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I know this has been discussed on many other blogs, but while shooting part of a 3D project in London, from a public right of way several private “security  guards” tried to move us on and prevent us from shooting the exterior of their building. The law in the UK is actually quite clear on this: This extract is from the Met police web site:

“Freedom to photograph/ film

Members of the public and the media do not need a permit to film or photograph in public places and police have no power to stop them filming or photographing incidents or police personnel.”

In addition there are no laws preventing you from shooting normal people and buildings in the street, there are exceptions for military establishments, buildings covered by the official secrets act and nuclear power stations. But normal office buildings etc can be filmed at will. The security officers were from the Santander Building on Euston Road. We were not on their property and had gone by the book informing Camden council that we were going to be filming in the street, yet still they insisted we move on. For half an hour they obstructed us, behaving as though they had some kind of legal right to stop us filming (which they did not). Had it not been for the pressures of the shoot and the need to go to another location we would have called the police. It is getting harder and harder to carry out your legal right to film in public places. Contrary to popular belief you do not need to obtain a permit to shoot on the public streets of London (with the exception of Trafalgar Square and Parliament Square). Using a tripod is not illegal or a crime, however causing an obstruction is. To move you on for causing an obstruction the police would have to show that you are impeding the passage of others. Clearly if you are a big crew it is wise to contact the authorities before hand to smooth the way and get assistance from the local authority. You do also need to consider that many seemingly public places may be private property and you may not be allowed to use a camera under the land owners terms of access. In this case the only offence you are committing is trespass which is a civil offence so you cannot be arrested. You should leave when asked and your equipment cannot be touched.

This popped up in the forums and I thought it really deserved to be here as it a very useful tool for anyone shooting timelapse. It’s a simple app that allows you to calculater the interval or duration of a timelapse sequence. Nice and simple but very handy. Another great I-Phone tool. Love the I-Pad concept BTW!

http://www.clamcamvideo.com/video_accessories.html#app

OK, not very scientific I know, but for those that want to see how close the pictures from theses two cameras are I have shot a quick clip with each and put them in a 54mb zip file for download. The PMW-350 clip is a 35Mb/s MP4 and the PDW-700 clip is a 50Mb/s XDCAM MXF.

The cameras were both set up with similar paint settings using Hypergamma 4. The detail is backed off a bit from the factory settings on both and I used the same lens on both cameras which was the Fujinon 16×8 lens that comes with the PMW-350. The clips have not been adjusted in any way other than trimed in length, this is how they look out of the camera.

Both are remarkably similar. I can see that the 350 is more highly saturated and that you can just about make out the difference between 4:2:0 and 4:2:2. The interesting area is how the 350 handles the overexposed sky behind the trees, or rather the way the trees don’t appear to blur into the overexposure as with the PDW-700.

Sony are to make an SD card adapter for the EX camera range. The MEAD-SD01 will use class 10! SD cards to allow HD recordings in EX cameras. A firmware update will be needed which should be available before the cards release some time around April.

http://www.sony.co.uk/biz/view/ShowProduct.action?product=MEAD-SD01&site=biz_en_GB

In the posts above I looked at how the gamma curves effect the contrast range within the picture and highlight handling. I also noted that while I like the latitude (range) offered by using the Hypergammas that they produce a very flat looking picture. One of the adjustments that you can make to the Gamma curves is the Black Gamma. Adjusting the Black Gamma stretches or compresses the bottom part of the gamma curve, this makes the darker parts of the picture darker (negative setting) or brighter (positive setting). When setting the Black Gamma you will find 4 different ranges to choose from. Low, Low-Mid, Hi-Mid and High. These settings determine the range over which the black gamma works. Low only effects the darkest 10% of the image, L-Mid the bottom 20%(approx), H-Mid the lowest 30%(approx) and Hi the lower 35% (approx). So if you just want to make your deep shadows and blacks darker you would use Low. If you want to make the overall image more contrasty you would use H-Mid or Hi. I like to give my images a bit more impact so I often use H-Mid at -30. If the pictures are to be graded I would not use any negative black gamma.

Before anyone complains that I have missed stuff out or that some technical detail is not quite right, one of the things I’m trying to do here is simplify the hows and why’s to try and make it easier for the less technical people out there. Lets face it this is an art form, not a science (well actually a bit of both really).

So what is a gamma curve anyway? Well the good old fashioned cathode ray tube television was a very non-linear device. You put 1 unit of power in and get one unit of light out. You put 2 units in and get 1.5 units out, put 3 in and get 2 out… and so on. So in order to get a natural picture the output of the camera also has to be modified to compensate for this. This compensation is the gamma curve, an artificial modification of the output signal from the camera to make it match TV’s and monitors around the world. See Wikipedia for a fuller explaination:   http://en.wikipedia.org/wiki/Gamma_correction

So, all video cameras will have a gamma curve, whether you can adjust it or not is another matter. Certainly most pro level cameras allow you some form of gamma adjustment.

The PMW-350 has 6 standard gamma curves, these are all pretty similar, they have to be otherwise the pictures wouldn’t look right, but small changes in the curve effect the relationship between dark and bright parts of the pictures. Todays modern cameras have a far greater dynamic range (range of dark to bright) than older cameras. This means that the full dynamic range of the sensor no longer fits within the gamma curves used for TV’s and monitors. In broadcast television any signal that goes over 100% gets clipped off and is discarded, so the cameras entire brightness range has to be squeezed into 0 to 100%. The PMW-350 sensors are capable of far more than this (at least 600%) so what can you do?

The older and simpler solution is called the “Knee”. The knee works because in most cases the brightest parts of a scene contains little detail and is generally ignored by our brains. We humans tend to focus on mid-tone faces, animals and plants rather than the bright sky. Because of this you can compress the highlights (bright) parts of the picture quite heavily without it looking hugely un-natural (most of the time at least). What the knee does is takes a standard gamma curve and up near it’s top, bends it over. This has the effect of compressing the brighter parts of the image, squashing a broad range of highlights (clouds for example) into a narrow range of brightness. While this works fairly well, it does tend to look rather “electronic” as the picture is either natural (below the knee) or compressed (above the knee).

The answer to this electronic video look is to replace the hard knee with gentle bend to the gamma curve. This bend starts some way down the gamma curve, very gentle at first but getting harder and harder as you go up the gamma curve. This has the effect of compressing the image gently at first with the compression getting stronger and stronger as you go up the curve. This looks a lot more natural than a hard knee and is far closer to the way film handles highlights. The downside is that because the compression starts earlier a wider tonal range is compressed. This makes the pictures look flat and uninteresting. You have to watch exposure on faces as these can creep into the compressed part of the curve. The plus point is that it’s possible to squeeze large amounts of latitude into the 100% video range. This video can then be worked on in post production by the editor or colorist who can pull out the tonal range that best suits the production.

These compressed gamma curves are given different names on different products. Panasonic call them “Film Rec”, on the EX1 they are “Cinegammas” on the PMW-350 they are “Hypergammas”. The 350 has four Hypergammas. The first is 3250. this takes a brightness range the equivalent to 325% and compresses it down to 100%. HG 4600 takes 460% and squeezes that down to 100%. Both of these Hypergammas are “broadcast safe” and the recordings made with them can be broadcast straight from the camera without any issues. The next Hypergamma is 3259. This takes a 325% range and squeezes this down to a 109% range, likewise 4609 takes 460% down to 109%. But why 109%? well the extra 9% gives you almost 10% more data to work with in post production compared to broadcast safe 100%. It also gives you the peak white level you need for display on the internet. Of course if you are doing a broadcast show you will need to ensure that the video levels in the finished programme don’t exceed 100%.

My preferred gamma is Hypergamma 4 (4609) as this gives the maximum dynamic range and gives a natural look, however the pictures can look a little flat so if I’m going direct from the camera to finished video without grading I use either a standard gamma or use the Black Gamma function to modify the curve. I’ll explain the Black Gamma in my next post.

There are 6 standard gammas to choose from. I like to stick with gamma 5 which is the ITU-709 HD standard gamma. To increase the dynamic range I use the Knee. The default knee point setting is 90, this is a reasonable setting, but if your shooting with clipping set to 100% you are not getting all the cameras latitude (the Knee at 90 works very well with clipping at 108%). Lowering the knee down to 83 gives you almost another stop of latitude, but you have to be careful as skin tones and faces can creep up towards 83%. It’s very noticeable if skin becomes compressed so you need to watch your exposure. This is also true of the Hypergammas and with them you may need to underexpose faces very slightly. The other option is to set the knee point to 88 and then also adjust the knee slope. The slope is the compression amount. A positive value is more compressed, negative less compressed. With the knee at 88 and slope set to +20 you get good latitude, albeit with quite highly compressed highlights.

If you want to play with the gammas and knee and see how they work one method you can use is to use a paint package on your PC (such as photoshop) to create a full screen left to right graduated image going from Black to white. Then shoot this with the camera (slightly out of focus) while making adjustments to the curves or knee and record the results along with a vocal description of each setting. Import the clips into your favorite editing package and use the waveform monitor or scopes you should be able to see a reasonable representation of the shape of the gamma curve and knee.

So my Gamma Choices are:

For material that will be post produced: Hypergamma 4609 (HG4)

For material that will be used straight from the camera: Standard Gamma 5 Knee at 90 with clip at 108% for non broadcast or Knee at 88 with slope +20 with white clip at 100% for direct to broadcast.

I decided to write a more detailed post to continue the discussions on scene file settings for the PMW-350. This is a work in progress. Some of this may also be of interest to other camera users as I hope to give a basic description of what all the various settings do.

First off let me say that there is no “right way” or “wrong way” to set up a scene file. What works for one person may not be to anothers taste, or suit different applications. For me, my requirements are a neutral look, not over corrected or too vivid, but retaining a pleasing contrast range. I hope, as this thread develops to explain a little bit about each of the settings and what they actually do in the hope that it will make it easy for you to adjust the scene files to suit your own needs. I hope others will jump in with their suggestions too!

So first of all I have been looking at the sharpness of the image. The principle settings that affect this are the Detail and Aperture settings.

Detail enhances rapid transitions from light to dark within the pictures by exaggerating the transition with the addition of a black or white edge. So it only really works on object outlines and larger details (low frequency). The circuitry that determines where these edges are uses an electronic delay to compare adjacent pixels to see whether they are brighter or darker compared to each other. Because of this any rapid movement within the frame stops the circuitry from working. If you have picture with a lot of detail correction and you do a pan for example the image will appear to go soft as soon as the camera moves as the detail circuitry can no longer determine where the edges within the image are and thus applies less detail correction. A good way to visually gauge how much detail a camera is applying to a clip is to look for this. With a good high resolution camera, set up well, it should not be all that obvious, but a low resolution camera that uses lots of detail correction to compensate will exhibit lots of softening on pans.

As well as adjusting the amount of detail correction (Detail Level), you can also adjust the ratio of horizontal and vertical correction, the maximum brightness or darkness of the applied edges (white and black limit). The thickness of the edges (frequency), the minimum contrast change that the correction will be applied to (crispening) and you can tell the camera not to apply detail correction to dark areas (level depend).

The other setting that effects picture sharpness is Aperture. Aperture correction is a high frequency boost circuit, it simply, in effect, enhances transitions from dark to light or light to dark in fine detail and textures such as fabrics, skin, hair, grass etc. It’s operation is not as obvious as “Detail” correction, but if overdone it can make textures sparkle with flashes of white or black, all very un-natural.

An important note about image detail is that if you have too much of it for the given image resolution then you get problems such as aliasing and moire which manifest themselves as rainbows of colour or buzzing, jittering areas in the picture. If you want to know more about this look up Nyquist theory. This is one of the reasons why downconverting HD to SD and getting a good picture can be harder than you might think as you are often starting out with too much detail (but that’s another topic on it’s own).

So… on to the PMW-350. Out of the box it’s really sharp. The camera has full 1920×1080 sensors, so even with all detail correction turned off the image is still pretty sharp. However most viewers are used to seeing picture with some detail correction, so if you turn it all off, to many it looks soft. If you were going for a really filmic look, detail off and aperture off would have to be a serious option. For my customers though a little bit of subtle “zing” seems to be what they like.

I found that these settings worked well for general all-round use.

Detail Level -14
H/V Ratio +20 (helps balance horizontal and vertical resolution)
Frequency +35 (makes the edges thinner, if your doing a lot of SD you may want to go the other way to -50 so that the edges can still be seen in SD)
White Limit +35 (limits brightness of white edges)
Black Limit +30 (limits darkness of black edges)

Aperture -20

If you are doing a lot of grading and work with low key scenes (large dark areas) you can use the level depend and crispening settings to help prevent “detail” being added to any picture noise. This makes any noise less apparent.

A starting point for this would be:

Crispening +35
Level depend +20

For normal light levels these are not needed with the 350 IMHO. If you are shooting with more than +6db gain then raising the level depend to +60 will help with noise.

I have finally managed to get my hands on a production PMW-350. I am going to start dialing it in. The first thing to address for me is the over sharpened pictures, so I have been playing with the Paint settings aiming towards a natural, yet sharp look. I have come up with these detail setings. Everything is default except:

Detail Level -16
H/V Ratio +20
Detail Frequency +35
White limit +39
Black Limit +20
Aperture -30

This is still a work in progress.

Next I’m going to start looking at the Gamma curves and Knee. I have a nice Hamlet MicroFlex scope to help with this. Previously I have had to rely on my eye and then check the footage against the scopes in the edit suite, now I can see the waveforms on location. I’ll be writting up both the gamma settings and a microflex review in due course.

I was asked to look at creating a picture profile for the EX1R in SD mode to make it look more like an older 2/3″ SD camera. I spent a couple of hours trying various settings and I came up with the ones below.

Matrix; cinema, level +8

SD Detail Level  +25, Frequency -65, crispening +10, White limit +50, black limit +55

Knee 90, Gamma: Std 2 level +5, Black Gamma +10

This profile gives some very hard detail correction, but the idea is to mimic an older SD camera that would also have similar strong detail correction. If the detail level is too high for your tastes reduce it to +8. If you would like more colour raise the Matrix level to +20 to +30.

I have been hearing quite a few stories of cameras that are getting severe internal corrosion damage. It appears at first glance that perhaps newer, file based cameras are less well built than older tape cameras, but there is more to this than meets the eye.  I have heard several stories of EX’s and PDW’s that have required expensive repairs due to corrosion. I’ve also found similar stories with other manufacturers solid state cameras. So what’s going on? These are worrying stories especially considering what I do with my cameras, so I have looked into the problem in some depth and found a couple of things.

In all the cases I have heard about, the cameras have been stored after the shoot in Pelicases. Pelicases are excellent at keeping moisture out, but also at  keeping it in and this may be preventing the cameras from drying out. This is not a criticism of the cases, they are excellent and I have several. It is the way they are being used which is at fault. A camera with condensation on the inside will not dry out in a sealed Pelicase, giving the moisture time to do it’s evil work. Prevention is better than cure, so the best thing to do is to never put a cold or damp camera in a Pelicase.  The other thing to do is is to keep large packs of silica gel in the pelicase. The silica gel should be re-charged regularly by baking in an oven. Storing cameras in Pelicases long term is not always wise. I store my cameras in soft bags and this may be why I have not had any problems despite the harsh hurricane and extreme weather environments I work in.

Perhaps just as importantly, there is I think, also another factor at play here. With a tape camcorder if there is condensation inside the camera you get a “dew” warning. As well as preventing recording it also tells you that you have moisture inside the camera. At this point most people will do something to dry the camera out, it also makes you take more care in the first place as you don’t want a dew warning to prevent you from shooting. So I think that camera manufacturers should re-instate “dew” sensors on cameras. It could prevent a lot of unseen damage, perhaps it would just be a warning to tell you about the moisture but not prevent the camera from being operated.

UPDATE: I have been informed that the PDW-700 and PDW-800 cameras DO HAVE MOISTURE SENSORS. Although I have never seen a warning from them.