I’m running a “Play with a 3D rig” session at the Phoenix Artists Club in central London between 12.30 pm and 6 pm on July 20th. This will be an opportunity to come and have a go with a Hurricane Rig and hopefully other related equipment. It is completely free and open to all. There will be discount prices on the rigs for those that attend as well as a free prize draw. It’s all free and if there is enough demand I will run a brief introduction to 3D workshop between 3pm and 4pm. Please fill out the registration form if you wish to join us. http://www.hurricane-rig.com/play-with-a-rig-london/
All posts by alisterchapman
Update to recent Negative Gain article.
I’ve added a graph and re-written parts of my recent article on Negative Gain to try to make it a bit clearer and easier to understand. I’ve also added it to my “Tech Notes” section.
FCP-X, My first look.
OK, I took the plunge and tried FCP-X to see for myself what it’s like, despite all the negative comments about it I though I would give it the benefit of doubt and try it for myself..
It’s very fast, the way you scrub through clips in the bins is impressive and the built in filters are a good start. I also note that decklink now have drivers for most of their cards so HDSDi out is now available, certainly things are strating to come together with FCP-X.
BUT… I wanted to add a simple colour correction to a clip, no problem with that using the colour board, but then I tried to add a keyframe so the correction would change slightly of the duration of the clip. Simple, basic stuff…. But you can’t. You can’t keyframe the majority of FCP-X’s effects, only the motion effects and a couple of others. This is such a simple, fundamental thing that I take for-granted with every other pro edit package. It’s not an advanced feature and yet it’s completely missing. FCP-X is not ready for me yet, too much stuff missing to make it useful as my NLE of choice. If I can’t keyframe effects then for me this is not a “Pro” edit package, it is a consumer product. Perhaps over time it will mature and things like this will get added. But I have on-going projects and who knows how long it will take to get FCP-X up to speed, it could be a year or more. So I either stick with now somewhat long in the tooth FCS or jump ship to Premiere CS5.5 which looks better and better by the day or maybe leave the Mac platform altogether and go with Vegas or Edius. Of course Avid is still an option too.
Motion “Judder” on the FS100 and other video cameras at low frame rates.
There have been a number of threads in various forums about the way the images from the new Sony FS100 appear to judder or stutter when shooting at 25P or 24P. Most of the complaints appear to be coming from PAL areas where shooting 25P is common. This is not an issue unique to the FS100, in fact motion judder is often more noticeable with video cameras than film cameras even though the frame rates and shutter speeds may be exactly the same. Why is this?
One of the key issues here and I believe a very strong clue to what is going on is that most complain that the issue is most pronounced in areas of high contrast.
Our visual system picks up edges and other areas of high contrast to detect motion, in areas of high contrast any non-smoothness of the images motion will be more noticeable. The higher the resolution/contrast or more precisely the higher the MTF of the camera system the more we will notice judder and stutter. Just take fast motion in an Imax film as an example, it stutters like crazy.
The FS100 and similar high contrast/resolution cameras will appear to stutter at low frame rates more than a low contrast/low resolution camera. Edges in film are almost never instant changes from black to white, there is almost always some smoothing or dithering caused by the grain structure of film. So when you consider the FS100’s near complete lack of noise, which through it’s random nature will help mask judder and stutter and you have a worst case scenario. A camera with sharp edges and no noise.
Another strong contributing factor is the use of detail correction that adds a very definite, hard, non-motion blurred black or white edge around any areas of medium to high contrast, so unlike the very slightly dithered edges we would see in film we have instant light to dark or dark to light transitions occurring over a single pixel. In the case of a pan that hard edge is going to step uniformly from one position to the next, it won’t have any motion blur and it will increase edge contrast compounding the images judder as our visual system will notice these hard edges jumping from one place to the next.
The PMW-F3 although it uses the same sensor is less prone to this effect as it has a more sophisticated DSP and uses less detail correction and more aperture correction for image sharpening. Aperture correction blurs with motion as it is a type of high frequency boost and as you pan the camera the motion blur of the image reduces high frequencies so the amount of correction also drops thus helping smooth edges as you pan.
You also need to consider the results of watching 25fps video on a computer monitor typically running at 60hz. You will get judder as 25 does not go into 60 evenly, this helps explain why this “issue” is getting more airtime in Europe than in the US where 24P with pull up to 30P is common and of course 30P will display on a 60Hz monitor with no additional problems.
So in the case of the FS100 (or other cameras exhibiting this effect), I would suggest turning off the detail correction circuits or at the very least reducing the detail level if you are shooting high contrast images or anything with a lot of motion. It would also be interesting to compare similar pans at different speeds with some gain added to see if that helps.
I don’t think this is, as claimed by some, to be camera fault, more likely a result of a very clean, detail corrected image. Even an EX1 or EX3 will do similar things if your detail settings are too high. It’s not unique to the FS100, just one of those things that can happen when you have sharp pictures. When I watched the Sony F65 4k demo film “The Arrival” I noticed a similar increase in motion judder compared to film, again I put this down to high edge sharpness catching my eye and making me notice the cameras motion more acutely. Ohh that F65 stuff looked stunning!
Why using negative gain can be bad, unless you have an F3.
One way to reduce the noise in a video camera image is to reduce the cameras gain. We all know that increasing the gain to lets say +6db will increase noise and generally the reverse holds true when you reduce the gain, the noise typically reduces and this may be helpful if you are going to do a lot of effects work, or just want a clean image.
However in most cases negative gain reduces dynamic range as it will artificially clip or limit your low key parts of the image. The maximum illumination level that a camera can capture is limited by the sensor or the amount of data used to transfer the signal from the sensor into the processing circuits, the cameras DSP (Digital Signal Processor). The black level or darkest part of the image is the point where the design engineers have deemed that the ratio of actual image signal to sensor noise is high enough to give a suitably noise free image (also known as noise floor). So the dynamic range of the camera is normally the range between the sensors noise floor and saturation point.
The gain of the camera controls the video output level, relative to the sensors signal level. If you use -3db gain you attenuate (reduce) the relative output signal. The highlight handling doesn’t change (governed by the sensor) but your entire image output level gets shifted down in brightness and as a result you will clip off or loose some of your shadow and dark information, so your overall dynamic range is also reduced as you can’t “see” so far into the shadows. Dynamic range is not just highlight handling, it is the entire range from dark to light. 3db is half a stop (6db = 1 stop) so -3db gain reduces the dynamic range by half a stop, reducing the cameras underexposure range.
So for cameras like the EX1 and EX3 or even PMW-500/PDW-700 using negative gain can be a bad thing to do. You need to be aware that there is a trade off of noise against dynamic range and need to be sure that the small noise benefit are worth the sacrifice of some latitude.
Interestingly the PMW-F3 has an excess of dynamic range for the normal gammas and cinegammas and the processing appears to take advantage of this to keep the images very clean. When you shoot with the standard gammas and cinegammas on the F3 the cameras base ISO (sensitivity) is 400 asa at 25p. In effect the arbitrary black level is kept some way up the sensors output range to keep the images well clear of the noise floor. This gives a very clean, ultra low noise image with 11.5 stops of dynamic range. When you switch the camera to S-Log, which gives a greater dynamic range (approx 13 stops by my estimation) the base ISO increases to 800 asa. When you increase the sensitivity like this you lower you black point lower down the sensors output range closer to the noise floor. Looking at some of my S-Log test footage a clear increase in under exposure latitude can be seen when you use S-Log. I suspect that the “0db” point in the F3 is actually 800 asa as used by S-Log, where maximising dynamic range and using the full sensor range is the priority. Meanwhile with standard gammas, which are limited to 11.5 stops anyway, you can reduce the gain by 6db (1 stop) sacrificing one stop of underexposure and raising the black point well above the noise floor but still have the full 11.5 stops but with 6db less noise.
Adaptimax Lens Mount Adapters for PMW-F3, Canon and Nikon.
I was sent a couple of Adaptimax lens mount adapters to test on my PMW-F3. I have used some of their EX3 adapters in the past and these worked very well. The new PMW-F3 adapters are finished with a very nice hard black anodised finish and look very smart indeed. I had 3 adapters to try, one F3 to Canon and two F3 to Nikon adapters. The Canon adapter is a “dumb” adapter, so there is no way to control the lenses iris. If your using Canon lenses this means using a DSLR body to set the iris before using the lens on the F3. Obviously this is not ideal, but you do have to consider that there is a massive range of lenses that can be used with this Canon adapter via a secondary adapter ring.
Canon’s flange back distance (the sensor to lens distance) is the shortest in the DSLR world. So this means that there is space to adapt to other lens mounts with longer flange back distances such as M42, Nikon, Pentax, Pentacon etc. This opens up a whole world of possibilities as now you can use those nice M42 Zeiss lenses that can be picked up cheap on ebay by adding a cheap M42 to Canon adapter.
If you have already invested in Nikon fit glass then you can use a Nikon to Canon adapter or you can use one of Adaptimax’s purpose built F3 to Nikon adapters.
There are two varieties, the original Adaptimax and the Adaptimax Plus. The Plus version includes a long screw that pushes the iris pin on the rear of the lens to give you iris control even when the lens does not have an iris ring. While this is not as elegant as MTF Services rotating adapter barrel, it works fine and the simplicity of the design means the adapter is a little cheaper. The standard version has no iris control, so you need to ensure your lens has a proper iris ring. Priced at £255 for the standard adapters and £265 for the plus versions these are good value for money.
Night Flyers. Shot with PMW-F3 in Singapore
I’m currently in Singapore staying at Clarke Quay. Most evenings a group of radio control kite flyers from a local store (goflykite.com) bring out their illuminated kites and fly them in the local park. It’s very pretty and seemed an interesting thing to try and shoot with my F3. As I’m travelling light, trying (and failing) to keep within a 20kg baggage allowance, I don’t have a tripod and I’ve only got a couple of lenses, my trusty 50mm Nikon f1.8 and my Tokina 28-70mm f2.6 zoom. Most of this was shot with the Nikon lens at +6db. I really wish I had a tripod and a longer lens! I did a little bit of grading work here and there to balance out the very orange street lights a little.
Today3D Electronic Follow Focus and 3D Rig Controller. FIZ
Here’s a very exciting new product I was first given a sneak preview of at Cinegear in LA a couple of weeks ago, but now I have had a slightly longer look and a chance to take some pictures at Broadcast Asia. It comes from a new name to the market, Korean based Today 3D, but don’t let that worry you, I know some of the guys behind this and they know what they are doing. In addition many of the products coming out of Korea in recent years have been very good, like the NextoDI range of media backup devices. The device is a full wireless electronic follow focus designed primarily for 3D applications. There will be different models capable of driving up to 8 motors for full stereo focus, zoom, iris, interaxial and convergence control down to an entry level 2D wireless follow focus.
The hand controller is beautifully well built, machined out of a solid block of alloy and it feels reassuringly solid, if just a little heavy in your hand. On the right side there is a nice big, silky smooth focus control that sits nicely in your hand. On the face of the controller there is a slide control that would normally be used for the other functions such as convergence or most commonly interaxial. The unit is full programmable via a small joystick and menu system with a multicolour display giving you information about your focus distance, zoom position and interaxial etc. It runs off rechargeable Canon DSLR batteries which easy enough to get hold of wherever you may be. The final price has yet to be announced but I have been reassured that it will be extremely competitive, probably a lot less than a comparable C-Motion controller. It won’t initially come with motors but it has the industry standard motor interface so can be used with motors from Heden, Preston, M-One etc. It’s a great looking piece of kit that really feels built to last. I’m hoping to get hold of one for a full review and test drive in the near future. There are also some other interesting 3D products coming from Korea including some innovative transparent alignment charts! Watch this space.
PMW-F3 S-Log and Cinegamma quick look.
Hello from hot and steamy Singapore. I’m at broadcast Asia doing some presentations on the PMW-F3, FS100 and 3D. On the Sony booth they have a PMW-F3 with all the options installed including S-Log and what also appears to be the 3D link firmware (mission for tomorrow – investigate 3D link). So I decided to quickly grab a couple of test shots with both S-Log and Cinegamma 1 to see how much of a difference there was. I was only able to record to the internal SxS card, but the results were quite enlightening. This was all done very quickly, so it’s not particularly scientific or accurate, but it does prove beyond any doubt that S-Log brings a significant boost to the dynamic range compared to the cinegammas. I estimate it gives you between 1.5 and 2 more stops to play with. Given that the F3 is already tested and shown to have around 11.5 stops with the cinegammas, this means that the F3 with S-Log is in the 13 to 13.5 stop range, very impressive indeed.
The shot is a pan from the darker side of the Sony booth to the very bright camera set. Exposure was set using the bright end of the shot and setting the iris so that the hotspots in the image were just below clipping, the idea being to look at what was going on in the shadows to get a feel for the dynamic range. Click on the images below a couple of times to get to the full resolution version if you want to see that.
What’s most striking is the difference in the shadow areas in the S-Log footage. Given that the peak white exposures were roughly the same (108ire) there is a huge difference in the darker shadow areas with much more information in the S-Log. It also surprised me just how well the bright part of the S-Log clip graded. Do remember that these clips were taken from recordings on the SxS cards, so they are 8 bit, 35MB/s.
I’ve put together a sequence of these clips for Vimeo. Click Here to go to the video on vimeo. The final test that I did, which you will see in the vimeo clip is to try to grade the shadow areas of the Cinegamma to bring them up to match the S-Log. The result was nowhere near as pleasing as the S-log as lifting the blacks introduces a lot of extra un-wanted noise and it still does not have the contrast range of the S-log.
New Video Clips added.
I have updated the “How To” videos page to include a couple more instructional videos on the Matrix and Progressive v Interlace shooting. I’ve also added a new page with some of my video reviews. You’ll find the links just below the picture at the top of the page.