Wait a Minute: Sony A7s Only Outputs 8 Bits?

by Hugh Brownstone15 Comments

The Sony A7s, along with the Panasonic GH4, are game-changers in the mid- to higher-priced video mirrorless/DSLR space. But hold on there, Slim: the trade-offs are just as real with these two cameras as with any other, and some of them are downright surprising. Today, we look at the Sony A7s 4K recording capability and conclude: huh? Welcome to the next installment in our occasional series called “Dr. Evil’s Sharks with Frickin’ Laser Beams.”

Shogun, baby! As in: the Atomos Shogun, the 4K, HDMI combination recorder/monitor that allows the Sony A7s with its incredible low light performance and wide dynamic range to output 4K.

Sure, the A7s and Shogun combo costs more than twice as much as the GH4 (which records 8-bit 4K internally) and it’s a whole lot bulkier, but holy smokes: for that, you get everything the GH4 is plus that full-frame sensor with razor-thin depth of field, knockout 14 stops of dynamic range and high ISO performance that is unrivaled at anything remotely near that price point!

Not quite.

It turns out that even at two and a half times the price, one of the things the A7s doesn’t do is 4K 10-bit color: it sends an 8-bit 4:2:2 signal through the HDMI cable to the Shogun.

iPhone screenshot of 55" Samsung HDTV showing a scene from the British crime mini-series "EXILE"

iPhone screenshot of 55″ HDTV showing a scene from the British crime mini-series “EXILE” with 8-bit and compression artifacts

Sony Outputs 8-bit. Not 10-bit.

That’s right: 8-bit. Not 10-bit, like the GH4 when it is connected to the very same Shogun (supposedly – we will see once the Shogun is actually shipping).

What?

Yup.

But let’s back up a minute and acknowledge a not particularly popular or well understood truth: 8-bit is all you need between 95% and 100% of the time – unless you’re always shooting landscapes early in the morning or late in the afternoon; you shoot a disproportionate number of high contrast back-lit shots; or your primary output is to the web.

Or Blu-Ray, for that matter.

It’s that incredibly fine, progressive gradation in the sky, or the similarly fine, progressive light fall-off from a bare bulb just behind the axe-murderer standing in the doorway that makes 8-bit capture with its 256 shades of color cry “momma” – and where the 4x tonality of 10 bit – 1,024 shades – comes into play.

So the question becomes: do you actually need 10 bits? Only you know the answer.

But if you’re someone who really cares about dynamic range, high ISO performance, 4K, and shallow depth of field, I’m betting you might.

By the way – did you know that you can set the GH4 to 4K; set it to auto down-convert to 1080p; and then send a 10-bit 4:2:2 signal to the Shogun’s little brother, the Ninja Blade, in ProRes?

Hmm…

(cover photo credit: snap from Hugh Brownstone)

Hugh Brownstone

Hugh Brownstone

Hugh is the founder of Three Blind Men and An Elephant Productions. He and the team write, direct, shoot, score, and edit web-centric films; conduct photo shoots; and write copy, white papers and blog posts. Hugh also writes screenplays (he recently optioned a TV pilot) and just published his first eBook (Apple's iPhone: The Next Video Revolution). If it's about telling stories, it's in their wheelhouse.

And always with the ambition of authenticity, humanity and wit.
Hugh Brownstone

Comments

  1. So I don’t understand why this image would be pushed this hard to be totally blown out. You may be hard pressed to see the artifact if infact it was graded or exposed in what would be considered a more normal or pleasant even if high contrast scenario.

  2. I pointed this out under Den Lennie’s debut video (he was hired by Sony to promote the a7S), when he said it was 10-bit, and after some surprisingly emotional defensiveness, he retracted and admitted it’s 8-bit while insisting it makes no discernible difference.

    On Gepo’s point, though, of course the a7S has a low-light advantage over the GH4 which performs poorly anywhere above ISO 800.

  3. LOL. Is this a joke? iPhone screenshot of a TV displaying footage from a blownout/over-corrected clip taken on the A7S!? I’m no expert, but, that seems like a lot of silliness. No clip would look this horrendous straight out of the A7s. I did like that you mentioned that 95-100% of the time 10-bit is meaningless anyways since almost all endpoints only display in 8-bits anyway. I definitely agree that 10-bit is great for color grading, though, and I wish the A7s had that out of the HDMI, it would make it almost perfect. I imagine the A7s ver. 2 will have internal 4k and 10-bit output as well as all the other awesomeness it already has.

    BTW, FWIW, from what I’ve seen, the 1080p from the A7s looks just as good as the scaled down 4k on the GH4. I’m betting the A7s is doing that internally on its sensor.

  4. kylefarris The purpose of the shot — done on an iPhone as mentioned in the caption — is to make clear why 8-bit vs 10-bit can be a meaningful difference.  It’s also clear, I hope, how compression artifacts — a function of the codec and in this case the carrier/provider itself most likely — can be an important to consider as well, and thus why an external recorder using ProRes can be appealing under certain circumstances.  It was certainly NOT my intention to assert that this shot is other than what I labeled it.

  5. Anthony Miles I’m sure EXILE was graded and exposed with great care and professionalism – and likely shot at 10-bits or higher — but the compression and 8-bit limits of the display medium are quite representative of why less lossy codecs and 10-bit color depth are important.

  6. Gepo The A7s has clear and compelling advantages over the GH4, beginning with high ISO performance and dynamic range. But both cameras have trade-offs, which is why some people are choosing to buy both.

  7. HughBrownstone Fair enough–you just wanted to get an extreme example to show what color banding is. I completely get the benefit of an uncompressed 10-bit prores (or similar) file especially when you’re dealing with special effects and compositing–the GH4 will probably be a better choice for those doing that type of work.

  8. Thanks Hugh, I doubt this image represents the way the show looks, or what would come out of camera. Images can be pushed to fall apart without question.

  9. Er….I already knew this….back in April. I’m unsure why everyone just assumed it did 10 bit without researching it.

  10. Anthony Miles Agreed, Anthony: it is inconceivable to me that this is the way it would look coming out of the camera or in final edit delivered via cable. We saw this on Netflix via the Internet, so other than some exposure tweaking, this is exactly, astoundingly what we saw!  Ah, the joys and limitations of Internet viewing!

  11. i have a theory.. thats been building up for the past couple months.
    As of right now- dec 17th 2014, the shogun is still only available for pre-order, and Atomos worked with Sony for the Shogun- even the ads were all about the marriage between the two.
    Now Sony is known for making loads of competing products, but the A7s stands alone as a mighty fighter against the rest, when you look at all it can do in such a small package.
    Heck if you spend the same amount of money you would on a F-5 on a fs7 you can get the shogun to theoretically do everything the f-55 does.  Even to the point of pushing it to DNG RAW and getting a global shutter. Can we assume there’s something Sony is holding back for the full release of the shogun??
    If you compare the shogun’s and a7s’ specs – “what they can do”  they aren’t that far from each other.
    In fact the shogun can do 120fps 720 and 120fps 1080.  The A7s can only internally do 120 at 720- one can assume that 120 at 1080 for its hardware is too much to process, just like it is too much to process 4k up to 30 or 60fps.
    Why would two companies talk about such a marriage between their products, when the recorder does more than the camera can… but yet, Sony’s A7s honestly relies on the Shogun to produce it’s 4k image for more practical users.
    I have a feeling that there will be a 10-bit out firmware update because, at the same time of it’s release, it’s number one competitor was the gh4 with 10-bit., Sony was and still is also releasing other prosumers and consumer cameras that record 4k 10bit, why hold back on 1 camera?? and finally, the rolling shutter–
    This is a big leap, but makes plenty of sense.  The rolling shutter on the a7s is arguably painful, but yet the advertise marriage was with a external recorder that can capture raw 4k, hd, DNG- thus global shutter and need to ever worry about the internal recording with it’s global shutter.

    Thus, with these little marketing tactics, is it too hard to believe that Sony, who is known for their firmware updates that improve their cameras into self competing products, are waiting for the mass release of their partnered product to release an update that will make customers want to buy their product even more?
    Thought, anyone?

  12. TheColfud Can’t help but wonder how far behind the A7 Mk II an A7s Mk II might be…

  13. I just hope there’s some 10bit on the way from Sony or Canon. 10bit was the first thing I thought of after being done with my 550d. fingers crossed, SONY, CANON, IF YOU ARE WATCHING THIS!!

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