Over the years there have been many, often heated debates over the differences between 8 bit and 10 bit codecs. This is my take on the situation, from the acquisition point of view.
The first thing to consider is that a 10 bit codec requires a 30% higher bitrate to achieve the same compression ratio as the equivalent 8 bit codec. So recording 10 bit needs bigger files for the same quality. The EBU recently evaluated several different 8 bit and 10 bit acquisition codecs and their conclusion was that for acquisition there was little to be gained by using any of the commonly available 10 bit codecs over 8 bit because of the data overheads.
My experience in post production has been that what limits what you can do with your footage, more than anything else is noise. If you have a noisy image and you start to push and pull it, the noise in the image tends to limit what you can get away with. If you take two recordings, one at a nominal 100Mb/s and another at say 50Mb/s you will be able to do more with the 100Mb/s material because there will be less noise. Encoding and compressing material introduces noise, often in the form of mosquito noise as well as general image blockiness. The more highly compressed the image the more noise and the more blockiness. It’s this noise and blockiness that will limit what you can do with your footage in post production, not whether it is 10 bit over 8 bit. If you have a 100Mb 10 bit HD compressed recording and comparable 100Mb 8 bit recording then you will be able to do more with the 8 bit recording because it will be in effect 30% less compressed which will give a reduction in noise.
Now if you have a 100Mb 8bit recording and a 130Mb 10 bit recording things are more evenly matched and possibly the 10 bit recording if it is from a very clean, noise free source will have a very small edge, but in reality all cameras produce some noise and it’s likely to be the camera noise that limits what you can do with the images so the 10 bit codec has little advantage for acquisition, if any.
I often hear people complaining about the codec they are using, siting that they are seeing banding across gradients such a white walls or the sky. Very often this is nothing to do with the codec. Very often it is being caused by the display they are using. Computers seem to be the worst culprits. Often you are taking an 8 bit YUV codec, crudely converting that to 8 bit RGB and then further converting it to 24 bit VGA or DVI which then gets converted back down to 16 bit by the monitor. It’s very often all these conversions between YUV and RGB that cause banding on the monitor and not the fact that you have shot at 8 bit.
There is certainly an advantage to be had by using 10 bit in post production for any renders, grading or effects. Once in the edit suite you can afford to use larger codecs running at higher bit rates. ProRes HQ or DNxHD at 185Mb/s or 220Mb/s are good choices but these often wouldn’t be practical as shooting codecs eating through memory cards at over 2Gb per minute. It should also be remembered that these are “I” frame only codecs so they are not as efficient as long GoP codecs. From my point of view I believe that to get something the equivalent of 8 bit Mpeg 2 at 50Mb/s you would need a 10 bit I frame codec running at over 160Mb/s. How do I work that out? Well if we consider that Mpeg 2 is 2.5x more efficient than I frame only then we get to 125Mb/s (50 x 2.5). Next we add the required 30% overhead for 10 bit (125 x 1.3) which gives 162.5Mb/s. This assumes the minimum long GoP efficiency of x2.5. Very often the long GoP advantage is closer to x3.
So I hope you can see that 8 bit still makes sense for acquisition. In the future as cameras get less noisy, storage gets cheaper and codecs get better the situation will change. Also if you are studio based and can record uncompressed 10 bit then why not? Do though consider how you are going to store your media in the long term and consider the overheads needed to throw large files over networks or even the extra time it takes to copy big files compared to small files.
I have been asked to show how I mount my NanoFlash on my EX3 so below are a couple of pictures of the full rig with some details of some of the various items that I use.
1. This is my Petroff 4×4 matte box with bellows hood. I love the old fashioned style bellows lens shade as you can adjust it in and out very quickly to eliminate stray light. A french Flag can be added if desired, but I find in most cases that the bellows shade is fine. Stray light causes reflections both between filters and within the lens, this can reduce contrast in the image so a good lens hood is essential for getting the best pictures. The Matte Box has 2 rotating filter holders. I often use some very gentle blue or grey grads to help with bright skies.
2. The standard EX3 lens. This lens is a remarkably good lens. Keep it between F8 and F2.8 for best results. The sweet spot is F4. Never use the Iris at F16 or F11, your pictures will be soft due to diffraction limiting. This is not a lens fault but something that would happen with any lens and 1/2? sensors (it’s even worse with smaller sensors). The beauty of the standard EX lens is that it incorporates automatic chromatic aberration correction which means no nasty blue or purple fringes around areas of high contrast.
3. SxS Cards. Even though I was one of the first people to work out how to use low cost SD cards with the fabled Kennsington Adapter I still use SxS cards. The reason is simple: reliability. If you look around the forums you will find lots of people having issues with SD cards. For example a wedding videographer that lost a large part of a service he had shot. If he had used SxS then that just would not have happened. I am a professional and my reputation is vital. That reputation could easily be destroyed if I came back from a shoot with nothing but corrupt data because I had tried to cut corners.
4. Kata Camera Glove. Protects the camera from everyday knocks and bumps as well as unexpected rain or dust.
5. The Cheek Pad. I know many EX3 users don’t fit these. It looks flimsy, but in use it’s strong enough and it really helps to stop the cameras tendency to want to tilt to the left. It makes the camera much more stable and really is worth trying.
6. Convergent Design NanoFlash. This incredible little box allows me to record from the HDSDi output at upto 160Mb/s long Gop. At 100 Mb/s you can’t tell the compressed from the uncompressed. By shooting with this I can grade and color correct my footage, make dubs, go multi generation without seeing any drop in quality. It also means my footage is accepted for HD broadcast by the BBC and the majority of other HD broadcasters. The EX 35Mb footage is good, don’t get me wrong but the 100Mb is sweet. It uses inexpensive Compact Flash cards and by recording to both SxS and the Nano at the same time I can be sure that even if I were to get a card failure I have a backup.
7. IDX V-Lock batteries. One of these will run this rig for around 5 hours. I am also looking at getting some of the Swit EX batteries with the Power-Con/D-Tap out to run the EX and NanoFlash, but by putting the battery out behind the camera the overall balance of the rig is improved. In fact without this larger battery the matte box tends to make it very front heavy.
8. Quick release shoulder pad. This is a home brew affair that incorporates a shoulder pad the V-lock battery adapter and NanoFlash or Radio Mic mount. It can be removed without tools in seconds. Perhaps one day I will get some Zacuto rails or similar, but they are rather expensive and this setup works very well for me.
9. Sony ECM-680S. This is a nice Stereo/Mono switchable gun mic. It is great for capturing nice stereo ambience and effects sound. Flick the switch and it becomes a useful interview mic.
10. DM accessories EX3 reinforcement plate. This is a MUST HAVE item. It provides you with a much stronger tripod fixing with both 1/4? and 1/2? threads as well as a host of other threaded holes for various applications. It makes the camera feel so much more solid on a tripod. I really can’t recommend it enough. below this is a cheap, Indian made Matte Box rail kit. It works, but again I could really do with some Zacuto rails or similar.
11. Chamois leather viewfinder cover. Much nicer against your skin than hard rubber. Also absorbs sweat and moisture which helps prevent the viewfinder from fogging. Another option is a small sweat band.
If money is no problem then the safest bet is to purchase a good quality HD lens, expect to spend at least £8k.
If you budget is restricted then the situation is much less clear. There are now several low cost 2/3? HD lenses designed for cameras such as the Panasonic HPX500. In my opinion these lenses are just not worth the money. They might be cheap (£4k ish) but the one’s I’ve played with have been pretty grim, suffering from lots of CA and soft corners.
If your on a tight budget the best thing you can do is take your camera to a good dealer and go through their second hand lenses, trying them on the camera. Check for resolution (use a chart), corner softness, CA and contrast. I did this and ended up with a Canon 16x8x2 IF lens. I found that lenses with lower zoom ratios tended to be better than those with higher ratios. I’m really pleased with my lens and when compared to the latest HD equivalents I can not tell the difference in real world use. It certainly outperforms all the budget HD lenses I’ve tried.
One interesting thing that I have discovered in my research into this subject is that Contrast is what makes the biggest difference in lens performance, not simply resolution as one might expect. Visually the next thing you notice is CA. This is a tough one as when you increase the resolution or sharpness of a lens you also tend to increase the CA.
Until lens manufacturers start to release MTF curves for their lenses the only thing we have as buyers to go on is the advertising blurb. It’s easy for a manufacturer to claim improved performance or new glass or other technology, but without accurate MTF curves it’s all pretty meaningless. You would only need the tiniest resolution improvement to be able to claim that you new HD lens range is sharper than your SD range, it could just be a fraction of a percent difference.
I’m off to Arizona on Thursday for a long weekend to shoot the monsoon thunderstorms. I had postponed this trip from earlier in the month when the weather just wasn’t right. This tim around the forecast is really good (for storms that is). I will be shooting with my PDW-700 and my EX1. I will also be giving the Nanoflash a shake down making good use of the cache function to capture what I hope will be some great lightning storms.?Anyone want to join me? I have a couple of spare seats in the car and motel rooms are peanuts.
There is far too much emphasis on color charts and 100% one to one – set it up with a scope settings. Very often a 100% accurate one to one response won’t look right as the video gamut is smaller and lopsided than that of the human eye so a small amount of skewing of the color gamut can often help produce a picture that visually looks more natural. One of the very best ways to set up a camera is to use a high quality color photograph of a known scene. Shoot the photograph and look at the picture on a monitor and adjust until it looks right. This will give a more natural looking image than aligning with charts and scopes and is a technique that has been used since the very beginnings of color television. I have a scene that contains vibrant colored cars, green fields and trees, buildings and blue sky. I have a dozen large copies of this picture and use it whenever I am making camera adjustments to make sure my pictures still look natural. Of course scopes should still be used if you are making any extreme settings to ensure your images are still legal, but at the end of the day what you are after is an image that looks right too you (or the producer) and whoever else will view your material, not what looks right according to a chart and a scope.
The PDW-700 cameras are balanced for daylight optically and then corrected electronically for tungsten etc.
Traditionally cameras were balanced for Tungsten and then added colour correction optical filters to get to daylight. This was done as CC filters absorb light and thus make the camera less sensitive. Normally when shooting outdoors in daylight sensitivity is not an issue while shooting indoors under tungsten light you used to need every bit of sensitivity you could get.
The down side to this approach is that tungsten contains very little blue light so to get a natural picture the blue channel was often running at quite a high level of gain which increases noise in the blue channel and thus overall noise. In addition when you rotated in the CC filters to get to daylight the sensitivity of the camera was reduced, so you did not have constant gain.
With the PDW-700 (and also the F350 I believe) the cameras are essentially balanced for daylight, without the use of any CC filters, which helps reduce noise in the blue channel. Then for tungsten shooting you electronically re balance the camera. By doing this the overall sensitivity of the camera is constant whether shooting at 3.2K or 5.6K and you only get additional blue channel noise while shooting under tungsten. If you are worried by blue channel noise you can always correct from daylight down to tungsten with an optical CC filter (80A) and leave the camera set to daylight, although this will reduce the systems overall sensitivity by around 1 and a half stops.
Last weekend was the Royal International Air Tattoo. The largest military air show in the world. I’ve filmed this event many times and every year we try to do things a little differently to jazz things up. We have been shooting the show in HD for the past 3 years, this year it was entirely XDCAM with the exception of the minicams which were HXR-MC1P HD minicams. We had an EX1, EX3 and 3x PDW-700?s. As well as the usual extra long telephoto lenses we had a couple of gyro stabilized lenses including a schwem gyrozoom. While not an HD lens we found that the performance of the lens wasn’t too bad. There is no other lens that offers the degree of stabilization offered by the schwem so for the applications we were using it for we were happy to accept the slight softness in the corners. The application we had was to use it in one of the “Follow Me” vehicles used to marshall the aircraft around the airbase.
The high point of this was doing a tracking shot of the recently restored Vulcan bomber landing at Fairford. To do this we drove along the taxiway parallel to the runway at high speed as the Vulcan came into land. Once it had landed we got some impressive shots as it taxied right behind us. The Vulcan is a huge aircraft and to have this bearing down on you as it taxies with all four engines running (they normally use only 2) is quite a rush! The Schewm is a long lens so the Vulcan completely filled the frame, despite this the gyro stabilisation kept the images rock steady. Over the weekend I shot aircraft startups and GV’s using an EX3, then the follow me stuff with the schwem and PDW-70 as well as flying and display footage using a PDW-700 and 42x Fujinon lens. The most reassuring thing is that as these are all XDCAM cameras we know they will all cut together well in the final edit.
The PDW-700 and F800?s are sold body only, so you have to choose which viewfinder you want. there are 3 choices. A cheap HDVF 200 mono CRT finder that is 480+ lines resolution, the mid range (top of the CRT range) HDVF-20A which is 500+ lines resolution and then there is the expensive colour HDVF-C35W.?I got the HDVF-20A. The viewfinder is a critical part of the package and I wanted a good viewfinder. For the past year my main camera has been my trusty EX3 which I love. This has a really good colour viewfinder with an excellent colour peaking function and image magnification. When I use my EX3 it is rare for me to not get my pictures pin sharp and spot on in focus. Plus I can frame my image taking into account both black and white contrast range and colour contrast. With the EX3 judging exposure is easy, you can see when your overexposing as you can see colours washing out. If I don’t want (or can’t) take a colour monitor on location then I really can light an interview or check colour balance without just using the EX3?s finder.?Now with the PDW-700 I am struggling. Going back to a mono CRT has been a bit of a shock, to be honest I am struggling with it. It’s not that there is anything wrong with the HDVF-20A but I have become used to working with a colour VF. I’m not sure I can live with the CRT VF for very long. I guess I am going to have to start saving my pennies as I think going back to a mono CRT is a retrograde step. I just wish the C35W was a little cheaper. Perhaps Sony could bring out a VF for the 700/F800 based on the rather good EX3 finder.?If I was making the purchase again I would opt for the more expensive C35W. I no longer see a colour VF as a luxury but more of an essential item. When you work with cameras day in – day out you want the tools that make your life as easy as possible and a good colour VF is one of them. On it’s own the C35W may seem expensive at £5.5k compared to the £3.5k of the 20A, but in terms of the total packing it’s another 10% to the cost but in retrospect I think it would have been worth it.
Just got back from my first PDW 700 green screen shoot. We were in a tiny room and it was a hot day, so it was certainly warm! Everything went well although I have to say that I am really struggling with the CRT viewfinder. I have become so used to a full colour viewfinder on the EX3 that it really is horrid going back to a monchrome viewfinder. I shall be playing with the footage on Monday so I’ll let you know how well it keys then.
Camera setup, reviews, tutorials and information for pro camcorder users from Alister Chapman.