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Shooting anamorphic with digital cameras, which lens desqueeze factor is the right one?

anamorphic digital lense desqueeze factor

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#1 davide sorasio

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Posted 12 August 2015 - 06:17 PM

Hi everybody. I have a doubt concerning shooting anamorphic on digital cameras. I know the different camera menus (I'm talking from my Epic and Alexa experience) give me the option to chose between 1.3x, 2.0x and 2.0mag (this last one I have no idea of what it is) anamorphic desqueeze factor but I have no idea of what the rule of tumb is and which one to chose according to what.

Feel absolutely free to add anything else that you thing might make things clearer.

Thanks a lot,

Davide

 

 


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#2 David Mullen ASC

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Posted 12 August 2015 - 06:47 PM

The majority of anamorphic lenses have a 2X horizontal squeeze, unless you rent the 1.3X Hawk anamorphic lenses, designed to squeeze 2.40 onto a 16x9 (1.78 : 1) sensor without cropping.  Standard 2X squeeze means that for a final unsqueezed 2.40 image, you're using a 1.20 : 1 area of the sensor.

 

So besides knowing what lenses you are renting, you have to know the area of the sensor you are recording and you have to unsqueeze the image for the monitors and EVF, unless you prefer to look at a skinny image.  The Epic has a 6:5 "ANA" mode for 2X anamorphic photography, basically just recording a 1.20 : 1 area of their sensor since that's all you need, saving you a little on the amount of data recorded.  It also unsqueezes the image for the viewfinder and monitors in that mode.  With an Alexa, you'd want to rent the 4x3 Alexas so you can use the taller sensor area.  With the other cameras, which almost all record a 16x9 or even 1.9 : 1 area, you'll be cropping the sides to get down to a 1.20 : 1 area of the sensor, probably cropping in post.


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#3 Kemalettin Sert

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Posted 12 August 2015 - 07:17 PM

6:5 is gonna be new 4:3 in future.

from ALEXA SXT Faq;

 

6:5? What the hell? I thought you needed 4:3 for anamorphic?

The 4:3 aspect ratio was originally left over from the film days, and now has been put to good use by VFX-heavy feature films. Anamorphic lenses don't actually need the full width of the 4:3 image; they squeeze the 2.39:1 image by a factor of 2, and the resulting area used on the sensor has a 1.195:1 aspect ratio, which is roughly 1.2:1, which is 6:5. When shooting with anamorphic lenses in 4:3 sensor mode, you always have to crop the extra area to the left and right of the image in post, an extra processing step that is avoided by shooting in 6:5.

In the ALEXA XT cameras with SUP 11 we have introduced this mode, however, there it was still called '4:3 Cropped', but that is the same thing as the ALEXA SXT/SXR 6:5 sensor mode

 

 

 

 

http://www.arri.com/...exa_sxtsxr_faq/


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#4 Satsuki Murashige

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Posted 13 August 2015 - 12:52 AM

I know the different camera menus (I'm talking from my Epic and Alexa experience) give me the option to chose between 1.3x, 2.0x and 2.0mag (this last one I have no idea of what it is) anamorphic desqueeze factor but I have no idea of what the rule of tumb is and which one to chose according to what. 
 


It's pretty simple. Use a 1.3x de-squeeze setting for anamorphic lenses with a 1.3x squeeze factor - basically only the Hawk 1.3x lenses.

Use a 2x de-squeeze for pretty much all other anamorphic lenses - Panavision, Hawk, Cooke, Arri, Lomo, JDC, Kowa, etc.

Use 2x Mag(nify) if you are using 2x lenses and want to blow up the image to fill the 16:9 frame vertically - basically if you want the anamorphic artifacts like horizontal flares and squeezed bokeh but want to record a 16:9 image.
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#5 Albion Hockney

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Posted 13 August 2015 - 01:07 PM

the 2x vs 1.3x call has a lot to do with look. 1.3x lenses don't give you the same strong effect at all.


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#6 David Mullen ASC

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Posted 13 August 2015 - 04:47 PM

The stretched bokeh of the 1.3X lenses is more subtle, plus the Hawk lenses in general don't easily give you a big blue horizontal flare.  But if you look at that trailer for "The Hateful Eight", shot with 1.25X anamorphic lenses on 65mm, you can still see some stretched bokeh, same goes for the 1.5X squeeze of Technirama.


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#7 davide sorasio

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Posted 06 September 2015 - 12:57 PM

thank everybody, onlu one last question to see if I got it right: so using "normal" 2X anamorphic I'm recording only the 1:1.20 portion of the sensor? and does that mean that some part of the sensor is not "used"? while the 2Xmag gives me the option of using the whole 16:9 sensor size?


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#8 David Mullen ASC

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Posted 06 September 2015 - 01:14 PM

Yes, the whole sensor is not used when you are recording only a 1.20 : 1 area of it for 2X anamorphic photography, if the end goal is a 2.40 unsqueezed image.  Why would you want to record a wider sensor area? I mean, you could if you wanted to, but what's the point?

 

Just think about it, your 2X anamorphic lens is squeezing the image laterally by 2X, meaning it has to be stretched back put laterally by 2X in post.  Max sensor size in the MX Epic is 5120 x 2700 pixels, a 1.896 : 1 ratio, so if a 2X anamorphic lens even filled that entirely (it might not being 27.7mm wide, and most anamorphic lenses were designed for a film frame that is 22mm wide), you'd have 3.79 : 1 aspect ratio image once unsqueezed.

 

If you want a 2.40 image but want to use most of the sensor, you'd have to use an anamorphic lens with less of a squeeze ratio, like the 1.3X Hawk anamorphics.

 

Since the Red camera doesn't support a 1.3X squeeze, you'd have to watch the image that way on your monitors, full-frame but with a 1.3X squeeze to it.

 

The 2X Mag function is still cropping the sensor, if Satsuki is correct in its function: in fact it is even cropping more than the normal 2X function does, because instead of cropping the unsqueezed image down from 3.79 : 1 to 2.40 : 1, it is cropping it even more down to 1.77 : 1.  If you want to end up with a 1.77 : 1 image (full-frame 16x9) but your lens has a 2X optical squeeze to it, then you only need to use a .885 : 1 area of the sensor.


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#9 David Mullen ASC

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Posted 06 September 2015 - 01:31 PM

2X anamorphic lenses were designed originally for 4-perf 35mm photography and projection.  The shape of the negative and print area is roughly 1.20 : 1, so when the image is unsqueezed by the anamorphic projector lens, it becomes 2.40 : 1 on the screen.

 

Therefore a digital camera would likewise have to have a more square-shaped sensor if you want to use 2X anamorphic lenses to squeeze a 2.40 : 1 image onto the sensor with little waste.

 

On the other hand, the resolution of the sensor is also a factor.  For example, 4x3 Alexa sensor records 2880 x 2160 pixels (1.33 : 1 aspect ratio).  So there is little waste to crop 1.33 : 1 to 1.20 : 1 for anamorphic photography, you'd end up using a 2592 x 2160 pixel area for 1.20 :1, expanded in post to 2.40 : 1.  So because there is little waste, is that better than using, let's say, a 6K Dragon Red camera where the sensor is more widescreen, and therefore more is wasted for 1.20 : 1?

 

With the 6K Dragon sensor, full-frame is 6144 x 3160, and in 2X "ANA" mode (6:5 mode, i.e. 1.20 : 1), you are only recording 3792 x 3160 pixels.  But that is still more than 2592 x 2160 pixels on the 4:3 Alexa for a 2.40 : 1 anamorphic image.

 

On the other hand, on the 6K Dragon, you'd be putting that 1.20 : 1 image in an area that is 18.95mm x 15.79mm.  On the Alexa, that 1.20 area of the 1.33 sensor is 21.38mm x 17.82mm.  On a 4-perf 35mm camera, the negative area for anamorphic is 22mm x 18.59mm, cropped in projection to 20.96mm x 17.53mm.

 

So in terms of field of view, the anamorphic lens on the 4x3 Alexa would be closer to what you'd get with that same lens on a 4-perf 35mm camera, while on the 6K Dragon, it would be cropped a little tighter in view.


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