[Jodokast96]

I'm not one for video in a DSLR, mostly because everything seen so far everyone is oohing and ahing about had nothing to do with the camera but rather the person using it. This clip makes me think a little more about that.

http://vimeo.com/4038064?pg=embed&sec=4038064

Opinions? Fast lenses and high ISO's is something I don't think can be had on a lot of video equipment. Am I wrong there?

[Philippos]

...everything seen so far everyone is oohing and ahing about had nothing to do with the camera but rather the person using it...

I don't mind you not caring about Video in a DSLR, but I believe that you are wrong about peole and cameras. Canon 5D mkII is not selling because some celeb or some "dude" looks cool when holding it.

BTW timelapse sequences are possible with any camera, since it's not actually video. In fact my old G6 might actually perform better than most DSLRs in this field, since it does not have a mirror/shutter that gets worn off by the process.

[Jodokast96]

I believe you misunderstood me. What I meant is we see these astounding videos, but it could have been shot with anything, including my 8 year old camcorder. What makes them good isn't the equipment but rather the talent using it.

As to the time lapse, the way I took it is that it was actually video shots sped up and not stills, which is why my thoughts on this were changing.

[Jodokast96]

I stand corrected, they are stills. So again, nothing special about the video function.

[falconeye]

because these video cameras use more than one sensor, their DR is far greater.

Can you provide a reference for this statement?

AFAIK, DR is basically a function of total available sensor surface. There are (sometimes) 3 chips in camcorders (because then they can record each color separetely to avoid the time-consuming demosaicing). But because their combined surface would still be a lot smaller than APS-C, DR should be (much) worse, not better, than with DSLR video.

But if what I say below is correct, than indeed, camcorders have better DR and ISO performance than DSLR video ...

Rest of discussion moved here:
https://www.pentaxforums.com/forums/pentax-news-rumors/58822-quality-k-7-video.html

[Philippos]

Can you provide a reference for this statement?

AFAIK, DR is basically a function of total available sensor surface. There are (sometimes) 3 chips in camcorders (because then they can record each color separetely to avoid the time-consuming demosaicing). But because their combined surface would still be a lot smaller than APS-C, DR should be (much) worse, not better, than with DSLR video.

But if what I say below is correct, than indeed, camcorders have better DR and ISO performance than DSLR video ...



Interesting math here.
BTW, HD camcorders record at much less than 40 MBit/s (less than half of this, actually). Only 5dmkii comes close. 40 MBit/s is the (max.) Bluray spec for the HD video part of a data stream.

First, and most importantly, we will have to know, if:

1920x1080@24fps is achieved by:
- subsampling (only 1/7 of pixels are read out): 142 MByte/s input rate (8 Bit RGB)
- supersampling (all pixels are read out, demosaiced in the trivial manner and supersampled to half size): 564 MByte/s input rate (16 Bit Raw) and (with ~4 instructions to supersample a pixel) about 0.3 GOps/s processing power to condense the input into a 211 MByte/s input rate (8 Bit RGB). To further reduce size and compress into H.264 is downhill from there (where realtime H.264 compression is requiring hardware acceleration, of course).

BTW, 3.5 fps shooting requires 97 MByte/s input rate (16 Bit Raw) and (with ~20 instructions to demosaice a pixel) 1 GOps/s processing power. The latter is not available which means that the buffer fills up faster than it can be written out in a burst. Maintainable speed suggests that about 0.5 GOps/s are available.

So, we see that supersampling is possible but requires ~5 times the speed of internal data busses compared to subsampling. Or it requires a so-called hardware-binning feature (or pixel binning, which can be done on the CMOS chip). Then, an increase by ~2 times the speed would suffice. Samsung did announce a CMOS chip with pixel binning in December. But only 720p for web cams


WHAT DOES IT ALL MEAN?

Well, most likely, the K-7 features 1080p@24fps HD video but NOT with the enhanced noise/DR performance as known from still photography. It features the DoF control but dismisses the superior IQ which would be possible as well.

There is a slight chance that Pentax increased the internal busses by 5x (or included hardware binning).

If they did, they may smash the entire competition for high end video. But I doubt so

Comparing a 3-chip camera with a single chip camera is very very interesting. Actually, it's the same amount of light that enters the lens, but in the 3-chip cameras, it gets split by a prism so it reaches all sensors. In the end what you get is better performance in low light for single-chip cameras (less luminance noise) but better performance in daylight or well-lit setups for 3-chip cameras (less color noise - better color rendition).
I had written an extensive article about it some 12-13 years ago, but it was very technical. The above sentence is the conclusion.
Overall however ,and that's not just my personal choice, most videographers prefer single chip cameras as long as the sensor is as big as possible for many reasons: DOF, light perception, good color rendition etc.

[falconeye]

Comparing a 3-chip camera with a single chip camera is very very interesting.

Oh, I now see how this is an interesting question. I learned a lot from your answer.

Rest of discussion moved here:
https://www.pentaxforums.com/forums/pentax-news-rumors/58822-quality-k-7-video.html

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Last edited by falconeye; 04-30-2009 at 11:14 AM. Reason: topic moved

[Philippos]

Supersampling a 15.1 MP sensor to 1080p would probably create much heat on the sensor and create too much unnecessarynoise, as the sensor would have to output huge amounts of data for a long time.
I do not know how the current burst mode in the K20D works, but I believe not all photodiodes on the chip function when recording. It's the most efficient way to go, both in terms of computing power needed but most important, it requires far less power.

[falconeye]

Supersampling a 15.1 MP sensor to 1080p would probably create much heat [...]

Philippos, I created a separate thread to continue our discussion. I invite you (and everybody else) to join in.

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