Can not connect

[Scott Leland]

I have a Nikon D7100. I can not connect to the Nikon Webcam utility. The camera is to old. I read that I should get a video capture card. I then can connect to OBS

 

[Lawrence_SoCal]

Assuming that was meant as a question:
A quick Google search shows a number of YouTube videos and articles regarding Nikon D7100 having the important feature of clean HDMI out.
So, yes, a common approach to turn a DSLR camera into a webcam is to use a HDMI capture device (which depends on your computer in terms of PCIe add-in card (AIC) vs a USB3 connected external dongle/adapter. Decent resolution, without fighting things, requires USB3 (not USB2.0) speeds.