How do I save an image in Tiff format within size range of 10mb to 25mb?

Question

I've an image and after editing it in Photoshop, I have to save it in Tiff format, with the size ranging from 10mb to 25mb.

I have to keep the dimensions as 305mm X 203mm at 300dpi.

When I don't use any compression, it goes over the size range.

When I use the highest compression, it is lower than the minimum size.

Is there anyway I can save a tiff file, 305mm X 203mm, at 300dpi and in that size range?

Answer 1

Setting a minimum filesize whilst fixing the image width and height is silly. If you don't use compression then the filesize is determined by the image dimensions. And if you do use compression then the filesize is determined by the level of entropy (disorder) in the image.

Some images have higher entropy because there is more going on, more detail etc. in the image. Some images have very low entropy because there are large areas with little detail, such as skies, or plain backgrounds. So it makes no sense to impose a minimum filesize because it depends on what sort of image yon have!

But if some deranged person was holding a gun to your head insisting that you make your 305mm X 203mm 300dpi image at least 10 megabytes then you could use lossless compression and add an increasing level of noise until you hit the desired filesize (noise is by definition uncompressable with lossless schemes such as LZW). If you're over 25MB then you can in a similar fashion reduce the filesize by repeatedly applying a blur with a small radius.

Personally I think this lower limit must be some sort of mistake as altering your image in this way to increase the size doesn't really do anything to improve image quality (unless you have posterization, but that's another story!)

Answer 2

Use JPEG compression and adjust the slider. Start from 100% going backwards until you go bellow max file size.

Answer 3

Smooth areas of color or darkness compress very well. Since your problem here is compression working too well, adding more detail is the trick you need.

Use a filter to add a little noise or a "grain" special effect, either all across the image or in non-critical areas. This will reduce the efficacy of either LZW or Zip compression, which should get you over the 10mb minimum.

I do think you should double-check this requirement, as it seems very strange.