I read a lot of tutorials, I thought I understood then make a very simple experiment and I'm am lost... Please help me understand this.

Facts:

1. First I owned a point and shoot Minolta Z1 with 10x optical zoom. On the lens is written "38 - 380 mm (Equiv.135)".

2. After a few years bought a DSLR Nikon D90 with Nikkor 18-105 mm lens kit.

3. Taking some wildlife pictures in the delta of Danube river, I observed that the maximum magnification of Minolta Z1 was bigger than the maximum magnification of D90 w Nikkor 18-105 mm.

The first questions for me was how big the magnification of D90 w. Nikkor 18-105 is (eventually compared with Minolta Z1)? So I red a lot of tutorials including the "Understanding Camera Lenses" which I found it to be a great tutorial for me. A big THANK YOU to the author/s.

Let's make some small calculation:

Crop factor for D90 is 1.5

35 mm equivalent for Nikkor 18-105 = 1.5 * 18...105 and the result is 27-157.5 mm

A "normal" focal lenght is 50 mm so the maximum magnification should be 157.5/50 = 3.15 x

The theory was great, now let's make some practical tests. According to theory a 50 mm (35 mm equiv) should give me a "normal" view. For this case 50 mm (35 mm equiv) means 50/1.5 = 33 mm. I set my lens to 33 mm, look into the wievfinder then compare the image in the viewfinder with the naked eye image...

The objects in the wievfinder are smaller and the distances looks longer then the naked eye view. Trying to find a match betwwen naked eye and the viewfinder i found out that i should set my lens somewere to 60 mm, not 33 as expected.

NOW I'M LOST.

Can anybody please explain me what I am doing wrong, or what is the explanation for this?

Why the perspective of the viewfinder looks different that the naked eye perspective on the calculated focal length of 33 mm (equivalent 50 mm for classic film)?