Problem with Camera settings ie. Focal Length and Aperture

felsenstern_9e51865eb7

Ok, lets start with Focal Length.

I've been trying to combine a DAZ render without background with a background 'rendered' in Unreal Engine 4. For that and to get a feeling for setting up identical cameras I've placed a Genesis 8 Figure on a Plane and a camera in 5m distance and a height of 85cm with a Frame Width of 36mm (35mm Still Photocam) and a Focal Length of 50mm. I did the same in UE4 but the results were frustratingly different. Then I started a 3rd try in Cinema 4d and came up with even a different result.

Now I wondered if someone had a similar problem and probably know what I'm doing wrong. In the end all 3 Softwares are used for real world problems and in productions so I can't believe that they are simply just delivering wrong results.

 

and now about the Aperture.

When I do DOF pictures until now I was setting up DOF by placing a kind of ruler below the object where I want the DOF. Calculate the DOF size with an Aperture / DOF Calculator and setup the right DOF with the top view in DAZ. As soon as the Camera is set up I add the necessary angles and positions and have the hopefully realworld DOF for my 1:2.8 or 1:4 aperture lens. The thing is now, is there a way to convert the Aperture to the Daz F-Stop value without going through this tedious process of measuring out the DOF in topview?

 

And yes, this has been asked already and answered, but I used search all over and couldn't find anything that really helped me. So please if you know where this was answered already please provide me with a link than just the simple answer to use the search function, because I did that already.

Thanks in advance and happy rendering.