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From what I understand TIFF is like the .mkv container for photography - it supports a variety of compressed and uncompressed formats.

But how would you go about checking if the data within the TIFF file is indeed uncompressed? I'm worried it could just contain a lossy photo.

TIFF is a container format. Some other formats, such as DNG, are based on TIFF containers.

You can use exiftool to determine whether a TIF file contains compressed data.

usr@hst:/tmp$ exiftool -compression test1.tif 
Compression : Uncompressed
usr@hst:/tmp$ exiftool -compression test2.tif 
Compression : JPEG

If you are using a Linux or Unix-like system (including MacOS), you can use the file command that comes built-in to most Linux/Unix distributions. In a terminal:

scottbb@mbp ~/Downloads $ file CCITT_1.TIF
CCITT_1.TIF: TIFF image data, little-endian, direntries=17, height=2376, bps=1,
compression=bi-level group 4, PhotometricIntepretation=WhiteIsZero,
name=Standard Input, description=converted PBM file, orientation=upper-left, width=1728

The file command is a Swiss Army knife utility that will tell you all sorts of information about almost any file you throw at it.

But how would you go about checking if the TIFF file is indeed uncompressed?

A quick test.

Open your photo, and re-save it as TIF with another name, with no compression. Compare the file weight.

The file size of an uncompressed image will be about the same.

I'm worried it could just be a lossless container for a lossy photo.

It is a very specific case. It is not about compression, as your first inquiry, it is about lossy compression.

Make some additional tests with different compression methods. LZW or ZIP.

If the file size is a lot smaller than those, it was probably saved using JPG compression, therefore lossy.

But the one and only exact test you can make is taking the original photo, overlay it using "difference" as blending mode, flatten it, and see the histogram. https://otake.com.mx/Apuntes/Imagen/PruebasDeCompresion/1-CompresionJpgProceso.phtm

But take into account that there is a big chance, the original photo was saved as JPG from start.

And yes, TIF format is very specific. I would not recommend it for normal photographers. I only would recommend it for specific cases:

1. When you need a 16 bits per channel image and you can not send a PSD file.




2. When you are saving a CMYK image, you do not want to use JPG and cannot send a PSD file.




3. Some weird file, like a multi-channel file, CMYK and transparency, etc... and you can not send a PSD file.

And that is probably it.