Hi Vicky
Hard to explain all what went on without a lot more specifics yet that may not be needed.
TIFF files can get larger or smaller on two major factors
a) Was it resized
b) Was the compression setting changed
It was not clear if you were saving form ACR or going from ACR to Photoshop then saving.
There are default or preferences for ACR that might have been changed accidentally (more likely than corrupted)
Those settings allow both automatically changing size as an option as well as choices of TIFF compression
That would be my best bet.
As far as color changes. That is probably a color management issue. It also depends on if you are using the default "Photos" viewer in Windows 10 (which is not color managed) or if you are using the Windows "Photo Viewer" that is an application that came with prior Windows OS.
The most likely guess that I have is that the default preferences for the color space were modified to wide gamut (e.g. Pro Photo RGB) and then the image was viewed on a non-color managed application such as "Photos". Having the image created in a wide color space (which for the same color saturation uses smaller RGB numbers) if viewed in a non-color managed application that just sends the color numbers on to the monitor would come out looking desaturated in most cases.
This desaturated look can also happen in a number of other situations yet the key elements are to
1) Create and view images only with color managed applications
2) Have the color space embedded in the image (default case for Photoshop, ACR, and Lightroom)
3) Use a monitor that has been color calibrated.
4) The color management settings in the OS settings are set properly
Hope this is a starting point for you to solve you problems
John Wheeler
