Sensor question regarding RED One and ARRIFLEX D-21

[Erik Lokegaard]

I've been under the impression that a camera's sensor size equates its image resolution. RED One and ARRIFLEX D-21 have Super 35-sized sensors. The former can record in 4K resolution, the latter cannot. Apart from the obvious difference that RED and ARRI are different manufacturers, why is that?

 

[Blair S. Paulsen]

This is a substantial area to cover (pardon the pun) and I am hardly the most qualified to do so, but I can tell you this. How many pixel sites one puts on a sensor of any size is a choice. Theoretically you could have a sensor the size of a sheet of paper with 4 pixels on it. Do some research, its a fascinating topic with a ton of new advancements.

 

[Nils J. Nesse]

I've been under the impression that a camera's sensor size equates its image resolution.

There are mobile phones on the market with 12 megapixel cameras. These obviously have much smaller sensors than the 12MP Canon 5D, and also much smaller than the 6MP Nikon D40.
Different sensors have different size pixels.

 

[Erik Lokegaard]

OK, thanks.

 

[David Mullen ASC]

Not all photosites are the same size.

The Arri D21 sensor is 23.76 x 17.82mm and has an array of 2880 x 2160 photosites.

The Red One sensor is 24.4 x 13.7mm and has an array of 4520 x 2540 photosites.

There are pros and cons to putting more photosites into the same size area. Arri rightly refers to the D21 as a "2K" camera since 2.9K RAW is roughly 2K in measurable resolution (the Red One's 4K RAW recording ends up around 3.2K in measurable resolution).

The D21 also has a 4x3 sensor, which can be useful when shooting anamorphic. The pixel resolution ends up very similar to the Red One with a 2X anamorphic lens, since you have to crop the sides on Red's 16x9 sensor.

Of course, let's not ignore the considerable price difference, not to mention that the Arri D21 does not have an internal compression scheme for RAW, though I suppose you could hook it up to a data recorder using some built-in compression scheme. Again, nowhere as cheap as what Red offers with in-camera REDCODE compression and recording to hard drives or CF cards.

 

[Mitch Gross]

And let's not forget the D-21's optical viewfinder or ability to work in a video stream or data stream mode.