

It will depend on your PDF output settings - images can be downsampled to whatever DPI you require for printing.

DPI is derived for lithograhic printing - a forumla based on the rotation of a halftone - which a square that is 1x1 on all sides will be 1.41 from tip to tip.

In lithogrpahic printing it's output on with an LPI (lines per inch) and this is where the DPI is derived.

The LPI on lithographic output for newspapers can be anywhere from 80-120

For magazine 120-150LPI

And for higher end books about 200LPI

The 1.41 is multiplied by the LPI - for example 150x1.41 = 211.5 DPI for best/minimum DPI.

If your book is printed digitally - digital printing can be a bit more forgiving as it's not really working with halftones - where it do or simulate it is debatable, but the printing process is completely different to lithographic printing involving screen angles and different plates for each colour (CMYK).

It's erroneous to think 1200PPI will print better because it's higher - the output device might resample images to suit it's output.

The only time it's probably advantageous for 1200 or 2400 PPI is when it's Line Art Drawings.

But for digital it might be irrelevant.

Best answer

Ask your print provider.

They'll probably just tell you 300. 

But you don't have to resample all your images to 300.

Place them into InDesign - and check the Links Panel

It will give an effective resoltluion

When outputing the PDF for print you can downsample the images to 300 DPI for print.

Then images that are too big will be resampled.