I have begun to produce video projects with my DSLRs and have learned that one way to achieve more of a film look is to record at 1/40th of a second when shooting 24 frames per second. The other recommendation was to shoot at f4 on a full frame sensor camera. There is NO way to shoot outside in Hawaii at those settings without a full range of Neutral Density filters, so I picked up 2 sets of 1, 2, and 3 stop (2, 4, and 8) NDs. I decided to use the filters on a still shootto rediscover what the bokeh buzz was all about.
I wrote about my "new" Canon/Bronica camera/lens system a few months ago. The maximum f stop on my Bronica 110 lens is f4. I know that the Bronica lens on a Bronica camera would yield a more shallow depth of field at a given f-stop than the same setting on 35mm system. My combination raised an interesting question: what effect on depth of field does a medium format lens have when used on a full frame (35mm) sensor?
Bob Atkins posted an addendum to the article I cited in my first "lens" article (http://www.bobatkins.com/photography/technical/digitaldof.html). Here he talks about using DOF preview dials that are on many prime lenses. Dr. Atkins said something that finally (sort of) made sense to me: "The circle of confusion value for the Canon APS-C crop sensor camera is reduced by a factor of 1.6x and what this means in terms of DOF scales is that you need to use the markings for about 1 1/3 stops wider aperture in order to estimate the DOF. So with the lens set to f16, we need to look at the DOF scale markings about 1/2 way between f8 and f11..." It sounds like I can expect a DOF range at about an f 2.8 level when shooting my "system" at f4. That "sort of" makes sense to me with my system because the actual lens that I am using is larger (with a different focal length to actual aperture ratio) than on a lens designed for 35mm, FF and crop frame sensor. I haven't quite got my head wrapped around the rationale when comparing a lens that was designed for the two smaller formats discussed. I'd love to hear someone's take on this issue. Shoot me an email with your thoughts.
There were some practical issues involved in creating these images. We chose the wooded area of the beach so that there would be a distinct background to judge the effect of shooting shallow. The sun dappling through the trees read f 5.6 5/10ths. This would theoretically be perfect with a one stop ND filter because the lens adaptor eats 1/3 of a stop. The first test shots were pretty bad at ISO 100. The backdrop went black. I changed the ISO to 400 and adjusted the strobe accordingly to get the overall exposure back to about f 5.6 and 1/2. We had to play with the distance between the strobe and Angellyn to get the ratios between ambient and strobe lights. Now it was time to shoot.
The major downfall of my camera/lens system is the lack of an auto focus feature. Let me tell you, manual focus is tough enough on my almost 50 year old eyes never mind shooting at f4 with an ND filter. I had to use the live view preview (magnified) and a Hoodman Loupe to focus. Angellyn was very patient as I went through the focusing process with each change of distance.
I was actually surprised at how much the trees behind Angellyn maintained decent focus for the full length images, especially if the assumption made above holds true. The DOF of course decreased as I moved the camera closer to our model. The trees become almost non-descript at a waist level shot and are just a green blur for the headshot.
Overall I found this to be an interesting experiment, but I still like f8 to f11--or maybe it is f11 to f16 now! Mahalos to our lovely model Angellyn and her mom! They were great to work with! Special thanks to Steve for all the help and for guiding us out of the trees in the dark!
© Steve Dantzig
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