The Cameras of NAB 2014

If we think back to last year’s NAB, I remember seeing popup posters of the Black Magic 4K Production Camera and the Pocket Cine Camera the night before their launch. I remember thinking ‘this is a joke – a cunning deception to raise our hopes’ and today people are taking delivery of their 4K cameras.

So this year, I was excited to hear about AJA’s entry to the market – the CION.

UPDATE: AJA is PL only, posing a problem to owners of EF and Nikkor lenses. This is, for many of us, a bit of a show stopper. Happiness to AJA for choosing a standard, but they have effectively cut out their main audience – those of us who are upgrading from DSLR.

It looks great, their intro video is great, the price (considering…) is great. It looks like a really solid bit of kit. Well thought out, designed for professional use, a sort of pocket-money Alexa if you will, even though we haven’t seen the pictures.

I immediately started a little ‘savings’ pot – a stash of money where I’ll fund its purchase when I’m ready. I’ve already stated clearly that I will not buy another 8 bit camera (sorry Sony, with your cute Alpha 7S, and Atomos with your Shogun) and I really don’t want to buy a Panasonic GH4 and its own set of lenses. I’m happy that JVC are finally moving into the market of buyable cameras and acknowledge their choice of Micro Four Thirds, but I must move on.

So AJA’s Alexalookalike looks just the ticket. So excited!

Until, of course, those Aussies stroll up to the bar.

The Black Magic Ursa isn’t quite the Cion – it’s a giant (!) bear of a camera that has a 10″ flop-out screen. It has built in rail adaptors, it has a big handle, it has 3 big LCD screens, it screams ‘Production Department’ and all, and actually looks a little amateurish compared to the Cion. But it has something new and incredible:

The Ursa has swapable sensors.

That’s right, folks. You can buy the S35 EF mount edition. Later on, you can get a 2/3″ B4 sensor and mount. So in a few moments you’ve converted your big beefy Cinema camera into a big beefy ENG camera. You can have both a large S35 sensor mode with all your EOS lenses (or use Nikkors, or even opt for a PL mount S35 sensor – boggle!), and with a smallish investment and a little patience, have a 2/3″ B4 mount with your choice of ENG parfocal long range zooms.

Now, that’s worthy of investment!

Before we get all frothy at the mouth and loose at the wallet, we haven’t seen pictures (though both are promising 12 stops, ProRes 10 bit capture as well as raw, global shutter, et al), we haven’t got an actual shipping date (Black Magic are on the spot here), and it could all be show-stopping hype. But both AJA and Black Magic have effectively put the kybosh on many people’s purchasing decisions and both cameras offer – on paper at least – excellent value.

EDIT: More details came out about the camera. It’s 10 Kilograms with a lens and battery, so purchasers may want to think about their tripod heads and getting a good physiotherapist. Furthermore, it uses two C-Fast CF slots, which are quite expensive and don’t hold much footage when you’re shooting 10 bit 4K in an I-frame format like ProRes. A 128GB C-Fast card costs around $1,200 for 20 minutes of ProRes or 6 mins of raw. Come back, XQD cards, all is forgiven!

Right now, I’ll give the MDMA tip of the hat to AJA for the most desirable camera, but egad – the Ursa is so close behind and if they can deliver B4 they will win my vote. The GH4 was looking like the HVX200 of 2014 but may miss out to many users because of its Micro Four Thirds status.

Sony’s Alpha 7S was launched with great pizzazz, and is probably going to light fires under the 5D Mk3 market. But it’s a DSLR, and many of us have found that a DSLR just isn’t nice to use as a video camera if you’re being paid to deliver video. I think it’s excellent that Sony have included an S35 sensor crop and so your investment in S35/EF-S e-mount lenses is protected – you’re effectively getting a Canon 7D and 5D Mk3 in one body – and you have access to XLR audio through a special hot shoe with a £600 accessory. The body is tiny and it’s not hugely expensive. But it’s a DSLR style camera and I got on better with an AX100 than i did with an A7R when I had a chance to try lots of body styles.

So, welcome, AJA, to the camera market. You have a handsome product, but Black Magic is hot at your heals with interchangeable sensors. I trust AJA for its IO (which replaced a £35k Avid suite for me), and the Ki Pro (which replaced the Grass Valley things we were offered before). Your camera will always remind me of a pocket money Alexa and perhaps the comparison is deserved. But be aware of what Black Magic has done. The idea of swappable sensors is mind boggling.

C100 AF Upgrade – worth it?

Canon’s introduced Dual Pixel autofocus for faster, more accurate focus on certain lenses. It cost an extra £340 plus VAT. Is it worth it?

The demos have been very convincing, though until Philip Bloom’s recent trial they’ve been fairly ‘safe’ studio-based tests. Like most C100 owners, I’m more ‘run and gun’ – and whilst I prefer manual focus, there are times when it’s a joy to let the camera help out when you don’t have a chance to plan. Hand-held pick-up shots of activities, children, animals, or when you’re unable to reach the camera – cranes and jibs for example.

So I decided to further demonstrate the tax-deductible nature of our chickens by employing them as models for my test shoot. They are suitable unpredictable, active, and feathers are something fairly easy to judge focus by. The result is shared below – it’s got no sound, this is NOT a Philip Bloom style video, but it demonstrates the Dual Pixel AF in use. There are situations where it snatches focus well and holds onto it. There are situations where it just gives up.

I’ve done some slow motion sequences too, and with Canon STM lenses it really is quick – useful in the (limited) C100 slomo situations.

Of course, it’s not perfect.

Continuous AF can be a little TOO helpful, and luckily ‘1 Shot AF’ is still fully functioning, using the same speedy mechanism.

This way, you press the AF button when your subject spends a second or so in the centre of the screen, the AF settles, and it locks at that point. Not good for tracking, but much more helpful when you’re not using a composition that’s centre weighted. It’s also smart enough not to ‘defocus to refocus’ unlike contrast detecting AF, so I’ll be testing it out on conference shots following a speaker up and down the stage. This way, I can select WHEN the AF does its magic rather than suffer the embarrassment of having the camera develop an obsession with the background, or for me not nailing the focus at the end of a ‘walk’.

The STM lenses are designed for this mode. They’re great. I tried a few other lenses, and the 70-200 f4 is pretty snappy. The 24-105 is okay.

The Sigma 50mm 1.4 is… a dog. But I knew this. The Sigma as a photographic lens was so bad I almost ditched it. As a manual video lens, it’s pretty darn good, my second favourite after the Samyang 85 1.4. But the Sigma’s conversation with the C100 is still so simplistic that it can’t take advantage of the Dual Pixel AF mode, and insists on defocussing and then grunting away at pulling it into sharp focus – frequently giving up or getting it wrong. This is how it behaved on my Canon C550, so it’s no surprise.

Be aware that image stabilisation and auto focus systems make a noise. Leaving the AF in continuous on an image stabilised 70-200 f4 made quite a racket. You would want to turn off both in an interview, or at least use ‘One Shot AF’ if you need to rely on a camera mounted microphone.

Overall, yes – to an event videographer who owns an STM lens, this upgrade is Sine Qua Non. In fact, most C100 owners are going to find uses for it.

And therein lies the rub: this upgrade is not cheap. You have to send your camera off to Canon for a few days, and there’s been a waiting list. This upgrade has taken Canon by surprise in its popularity, it seems.

Canon initially offered this AF upgrade for C100 owners only. No, it wasn’t going to be available for the C300, and no, it would only be offered as an upgrade. Not ‘off the shelf’.

Well, guess what? You can now get the C100 with the AF ‘pre-installed’ at $500 extra on the price, there’s a waiting list for C300 owners to get the upgrade, and I’m pretty sure that at some stage the AF function will be on the C100 and C300 (or their newer siblings after NAB perhaps) at ‘no extra cost’. But hey – the original owners of the C100 got to pay the ‘shiny’ tax, but we had the camera earning its keep for 12-18 months before the upgrade. It’s not quite the ’S-Log upgrade’ that hung over the first PMW-F3 owners.

So, get your C100 upgraded – you’ll find the firmware goes up from 1.0.3.00 to 2.0.3.00 – showing that the hardware has been tweaked and proving it’s got the Dual Pixel AF upgrade installed.

Talk to the Badger

Badger SoftieHooray, Rycote have delivered my Badger wind-jammer! After a week that revolved around filming and editing talking heads and vox pops, it still struck home how aggressive and threatening a Sennheiser 416 can appear to interviewees when it’s hand held for interviews – like having a gun pointed at them.

This will break the ice, it’s cute and fun, and it’s REALLY good in the wind!

So we’re all on the same page, underneath that fake fur is a long microphone ‘pipe’ that’s sort of the ‘telephoto lens’ of the microphone world. If you use it outside, and the merest zephyr of wind plays across this long black thing, it creates a nasty rumble that drowns the interview with rumbles, bumps and that ghastly scratchy ‘audio overload’ interference that completely ruins your audio. So a wind jammer is Sine Qua Non outside, but can be redundant inside. In fact, it becomes more of an audio recorder’s codpiece. But in my previous post, I came to terms with why one should use a ‘fluffy’ or a ‘wind jammer’ indoors where it serves no purpose. But I digress.

Rycote will make you one to special order – no extra cost (thanks, guys!) but of course you’ll have to wait for it. Sure there’s skunks and zebras, but I like the badger – and especially considering that Rycote are in Gloucestershire, which was the epicentre of the Badger Cull Debacle – so, I feel this is in memoriam of the Badgers Who Fell.

To be clear, the badger effect only comes on strong at certain angles. This is not an anatomically correct badger. Don’t expect this to pass muster at a children’s puppetry party. But that’s the strength. It ‘hints’ at badgerness, but it’s still actually a proper pro-level bit of kit that will allow you to shoot outside with sensitive mics.

It’s not frivolous – just a little nod to those who get the joke. Of course, if I were shooting a drama or a difficult investigative journalism piece, this is not the thing to bring. But I shoot corporates. I shoot shiny, happy video full of shiny, happy people, and I’m looking forward to interviewing people with it. It? Him? Her? Should one name it? Or is that going too far?

Yes. It is. It’s just a socially acceptable iteration of the dead cat.

Preset white settings – Danger, Will Robinson!

Many cameras allow us to dial in a specific colour temperature for a shot, rather than manually set it with a white or grey card. It sounds good, but can deliver alarming results.

Consider these two images shot under different lighting systems. In both cases, I’ve put a daylight Dedo DLED-4 over the shoulder as a sort of 3/4-backlight-kicker thing. It’s a look I like. That’s a fixed constant. I like to light to 4500 ºK which gives me wriggle room over colour temperature, and is a piece of cake with a bi-colour device like the Dedo Felloni. I had to shift the camera to 5600 to match the lighting sources with my cheaper LED panel lamps.

The camera was a Sony PMW F3 with Nikkor 35-70 at around f4.

Immediately, you can see that the Non-brand LED panels are green. Not just a little, green, they are Incredible Hulk Green. Note the daylight highlight on Rick’s temple – its about the same in both images, though I did use 5600 ºK on the F3 for the Non-brand LEDs. I tried using half CTO, but the results were absolutely hideous.

Both images are from LED sources and are untouched in terms of grading. The Fellonis are neutral, accurate and appear to all intents and purposes to be full spectrum. I also find the diffusion and fill tweaks to be particularly nice, considering the cramped location and speed at which we had to work.

So it’s plain: be careful of setting a colour temperature in-camera – it works well with continuous spectrum lighting, but looks horrible if you use more restrictive sources – especially LED devices from the lower end of our budget. They output a very restrictive light.

But that’s not the whole story.

Let’s do what we’re supposed to do: let’s white-set on a known white reference (not just a bit of photocopier paper). Let’s re-light with our non-brand LED panels. At first glance, hey! It looks good!

Let’s compare with the more ‘continuous spectrum’ Fellonis on the right. Note that Rick’s skin tone on the left is far flatter with a hint of grey and yellow. Note also that the pure daylight source behind him is now casting a MAGENTA light over his hair and shirt – all that green has been neutralised, leaving a nasty Magenta odour hanging about. If we try and cancel that out, it will bring the green back in. Meanwhile, the brighter reds and oranges have been tempered by removing so much green.

The result? There’s an ashen look to the skin. It’s a bit dull. It lacks life. On the right, there’s some flush to the face around and under the eyes. The backlight and his shirt pick up the fresh daylight from the three-quarter back. It’s natural, rather than made up.

But bear in mind that if I were using the Non-brand LEDs in a mixed environment, trying to blend them with existing daylight or tungsten or – egad, even worse – both, the results are just awful. That green tinge is back, and it really doesn’t sit with anything else. I remember vividly a shoot trying to use these No-name panels in a mixed lighting situation, pinning half-CTO and diff over them to try and calm them, and still seeing the green tinge seep through.

  • Take home 1: be careful using pre-set Kelvin settings as not all lighting is full spectrum. You’re choosing a compromise. It can be the best decision, but it can also be wrong.
  • Take home 2: a proper white-set is the way to go in difficult situations, but strong corrections will impact other lighting sources (ambient, backlight, fill, etc)
  • Take home 3: Unless shooting raw, correcting for White Balance issues can only take away data from your image and reduce its quality.

Note: look out for the full story (and more) on moviemachine.tv soon.

MXF to FCPX not working? A possible fix

Ingesting C300 rushes using the Canon FCPX plug-in
Ingesting-C300-rushes-using-the-Canon-FCPX-plug-in
Canon provide a free plug-in to enable the C300′s MXF files to import directly into FCPX without the need to transcode to ProRes. Many users report that they have no problems with the installation and it ‘just works’. However, other users with similar setups report that they cannot import C300 rushes in FCPX, though it works through Log and Capture in FCP7, additionally Adobe Premiere successfully imports C300 MXF. Only FCPX seems affected, and for a limted subset of FCPX users.

C300 rushes don’t work
C300-rushes-don-t-work

Here’s the typical scenario: having run the xpfm211 installer. FCPX sees the folder structure, even the MXF files themselves, but does not recognise either. This is as far as some users get. For some reason, the installer has completed successfully, we are seeing files, but nothing imports. De-installing and re-installing brings the user back to this situation. Very frustrating.

After installing
After-installingTrying to track the activity of the installer, we see two new plug-ins highlighted in the MIO/RAD/Plugins folder – CanonE1.RADPlug and CanonXF.RADPlug. The latter would appear to be the ‘magic smoke’ for the MXF format. However, this isn’t working. There’s a second empty RADPlugins folder below – should the plugins be in there?
Moving the plugins
Moving-the-pluginsWhilst it may seem a bit ‘cargo cult’ to shift the contents from a RAD/Plugins heirachy to a RADPlugins, it was worth a shot. No, it didn’t work.
Comparing folders with a working configuration
Comparing-folders-with-a-working-configurationHere’s where it got interesting. I was able to confer with another editor who had a system that did import MXF successfully. The key difference was that he had a CanonXF64.RADPlug folder – not an XF, an XF64. I could not find a similar folder, nor could I make the installer create one. In the end, he just sent me a copy of that folder, and I dragged and dropped it into the same folder I had.
C300 rushes now appear normally
C300-rushes-now-appear-normallyAnd it worked! It’s pretty obvious because you can see the clips, but also note that the MXF folder heirachy has gone, replaced simply with the usual list of clips on a card or archive.
The Secret Sauce of C300 Import
The-Secret-Sauce-of-C300-ImportSo this folder appears to be the missing link. Depending on your system, the installer either creates this folder, or it doesn’t. Both of us had the XDCAMFormat.RADPlugin, removing both did not make my installer create this file, the only way was to use somebody elses copy. It would be useful to provide this folder as a download to those who need it, but license agreements seem to forbid this sort of activity – probably for good reason.
It comes down to an issue with the installer, which isn’t written by Canon staff, and so it’s difficult to work out who to alert to the situation. However, as seen here, access to the CanonXF64.RADplug folder cures the problem for now.

Ninja Blade – 2:2 Pulldown with Canon C100 Fixed

ninjabladeUPDATE: 2:2 PULLDOWN FIXED IN AtomOS 5.1.1…
Early adopters frequently find little snags that are quickly patched, and this week is no different. I have taken delivery of the new Ninja Blade recorder last week.

It’s an awesome piece of kit for the C100 user – but when I record 25PsF, I noticed that the images are shifted two pixels to the left with a black line running down the right hand edge.

Atomos support are on the case have fixed it, they suggest we update to version 5.1.1 here. we keep the C100 set to 25PsF and set the Ninja Blade to 50i. In FCPX and Premiere (I don’t use Avid) simply do the 2:2 pulldown trick by treating it like AVCHD footage, manually switching the files from interlaced to progressive as described in PSF – the fix.

As a C100 user, I am very impressed by the Ninja Blade in a number of areas:

  • screen quality and fidelity with the option to calibrate
  • ability to use a LUT when shooting C-Log
  • audio meters that put the C100′s to shame
  • waveform monitor and vectorscope
  • shot logging features – both live and after the shoot

Combine all this with very low power consumption, a lightweight chassis and a wide range of media choices, it closes the gap between the C100 and C300.

I’ll do an in-depth review when I’ve cleared my current workload, and I’ll go into a bit of depth over the shot logging facilities which will really make a difference to shooting interviews and long form events such as presentations and conferences.

But not now. I really should be editing! Until then, remember the 50i to 25p trick.

UPDATE:

Well, it’s easy to deal with this little inconvenience in PAL-land. If you shoot in 24p or 23.976 PSF mode, you’ll find the same black line, so you’re recommended to shoot in 59.973 and you’re on your own.

So, whilst I don’t shoot for 24p or 23.976 most of the time,  when I shoot 29. 973 it’s fairly easy. So I had to find a solution that would make shooting 24p (or 23.976) work. It appears that the only way is to transcode the rushes. So…

With a drum roll and a nod to Abel Cine and all those who got there before me, here’s an Apple Compressor droplet that sorts your Ninja rushes out before you import them:

Apple Compressor Droplet.

C100 noise – the fix

The Canon C100 is an 8 bit camera, so its images have ‘texture’ – a sort of electronic grain reminiscent of film. Most of the time this is invisible, or a pleasant part of the picture. In some situations, it can be an absolute menace. Scenes that contain large areas of gently grading tone pose a huge problem to an 8 bit system: areas of blue sky, still water, or in my case, a boring white wall of the interview room.

Setup

Whilst we set up, I shot some tests to help Alex with tuning his workflow for speed. It rapidly became obvious that we’d found the perfect shot to demonstrate the dangers of noise – and in particular, the C100’s some-time issue with a sort of pattern of vertical stripes:

Click the images below to view the image at 1:1 – this is important – and for some browsers (like Chrome) you may need to click the image again to zoom in.

So, due to the balance of the lighting (couldn’t black the room out, couldn’t change rooms), we were working at 1250 ISO – roughly equivalent to adding 6dB of gain. So, I’m expecting a little noise, but not much.

Not that much. And remember, this is a still – in reality, it’s boiling away and drawing attention to its self.

It’s recommended to run an Auto Black Balance on a camera at the start of every shoot or if the camera changes temperature (e.g. indoors to outdoors). Officially, one should Auto Black Balance after every ISO change). An Auto Black Balance routine identifies the ‘static’ noise to the camera’s image processor, which will then do a better job of hiding it.

So, we black balanced the camera, and Alex took over the role of lit object.

There was some improvement, but the vertical stripes could still be seen. It’s not helped by being a predominantly blue background – we’re seeing noise mostly from the blue channel, and blue is notorious for being ‘the noisy weak one’ when it comes to video sensors. Remember that when you choose your chromakey background (see footnote).

The first thought is to use a denoiser – a plugin that analyses the noise pattern and removes it. The C100 uses some denoising in-camera for its AVCHD recordings, but in this case even the in-camera denoiser was swamped. Neat Video is a great noise reduction plug-in, available for many platforms and most editing software. I tried its quick and simple ‘Easy Setup’, which dramatically improved things.

But it’s not quite perfect – there’s still some mottling. In some respects, it’s done too good a job at removing the speckles of noise, leaving some errors in colour behind. You can fettle with the controls in advanced mode to fine tune it, but perversely, adding a little artificial monochrome noise helped a lot:

We noticed that having a little more contrast in the tonal transition seemed to strongly alter the noise pattern – less subtlety to deal with. I hung up my jacket as a make-shift cucoloris to see how the noise was affected by sharper transitions of tone.

So, we needed more contrast in the background – which we eventually achieved by lowering the ambient light in the room (two translucent curtains didn’t help much). But in the meantime, we tried denoising this, and playing around with vignettes. That demonstrated the benefit of more contrast – although the colour balance was hideous.

However, there’s banding in this – and when encoded for web playback, those bands will be ‘enhanced’ thanks to the way lossy encoding works.

We finally got the balance right by using Magic Bullet Looks to create a vignette that raised the contrast of the background gradient, did a little colour correction to help the skin tones, and even some skin smoothing.

The Issue

We’re cleaning up a noisy camera image and generating a cleaner output. Almost all of my work goes up on the web, and as a rule, nice clean video makes for better video than drab noisy video. However, super-clean denoised video can do odd things once encoded to H.264 and uploaded to a service such as Vimeo.

Furthermore, not all encoders were created equal. I tried three different types of encoder: the quick and dirty Turbo264, the MainConcept H.264 encoder that works fast with OpenCL hardware, and the open source but well respected X264 encoder. The latter two were processed in Epsiode Pro 6.4.1. The movies follow the above story, you can ignore the audio – we were just ‘mucking around’ checking stuff.

The best results came from Episode using X264

Here’s the same master movie encoded via MainConcept – although optimised for OpenGL, it actually took 15% longer than X264 on my MacBook Pro, and to my eyes seems a little blotchier.

Finally Turbo264 – which is a single pass encoder aimed at speed. It’s not bad, but not very good either.

Finally, a look at YouTube:

This shows that each service tunes its encoding to its target audience. YouTube seems to cater for noisy video, but doesn’t like strong action or dramatic tonal changes – as befits its more domestic uploads. Vimeo is trying very hard to achieve a good quality balance, but can be confused by subtle gradation. Download the uploaded masters and compare if you wish.

In Conclusion:

Ideally, one would do a little noise reduction, then add a touch of film grain to ‘wake up’ the encoder and give it something to chew on – flat areas of tone seem to make the encoding ‘lazy’. I ended up using Magic Bullet Looks yet again, pepping up the skin tones with Colorista, a little bit of Cosmo to cater for any dramatic makeup we may come across (no time to alter the lighting between interviewees), a vignette to hide the worst of the background noise, and a subtle amount of film grain. For our uses, it looked great both on the ProRes projected version and the subsequent online videos.

Here’s the MBL setup:

What’s going on?

There are, broadly speaking, three classes of camera recording: 8 bits per channel, 10 bits per channel and 12 bits per channel (yes there are exotic 16 bit systems and beyond). There are three channels – one each for Red, Blue and Green. In each channel, the tonal range from black to white is split into steps. A 2 bit system allows 4 ’steps’ as you can make 4 numbers mixing up 2 ‘bits’ (00, 01, 10 and 11 in binary). So a 2 bit image would have black, dark grey, light grey and white. To make an image in colour, you’d have red green and blue versions stacked up on top of each other.

8 bit video has, in theory, 256 steps each for red, green and blue. For various reasons, the first 16 steps are used for other things, and peak white happens at step 235, leaving 20 steps for engineering uses. So there’s only about 220 steps between black and white. If that’s, say, 8 stops of brightness range, then a 0.5 stop difference in brightness has only 14 steps between them. That would create bands.

So, there’s a trick. Just like in printing, we can diffuse the edges of each band very carefully by ‘dithering’ the pixels like an airbrush. The Canon Cinema range perform their magic in just an 8 bit space by doing a lot of ‘diffusion dithering’ and that can look gosh-darn like film grain.

Cameras such as the F5 use 10 bits per channel – so there are 1024 steps rather than about 220, and therefore handle subtlety well. Alexa, BMCC and Epic operate at 12 bits per channel – 4096 steps between black and white for each channel. This provides plenty of space – or ‘data wriggle room’ to move your tonality around in post, and deliver a super-clean master file.

But as we’ve seen from the uploaded video – if web is your delivery, you’re faced with 4:2:0 colour and encoders that are out of your control.

The C100 with its 8 bit AVCHD codec does clever things including some noise reduction, and this may have skewed the results here, so I will need to repeat the test with a 4:2:2 ProRes type recorder, where no noise reduction is used, and other tests I’ve done have demonstrated that NeatVideo prefers noisy 10 bit ProRes over half-denoised AVCHD. But I think this will just lead to a cleaner image, and that doesn’t necessarily help.

As perverse as it may seem, my little seek-and-destroy noise hunt has lead to finding the best way to ADD noise.

Footnote: Like most large sensor cameras, the Canon C100 has a Bayer pattern sensor – pixels are arranged in groups of four in a 2×2 grid. Each group contains a red pixel sensor, a blue pixel sensor and two green ones. Green has twice the effective data, making it the better choice for chromakey. But perhaps that’s a different post.