Placed image scaling problem

Question

Hello,
just need one advice from the gurus out here.
i have placed few images in adobe indesign , now after placing image in indesign if i scale the image to 102 or 103 or 105% will it effect printing quality in offset printing ??? i mean i am increasing the size by 1% or 2% or 4% will it effect printing ? becuase scaling in photoshop is going to take lot of time because i have 1500 different products and all have different scaling issue so i thought of scaling bit more in indesign itself, please advice.
regds
Chako

Answer 1

If you know what line screen you're printers is using then you can calculate your minimum PPI.
The general rule has been to multiply the LPI x 2 = ppi | Which a lot of people take to assume that the LPI will be 150 in most cases, and that's where the 300 ppi for images originates.
But in truth different mediums would use different line screens, like newspapers, magazines, high-end art books etc. And the x 2 rule is a safe play, but it really should be 1.41 (or 1.5 to keep  it simple).
Newspapers generally at 85 - 105 lpi
127.5ppi to 157.5 ppi
Magazines generally around 133 - 150 lpi (some high end magazines may even use 175lpi)
199.5 ppi to  225 ppi
Art books - high end printing etc around 175 - 200 lpi.
262.5 - 300 ppi
But as a rule of thumb it's best to keep your print images at 300 ppi for printing - but you can go lower, check with your printers as to what they recommend if you really need an image to go below 300 ppi for printing.
But the next time your printer tells you that your images are 250ppi and not good enough for printing you tell him that his halftone cells are rotated 45 degrees and that a2 + b2 = c2