Emmulating 35mm FOV with Letus Mini

I will continue the manual controls topic soon. In the meantime, I am going to go in a different direction. I spend my research and review time split between the philosophical micro-budget sphere and the technical geeky side of production. Over the last few days I have spent some time studying up on field of view—first prompted by Stu Maschwitz's tweet about Abel Cine's field of view "comparator", then reviewing a couple of Barry Green/DVXUser/DVInfo comments about the 35mm adapter field of view. Something that had not dawned on me is the angle/field of view difference between Super35 film and the full 35mm frame. Shape alone should have made it obvious, but it never dawned on me, mostly because I was focused on depth of field. But after review—and testing—it is true that the field of view is different and that my Letus Mini can be "calibrated" to either. I decided to test out my gear and write up the results. The following will be quick and dirty (again) because I discovered some cropping issues after I shot some test images. Also, I did not light for this, using only available indoor light and did not post on the images.

Calibration and Error

First, I set my up my camera and adapter by using Barry Green's math for a 35mm movie frame: at 2 feet with a 50mm lens, you should have a horizontal field of view of approximately 10.5 inches. I used a piece of paper with a mark drawn 10.5 inches from one edge, then lined this up in my viewfinder. Unfortunately, the still I took was wider:

Good to know that the viewfinder is cropped. At first I was disappointed, but if this frame is in anyway consistent with the HDV frame, I can deduce that the viewfinder by 10%, and should be able to reproduce and correct this test in the future by drawing my mark 9.5 inches from the edge instead. So, even though this test is not perfect, at least it provides a rough baseline. Keep this in mind as you review the rest of the images. I know I will keep in mind when i compose my images in the future (and when prioritizing an external HD monitor for my rig.)

Emulated Super35 Frame

This handsome fellow is me being disgruntled about being the subject of the most uninteresting image of all time. Next time I may put some thought into composition, lighting, etc. This time I just locked the camera, chair and focus at 5 feet. I did this for two reasons: to create a lazy but repeatable setup (I didn't have to move my tripod, just pan from the calibration wall 2' away from the focal plane and my happy subject 5' away) and because I wanted to test my lens focus barrel settings—I adjusted the back-focus on my FD mount a couple weeks back; it was obviously better, but I wanted a more accurate test. More on that in a later post.

You can see here that I have a decent medium shot with my normal lens. White balance is set to incandescent for my living room ceiling lights; the daylight coming through the shades is very blue. Also, hello vignetting. More on that later too.

Emulating "Full-frame" 35mm Framing

Next I used some online calculators to setup my full-frame calibration (no image.) The result:
Lo, it is wider! Yeah, this should be expected. Also, hello worse vignetting. Again, not surprising. Finally:

Frame While Attempting to Mitigate Vignetting

Here I zoomed all the way in on the adapter trying to frame out the vignetting:

Well, less, vignetting—note that it is not NO vignetting. Also, notice how the subject is more disgruntled as he is now in a closeup that emphasizes the uninterestingness and poor lighting of this composition—or perhaps due to the extreme deviation from the wonderful normal feel of the "real" normal framings.

Bonus: No Adapter 50mm Approximation

Here I removed the adapter and guesstimated the full-frame equivalent of a 50mm normal lens:

Not bad for mental math + eyeballing the zoom readout, though not great either. It is certainly wider. However, look at that infinite depth of field! Damn 1/3 inch sensor! And I still had the focus locked at about 3 inches for the adapter's ground glass! Gasp you should! This is of course, the real reason I opted for the adapter in the first place: Bokeh.

In this case the vignetting is caused by leaving the adapter's threaded attachment on the camera; this is the inside of the attachment's barrel. Also, please note HOW MUCH BRIGHTER this shot is than the others. I have avoided this subject on purpose, but it is obvious how bad this rig is in low-light. Not all the blame falls to my f/1.8 lens and half-stop eating Letus: this camera is not good in low-light, and my apartment is dark as hell. This further emphasizes the need to consider lighting when shooting. That brings me to:

VIGNETTING!!!

Some people—Philip Bloom, I am looking at you—love vignetting. I will admit, it can be nice. However, I will let you in on a secret: the best vignetting is added in post, and then, only when it feels right. I am already wondering if I can create a post workflow for brightening my corners with gradient masks. On the other hand, I am not freaking out at the moment. I have only really shot in awfully dark conditions, which makes the vignetting worse, I think. And I did nothing to help with the exposure, in fact, the opposite, since I was taking stills using the video settings. Hopefully I can actually test this outdoors again soon and see if I can minimize the vignetting with bright lighting. Actually, I kind of already did this:

Mike is Cinematic from Mitch McLachlan on Vimeo.

However, this was my very first try with this rig, so I have no idea how far I zoomed into the ground glass, but I would like to think it was close to the Super35 frame, likely zoomed in a little further to fight the vignetting. But, I also used two lenses that are a full 2 stops slower than today's test lens. Either way, that isn't nearly as bad as saw in my tests.

Wrap Up

You may be wondering why I care about this at all. To be honest, I had never even considered this until very recently—I opted for this setup for 35mm bokeh and nothing else. But I think that Barry Green (and Stu Maschwitz) have a point. Taking advantage of the traditional Hollywood frame further enhances the production value of the shot. If a cine 50mm lens equates to a still 50mm lens on my rig, then I am really happy. I may be cropping my still lens a bit—making my 50mm lens a still 72.5mm equivalent, my 28mm a 40mm equivalent and my 135mm a 200mm equivalent—but that is okay if I am able to get one step closer to the big budget feel.

For now I will opt for emulating Barry's Super35 frame while keeping a close eye on the vignetting. But This has inspired me and I will be doing some more testing and shooting soon.