All posts by alisterchapman

Uncategorized

TVLogic VFM-056WP 5.6″ Monitor/Viewfinder Review.

Leave a comment
TVLogic VFM-056WP 5.6" monitor.

At NAB I was offered a TVLogic 5.6″ monitor kit for review and assessment. The VFM-056WP sits somewhere between being a monitor and a viewfinder. It’s not as big as most monitors and it’s not really a viewfinder, like the soon to be released Alphatron/TVlogic EVF. So I was somewhat sceptical as to how useful it would be as my normal cameras all have built in LCD panels.

The kit included the monitor, a deep detachable hood, battery adapter for the ever so common Sony NP-F batteries, mounting ball joint, power supply and a few other small accessories, all inside a good quality flight case.

The rear of the VFM-056W

One of my few criticisms of this kit is the size of the flight case. The monitor itself is very compact and lightweight, but the flight case really is quite big. For my fly-away jobs I probably wouldn’t use this flight case, it’s just to big for such a small monitor. Anyway back to the monitor. Externally it feels nice and solid and to be made of good quality materials. On the bottom there are a pair of BNC’s for the HDSDi input and output. The HDSDi input works in both conventional 1.5G and 3G modes (WP version only) making it suitable for use with cameras that have a 3G 4:4:4 output, so it works great with the S-Log output of my PMW-F3. As well as the HDSDi there is also an HDMI input plus 3 phono connectors for the composite and component input. So all in all there is just about every type of input you could possibly want. In addition the WP version will convert any connected HDMI signal to HDSDi

VFM-056W with deep hood on top of my PMW-F3

On plugging in the HDSDi feed from my F3 I was presented with a very good looking, sharp and clear display. Checking the colour response using a DSC Chroma Du Monde chart showed very accurate colour reproduction, brightness and contrast. Although the LCD panel is quite small the resolution at 1280×720 makes the image look nice and crisp. Next I tried using it to focus. On the whole I found I could achieve reasonably accurate focus without resorting to peaking, but turning on the monitors coloured peaking function does make it much easier to find optimum focus. The other tool that helps focussing is a 1:1 pixel image zoom that is accessed using the menu switch on the rear.

The VFM-065WP has all the usual tools in the menu’s. The menu system is easy to use with a Function button on the rear of the monitor and a rotary dial on the side used to select and change settings. One thing that would be nice perhaps is a couple of assignable buttons to which you can assign your favourite functions.

The clear display of the VFM-056WP (click to enlarge)

As well as the common stuff like markers, false colour and zebras, it has some nice extra functions like a DSLR zoom feature that will expand the less than full screen output of Canon and Nikon DSLR’s so that it fills the screen. There is also a Range Error feature that allows the user to set maximum and minimum levels for luma and chroma. If these levels are exceeded, the areas in excess of these values blink on and off. The WP model includes waveform and vectorscopes that can be superimposed over the pictures in 3 different sizes, small, large and full screen.

So with it’s full set of features and tools, excellent build and image quality, the diminutive  TVLogic VFM-056WP is a great little monitor that can be camera mounted without adding a lot of extra weight to your kit. I have been quite impressed by this neat little monitor and I’m sure it will end up in my kit for most shoots. It’s small size and low weight makes it particularly suitable for overseas shoots where I need to keep the total weight of my kit to a minimum to avoid excessive airline baggage charges.

Uncategorized

REC-709 – A true REC-709 camera should only have 5 stops of dynamic range!

1 Comment

In theory if two cameras are both set to REC-709 then the dynamic range should be identical as both cameras responses will be limited to the REC-709 specifications. The original REC-709 specification only allows for 5 stops of dynamic range from 0 to 100%. The addition of superwhites at 109% gives a little more and then the knee on top gives a bit more again. The whole point behind REC-709 is that when a REC-709 camera captures something of a specific brightness, then when that image is shown on a TV or monitor, the apparent brightness will be exactly the same. As REC-709 is based on legacy television standards that go back to the very beginning of television broadcasting, it only allows for the dynamic range of older television sets. If a camera deviates from REC-709 then there will be a miss-match between the image the camera records and the image the viewer sees.

So, if we have two cameras with sensors capable of a dynamic range greater than the REC-709 specifications and then we restrict them to REC-709, they should exhibit identical dynamic range. Just like two cars fitted with speed limiters, they would both have identical maximum speeds.  In fact the REC-709 specification is actually a viewing and display specification, not a camera specification and in reality the REC-709 gamma curves in most cameras don’t correspond exactly to the true 709 monitor specs as everyone would be up in arms if the camera only had a 5 stop range.

With almost any reasonably up to date cameras, anyone comparing a couple of cameras dynamic range with REC-709 and saying A has more dynamic range than B is a bit of a misnomer. Yes there will be differences in the way the gamma curve has been interpreted by the manufacturer or the way the knee works and perhaps camera A will give a more pleasing picture than B, but this is unlikely to actually be due to the dynamic range of the camera, just different ways the manufacturer has chosen to interpret the restrictions imposed by REC-709.

In my opinion, the only times you would want to use 709 is when you are shooting direct for broadcast where there won’t be time for grading or if you have enough control over your lighting to stay within a 6 stop range and that 6 stop range gives you the look you want.

Otherwise, I would use one of the extended range gammas included in most cameras these days, log, cinegamma, hypergamma etc, as these extended range gammas don’t try to comply to the REC-709 specifications they are not restricted to the legacy dynamic range imposed on us by REC-709. As a result they can easily accommodate much greater dynamic ranges and get closer to utilising the camera sensors full range, but at the expense of requiring some grading to restore contrast.

Uncategorized

Alphatron EVF-035W Getting closer!

4 Comments

The Alphatron EVF-035W is getting closer to launch. I was able to play with one in Las Vegas at NAB and image in the finder really was very good. I’ve used Cineroid and Zacuto finders and they are not nearly as clear or as sharp as the Alphatron. With the Alphatron I found that I could see the image come in and out of focus quite clearly without resorting to large amounts of peaking, nor could I easily make out the pixel structure of the screen as I can with my Cineroid. With the peaking activated, the fine resolution of the screen means that the peaking edges themselves are much finer so they don’t obscure the image making the peaking more precise and less obtrusive. The Alphatron EVF also has a manually operated shutter in the monocular eyepiece which allows you to prevent sunlight from accidentally burning the LCD screen, that’s a nice touch, I’ve seen many viewfinders destroyed or damaged by the sun. There were still some bugs to be ironed out in the prototype that I used, but TV-Logic make good kit and I’m sure that once the firmware is sorted the Alphatron EVF-035W will become the gold standard by which other aftermarket EVF’s are compared. Looking into the Alphatron reminded me of looking in to a Sony C35W EVF. The Sony costs in excess of £4k while the Alphatron is going to be around the £1k mark. Looking forward to testing a full production unit.

 

Uncategorized

“A Diamond in the Mind” Available for pre-order on Amazon

3 Comments

The incredible Duran Duran concert that I was involved with shooting at the end of last year is available for pre-order on Amazon. “A Diamond In The Mind” is due to be released on July 2nd. I was responsible for the camera setups and picture profiles used on the shoot and having seen the end result, I’m really pleased. The film has an incredible look that really captured the magic of the moment. 11 x PMW-F3’s, FS100’s, mini-cams, jibs, Alura and optimo lenses all contribute to an incredible looking concert video.

Uncategorized

What is a “Slow Shutter” or SLS

Leave a comment

“Slow shutter” is a video term for an electronic shutter that is open for longer than the duration of a single recorded frame. It’s not actually a shutter as in a stills cameras physical shutter, most video camera don’t have a physical shutter. Normally a video camera operates at 25 or 30 frames per second. So, the camera sensor normally captures light for 1/25th or 1/30th of a second in progressive, for interlace it’s half of this as the shutter is open for the duration of each field, one field is half the duration of one frame, before writing the data to one frame of the video.

The sensor is then reset, captures for the next 1/25th or 1/30th and then writes the next frame and so on, creating a video sequence. With a slow shutter the sensor is allowed to capture light for – (the slow shutter speed in fames) x (the number of frames) before that data is written as a single frame. So with a 16 frame slow shutter the sensor is allowed to capture light for 16 x 30 (or 25) frames before creating an image.

So at 30fps, one frame lasts 1/30th. Therfore, 16 x 1/30th = 0.53 seconds. The sensor is being allowed to capture light for 0.53 seconds before getting reset. If you do not use an interval recording mode or time-lapse, each of the 16 video frames the camera records  while the sensor is being allowed to capture light gets written with the same image data (from the previous shutter cycle). So with a conventional video recording the image only refreshes once every 16 frames.

Uncategorized

Camera Gain: It doesn’t make the camera more sensitive! (also relevant EI S-Log).

1 Comment

This is something that’s not well understood by many people. It helps explain why the PMW-F3 (and other cameras) EI S-Log function is so useful.

You see, camera gain does not normally actually change the cameras ability to capture photons of light. A CCD or CMOS sensor has a number of photo sites that capture photons of light and convert those photons into electrons or electrical charge. The efficiency of that capture and conversion process is fixed, it’s known as the QE or quantum efficiency. There are a  lot of factors that effect this efficiency, such as the use of micro lenses, whether the sensor is back or front illuminated etc. But all of these factors are physical design factors that do not change when you add extra camera gain. The sensitivity of the sensor itself remains constant, no matter what the camera gain is set to.

Camera gain is applied to the signal coming out of the sensor. It’s a bit like turning up the volume on a stereo amplifier. If you have a quite piece of music, turning up the volume makes it louder, but the original piece of music is still a quiet piece of music. Turning up the volume on your stereo, as well as making the music louder will also make any hiss or background noise in the music louder and it’s exactly the same with a video camera. As you increase the gain, as well as the wanted video signal getting bigger (brighter) all the unwanted noise also get bigger. So adding gain on your video camera doesn’t actually make the camera more sensitive, but it does make what light the camera has captured brighter in the recordings and output, giving the impression that the camera has become more sensitive, however this is at the penalty of increased background noise.

As well as adding gain to the image in the camera, we can also add gain in post production. Traditionally gain has been added in camera because the gain is added before the recording process. In the uncompressed analog days the recording process itself added a lot of noise. In the digital age the process of compressing the image adds noise.  8 bit recordings have quite small number of grey shades. So any gain added in post production amplifies not only the camera signal but also the added recording or compression noise so generally gives an inferior result to adding gain in camera. With an 8 bit signal the stretching of the relatively few grey shades results in banding.

Now, however the use of lower noise sensors and much improved 10 bit or higher recording codecs or even uncompressed recording means that adding gain in post as opposed to in camera is not such a bad thing. In some cases you can use post production noise reduction prior to adding post gain and by leveraging the processing and rendering power of a computer, which will normally be of greater quality than the in camera processing, you can get a cleaner, lower noise output than you would using in camera gain. So before you flick on the gain switch of your camera, if your using only very light 10 bit or higher compression (HDCAM SR, Cineform, ProRes HQ) or uncompressed do consider that you may actually be better waiting until you get into post before you add gain.

Some modern cameras, like Red or the Sony F3 can use something called EI gain. EI gain does not actually add any gain to the recorded signal (or signal output in the case of the F3). Instead it adds gain to the monitor output only and adds metadata to the recording to tell the post facility or conversion software to add gain. This way you see on the monitor what the image should look like when the gain has been added, but the recording itself has no gain added giving the post production team the ability to fine tune exactly how much gain is applied.

Uncategorized

Can I use 8 bit to record S-Log?

2 Comments

My opinion is that while 8 bit, 422 can be used for S-Log, it is not something I would recommend. I’d rather use a cinegamma with 8 bit recording. 10 bit 422 S-log is another matter altogether, this is well worth using and works very well indeed. It’s not so much whether you use 444, 422 or maybe even 420, but the number of bits that you use to record your output.

What you have to consider is this. With 8 bit, you have 240 shades of grey from black to super white. of the 256 bits available, 16 are used for sync, white is at 235 and super white 256 so black to 100% white is only 219. With Rec-709, standard gamma, on an F3 you get about an 8 stop range, so each stop of exposure has about 30 shades of grey. When you go to S-Log, you now have around 13 stops of DR, so now each stop only has 18 shades of grey. Potentially using 8 bit for S-Log, before you even start to grade, your image will be seriously degraded if you have any flat or near flat surfaces like walls or the sky in your scene.

Now think about how you expose S-Log. Mid grey sits at 38% when you shoot. If you then grade this to Rec-709 for display on a normal TV then you are going to stretch the lower end of your image by approx 30%, so when you stretch you 18 steps of S-Log grey to get to Rec-709 you then end up with the equivalent of only around 12 shades of grey for each stop, that’s less than half of what you would have if you had originally shot using Rec-709. I’m sure most of us have at some point seen banding on walls or the sky with standard gammas and 8 bit, just imagine what might happen if you effectively halve the number of grey shades you have.

By way of a contrast, just consider that 10 bit has 956 grey shades from black to super white. the first 64 bits are used for sync and other data, 100% white is bit 940 and super white 1019. So when shooting S-Log using 10 bit you have about 73 grey shades per stop, a four fold improvement over 8 bit S-Log so even after shooting S-Log and grading to Rec-709 there are still almost twice as many grey shades than if you had originally shot at 8 bit Rec-709.

This is a bit of an over simplification as during the grading process, if your workflow is fully optimised you would be grading from 8 bit to 10 bit and there are ways of taking your original 8 bit master and extrapolating additional grey shades from that signal through smoothing or other calculations. But the reality is that 8 bits for a 13 stop dynamic range is really not enough.

The whole reason for S-Log is to give us a way to take the 14ish stop range of a typical linear 12 bit camera sensor and squeeze as much of that signal as possible into a signal that remains useable and will pass through existing editing and post production workflows without the need for extensive processing such as de-bayering or RAW conversion. So our signal which starts at 12 bits has already been heavily processed to get it from 12 bits to 10. Going from 10 bit down to 8 is a step too far IMHO.

Uncategorized

Adobe CS6 new pricing model.

Leave a comment

I think I have got this right! Instead of buying Adobe’s production suite software outright, you can now licence the entire suite on a monthly basis, choosing either a year long renewable contract or a month by month contract. If you already have a CS3 or higher product there is a reduced subscription rate. So now for just $49 a month ($29 if you already have a CS3 or higher licence) I can have access to all the latest creative suite applications. Compared to paying thousands of dollars for the full suite of Adobe software applications this new subscription model looks to be much more affordable. I do note however that you can still buy various creative suite bundles and the new prices appear lower than before. CS6 now includes Speed Grade which is a fantastic grading tool that even includes correction and alignment tools for 3D material too. Another addition is Prelude which is an ingest and logging tool that allows you to create log sheet, plus add markers and notes to clips which will pass through the complete CS6 workflow. The licence allows you to instal the apps on two machines, so this great for those of us with a laptop on the road and a workstation in the office.

Uncategorized

Sonnet EchoExpress Thunderbolt Adapter SxS Speed Tests.

6 Comments
Sonnet EchoExpress

I have had this little box for a couple of months now, but until the recent release of SxS drivers by Sonnet you couldn’t use it as an SxS card reader. There are two versions of the EchoExpress, the standard one, which is the one I have and a “Pro” version that offers higher speed transfers when using PCIe 2.0 adapters. When Apple removed the express card slot from their MacBook Pro laptops, they severely restricted the ability to connect high speed external hard drives. I have a Convergent Design Gemini which records on to SSD’s and the fastest way to offload these on location (for me at least) was to plug an eSATA PCI Express card into the slot on may older MacPro and then connect the Gemini Docking station to one port and then an external eSATA drive to the other. However, the processing power on my older MacBook was falling somewhat behind the modern machines and when trying to transcode from the uncompressed Gemini DPX files to ProRes or DNxHD was taking ages. So I decided to upgrade to a new MacBook Pro, but this then meant the loss of the Express Card slot. This is where the Sonnet EchoExpress became a “must have” add on, as it provides an external ExpressCard slot connected to the computer using Thunderbolt.

By using the EchoExpress box along with a Sonnet eSATA express card adapter I can connect eSATA devices to my MacBook Pro. The transfer speeds with my original version EchoExpress are not as fast as when I had a built in ExpressCard slot, but it’s still a massive improvement over USB, about 4 times faster. Initially SxS cards didn’t work with the EchoExpress, but Sonnet recently released a dedicated SxS driver that allows the EchoExpress to work as a SxS card reader.

So how fast is it? One thing to consider is that when using the EchoExpress as a card reader, on a MacBook Pro or 21″ iMac you only have a single Thunderbolt port, so there is no way to connect a second EchoExpress to add an eSATA port. That restricts you to using either the computers internal drive or an external Firewire 800 drive. For my tests I made copies of a full 16Gb Blue SxS card to both the internal drive as well as an external Seagate GoFlex FreeAgent drive fitted with a Firewire 800 interface.  There was very little difference between the transfer speeds to the laptops internal drive and the Firewire drive, so I suspect that the transfer speed is limited to that of the Sonnet EchoExpress.

Copying 16Gb from the SxS card via the EchoExpress took just a shade over 4 minutes. That’s pretty good performance and only marginally slower than when I had an express card slot built in to the computer. Typically with a built in slot it would take about 3 1/2 minutes. Compare that to copying the exact same data from the camera using USB which took 11 minutes! So, as an SxS card reader the Sonnet EchoExpress works really well offering transfers around 3 times faster than USB which is a big time saver. Imagine you have been shooting all day and have 5 hours of footage. With USB it would take you at least an hour to transfer your data, with the EchoExpress just 20 minutes.

I give the Sonnet EchoExpress a big thumbs up. Now all I need is a Thunderbolt hub.