Images look sharp in Photoshop. After saving, the saved image appears slightly blurred in every image viewer I try. The file type doesn't matter. I've tried saving as PNG, TIFF, and Jpeg with the same result - It always appears slightly blurred after saving.
If I open the saved file in photoshop again, it appears sharp. Here's a screenshot of the same image opened in photoshop and irfanview at 100%.
Nopthing to do with sharpness. PS simply brings out more noise and produces a more contrasty image, which indicates that your system does not use color management and/ or you have set it up wrongly, so the results don't match. As a start you should therefore read the respective sections of the online help and check your settings: