This post will detail how to most accurately get your 35mm adapter to represent true 35mm focal lengths. i.e. getting the equivalent of an 85mm lens on s 35mm camera body to be the same as using an 85mm lens on your Redrock adapter.
As a DP who transitions back and forth from film to video I found things began to get a little confusing when selecting lenses for use with the Redrock Micro M2 Encore. When using an HD camera with a 35mm adapter, as most of you already know, you have to zoom the camera’s stock zoom lens in on the adapter’s ground glass until the frame is completely filled. Most of us do this by pushing in on the zoom until we see nothing but ground glass, once the ground glass fills the screen we lock the ring down and move on. The problem with this is that on any given camera there is a lot of float room in between when the ground glass fills the screen, on the wider end of the zoom and the long end of the HD camera’s zoom.
This led me to doing what I consider a somewhat accuarte test to find out what millimeter you would need to set the Panasonic HPX-170′s zoom to most accuratley represent real 35mm lenses. The HPX-170′s zoom ranges from 3.9 – 51mm. When the camera is set to 3.9mm you will see a good portion of the internal elements of the adapter, but when it is pushed in to 51mm you see nothing but ground glass. Somewhere in this range a lenses’ given millimeter will be most accuratly represented by where you stop your zoom on the HPX.
I conducted this test by using my old still 35mm Pentax camera with a 50mm prime lens and my Redrock Micro M2 Encore with a 50mm prime lens. I started by taking a 16×9 chart and mounting it on my wall. I then took my Pentax camera on a tripod and framed the 16×9 chart through the viewfinder so that it filled the screen.
*Note – the Pentax K-1000 is a full frame camera, you will need to frame the 16×9 chart from side to side, it will not fill the viewfinder from top to bottom. I am also aware that there may be a small margin of error due to the fact that the viewfinder on the Pentax does not, in video terms, underscan, or for those of you who still speak in film, it is not full frame.*
Once I had the chart framed up I measured the distance from the chart on my wall to the film plane. This distance worked out to a convenient 20″
Once I had the measurement, I swapped out the Pentax camera for my HPX-170 with the Redrock Micro M2 Encore adapter. I again measured 20″ from the film plane of the M2 Encore to the 16×9 chart on my wall.
Once I knew I had the distance right from the film plane to the chart, I began to slowly push in on the HPX’s zoom so that the chart would perfectly fill the entire frame. This took place at almost exactly 28mm on the HPX’s zoom.
In order to further verify my results I took the Pentax camera with the 50mm lens and walked across the room to shoot a wide shot. Once I had framed up a shot I mentally marked off the frame using some pictures I had on the wall. I again swaped out cameras and tested the frame from the same distance. My results once again matched.
My testing leads me to believe that if you are using a Panasoic HPX-170 camera with a Redrock Micro M2 Encore system with a flip, zooming the HPX into 28mm on the camera body will most accuratly represent true 35mm lens lengths. i.e. 50mm lens on a 35mm camera body will equal the same as a 50mm lens used on a Redrock system.