5k retina iMac - photoshop

Hi,

I have a problem with my 5k screen and photoshop. I saw this question on many websites but no solutions regarding the imac. I'm using photoshop a lot to create images that I use on websites. So it's important that I work at a 100% resolution. With my new i-mac these 100% 72dpi images appear much smaller in photoshop. If I zoom in to 200% the image is what it used to be before my new screen. Below the resolution my screen uses right now.

This is a screenshot from photoshop.

Want I want is that photoshop shows the images like it did before. So that the images in my webbrower are the same size on screen as in photoshop. Because I cannot work in this tiny version.

Hope that there is someone who can help me solve this problem. tnx