I have a bit of an issue that I was wondering someone might have the answer to.

I'm working with some images, that are 24mm x 17mm (they're really small 35mm slides) at 3600dpi. I need these to be this is exact size.

However, when I come to place the image into InDesign, my image is then 24mm x 16.994mm. Normally, i'm not that fussy about this kind of thing, but the client wants the to be the exact size, as he wants them to be truly represented in the publication. Can anyone help me fix this horrible 3 decimal place thing?


I believe this is the best you can do. It is an expected rounded error coming from converting from mm to inch:

(17 mm * 3600 pixels/inch) / 25.4 inch/mm ≈ 2409.4488 pixels

Since we can only have whole pixels, the number is rounded down to 2409 pixels. This doesn't give us exactly the 17 mm we wanted:

(2409 pixels / 3600 pixels/inch) * 25.4 mm/inch ≈ 16,997 mm

But, there is nothing we can do about it. If we make the image 1 pixel taller we get:

(2410 pixels / 3600 pixels/inch) * 25.4 mm/inch ≈ 17,004 mm

Which is 0.001 mm less precise.

The conclusion is that at the chosen resolution it isn't possible to make an image exactly 17 mm tall. It is a bit annoying, but you shouldn't worry too much. It will not be possible for the customer to see or measure an inaccuracy of 0.003 mm.

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