Weird thing : all my .TIFF have the same weight

[TomaD]

Hi.

When I save as .tiff from Photoshop (no layers, flatten image), all my tiff files (with the same size) have the same weight.... even if the image is all white.

Does anyone have an explanation for this strange phenomenon?

Mac OSX 10.14/ Photoshop 20.0.6

[D Fosse · Accepted solution]

If they are all the same pixel dimensions, and uncompressed, then yes, they will all be the same size on disk.

Uncompressed TIFF records the values of each and every pixel regardless of what those values are.

Compression takes the pixel values into consideration, and attempts to find patterns and redundant information, and in the case of lossy compression, remove less critical data. So here you will see variation in file sizes on disk.

[TomaD]

Ah OK. . So, it's normal...

Thanks for the quick answer.

[Per Berntsen]

When saving without compression, they will be the same file size if they have the same pixel dimensions.

If you use compression, the file size will be more varied, the degree of compression depends on subject matter, focus/blur, sharpening and noise.

Assuming that these are 8-bit files, the all white image should only be a few hundred kilobytes, if saved with LZW compression.

LZW is best for 8-bit files, ZIP is best for 16-bit files.