Here’s a few clips shot with the FS700 from last weekends Royal International Air Tattoo. Check out the DHL 767 just hanging in the sky, also notice the almost complete lack of skew on the propellors.
NEX-FS700 Significantly reduced shutter when in Super Slow Mo!
UPDATED WITH NEW FRAME GRABS FROM STROBE LIGHT AT BOTTOM.
One of the things that did concern me slightly about the FS700 was how would the sensor behave in Super slow Mo. The sensor is a CMOS sensor, so I expected it to exhibit rolling shutter artefacts, which it it does indeed do when in standard shooting modes and S&Q motion. It’s not bad, but you can make the pictures skew and when you try to shooting something like a spinning propellor you can get some weird effects, especially at higher shutter speeds. However when you switch the camera to Super Slow Mo the rolling shutter effects appear to go away. I was able to shoot propellors, do fast pans, shake the camera about etc and there was little sign of the usual rolling shutter artefacts.
Just take a look at these two frame grabs. One shot done at 25P with a 1/100th shutter, the other done at 100fps with a 1/100th shutter, so in both cases the shutter speed is the same, so you would expect the rolling shutter artefacts to be the same, but clearly they are not. In standard mode the fan exhibits a typically lop sided, asymmetrical look and the fan blades appear curved, the upper and lower fan blade both bent towards the right of the frame. But in Super Slow Mo mode the fan blades are straighter and the fan is a lot more symmetrical with noticeably less bias towards the right, notice in particular the differences in the lower fan blade.
You can tell the shutter periods are the same as the amount of motion blur and spreading of the fan blades is near identical, so it’s not a shutter speed difference, this is clearly a sensor scan difference. This is very interesting and requires further investigation as it suggests that the sensor read out process is different in the high speed mode. It is probably just a significantly faster scan rate, but it could also possibly be a global shutter of some kind. It’s just a shame that you can’t access this read out mode for normal shooting.
UPDATE:
Here are a couple more frame grabs done with the strobe focussing flash from a Canon DSLR. In both cases the shutter speed is 1/100th of a second so you would expect the width of the “Flash Band” to be the same. The narrower the band, the slower the sensors scan speed. These frame grabs suggest the scan speed is around twice as fast when in Super Slow Mo. It’s not a global shutter, but certainly a nice improvement. This is 100% repeatable.
You can take advantage of this for normal speed shooting by setting the camera to SSM and recording the SDior HDMI feed to an external recorder.
Speculation: There is a little more aliasing when shooting in SSM. Is there some line slipping going on perhaps during SSM? This would allow a faster scan speed as fewer lines of pixels are read and thus might account for both the slight aliasing increase and the faster read out speed.
A Diamond In The Mind. Blu-Ray available now.
Many of you will have heard about my involvement in the recent production of a film about one of Duran Duran’s concerts last December. Well it’s out on Blu-Ray and DVD now and I think it looks might fine. Directed by Gavin Elder, Produced by James Tonkin it was a great pleasure to work with Den Lennie to help create a special picture profile for the F3’s used to shoot the concert. Here is a track from the Blu-Ray to give you a taste of the look of the video. Please click through and play it full screen in HD for the full effect.
Lightweight Tripod Help Please.
Hello all.
I really need to get an ultra light tripod for my travels. I love my Vinten 5AS and 100AS with CF legs, these are great, but they are around 6kg/8kg and possibly more of a bind is the length of the legs when collapsed. I really need something a bit easier to travel with, especially for my arctic expeditions and overseas workshops. On my recent Asia trip I was typically around 5kg over my baggage allowance on many flights, partly because of the weight of the tripod but also because of the size of the case required to transport it. In addition a big broadcast tripod does tend to catch the attention of customs officials. So I need something that will work with a bare bones FS700 or F3 (3-4kg payload). I realise that cutting back to the minimum on the tripod will effect my ability to achieve stable shots and smooth pans, but most of the shots I do are wide angle.
I’ve looked at a few options. Maybe a Manfrotto 504 head with the single tube CF legs, or one of the Miller Solo systems. I don’t have a big budget for this so perhaps I’ll just get a set of single tube 75mm bowl legs to use with my Vinten 5AS head. So what do you guys use, what are your recommendations? Please leave a comment with your suggestions.
Singapore by Night. Shot with FS700, PMW-F3 and NEX5N
This is a video of Singapore I shot while at Broadcast Asia. I used a variety of Sony cameras to shoot this. The principle camera was a Sony FS700, used for the slow mo at the beginning and end as well as many of the time-lapse shots which were done by shooting using S&Q mode at 1 frame per second. Also used was a Sony PMW-F3 in frame interval mode and a Sony NEX5 stills camera triggered with a Gentled time-lapse controller.
Why Nailing Your Mid Range Will Make Post Production Happy. Even with Cingammas and Hypergammas.
One of the concepts that’s sometimes hard to understand is why mid range exposure is so critical with most video cameras, even cameras with extended dynamic range. Cameras that use Cinegammas, Hypergammas may give you great dynamic range and extra latitude but it’s still vital that you get your mid range exposed correctly. In many cases, the greater you cameras ability to capture a wide dynamic range the more critical mid range exposure becomes. I’ve often heard comments from users of XDCAM cameras complaining that they find it harder to work with cinegammas and hypergammas than the standard REC-709 gamma.
So why is this, it seams counter intuitive, surely a greater dynamic range makes exposure more forgiving?
First lets take a look at a standard gamma curve. These graphs are not accurate, just thrown together to illustrate the point. The standard gamma for HD, REC-709 can be considered to be near linear. Certainly in terms of “what you see is what you get” the idea behind REC-709 is that if the camera is set to 709 and the TV or monitor is 709 compliant then we will get a linear 1:1 reproduction of the real world. However REC-709 is based on the gamma curves used at the very beginnings of television broadcasting where TV’s and cameras had very limited dynamic range. True REC-709 only allows for about 6 stops of dynamic range and as a result the version of REC-709 used in most video cameras is tweaked somewhat to allow a greater dynamic range in the region of 8 to 10 stops while still producing a pleasing image on most TV’s. Another way of increasing dynamic range is to introduce some form of signal compression. The simplest form of this in common use is the cameras knee circuit. This simply takes anything above a certain brightness level (typically between 80 and 95%) and compresses it. We normal get away with this compression because it’s only affecting highlights like clouds in a bright sky or a bright window or lamp in the shot. Our own visual system is tuned primarily to mid tones, faces, plants and things like that so we don’t tend to find highlight compression overly obtrusive.
When considering your post production workflow and grading in particular, it’s important to remember that in most cases whenever anything is compressed then some of the original data is being discarded. In addition if the amount of compression is non-linear (increases or decreases with amplitude) then when we add a linear function to that, like adjusting the signal gain the non-linearity is also increased.
Based on these assumptions, you should be able to understand that anything exposed in the linear part of a gamma curve will grade very well because there is no extra compression and gain adjustments will behave as expected. Now if you look at the graph of a typical standard gamma curve (as above) you can see that everything below the knee point is pretty linear, so anything exposed in this range will grade easily and well (assuming it isn’t actually overexposed). For this reason standard gamma can be very forgiving to small over exposure problems as a slightly bright face should still be in the linear part of the curve. However overexpose to the point where the face starts to enter the knee area and all is lost, you’ll never make it look natural.
Now look at the curve for a typical Cinegamma or Hypergamma. You can see that this curve starts to become more curved and less linear much earlier than a standard gamma. This is how the extra latitude is gained. Compression is used to allow the camera to record a greater brightness range. This extra compression though comes at a price and that is linearity. The further up the exposure range you go the less linear the response (it’s actually becoming logarithmic). The result is that even though you have more dynamic range, if you do overexpose faces and skin tones by even just a small amount they will start to creep into the non linear part of the curve and this makes them harder to grade naturally. You may be less likely to get those ugly blown out highlights on a shiny face typical of video knee compression with cine/hypergammas, but you must still be very careful not to overexpose.
So there you have it. Greater dynamic range does not necessarily equate to more exposure tolerance. In fact it’s often the opposite. You might get better highlight handling, but you may find you need to be even more careful with how you expose. As we go forwards (or sideways at least) and linear raw becomes more common place then you will be able to shift you mid tone exposure up and down with a lot more flexibility as with a linear raw camera the last stop of exposure has the same linearity as the first, so in theory your mid tones can sit anywhere in the exposure range. Sony’s F65 is a great example of this. It has 14 stops of linear dynamic range. A face lit with a 3 stop range could be placed in stops 11-14 and would grade down to wherever you want just perfectly.
How important is raw?
One of the key benefits of a raw workflow is that normally you will be working at a higher bit depth, at least 12 bit if not 14 bit or 16 bit. This in turn allows the use of linear capture as opposed to the log capture normally associated with conventional video.
Don’t get me wrong, log capture and recording (even things like hypergammas and cinegammas are closer to log than linear) is very good and works remarkably well. But it is limited as it compresses highlight information. Each extra stop of over exposure with a linear recording will contain twice as much data as the previous, while with log each stop contains the same amount of data, so as a result each brighter stop only has half as much information as the previous. Log does allow us great scope when it comes to grading and post production image manipulation, but the higher up the exposure range you go, the less data you have to work with, so how much you can manipulate the image decreases with brightness. As our own visual system is tuned for mid tones this log behaviour goes largely un-noticed. But as modern sensors achieve greater and greater dynamic ranges log starts to struggle while linear copes much better.
It’s not until you try linear raw with a camera like the Alexa or F65 that you realise just how forgiving it is. In log mode the Alexa (and other log cameras like the F3) need to be exposed accurately. Over expose and you risk not only your highlights blowing out but also it becomes harder to get good looking skin tones as these may be up in the more compressed parts of the curve. However with linear, it doesn’t really matter if faces are higher up the range, jus as long as they are not actually at sensor overload.
When you shoot with a log camera it must be treated like any other conventional video camera. Exposure must be correct, you need to watch and protect you highlights, expose to the left etc. A camera shooting raw behaves much more like a film camera, you can afford to push the exposure higher if you want less noise, just like film.
But linear raw comes at a cost, mainly a time and storage cost. We have become very used to the simplicity of working with video. Modern file based workflows are fast and efficient. Raw needs more work, more processing, more storage (compared to compressed at least). But computers are getting faster, storage is getting cheaper. Right now I believe that raw is only going to be used by those that really do need and want the very best flexibility in post production while log will become more and more common for episodic and documentary production. But, the time will come when we can handle raw quickly and easily and then perhaps we will look back at legacy codecs and wonder how we managed. Although saying that, while we still broadcast and distribute programmes using backwards compatible legacy gamma with it restricted dynamic range for display on devices with only 6 stops of display latitude, a general shift to raw with all it’s extra overheads may never happen.
XDCAM Firmware and software updates.
Sony USA has compiled a single web page with all the latest XDCAM firmware updates for you including the F3 V1.4 firmware. Here’s the link.
Zacuto Revenge of the Great Camera Shootout.
I spent some time today in Soho, London watching the latest Zacuto camera shootout. It was really interesting and quite enlightening. I don’t want to go into to many details here as it may spoil it for those of you still waiting to see the results. But what I will say is that Steve Weiss certainly achieved what he set out to do and that is to question what’s more important, the camera, the operator or something else and whether the camera makes the difference between a good movie and a bad one.
First we were shown footage from each of the cameras tested, shot under matching lighting. You could clearly see differences between each camera, as you would expect. The majority of the cameras were however remarkably similar. Maybe one would have better dynamic range, maybe another would have better colour. Next we were shown a blind screening of each camera where we did not know which camera was which. A letter from A to I was assigned to each camera. For these shots the DoP responsible for the camera was allowed to tweak the lighting to get the most from his or her camera. Then the DoP was allowed some time in the grading suite to do pretty much whatever they wanted to make the camera shine.
The discussion at the end of this set of clips was very interesting. One of the main conclusions drawn was that as much as assessing the actual look of the camera we were also assessing the DoP’s artistic interpretation of what made a good shot. Some clearly favoured highlights, some shadows. It was clear to us all that in the right hands almost all of the cameras were capable of producing great looking pictures in this controlled environment (would be interesting to see a less controlled scenario). Each person at the screening was given a card so they could list their top 5 cameras and most of us were asked to name the worst. There was generally a feeling that of the 9 cameras there were 3 or 4 that most of us liked the most, a couple that were not liked at all and the remaining sat in the middle as perfectly useable but maybe not quite in the same league as the top 4. Even so they were all remarkably close.
So from this I draw some interesting conclusions. The current large sensor cameras are all pretty good. Lighting and careful grading can overcome or at least mask most of any specific shortfalls. The general public audience would be hard pushed to tell.
Adding to this though I would say that one of the cameras that was quite weak in the reference test, but did look so much better in the DoP lit test required a lot more work in extra lighting and grading to get it that way, so obviously there are advantages to be had in having a higher performing camera, but also a good DoP makes all the difference.
There were some definite surprises in the cameras that were liked. One of the higher end cameras was not liked as much as expected and this surprised everyone. An old favourite also failed to perform as expected. When I watched the blind test I scored each camera out of 10. My top camera scored 8, second best was 7.5, third 7, forth 6. So there was very little between my top 3, in fact I really struggled choosing between F and A. My top 5 were F, A, H, C and then E. If you want to know which is which you will have to go to a screening or wait till the online video comes out.
Single Sensor Cameras: Pixel count is not the same as resolution!
Oh I get fed up with this. Just came across a product manager claiming that the resolution of his bayer sensor equipped camera was the same as the horizontal pixel count. Come on guys, know your products, know what your talking about. With a single chip camera the resolution will always be lower than the pixel count. This is pretty basic stuff. With a bayer sensor the resolution is at best 0.8 x the horizontal pixel count. But manufacturers like to pull the wool over the customers eyes spouting erroneous claims that the resolution is the same as the pixel count.
If you want to call your camera 5k, 4k or 2.5k that’s fine, but don’t claim the resolution is 2.5k when the camera only has 2.4k of active pixels on a 2.5k pixel wide sensor. It’s impossible and it’s incorrect and I’m not even going to go into how much lower the diagonal and colour resolution is with bayer.
Rant over.