Tag Archives: FS7

cameras, HDR, PXW-FS7, Technology

What does Rec-2020 on the PXW-FS7 II really mean?

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So, as you should have seen from my earlier post Sony has included Rec-2020 as a colorspace in custom mode on the new FS7 II. But what does this mean and how important is it? When would you use it and why?

Recommendation ITU BT.2020 is a set of standards created by the International Telecommunications Union for the latest and next generation of televisions. Within the standard there are many sub-standards that define things such as bit depth, frame size, frame rates, contrast, dynamic range and color.

The colorspaces that Sony's cameras can capture.
The colorspaces that Sony’s cameras can capture.

The Rec-2020 addition in the the FS7 II specifically refers to the color space that is recorded, determining the range of colors that can be recorded and the code values used to represent specific tones/hues.

First of all though it is important to remember that the FS7 II shares the same sensor as the original FS7, the FS5 and F5. Sony has always stated that this sensor is essentially a “709” sensor. The sensor in Sony’s PMW-F55 can capture a much greater color range (gamut) than the F5, FS5 and FS7, only the F55 can actually capture the full Rec-2020 color space, the FS7 II sensor cannot. It’s very difficult to measure the full color gamut of a sensor, but from the tests that I have done with the F5 and FS7 I estimate that this sensor can capture a color gamut close to that of the DCI-P3 standard, so larger than Rec-709 but not nearly as large as Rec-2020 (I’d love someone to provide the actual color gamut of this sensor).

So given that the FS7 II’s sensor can’t actually see colors all that far beyond Rec-709 what is the point of adding Rec-2020 recording gamut as the camera can’t actually fill the recording Gamut? Similarly the F5/FS5/FS7 cannot fill S-Gamut or S-Gamut3.

The answer is – To record the colors that are captured with the correct values. If you capture using Rec-709 and then play back the Rec-709 footage on a Rec-2020 monitor the colors will look wrong. The picture will be over saturated and the hues slightly off. In order for the picture to look right on a Rec-2020 monitor you need to record the colors at the right values. By adding Rec-2020 to the FS7 II Sony have given users the ability to shoot Rec-2020 and then play back that content on a Rec-2020 display and have it look right. You are not capturing anything extra (well, maybe a tiny bit extra), just capturing it at the right levels so it at least looks correct.

As well as color, Rec-2020 defines the transfer functions, or gamma curves to you and me, that should be used. The basic transfer function is the same as used for Rec-709, so you can use Rec-709 gamma with Rec-2020 color to get a valid Rec-2020 signal. For full compatibility this should be 3840×2160 progressive and 10bit (the Rec-2020 standard is a minimum of 10bit and as well as 3840×2160 also includes 7680×4320).

But, one of the hot topics right now in the high quality video world is the ability to display images with a much greater dynamic range than the basic Rec-709 or Rec-2020 standards allow. There is in fact a new standard called Rec-2100 specifically for HDR television. Rec-2100 uses the same colorspace as Rec-2020 but then pairs that bigger colorspace with either Hybrid Log Gamma or ST2084 gamma, also know as PQ (Perceptual Quantiser). As the FS7 II does not have PQ or HLG as gamma curves you cannot shoot material that is directly compatible with Rec-2100. But what you can do is shoot using S-Log2/S-Log3 with S-Gamut/S-Gamut3/SGamut3.cine which will give you the sensors full colorspace with the sensors full 14 stop dynamic range. Then in post production you can grade this to produce material that is compatible with the Rec-2100 standard or the Rec-2020 standard. But of course you can do this with an original FS7 (or F5) too.

So, when would you actually  use the FS7 II’s Rec-2020 colorspace rather than S-Log/S-Gamut?

First of all you don’t want to use it unless you are producing content to be shown on Rec-2020 displays. Recording using Rec-2020 color gamut and then showing the footage on a Rec-709 display will result in washed out colors that don’t look right.

You would probably only ever use it if you were going to output directly from the camera to a monitor that only supports Rec-2020 color or for a project that will be specifically shown on a standard dynamic range Rec-2020 display. So, IMHO this extra colorspace is of very limited benefit. For most productions regular Rec-709 or S-Log/S-Gamut will still be the way forward unless Sony add Hybrid Log Gamma or PQ gamma to the camera as well. Adding HLG or PQ however has problems of it’s own as the existing viewfinders can only show standard dynamic range images, so an external HDR capable monitor would be needed.

Rec-2020 recording gamut is a nice thing to have and for some users it may be important. But overall it’s not going to be a deal breaker if you only have a standard FS7 as the S-Log workflow will allow you to produce Rec-2020 compatible material.

 

 

cameras

PXW-FS7 firmware version 4.0 now available to download.

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FS7-Firmware-V4Sony have released firmware update version 4.0 for the PXW-FS7. This new firmware brings some welcome updates to the FS7 including the ability to move the focus magnification area away from the center of the screen.  Other new features include true 24p (as well as 23.98fps).

1. Support for Flexible Spot in Focus setting.
2. Support for XAVC-I 4K 24.00P.
3. Display for Video Signal Monitor is improved.
4. Operability of S&Q setting by assignable button is improved.
5. Remove Basic Authentication from items saved in all file.
6. Auto knee stability is improved.
7. Overall stability and operability of the camera is improved.
The firmware can be downloaded from here: https://www.sony.co.uk/pro/support/software/SET_BPE-SS-1238
cameras

PXW-FS7 Firmware Version 3.0 Released

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fs7-firmware3Good news. Firmware version 3.0 has just been released for the PXW-FS7. This is a major update for the FS7 and adds some important new features such as a 2K center scan mode that can be used to allow you to use super16 lenses or more importantly eliminate aliasing and moire when shooting above 60fps.

For users of the Cine-EI mode there are major improvements to the usability of the waveform display as this now works with most LUT combinations (but not in S&Q or when outputting 4K). In addition you can now enable noise reduction in Cine EI, although be aware that this may introduce banding artefacts in some situations.

Zebras now go all the way down to 0% so if you want you can use zebras to measure white or grey cards when shooting log or to measure the recommended skin tone levels for S-log (40-55%) and hypergamma (55-60%) recordings.

Also there is a proper time-lapse mode and some improvements to the quality of the raw recordings when using an external recorder raw such as the 7Q.

https://www.sony.co.uk/pro/support/software/SET_BPE-SS-1238

 

cameras, cinematography, lenses, PMW-F55, PXW-FS5, PXW-FS7, Shooting Tips, Technology

More info on CMOS sensor grid artefacts.

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Cameras with bayer CMOS sensors can in certain circumstances suffer from an image artefact that appears as a grid pattern across the image. The actual artefact is normally the result of red and blue pixels that are brighter than they should be which gives a magenta type flare effect. However sometimes re-scaling an image containing this artefact can result in what looks like a grid type pattern as some pixels may be dropped or added together during the re scaling and this makes the artefact show up as a grip superimposed over the image.

Grid type artefact.
Grid type artefact.

The cause of this artefact is most likely off-axis light somehow falling on the sensor. This off axis light could come from an internal reflection within the camera or the lens. It’s known that with the F5/F55 and FS7 cameras that a very strong light source that is just out of shot, just above or below the image frame can in some circumstances with some lenses result in this artefact. But this problem can occur with almost any CMOS Bayer camera, it’s not just a Sony problem.

The cure is actually very simple, use a flag or lens hood to prevent off axis light from entering the lens. This is best practice anyway.

So what’s going on, why does it happen?sony-grid-artefact-explained

When white light falls on a bayer sensor it passes through color filters before hitting the pixel that measures the light level. The color filters are slightly above the pixels. For white light the amount of light that passes through each color filter is different.  I don’t know the actual ratios of the different colors, it will vary from sensor to sensor, but green is the predominant color with red and blue being considerably lower, I’ve used some made up values to illustrate what is going on, these are not the true values, but should illustrate the point.

In the illustration above when the blue pixel see’s 10%, green see 70% and red 20%, after processing the output would be white. If the light falling on the sensor is on axis, ie coming directly, straight through the lens then everything is fine.

But if somehow the light falls on the sensor off axis at an oblique angle then it is possible that the light that passes through the blue filter may fall on the green pixel, or the light from the green filter may fall on the red pixel etc. So instead of nice white light the sensor pixels would think they are seeing light with an unusually high red and blue component. If you viewed the image pixel for pixel it would have very bright red pixels, bright blue pixels and dark green pixels. When combined together instead of white you would get Pink or Blue. This is the kind of pattern that can result in the grid type artefact seen on many CMOS bayer sensors when there are problems with off axis light.

This is a very rare problem and only occurs in certain circumstances. But when it does occur it can spoil an otherwise good shot. It happens more with full frame lenses than with lenses designed for super 35mm or APSC and wide angles tend to be the biggest offenders as their wide Field of View  (FoV) allows light to enter the optical path at acute angles. It’s a problem with DSLR lenses designed for large 4:3 shaped sensors rather than the various wide screen format that we shoot video in today. All that extra light above and below the desired widescreen frame, if it isn’t prevented from entering the lens has to go somewhere. Unfortunately once it enters the cameras optical path it can be reflected off things like the very edge of the optical low pass filter, the ND filters or the face of the sensor itself.

The cure is very simple and should be standard practice anyway. Use a sun shade, matte box or other flag to prevent light from out of the frame entering the lens. This will prevent this problem from happening and it will also reduce flare and maximise contrast. Those expensive matte boxes that we all like to dress up our cameras with really can help when used and adjusted correctly.

I have found that adding a simple mask in front of the lens or using a matte box such as any of the Vocas matte boxes with eyebrows will eliminate the issue. Many matte boxes will have the ability to be fitted with a 16:9 or 2.40:1 mask ( also know as Mattes hence the name Matte Box) ahead of the filter trays. It’s one of the key reason why Matte Boxes were developed.

Note the clamp inside the hood for holding a mask in front of the filters on this Vocas MB216 Matte Box. Not also how the Matte Box’s aperture is 16:9 rather than square to help cut out of frame light.
Arri Matte Box with Matte selection.

You should also try to make sure the size of the matte box you use is appropriate to the FOV of the lenses that you are using. An excessively large Matte Box isn’t going to cut as much light as a correctly sized one.  I made a number of screw on masks for my lenses by taking a clear glass or UV filter and adding a couple of strips of black electrical tape to the rear of the filter to produce a mask for the top and bottom of the lens. With zoom lenses if you make this mask such that it can’t be seen in the shot at the wide end the mask is effective throughout the entire zoom range.

f5-f55-mask

Many cinema lenses include a mask for 17:9 or a similar wide screen aperture inside the lens.

 

cameras, PXW-FS7, Review

Sony’s new PXW-FS7. First Impressions.

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I was lucky enough to get a chance to go out and shoot with a pre-production PXW-FS7 in Amsterdam during IBC. Guess what? It makes some very nice pictures!

In case you’ve had your head in the sand the last couple of weeks the PXW-FS7 is a new super35mm camcorder from Sony. It uses the same sensor as the Sony PMW-F5 and a lot of the camera is, I am sure, shared with the F5. Even the menu’s are almost exactly the same. It can record 4K internally on XQD cards using Sony’s XAVC codec. When the cameras start shipping next month you will be able to record 3840×2160 UHD/QuadHD as well as HD. Next year there will be an update to add 4096×2160 at up to 60fps.

Sony's PXW-FS7Want to shoot slow motion? That’s no problem as the camera can go up to 180fps internally in HD and if you add an external raw recorder you can stretch that out to 240fps.

The XAVC codec options are great. You can choose between I frame for easy editing or long GoP which gives a smaller file size but needs more processing power to decode. The 10 bit 422 image quality is very similar in both cases, so choose which to use based on how much recording media you have and how powerful your edit machine is. If you still need the legacy HD XDCAM Mpeg codec then you have that too.

Extension Unit:

By adding the optional extension box to the rear of the camera you can even record ProRes HQ to the XQD cards (after a firmware update early next year). The extension box also adds the raw output needed to record raw to an external recorder such as The Odyssey 7Q or Sony R5 recorder. On top of that you also gain Timecode in and out plus genlock. To power all of this (and the camera) the extension box has a V-Mount battery plate on it’s rear. When not using the extension box the camera runs off BP-U type batteries, the same 12V batteries as used by an EX1 or PMW200 etc.

The right side of the FS7 showing the XLR connectors.
The right side of the FS7 showing the XLR connectors.

The FS7 has two different shooting modes. In custom mode the camera behaves pretty much like any other conventional camera where what you see in the viewfinder is what’s recorded on the cards. You can alter the cameras gamma curve, matrix and other settings, but basically what you see is what you get. The other mode is the CineEI mode (just like an F5 or F55) and in this mode the camera records using SGamut3.cine and S-Log3. The aim being to capture the maximum possible dynamic range and in this mode the cameras sensitivity is locked to it’s native ISO of 2000. As S-Log3 results in a very flat picture (that’s great for grading and post work) the camera includes the ability to add a range of Look Up Tables (LUT’s) to the viewfinder or HDSDI output. LUT’s help you better judge exposure and give a more pleasing image prior to grading. You can even generate your own LUT’s in software such as Resolve and load them in to the camera. For exposure assistance the camera has a range of tools including a waveform, vectorscope or histogram display as well as zebras.

The FS7's handgrip and control unit.
The FS7’s handgrip and control unit.

Ergonomically the camera is very interesting. It has Sony’s E-Mount lens mount so you can use just about any lens you want simply by adding a lens adapter. Using a metabones or Commlite adapter you can use Canon EF lenses with ease. Likewise PL or Nikon lenses with the appropriate adapters.

Designed to sit on the front of your shoulder and supplied with a handgrip on an adjustable arm (attached via a standard Arri type rosette) the camera is easy to use. There are a couple of assignable buttons on the hand grip as well as a small joystick for navigating through the cameras menu system. A large zoom rocker will control any E-Mount zoom lenses used such as the new 28-135mm f4 lens and a further assignable dial wheel can be used to control the lenses aperture or other functions. The hand grip uses the LanC protcol so it should be possible to use other LanC devices with this camera.

The PXW-FS7 with the extension unit fitted, a V-Mount battery and a Vocas base plate.
The PXW-FS7 with the extension unit fitted, a V-Mount battery and a Vocas base plate.

The camera is a little front heavy as it sits on the front of your shoulder. When you add the extension box and a V-mount battery the balance is much better as the weight is now set much further back. With a 3rd party shoulder mount such as the new Vocas one or the dedicated Sony VCT-FS7 mount the camera can be turned into a true shoulder mount camera.

The LCD viewfinder is mounted on a thin arm that gives it forwards and backwards adjustment as well as up and down adjustment, but there is no left right adjustment.

The viewfinder on the PXW-FS7
The viewfinder on the PXW-FS7

Overall I think the viewfinder is the weakest part of this camera. The images in the VF are quite reasonable (its 940×560 resolution) but the mounting mechanism and loupe are not the best. Maybe this will be improved before the camera ships. I made a lot of use of one of the hand grip assignable buttons to provide focus magnification while shooting to ensure focus was spot on and it’s nice to have the focus mag function so easily accessible.

One issue I did find with the arm for the hand grip was that unless you fold it up out of the way you can’t slide the camera on and off a tripod. If you are using a base plate this is less of a problem but with a bare camera it’s a bit of a pain.

The XQD card slots on the PXW-FS7, also there is an SD card slot for loading LUT's, user files and setup information.
The XQD card slots on the PXW-FS7, also there is an SD card slot for loading LUT’s, user files and setup information.

I found the operation of the camera almost identical to the PMW-F5. There are some differences however. The FS7 does not have a 2K center scan mode for the sensor. This is used on the F5/F55 to eliminate aliasing problems when shooting above 60fps where the 4K sensor is read out as a 2K sensor. On the F5/F55 if you don’t want to use the 2K center scan mode you can fit a special 2K low pass optical filter to eliminate aliasing above 60fps, but again this is not possible on the FS7.

Another thing the FS7 doesn’t have is the large side display of the F5 and F55. For conventional shooting this is not really a big deal. But if you are using the CineEI mode where you may be using LUT’s on different outputs not having this information clearly displayed is a bit of a nuisance. In fact during the shoot with the FS7 at one point I though I was shooting with a LUT when in fact I was not. The only way to be sure of how everything is set is to go into the cameras menu system.

The PXW-FS7 fitted with the 28-135mm f4 servo zoom lens.
The PXW-FS7 fitted with the 28-135mm f4 servo zoom lens.

But what about the image quality? Frankly it’s amazing! For the money the images this camera produces are remarkable. It is using the F5’s sensor and it does have 14 stops of dynamic range. S-log3 is a great gamma curve and the camera is very low noise, even at it’s native 2000 ISO. It was hard to tell as most of the shooting took place at night, but initially it doesn’t look like there is any difference between the quality of the footage from the FS7 and the PMW-F5. Great colours, low noise, high dynamic range with very pleasing roll off what more can you want? One area where there will be a difference is with raw. The PMW-F5 takes the Sony R5 directly docked on it’s back. The raw form the F5 is 16 bit while the raw from the FS7 is going to be recorded on an external recorder at only 12 bits. 12 bit linear raw is really pushing the limits of what is needed for linear raw. However we do already know that the 12 bit raw from Sony’s FS700 works well, so this should be no different.

Where this camera will be really good is when combined with the new 28-135mm f4 servo zoom lens. Typically par-focal lenses with this kind aperture and zoom ratio cost in excess of $30K. This lens will be around $2.7K. Being able to zoom in and out on a large sensor camera smoothly really increases the cameras flexibility making it much easier to use in run and gun type situations. The lens is never going to be an incredible performer at this price and when wide open I did find it a little soft, but for shear ease of use it’s really remarkable. The FS7 combined with this lens will be a killer combination and that’s why I have ordered one. It’s NOT replacing my F5, I love my F5 and I think that the F5 is a much better camera for drama or studio type shoots. But the FS7 will be very handy for fast and fluid productions. In addition, for the money this camera is an absolute bargain.