PrintCalc app

[NoBob]

Hi,

Anyone use the PrintCalc app on the iPhone?

Just wondering what I'm missing, because if I input the desired resolution, say 300 ppi, and then the desired print dimensions (cms or inches) it gives me the correct dimension in pixels (same as in Photoshop), but the size of the file in megapixels doesn't correspond to what you get if you save a photo with those dimensions as an 8-bit TIFF or JPEG.

For example

If required print resolution is 300 ppi and if required print size is 29 cms x 21 cms (approx A4)

then the required image size is 3425 x 2480 pixels (aspect ratio of 1.38)

According to PrintCalc, the file size will be 8.50 megapixels.

[NoBob]

Mmmm, 8.5 megapixels is just the result of multiplying 3425 by 2480. Doesn't tell you how big the file is. The TIFF (8-bit) is around 25 MB. JPEG (saved at setting 10) about 4 MB.

[Henry Ambrose]

That you depend on an iPhone App to do this tells me that you might not understand what's happening behind the scenes. The math is simple. If you understand the background the whole issue becomes clear.

Do a search here at LFF on the subject of file size and resolution. This has been discussed many, many times.

Here is a trust worthy authority for info on this subject:
http://www.digitaldog.net/tips/

In your case, especially the file titled "Resolution"

[NoBob]

Thanks Henry.