Another Newbie Question on Lens

[BOSS65]

I have a RM3 with frame lines for 40/50/75/90. Here is my question - if I purchase as 35mm lens, and don’t buy a viewfinder, do I estimate my viewing area? For example set the camera a 40mm and estimate that I have about 12% less viewing area? I already own a 50mm lens, and doubt that a 40mm would offer that much of a difference. Thanks for the future help.

 

[rover]

Plug in the 35 and just estimate that the entire field of the viewfinder plus some is the view of the lens. Careful composition at the edges of the images will be difficult as you will not be able to see that in the viewfinder, but you should be able to get used to that if that reality is ok with you.