F65: F65 F65RAW-HFR Compression Ratio????

abreu-canedo

abreu-canedo

Well-known member
Hello there, folks!

I have been looking all over the place, perhaps in the wrong places, for specs on F65RAW-HFR 120fps. Sony says it is 4K no crop, but do not mention compression ratio on their documentation. All I have found is that you get 5mins per 256GB card at 120fps.

I have a 120fps shoot with the F65 next week and would love to be able to tell my client what they can expect in terms of image compression compared to the F65RAW-SQ @ 3.6:1.



Has anyone gotten to the bottom of this???? I will keep looking, but any help is greatly appreciated.



And since I am asking for something, I figured I would offer something. Below is the link to a nerdy camera test, in case anyone is interested. Color and dynamic range test. Of course, this may not mean much to anyone through vimeo compression and computer monitors, but what the heck...

https://vimeo.com/150983655
 
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Sony F65

1-60 fps
RAW-SQ = 3.6:1 @ 8K
RAW-LITE = 6:1 @ 8K

The HFR mode uses only half of the pixels on the sensor for a "4K" image, but deploys a special anti-aliasing filter to prevent moire artifacts and such. This is why you can't use the NDs in HFR mode. The compression of HFR mode is locked to 3.6:1. You can confirm this by going into HFR mode, then dial down the frame rate of the camera to 24fps and you'll see it gives you double the same recording time as SQ would at that frame rate, because it's half the resolution.
 
Thank you, James!

Much appreciated. I am going to run some camera tests on Sunday to see how the image stands up to the RAW-SQ. The client will want to use the footage for trade-shows and conventions on very large displays, so they want it to stand up to that.

Have you worked with the HFR mode much? Can you speak to the image quality. and how it compares to RAW-SQ? I will be testing it, but I'm curious to get other opinions as well.
-Thanks again!
 
Yes, quite a bit. The quality is fantastic. You have to remember that in half-res mode the F65 has "only" the resolution of an F5/F55, and still more than an ALEXA! It's a super image.

A lot of the stuff Sony used to demo the camera early on was actually HD!
 
That's music to my ears. Glad to hear, James. I will do some testing tomorrow, and shoot Tuesday and Wednesday.

Thanks again!
 
JMtheDP said:
Yes, quite a bit. The quality is fantastic. You have to remember that in half-res mode the F65 has "only" the resolution of an F5/F55, and still more than an ALEXA! It's a super image.

A lot of the stuff Sony used to demo the camera early on was actually HD!
Click to expand...
Not really true if you count the actual number of pixels. Still looks great, but numbers are also numbers.
 
Mitch Gross said:
Not really true if you count the actual number of pixels. Still looks great, but numbers are also numbers.
Click to expand...

Mitch, would you be so kind as to elaborate? To my knowledge the F65 is shutting off every other vertical line in this mode, reducing res from 8192 x 2160 to 4096 x 2160... if you can find anything to describe otherwise I would be very grateful? Sony are quite coy about what the mode actually does
 
The photosites on the sensor are not laid out on the same grid as the pixels in the resulting image. Instead of the familiar rectangle, the F65 sensor's photsites are rotated 45 degrees, making them into diamonds (or squares that are resting on a corner rather than a flat side if that helps you picture it). So there are not in fact true rows of photosites, because the next photosite is a little below or a little above depending on how you see things. Sony's way of seeing things here is to extrapolate the information from the upper and lower photosite to create a virtualphoto site in line. The same thing happens in the row below, but offset by one photosite along the horizontal axis.

If you count the actual number of true photosites on the sensor, the F65 is more like 6K, not 8K. Sony didn't do this to "cheat" or "lie" or any other subterfuge. The idea was to smooth edges and improve diagonal lines, which are always more present in nature than a pure horizontal or vertical stripe. But for those who count simple strict numbers as a way of measuring complex data, it could make for a bit of a head scratch. At the time the camera was released there were some at RED who called foul.

Sony had experimented with this sensor layout previously on some consumer and prosumer cameras, but the F65 was the first time they tried it with a pro camera and the first time in using this design that they purposefully tried to throw more photosites then resulting pixels (6K-ish to get 4K) for a clean oversampling effect. But when the camera did not sell as well as hoped Sony came out with the 8K output from the camera, which was in fact a generated option, not a native one. This data flow could not be sustained at high frame rates -- the sensor sampling was not changed, only the processing for extrapolated pixels from the photosites. The camera as originally designed was only supposed to deliver 4096x2160. The 8K that it delivers in slower frame rates is extrapolated pixels, rather than the interpolated pixels of the 4K (extrapolated meaning creating more and interpolated meaning generating fewer). I'm not sure if the reason for the limitation in frame rates for the 8k format was in the camera processing or in the media write speed, but I suspect it was the media. That's a HUGE amount of data to deal with.

Hope that answers things.
 
Mitch I'm familiar with the Q67 pattern employed by the F65, but what you're describing seems very different to my understanding of the camera. I know that the camera records 4K/8K/whatever we want to call it in RAW mode - doing little to no processing/interpolation in camera. I am reasonably sure though that the sensor DOES sample differently in HFR mode - and Sony have told me as such. I am pretty sure you are correct though that it is a media limitation that necessitates this, rather than a camera or sensor based one.

To my knowledge the final "4K" picture is only assembled in software/hardware outside of the camera - in Resolve or wherever. I don't think the camera is binning 8K into 4K in-camera in HFR mode.
 
Yeah, there was a website somewhere which said that the binning happened in the recorder but I was told by Sony that was "bad info" and it happened on a sensor level. In any case - the picture created is still of a very high quality.
 
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