How to make my own 4x5 zoom viewfinder?

[l2oBiN]

The title has poses the question.

[Joanna Carter]

This has been discussed many times before. Take a 5" x 4" piece of card, cut a hole 2.5" x 2" and hold it in front of your eye with a piece of string, knotted at half the focal length of your lenses, to measure the distance from your eye to the card.

It's cheap and effective.