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I have a tiff with a pixel/cell size of (x,y) 0.6,0.6 (it's a satellite image at 0.6m resolution).

When I save this in photoshop, the pixel/cell size changes?

Initial Cell size (x,y) = (0.6, 0.6)

After saving in photoshop (x,y) = (0.013888889, 0.013888889)

I've tried simply opening the file and saving it (save as -> tiff) without making any colour-balance edits and the results are the same.

Note: the column/rows of pixels, the pixel depth and number of bands all seem remain the same...its simply the pixel/cellsize that changes after saving as a tiff.

How can I open a tiff in photoshop and maintain the cell size when saving a copy?

  • Sure if the tif has correct metadata to begin with (which it does not). But may be easier just to re insert it – joojaa Jun 4 '18 at 18:53
  • Sorry, I don't quite understand. Why does it not have the correct metadata to begin with and how would one add this initially or reinsert as you say. – user3200293 Jun 4 '18 at 18:57
  • If photoshop does not detect the resolution in your image it will just assume you have 72 pixels per inch reflecting in your value. Photoshop an not know this data unless your source wrote it into the tiff file. But yuo can just instruct Photoshop to reinsert this value. – joojaa Jun 4 '18 at 18:59
  • If this is the case, why does the original tiff open in mapping programmes with a correct cell size of 0.6, but the copy saved via PS does not? There must be someway of PS maintaining this cell-size information as it's obviously within the original file. – user3200293 Jun 4 '18 at 19:06
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    TIF has lots of custom support areas so just because cartography applications have standardized one info filed does not mean Photoshop uses that data. There is infinite potential for adding industry specific stuff in a TIFF dont expect these to be generally understood across all software. Hell even my tiff files have custom handling data that can only be read by my own code. Just tell photoshop what your resolution is in Image -> Image Size... Photoshop is meant for print it can not define pixels to be meters wide. – joojaa Jun 4 '18 at 19:15
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A TIFF is not a simple image format, but rather a tagging system for a many different image like formats. Tiff stands for Tagged Image File Format, and is a bit like a binary version of a markup language like HTML. And just like HTML it can contain just about anything. It is perfectly possible to embed all sorts of things in TIFF images, some of which Photoshop does not support. The file is still a TIFF file, but which Photoshop can not read some or all of it.*

Now even if Photoshop can read the image data part, theres no guarantee it understands the other metadata included in the file. Or it might be able to but doe not have the capability to set the values in the range you need. Photoshop is a print preparation device after all, so it does not have a need for pixels the size of cars, which is perfectly valid for cartographers. So the pixel pitch in Photoshop is limited to 1 inch - 1/300 000:th of an inch.

In any event when Photoshop does not understand or find resolution info it will revert to 72 pixels per inch or 1/72:th of an inch which conveniently is ~0.013888889. So that adds up. The value can simply not be as large as you would want it to be in Photoshop.

This is a rather arbitrary limitation, but its built into the software not much you can do about that. So no you can not do this, but since you might not care about the unit then you may scale the data so that 1 inch = 1 meter or 10 meters, just go to Image -> Image Size... and set resoultion to be something more suitable. Just remember the resolution field is the inverse of the pixel pitch.

* So making a file a TIFF is not really a guarantee that it opens in a editor that supports TIFF files because theres always that one TIFF format it won't support.

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    The sheer fact that Photoshop doesn't support multi-page tiffs is a clear indicator that Adobe purposefully ignores some possible features supported for some formats. – Scott Jun 4 '18 at 19:51
  • @Scott I havent seen any program that supports all features of TIFF. It may not be practical. A bit like nothing supports all features of SVG. But yes photoshop is not really a paragon of standards compilance, there is lots of features in PNG standard it does not support. In general assuming any format to work magically so that all features and info is preserved in any application is a bit naive. – joojaa Jun 5 '18 at 4:29

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