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Digital Sensors = Anamorphic Redundant?


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#1 Ben J. Abbey

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Posted 15 February 2014 - 07:31 PM

So here's a thought... and sorry for the long post but this has been on my mind for a while.

 

We keep talking about how an anamorphic lens uses the entire imaging sensor and is then compressed in post.  We always follow up by saying that just cropping isn't the same.  But isn't it?  Warning that this is looking at cropping vs. squeezing in a vacuum - I'm not talking about the other archetypical considerations of an anamorphic lens.  Bokeh, flare, compression can all be achieved to a degree with the right type of filter (see: Cinemorph by Vid Atlantic), and the compression can be achieved both H+V with a wide angle adapter, so let's just talk about the cropping vs. squeezing.

 

Let me explain.  With my camera, the 5D Mark 3, there's a fixed number of horizontal and vertical pixels which are available to be exposed.  There's no in-between or random arrangement like there'd be with silver halide grains in analog film.  When I record MLV at 1920 x 1080 I'm getting 2,073,600 pixels.  When I record 1920 x 804 (scope) I get 1,543,680.  So yes, 25.56% less pixels. But!  An imaging sensor isn't a perfect pickup mechanism. It doesn't have pixels all over it. That's why it's digital - it's quantized.  It's a representation, as best as possible, of an analogic wave, which turns into a stair-stepping wave when it goes through the ADC due to there being no infinite quanta (even the current standard 64 bit is "only" 18,446,744,073,709,551,616 steps).

 

What happens when you squeeze an image from 1920x1080 to 1920 x 804? You don't gain any resolution. In fact you may introduce aliasing due to lines being squeezed which weren't squeezed before, and the stair-stepping we're all familiar with (jaggies) comes out.  Yes, we started with more pixels, and I understand the value in starting with more instead of starting with less. Analog mediums - sure - squeezing leads to resolution advantages. But digital is a fixed number of lines.

 

But if in the end it all has the same aspect ratio, just one didn't have any squeezing done to it (and thus no pixels deformed and/or aliased), wouldn't just cropping make sense?

 

 


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#2 Tim Tyler

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Posted 15 February 2014 - 08:54 PM

We keep talking about how an anamorphic lens uses the entire imaging sensor and is then compressed in post.


Anamorphic lenses are also "wider angle" than spherical lenses.

 

Have a look at this informative post: http://www.cinematog...?showtopic=4690


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#3 Ben J. Abbey

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Posted 15 February 2014 - 11:54 PM

I'm intimately familiar with the optical effects of the anamorphic lens. Remember I said that I'm looking at resolution "in a vacuum" i.e. on its own.

My point is that going from 1920x1080 full HD frame to 1920x1080 scope with bars is a resolution reduction, and my thesis is that there's inherent dithering when downsampling and why not just capture at the final resolution (or slightly over for safe area).

I'd be interested in anyone's opinion/thoughts on cropping to anamorphic vs shooting, just on a resolution basis.
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#4 David Mullen ASC

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Posted 16 February 2014 - 12:32 AM

In 35mm, the advantage of anamorphic is that is uses the full height of the 4-perf 35mm negative for a 2.40 picture, so it uses more negative area than Super-35 cropped to 2.40 (which is about 2.5 perfs worth) -- and more negative means less grain and better resolution due to being enlarged less.  Plus it allowed contact printing through all generations to release print.

 

So with digital, the advantages in grain reduction are lost.  With digital projection, the advantages of contact printing are irrelevant. The advantages of resolution would only happen if you were using a 4x3 sensor and were using the full sensor height in anamorphic versus cropping to get 2.40 with spherical lenses.

 

However, even there, if the end goal is a 2K DCP, you don't get as much of an advantage because a digital projector uses a shorter frame height for 2.40 projection because it uses spherical projection lenses.

 

So, in general, yes, on a digital camera there isn't any real advantage to anamorphic photography over cropping in terms of resolution, particularly if the sensor is 16x9... it really only makes sense to shoot in anamorphic if you want those unique optical artifacts.

 

However, if you are using the 4x3 sensor version of the Alexa and recording raw, there is some resolution advantage (minor probably) over cropping spherical to get 2.40, but as I said, it would not really be seen much in 2K projection, you'd see it better in 4K projection.  I have found that if you crop less, sometimes artifacts like noise can look smoother, less obvious.

 

Another thing to keep in mind that if you are talking about shooting 1080P and showing it on an HD monitor, then letterboxing the image to 2.40 doesn't lose you resolution, it's just that a certain percentage of the pixels and screen image are used by the black borders.  The image doesn't get sharper or softer as you pop the letterbox bars on and off in post.


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#5 Chris Millar

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Posted 16 February 2014 - 01:14 AM

Interesting query Ben, I think I (might) understand what you're saying but by the time the forum and its many personalities and attendent knowledge levels comes to a consensus on the basics (eg. what actually is 'resolution') the question will likely be lost in a sea of dither itself ;) Good luck though! Hopefully it won't go that way...
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#6 Martin Ubilluz

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Posted 16 February 2014 - 06:34 AM

You started off talking about the anamorphic aspects and saying lets not talk about that just resolution but your topic is called "Digital Sensors = Anamorphic Redundant?" to answer that question ... no digital sensors do not make anamorphic redundant because anamorphic is so much more then gaining resolution.  There is no filter or adapter especially any thing from vid atlantic that can capture a beautiful anamorphic image and the flares. Many people think anamorphic is just about the flares but its not its every thing else that the lenses give. If your after gaining resolution your correct but anamorphic is not used for that on digital cameras any more except for 4x3 sensors.  As some one who owns and shoots with anamorphic lenses to me  anamorphic lenses have given a new breath to digital sensors.  I think the correct equation should be :

Digital sensors + anamorphic = organic beautiful images.


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#7 Chris Burke

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Posted 16 February 2014 - 07:47 AM

there are 1.33x anamorphic lenses


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#8 Ben J. Abbey

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Posted 16 February 2014 - 10:24 AM

I agree with everything everyone is saying. Again I'm intimately familiar with the desirable effects of anamorphic lenses. My whole point is that tutorials and posts always talk about how simply cropping is bad.

Based on our discussion here I'd think the zeitgeist is changing and with the current large sensor cameras, it's time to correct that misinformation.

I made a "poor man's anamorphic" with the Cinemorph filter and a 0.7x enormous wide-angle adapter in front of it. It looks SPECTACULAR, flares horizontally, stretches bokeh vertically, the lens introduces the compression both horizontally and vertically and on the z-axis, and a degree of barrel distortion on the periphery of the image.

It's a convincing effect and my last doubt about its utility is now moot.

Thanks to all!
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#9 Phil Rhodes

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Posted 16 February 2014 - 02:43 PM

What happens when you squeeze an image from 1920x1080 to 1920 x 804? You don't gain any resolution.

 

One thing is that this isn't actually being done very often. 1.33:1 anamorphics are rarer than hen's teeth and good ones are ferociously expensive. People are so desperate for this that there are even stories of using the Panasonic LA-7200 optical adaptor, which is a 1.33:1 cylindrical element designed to turn a DVX100 into a widescreen camera, on HD shoots, to turn a 16:9 camera into a scope one. And the LA-7200 is certainly not an HD piece of glass.

 

So if your question is: are people doing it solely for the artifacts and not for the resolution - yes, they certainly are. This was certainly the gist of the discussion when I was at Cooke's HQ the other day, looking at their new stuff (which I wrote about here), and is really the main reason why it was developed. This may be the root cause of Cooke's recent ascendancy, inasmuch as people are interested in glass which has some sort of personality to take the edge off digital cameras. I'm not sure this is the right approach, to be honest; if I want it filtered I'll filter it, but that's why we rent these things when we want them...

 

P


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#10 Ben J. Abbey

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Posted 16 February 2014 - 06:09 PM

Agreed with everything you said, Paul!
 


This is a quick shot with my "Poor Man's Anamorphic". I think the effect is convincing. Out to shoot some snowy Toronto sights tomorrow to play with it some more.
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