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What exactly makes a camera 4k?


jasondhsd

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I'm curious all these cheap 4k cameras and even smart phones that shoot 4k. If I understand correctly 4k equals about 8.8 megapixels so that means almost any sensor that's 10 megapixels should be able to shoot 4k video depending on how much time it takes to overheat the sensor. So if it's not the sensor per say then it must be how much processing power is inside the camera, right?  Basically what I'm wondering the current crop of crop sensor high-end consumer / semi-pro etc would they be capable of shooting at 4k if the manufacturer decided to upgrade their firmware?  Not that I expect them too, just curious. 

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You are not exactly right. The fact that the sensor has enough pixels does not mean it can output full resolution images at video speeds (24, 25, 30 frames per second).

It all has to do with sensor output, processing power (compressing the video), buffer and output writing speeds. The camera has to read out a hell of a lot pixels from the sensor at least 24 times per second, process it and compress it so you can store it properly on the camera's SD.

 

Check out the still camera, how many FPS do you get from burst mode? 3? 5? 10? That is still not 24.

 

Overheat is one issue, but not the main issue here. You can always use fans, like some pro cameras do.

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4K is four times as much data. Most dslrs do 1920x1080 by not reading out the whole sensor, but only 1920 colums and 1080 rows and skip the other lines in between so they use less pixels, less data (this causes moiré and aliasing). For 4K it would need to read out 2 times as much colums and 2 times as much rows of pixels. This is a lot of work. It would also need much much higher bitrate compression to achieve the same quality.

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What about the dslr can can do video, especially those that can do 1080p @ 60fps, surely they should be capable of doing 4k at say 24 or 30fps, no? Since it's essentially the same amount of information being captured in a second since 4k is just doubling 1920x1080. 

4K is 4 times the amount of pixels.

Most DSLR's have readouts optimized for low readout noise, when it comes to readout speed they are so slow that they can only read one third of their lines (moiré). Some sensors are fast enough but don't have the processing power, bandwidth or whatever.

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Check out the still camera, how many FPS do you get from burst mode? 3? 5? 10? That is still not 24.

 

In the case of the Panasonic GX7, I do wonder if there's enough bandwidth in it to eventually pull off 24fps @4K.  Sure would be a nice bonus to have that option in the future.  The sensor specs certainly allow it; not sure on the other bandwidth components.

 

Also, the cheap little Nikon V1 does a short 1sec burst at 60fps.  You can check out the popular thread here on EOSHD for examples.

 

If these cameras could even just manage a modest 10 second record time with a firmware update, then lots of high res creativity would be available for the filmmaker.  It would be great for music vids, for instance.

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Noone will release a firmware that allows only 10 seconds of 4K I think. I know about the V1 but it can only do that in raw image mode, no compression, no audio. You need to process and compress raw data for consumer 4K video. Even the better amateur filmmakers and even professionals suffer with raw workflow so that is clearly not an option for consumer 4K which we are talking about.

 

The device needs to be built with component intended for 4K.

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Noone will release a firmware that allows only 10 seconds of 4K I think. I know about the V1 but it can only do that in raw image mode, no compression, no audio. You need to process and compress raw data for consumer 4K video. Even the better amateur filmmakers and even professionals suffer with raw workflow so that is clearly not an option for consumer 4K which we are talking about.

The device needs to be built with component intended for 4K.

on a side note; v1 does 1 sec at 30fps, or 60 fps for 0.5 secs.

edit: sorry looks like fuzzy normal already mentioned v1 recording time.
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No one will release a firmware that allows only 10 seconds of 4K I think.

...

The device needs to be built with component intended for 4K.

 

It might appear someday as a hack on cameras like the GX7.  You never know.  At least I can hope.

 

And, of course, Panasonic is hitting the market with a 4K camera this year that (from what I've seen with my limited wisdom) may share the same sensor as the GX7 and GM1.  

 

The point being that 4K is happening in the marketplace.  More important, it looks like it has a chance to be a big deal in the consumer market -- because of companies wanting to upgrade/sell 4K monitors.

 

As you know, the consumer market is where the DSLR/M43/Mirrorless products are.  As such, adapting them to a useful workflow is important.  It'll happen fast.

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