Pro DX is Dead

Started Nov 7, 2012 | Discussions thread
jfriend00 Forum Pro • Posts: 12,023
Re: Pro DX is Dead

Theodoros Fotometria wrote:

jfriend00 wrote:

Theodoros Fotometria wrote:

24mpx (6000x4000) is ideal for video in both APS-c and FF... why? Because 1920x3=5760 which is very close to 6000mpx... then (by subtracting a little from the frame horizontally) you can use exactly 3pixels for 1 of 1920 info and hence with a 9 pixel array (3x3) you can have that for each 1920x1080 info... Now on FX, you can subtract one pixel from each side and get 2x1920=3840 pixels to do the same when you use the DX area only of the FF sensor.... Note that Nikon FFs have slightly better performance when used in DX for video...

Why, if you have an FX camera would you shoot video only in a DX crop or why would that be better than using the whole sensor? Why not use all 24MP of a D600-type sensor for video, just like the 24MP DX you proposed? Won't you get better low light performance by using the whole FX sensor? So, why is DX better than FX for video?

I didn't say its better (or worst) it isn't either.... the 1920x1080 area makes the pixel area huge anyway so noise isn't a problem anymore. It's different than photography were sensor noise is relevant to per pixel noise and size.... Take my 2 D800s for instance... either if you shoot the whole frame or choose DX for video, noise is the same for the same Iso.

What makes APS-c appeal more (and all high end cameras to use that size of sensor) is that cinema usually needs huge DOF and APS-c has more than 1.5 stop advantage on that... The main thing however is that directors minds, cameramen, lighting technicians, amature film makers/enthusiasts, etc ...even students in filming schools have learned to work with it after coming from even more DOF (16mm, 8mm) to them APS-c is like a photographer shooting with 8X10 LF... They simply need to revise all they know up to now in terms of composing, lit and control a scene to move in considerably larger format. The other thing is lens performance... now they can have great DOF at 100 Iso at medium apertures... If they move to larger format... they will have to drive their lenses into diffraction to observe the same DOF.

FF sensors are good to have only as an alternative, in the (extremely) rare situation where ultra thin DOF is required and mainly in UWA filming where huge DOF isn't a problem but AOV may be... In fact Canon 5Dmkiii sales have been affected by the fact that it doesn't offer APS-c video, ....while Canon's higher end models that aim to the pro market bare an ...APS-c sensor!

A couple of your assumptions/statements are not quite the way you think they are.  You don't get the same visible noise in a given output image whether you shoot with the full FX sensor or the DX cropped portion.  The overall noise is much less visible if you use all the MP because the additional downsizing reduces the appearance of the noise.  So that assumption you based some of the rest of your conclusions on is not correct.

Further, you can take an FX sensor and stop it down a stop and raise the ISO one stop to match the DX DOF and get very similar IQ performance as DX.   The larger sensor gives you one stop more light on the sensor so it starts with that advantage.  Thus, you can give that advantage back by raising the ISO by one stop and stopping the aperture down by one stop and get the same DOF as DX (until you are diffraction limited).

If filmmakers are used to the APS-C field of view, that indeed could be an advantage for DX (I'll have to take your word on that one), but that presumes that the main market for such a video-centric camera is actually people with enough filmmaking experience to have this preference.

The argument that I would find more compelling is that FX just doesn't really offer much of an advantage for video (since everything is getting downsized anyway and shallow DOF is usually not desirable) so the 3-10x less expensive DX sensor and somewhat smaller/cheaper mid-focal-range lenses are an advantage for DX for video (as long as you don't need to go super wide angle or really low light).

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