I only suggest that I have used auto adjustments for color and levels as these adjustments would be independent of anything my monitor is displaying. In fact using those auto levels doesn't change the levels in any substantial way. Surely if I use auto levels and the image looks great on my monitor, and my prints are still dark, there is something else amiss.
I do take your point that .jpg isn't the best for editing and I will try another file type, but I still don't understand how these changes would affect my printer's output insofar as printing too dark.
But I will perform some more experiments.
Thanks
'I only suggest that I have used auto adjustments for color and levels as these adjustments would be independent of anything my monitor is displaying.'
The auto adjustments may give a spread of values from dark to light and avoid you compressing everything at the dark , or light, end of the scale. But if you expect your print to match what you see on your monitor then, as D Fosse and Per Bernsten have already said, if your monitor is set up so that the white is too bright then your prints are always going to look darker in comparison even if the image values are well adjusted.
There are a few steps along the way to that match.
1. Your monitor, ideally it should be calibrated and profiled with a hardware device. But whether that is the case or not, as stated in the earlier posts, the white should be close in brightness to a sheet of your printer paper under normal viewing lighting. At first you may feel that your monitor looks too dim when you do this. But your eyes will quickly adjust to that and it is well worth it to ensure that your prints become predictable.
2. The document should have a colour profile which it sounds like yours does. That does not have to match the Photoshop default which is just there for when you start a new empty document with File - New.
3. When printing you should use the printer profile that matches the Printer, Ink and Media used when the profile is made. So that means, in Photoshop's print dialogue, set 'Photoshop manages colours' and choose the appropriate printer profile for your printer and paper. In the Epson printer driver (accessed through Photoshop's 'printer settings' ) ensure the correct media is chosen and ensure Colour Management is set to 'Off' in that Epson driver - that is important as you do not want to have the colours adjusted twice).
Dave