Depth-of-Field

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Noel Sterrett

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Depth-of-Field

PostMon Aug 27, 2012 6:08 pm

When HD 24P was first introduced in the form of an ENG broadcast camera (e.g. Sony HDW-900), one of its main drawbacks (as compared to film) was that the 2/3" sensor size made it difficult to achieve the shallow depth-of-field which was and still is used extensively (and occasionally overused) in feature films.

In response, Zeiss and others produced fast lenses designed specifically to address that deficiency (e.g., Digiprimes http://www.zeiss.com/c125756900453232/C ... 6f0044961f).

Even so, the problem remained. As an example, a 7mm Zeiss Digiprime at T1.6 provides roughly the same depth-of-field and angle-of-view as a 24mm would in a Full Frame camera at T5.6!

When the next generation of cameras arrived with larger sensors (Super 35), a large selection of traditional film (and DSLR) lenses could be used to provide the "filmic" look, and the need for specialized lenses waned. In fact, the recent success of the Canon 5D and other DSLR's was due in large part to their large sensor size, and, fortunately, ample supply of new and used fast high quality lenses.

Now, history repeats, and with the BMCC we're in a similar fix, if not quite as bad, as was the case in those early digital days.

The BMCC sensor size lies between 2/3" and Super 35. It is too large for 2/3" or most Super 16 lenses to cover. The Tokina 11-16mm f2.8 seems an obvious match. It is approximately equivalent to a 24-35mm on a full frame camera (still not that wide). However, to achieve roughly the same shallow depth-of-field as the Tokina wide open at f2.8, the 24-35mm would need to be stopped down to around f6.7. So the Tokina won't really fit the bill.

Hopefully, Zeiss or other lens makers can re-purpose some of their existing lenses, or make lenses targeted for the BMCC. A Digiprime T1.6 would certainly help (~f2.8 in Full Frame).

Barring that, wide angle and shallow depth-of-field shots will be difficult with the BMCC. Wide angles are particularly important for low-budget independent features which rely heavily on existing (often cramped) locations, and low-budget features would seem to be a good fit for the camera.

No doubt, there are a number of features I would like to see added to the camera. But this is a case where there really is no competition. First and foremost, I am hopeful that the next version of the camera will sport a larger sensor and different mount (I have never felt the Canon mount is the best choice for cinema).

In the mean time, I would simply encourage Blackmagic (if they haven't already done so) to put someone on a plane with a box of chocolates, and visit a few lens makers.

Please note, this is not a criticism of the camera. I've been on the BMCC preorder list since NAB, and hope to be opening the box soon. It is truly a groundbreaking camera, and I understand the enormous challenge and difficulty of producing any camera, much less one at this price point with great dynamic range and 12 bit open format RAW uncompressed recording. And in the package is a full copy of Resolve!

If I'm dreaming, don't wake me up.

Great company, historic camera.

Cheers.
Admit One Pictures
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rick.lang

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Re: Depth-of-Field

PostTue Aug 28, 2012 4:42 am

Warning: tongue-in-cheek rant to follow...

Let's see if my memory serves me well. A company with a lot of experience with electronic devices that knew nothing about phones built a revolutionary product which had many shortcomings and that some predicted would amount to 1% of the market. I think it's called the iPhone.

Now another company that knows a lot about live and post production but knows nothing about camera bodies is about to release a revolutionary product that some find sorely lacking for one reason or another. How can a camera body without a lens succeed? It has major shortcomings in spite of it's brilliance.

You have an interesting suggestion for BMD to visit lens makers presumably to define the best set of quality reasonable-cost cinema lenses with fast apertures, external geared rings for long-throw smooth focus and external stepless aperture, no breathing, no change in length of the lens when zooming, no change in aperture over the zoom range, shallow depth of field (some want deep DOF), and so on.

Not a problem. The world is full of options to satisfy these needs at different price points; so many options your head is spinning but few seem just right for the unique BMCC. But I'm beginning to think some company that knows nothing about cinema lenses may just do it. Just not quite yet.

You know I never missed a shot on my early 60s Nikon where everything was manual and I usually didn't even use my exposure meter once I knew what the camera and the film could do. And I shot raw in the sense that many pictures were rescued in the dark room, dodging, burning, rubbing in the developer. I'm trying to say, it will work.

You'll find what the BMCC and Resolve can do and it will be great in your hands. You know the tune, "Don't worry, be happy."
Rick Lang
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Nick Bedford

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Re: Depth-of-Field

PostTue Aug 28, 2012 5:59 am

Spend less time worrying about the depth of field (which is relatively decent despite the misconception that it's going to be troublesomely deep) and more time worrying about your exposure and lighting (and set production and actors and script yadi-yada...).
Nick Bedford, Photographer
http://www.nickbedford.com/
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Noel Sterrett

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Re: Depth-of-Field

PostTue Aug 28, 2012 11:53 am

rick.lang wrote:But I'm beginning to think some company that knows nothing about cinema lenses may just do it. Just not quite yet.


My first stop would be Samyang (Rokinon). Same neck of the woods as BM. I just tried a Rokinon 35mm T1.5 Cine and it's quite impressive full frame (http://www.bhphotovideo.com/c/product/8 ... _Lens.html). Unfortunately, their 8mm Cine is a fisheye. I'm on the list for their 14mm Cine when it's available, but that's still not quite wide enough for small spaces. I use a 17mm often, and that's only around 7.5mm on the BMCC.

Ultra wide-angle lenses for a Canon mount present a difficult problem for a lens maker. They could make a lens better/faster/wider/cheaper if it only need cover the BMCC and not APS-C. But unless it was clearly marketed as a "Blackmagic Lens" lens, much vignetting would likely follow.

I spent a decade trying to minimize this issue for director's and DP's. The Digiprimes helped, but it never went away. I doubt that's changed.

Cheers.
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rick.lang

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Re: Depth-of-Field

PostTue Aug 28, 2012 1:02 pm

Noel, I do agree with your post and if I was buying lenses today, I'd buy into the Samyang primes as they are or become available. Obviously not the highest quality but seems to be good value for those on a budget. Nick reminds us that it isn't all about the technology all of the time. Nice to find the very best tools but some of these options are so close, I can't help think that great stories told well will trump everything given the basic quality inherent in using the BMCC.
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Noel Sterrett

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Re: Depth-of-Field

PostTue Aug 28, 2012 1:51 pm

rick.lang wrote:Nice to find the very best tools but some of these options are so close, I can't help think that great stories told well will trump everything given the basic quality inherent in using the BMCC.


I agree Rick. Great stories told well have always trumped everything and always will. But here, we're talking about a particular tool to help do that.

All too often, I've wanted to bust down a wall when I'm backed into a corner because my widest lens is too long.

If you haven't had one in your hand yet, I think you'll be surprised by how high quality the Rokinon's look and feel. I just hope they decide to go wider than 14mm with the new Cine series. Maybe this camera will push them in that direction.

Cheers.
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rick.lang

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Re: Depth-of-Field

PostTue Aug 28, 2012 4:48 pm

Noel Sterrett wrote:All too often, I've wanted to bust down a wall when I'm backed into a corner because my widest lens is too long.

If you haven't had one in your hand yet, I think you'll be surprised by how high quality the Rokinon's look and feel. I just hope they decide to go wider than 14mm with the new Cine series. Maybe this camera will push them in that direction.


Thanks for treating my rant in the way it was intended. I know there are too many walls you'd live to tear down literally and figuratively! I've never had a real 'cinema' lens and my research related to the BMCC has led me to the conclusion that they are the way to go as they approach the characteristics I described in my previous rant. But I am leaning towards a few Samyang (aka Rokinon) primes rather than using a couple of zooms just to get consistent quality and performance characteristics. I think the 35mm, 50mm, and 85mm are available now and the wider lenses hopefully next year (I'm not able to buy anything related to the BMCC this year so waiting isn't so bad; next year I hope to jump start the economy!). I'll likely buy the 35mm first (just cannot stray too far from my love of portraiture and best lens for single person shots?) and use the experience to know if I should go wider or longer for the next lens, etc. Unless there's a 2-for-1 sale, I won't buy the entire family at one time.
Rick Lang

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