Choosing sensor size, resolution, and lenses on cine cameras

Choosing sensor size, resolution, and lenses

When making original 4K content for Netflix, you need to use lenses that fit inside the approved sensor size and resolution made by Netflix for the cine camera you are using.

When choosing sensor size, resolution, and lenses to use for cinema, you normally choose between:

  • 1.85 or 2.39 and
  • 2K and 4K.

    Other aspect ratios like 1.37 and 2.2 can be used inside 1.85

Normal cinema resolutions/aspect ratios:

  • 4K Scope 2.39:1 4096 x 1716
  • 4K Flat 1.85:1 3996 x 2160
  • 2K Scope 2.39:1 2048 x 858
  • 2K Flat 1.85:1 1998 x 1080

Other aspect ratios are placed inside one of these four resolutions when making a DCP (digital film print). All cinemas should have side masking for Flat and Scope if they follow the DCI/SMPTE standards.


Read more here: What is the DCP format

Some cinemas have side masking for custom aspect ratios like 2:1, 2.2:1, and 1.33:1.

Most cinemas are common height where Flat and Scope share the same height, and the screen is 2.39:1.

Some cinemas are common width, where the screen is 1.85:1. and Scope and Flat have the same width. This is the same as on a normal computer screen and on television.

Read more about Flat and Scope in cinemas in this post

Traditional analog film sizes

  • 4 perf Academy = 21.0 by 15.2 
  • 4 perf 2x anamorphic = 20.96 × 17.53 mm. 2.39 anamorphic 35 mm print.
  • 2 perf Techniscope = 22 x 9.47. Cropped to 2.39
  • 4 perf Super 35 = 24.89 x 18.66 mm. Often cropped to 2.39 or 1.85.
  • 3 perf Super 35 = 24.9 x 14 mm.
  • Vistavision =  37.72 mm x 24.92 mm. Shown in 1.66, 1.85, or 2:1
  • 135 film/Full frame = 36 x 24 mm
  • Super-16 = 11.76 x 6.37 mm (1.85 print)
  • 5 perf 65 mm = 48.56 x 22.10 mm. (Print)

Modern cine-camera sensor sizes :

  • 2X Anamorphic 4 perf crop of 4/3 Super 35 sensor (Alexa 35 =20.21 x 16.95)
  • 2X Anamorphic Large Format/full frame crop ( Alexa LF mini = 25.97 x 21.75)
  • Alexa LF Large format/full frame (36.70 x 25.54)
  • 65 mm 1.85 aspect ratio (Alexa 65 = 47.32 x 25.58)
  • Super 16 sensor crop (Alexa 35 = 12.44 x 6.73)
  • 1.85 Super-35 4K sensor crop (Alexa 35 =24.27×13.12)
  • 2.39 Super-35 4K sensor crop (Alexa 35 = 24.88 x 10.42 sensor size)
  • Alexa 35 Open Gate (Bigger than Super-35) (27.99 x 19.22)

Examples in this post:

  • 2X Anamorphic 4 perf crop of 4/3 Super 35 sensor in 4K Scope (ARRI Alexa 35)
  • 2X Anamorphic 4 perf crop of 4/3 Super 35 sensor in 2K Scope (ARRI Alexa Mini)
  • 2X Anamorphic Large format crop in 4K Scope (ARRI Alexa LF Mini)
  • 1.85 Super-16 sensor crop in 2K Flat (ARRI Alexa 35)
  • 1.85 Super-35 sensor in 4K Flat (ARRI Alexa 35)
  • 2.39 Super-35 sensor crop in 4K Scope (ARRI Alexa 35)
  • Bigger than Super 35 Open Gate with 2.39 framing lines in 4.6 K (ARRI Alexa 35)
  • LF/Full frame Open Gate with framing line for 1.85 (ARRI Alexa LF Mini)
  • 65 mm Open gate with framing line for 1.85 (ARRI Alexa 65)

Different lens sensor coverage specifications

Lens manufacturer’s specifications use different ways to tell which sensor area a lens will cover:

  • Image circle
  • Analog film formats like VistaVision
  • Sensor types like Alexa LF
  • The image sensor size the lens will cover
  • Full frame
  • 16/9 cropped full frame
  • 4 perf super-35
  • 3 perf super-35 (16/9 crop)

Examples:

  • Summicron-C lenses cover super-35 and a 36 mm image circle (Ø). An image circle around 28-32 mm is normal for super-35 lenses, these lenses will also cover larger sensors like ARRI Alexa 35 Open Gate ( Ø 33.95).
  • Atlas Orion anamorphic lenses cover a 24.89 mm x 18.66 mm sensor size
  • Leitz Leica M 0.8 F.0.95 50 mm cine lens covers full frame (24 x 36)
  • Cooke S4 /I cover Super 35


2X Anamorphic crop of 4/3 Super 35 sensor in 4K Scope (ARRI Alexa 35)

The ARRI Alexa 35 has a Super 35 4/3 sensor with 4.6K resolution.

With the ARRI Alexa 35, you can record directly in 4K DCI resolution in C-LOG4 ProRes 4444 4K 2.39:1 Anamorphic 2x 3328×2790 (20.21 x 16.95 mm) desqueezed and scaled to Scope 4K DCI 2.39 (4096×1716).

Using the Arri framing lens and illumination guide, you can choose the Prores 4K anamorphic mode

Because the sensor area is 20.21 x 16.95 mm you can use traditional 4 perf anamorphic lenses like the Atlas Orion lenses without an LF extender.

2X Anamorphic 4 perf crop of 4/3 Super 35 sensor in 2K Scope (ARRI Alexa Mini)

The ARRI Alexa Mini has a sensor with 3.4K resolution. The 4K anamorphic sensor size on the ARRI 35 is similar to the 2K anamorphic mode on the Alexa Mini, which has a 21.12 x 17.70 mm sensor size when recording 2K Scope 2560×2145 desqueezed and scaled to Prores 2K DCI 2.39 2058×858.

2X Anamorphic Large format crop in 4K Scope (ARRI Alexa LF Mini)

The ARRI Alexa LF and LF mini are allowed by Netflix to shoot with 2X anamorphic lenses in a 3148 x 2636 crop of the 4.5 K LF Open Gate sensor.

When making a custom framing line in the Arri framing lens and illumination guide for 3148×2636, you can see the sensor size used is 25.97 x 21.75 mm, which is larger than the normal 4 perf anamorphic sensor size.

The Netflix guide states that ARRI Master anamorphic lenses from 40 mm cover this area, but some anamorphic lenses need an LF extender because of the large sensor size. You can check this in the Lens Illumination Guide.

Using a 40 mm Master Anamorphic clears the 3148 x 2636 framing line


The Arri Rental Alfa lenses are detuned and modified versions of these lenses that were made for ARRI Alexa LF and were used on the Netflix tv-series 1899.

1.85 Super-16 sensor crop in 2K Flat (ARRI Alexa 35)

Because the ARRI Alexa 35 has 4.6K resolution, you can use it with super 16 lenses in s16 16/9 mode (2048×1152) and use a 1.85 framing line (2048×1108)

Sensor size is 12.44 x 6.73 /Ø 14.27 mm, Can be downscaled to 2K Flat 1.85:1 1998 x 1080 for 2K DCP delivery.

1.85 Super-35 sensor in 4K Flat (ARRI Alexa 35)



Example: ARRI 35 with Cooke S4/i 25mm. in 4K DCI 16/9 4096×2304 recording mode with custom 4K DCI Flat 1.85 (3996×2160) framing line.

24.27 x 13.12 sensor size / Ø 27.59

2.39 Super-35 sensor in 4K Scope (ARRI Alexa 35)

Example: ARRI 35 with Leitz Summicron-C 35 mm in 4K DCI 16/9 4096×2304 recording mode with DCI 4K Scope (4096×1716) framing lines.

24.88 x 10.42 sensor size / Ø 26.97 mm

Open Gate ARRI Alexa 35 with framing lines for 2.39

Instead of shooting in 4K mode, you can use 4.6 Open Gate ArriRaw on the Alexa 35. You can record the whole sensor and use framing lines for different aspect ratios like 2.0, 2.39, or 1.85. The Open gate sensor size is slightly bigger than Super-35, so not all Super-35 lenses will cover it. The framing line can be scaled down to fit these lenses.

The ARRI Alexa 35 4.6K Open Gate specification:
Resolution:
4608 x 3164
Sensor Size:
27.99 x 19.22
Image Circle
33.95 mm

The Leitz Summicron-c lenses cover a 36 mm image circle and cover 2.39 (4608 x 1930/ Ø 30.34) and the open gate sensor (4608 x 3164/ Ø 33.95) area.

Other lenses like the Cooke S4/I 16 mm cover 2.39 (image circle 30.34), but not the whole sensor area. The framing line can be scaled down to fit the sensor coverage of different lenses when using the open gate sensor size.

LF/Full frame Open Gate with framing line for 1.85 (ARRI Alexa LF Mini)

LF open gate sensor on the ARRI Alexa LF Mini is a bit larger than the 36 x 24 full frame sensor size:

Sensor Size:
36.70 x 25.54 mm
Resolution:
4448 x 3096 
Image circle:
44.71 mm

Lenses like the Leitz Cine Leica M 0.8 50 mm F 0.95 will cover 36 x 24. but the Leitz lens specifications warn that there can be some shading/vignetting on the Arri LF mini open gate mode (36.70 x 25.54)

There is some vignetting outside the 1.85 framing line in open gate mode at F 0.95 on the 50 mm lens. But when stopped down, this will be reduced, and at F 4, there is no vignetting. Custom framing lines can be made if there is too much vignetting.

At F 4, there is no vignetting.

65 mm sensor size Framing lines for 1.85 (ARRI Alexa 65)

ARRI Alexa 65 can record in 65 mm Open Gate mode
Specifications:
6560 x 3100 Open gate

With framing line for 1.85:1
Resolution:
5736 x 3100 px
Sensor Size
47.32 x 25.58 mm
Image Circle:
53.79 mm

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