Download and print your own test charts.

Clearly these will never be as good as, or as accurate as properly produced charts. Most home printers just don’t have the ability to produce true blacks with razor sharp edges and the paper you use is unlikely to be optimum. But, the link below takes you to a nice collection of zone plates and resolution charts that are useful for A/B comparisons. I split them up into quarters and then print each quarter on a sheet of A4 paper, joining them all back together to produce a nice large chart.
http://www.bealecorner.org/red/test-patterns/

Hurricane Rig Update. Available via Manfrotto.

My 3D rig will be available in many countries via Manfrotto from the 1st of March. Production has been in full swing for the last few weeks and we now have finished rigs in stock at the factory. In the UK rigs will be available from Manfrotto or from the Hurricane-Rig.com website (approx €6700 euros, £6000 GBP plus VAT, price TBC). In the USA select Manfrotto Dealers will be selling the rig for $7995 USD.

We are working on a range of add ons for the rig which include a motorisation kit that will add motorised Interaxial only, interaxial plus convergence as well as dual focus and zoom options. These will options will fit all Hurricane rigs so there is no need to wait for these options to become available. Pricing TBA, but it will be very competitive and you can pick and choose the modules that you need.

Canon XF105, using OIS to correct zoom axis shift. (3D applications)

While I was in Singapore last week I got to play with a pair of Canon’s XF105’s on a Genus Hurricane 3D rig. We were able to use the programmable axis shift function to compensate for the way the zoom lenses don’t remain centred as you change focal length. Zooming in 3D with two cameras is very hard to do because of this shift, normally requiring very expensive matched lenses. With the 105’s and and a few minutes of adjusting we were able to do synchronised zooms (using the IR remote) that retained very good tracking and accuracy. This really is quite remarkable at this price point!

Are Cosmic Rays Damaging my camera and flash memory?

Earth is being constantly bombarded by charged particles from outer space. Many of these cosmic rays come from exploding stars in distant galaxies. Despite being incredibly small some of these particles are travelling very fast and contain a lot of energy for their size. Every now and then one of these particles will pass through your camcorder.  What happens to both CMOS and CCD sensors as well as flash memory is that the energetic particle punches a small hole through the insulator of the pixel or memory cell. In practice what then happens is that charge can leak from the pixel to the substrate or from the substrate to the pixel. In the dark part of an image the amount of photons hitting the sensor is extremely small, each photon (in a perfect sensor) gets turn into an electron. It doesn’t take much of a leak for enough additional electrons to seep through the hole in the insulation to the pixel and give a false, bright readout. With a very small leak, the pixel may still be useable simply be adding an offset to to the read out to account for the elevated black level. In a more severe cases the pixel will be flooded with leaked electrons and appear white, in this case the masking circuits should read out the adjacent pixel.

For a computer running with big voltage/charge swings between 1’s and 0’s this small leakage current is largely inconsequential, but it does not take much to upset the readout of a sensor when your only talking of a handful of electrons. CMOS sensors are easier to mask as each pixel is addressed individually and during the camera start up it is normal to scan the sensor looking for excessively “hot” pixels. In addition many CMOS sensors incorporate pixel level noise reduction that takes a snapshot of the pixels dark voltage and subtracts it from the exposed voltage to reduce noise. A side effect of this is it masks hot pixels quite effectively. Due to the way a CCD’s output is pulled down through the entire sensor, masking is harder to do, so you often have to run a special masking routine to detect and mask hot pixels.

It may not sound much getting a single hot pixel, but if it’s right in the middle of the frame, every time that part of your scene is not brightly illuminated you see it winking away at you and on dark scenes it will stick out like a sore thumb, thankfully masking circuits are very effective at either zeroing out the raised signal level or reading out an adjacent pixel.

Flash memory can also experience these same insulation holes. There are two common types of Flash Memory, SLC and MLC. Single Level Cells have two states, on or off. Any charge means on and no charge means off. A small amount of leakage, in the short term, would have minimal impact as it could take months or years for the cell to full discharge, even then there is a 50/50 chance that the empty cell will still be giving an accurate ouput as it may have been empty to start with. Even so, long term you could loose data and a big insulation leak could discharge a cell quite quickly. MLC or Multi Level Cells are much more problematic, as the name suggests these cells can have several states, each state defined by a specific charge range, so one cell can store several bits of data. A small leak in a MLC cell can quickly alter the state of the cell form one level to the next, corrupting the data by changing the voltage.

The earths magnetic field concentrates these cosmic rays towards the north and south pole. Our atmosphere does provide some protection from them, but some of these particles can actually pass right through the earth, so lead shielding etc has no significant effect unless it is several feet thick. Your camera is at most risk when flying on polar routes. On an HD camera you can expect to have 3 or 4 pixels damaged during a year at sea level, with a CMOS camera you may never see them, with a CCD camera you may only see them with gain switched in.

SxS Pro cards (blue ones) are SLC, SxS-1 (Orange cards) use MLC as MLC works out cheaper as fewer cells are required to store the same amount of data. Most consumer flash memory is MLC. So be warned, storing data long term on flash memory may not be as safe as you might think!

Can you use a 2/3″ Zoom on a 35mm camera??

Can you use a 2/3″ B4 broadcast zoom on a 35mm camera. Well yesterday I would have said “no”, but having seen this video on the AbelCine web site, now I’m not so sure. UPDATE: OK Should have read the specs…. it’s only suitable for smaller sensors as it has a 22mm image circle, the F3 has a 27mm diagonal. It’s still a viable option for the AF100 however.

http://blog.abelcine.com/2011/02/11/using-23-lenses-on-the-panasonic-af100/

The HDx2 adapter magnifies the image to fill a 35mm sensor, doubling the focal length at the same time. This is very intriguing as 35mm zooms are few and far between and very expensive. There is a 2 stop light loss (well if you expand the image 2 times that’s what happens) but most broadcast zooms are pretty fast lenses to start with. I can’t help but think that the pictures might be a little soft, but if you already have decent 2/3″ glass then the $5,500 for the adapter might make a lot of sense. Anyone out there with experience of one of these? I’d love to know how it performs.

Juice Designs EX1R base plate. Curtis does it again!

juiced-ex1r-3-300x214 Juice Designs EX1R base plate.  Curtis does it again!
Juice Designs EX1R CNC Base Plate

I had one of Juice Designs base plates on my EX1 and it was fantastic. It never came off the camera and gave me the confidence that any loads exerted on the base of the camera were spread over the entire EX1 base rather than the weedy single 1/4″ screw hole on the bottom of the EX1. When the EX1R arrived things were somewhat improved as now instead of one weedy 1/4″ thread there are two weedy 1/4″ threads. Great you think, two is better than one, but the little postage stamp sized plate that has the tripod mounting holes is attached to the EX’s chassis by 4 teeny tiny screws. These have a tendency to work loose over time and can break quite easily if over stressed. If you really load up the tripod mount you can fracture the casting or worse still the chassis of the camera. If all that isn’t bad enough the other issue I have with my EX1R in particular is that the tripod mount casting is very slightly proud of the base of the camera, so when its on a tripod (or my 3D rig) it wobbles about quite a bit as there is only about 1 square inch of metal in contact with the tripod. Clearly none of these are desirable and that’s where the Juice designs base plates come to the rescue. The EX1 version is attached to the base of the camera in four places. The obvious 2 are the normal pair of 1/4″ tripod threads. The other two are a couple of small screws that normally hold some of the plastic camera body parts on to the chassis. By spreading any loads across much more of the base of the camera the tripod to camera interface will be much stronger. In addition the camera is now rock solid on my tripod and 3D rig. If anyone is thinking of using an EX1 or EX1R on a 3D rig a base plate like this is not an option, it is absolutely essential!

juiced-ex1r-2-300x168 Juice Designs EX1R base plate.  Curtis does it again!
Juice Designs Accessory Arm and Cold Shoe

The base plate is machined from a single piece of aluminium and anodised black. It is clearly a well though out design with nice curves that make follow the contours of the camera, indeed it looks like it really is park of the camera. It even has small recesses in it to clear some of the lumps and bumps that are on the base of the EX1R. At the rear of the base plate there is a small cut out area that allows you to add an optional bolt on accessory arm or “wing”. You can use the arm to attach devices such as the NanoFlash or Radio Mic receiver. The arm is supplied with a cold shoe mount which can be attached in a variety of positions making it very flexible indeed.

It took just minutes to fit the plate. It comes with all the screws that you need plus a couple of allen keys. You will need a small jewellers screwdriver to remove two small screws from the base of the EX1R. This is a high quality product that should help protect you investment and make the camera more stable, so highly recommended. See Juice Designs web site for more information.

juiced-ex1r-1-300x202 Juice Designs EX1R base plate.  Curtis does it again!
Accessory Arm and Cold Shoe

When is 4:4:4 not really 4:4:4.

The new Sony F3 will be landing in end users hands very soon. One of the cameras upgrade options is a 4:4:4 RGB output, but is it really 4:4:4 or is it something else?

4:4:4 should mean no chroma sub-sampling, so the same amount of samples for the R, G and B channels. This would be quite easy to get with a 3 chip camera as each of the 3 chips has the same number of pixels, but what about a bayer sensor as used on the F3 and other bayer cameras too for that matter?

If the sensor is subsampling the aerial image B and R compared to G (Bayer matrix, 2x G samples for each R and B) then no matter how you interpolate those samples, the B and R are still sub sampled and data is missing. Potentially depending on the resolution of the sensor even the G may be sub sampled compared to the frame size. In my mind a true 4:4:4 system means one pixel sample for each colour at every point within the image. So for 2k that’s 2k R, 2K G and 2K B. For a Bayer sensor that would imply a sensor with twice as many horizontal and vertical pixels as the desired resolution or a 3 chip design with a pixel for each sample on each of the R,G and B sensors. It appears that the F3’s sensor has nowhere near this number of pixels, rumour has it at around 2.5k x 1.5k.

If it’s anything less than 1 pixel per colour sample, while the signal coming down the cable may have an even number of RGB data streams the data streams won’t contain even amounts of picture information for each colour, the resolution of the B and R channels will be lower than the Green, so while the signal might be 4:4:4, the system is not truly 4:4:4. Up-converting the 4:2:2 output from a camera to 4:4:4 does not make it a 4:4:4 camera. This is no different to the situation seen with some cameras with 10 bit HDSDI outputs that only contain 8 bits of data. It might be a 10 bit stream, but the data is only 8 bit. It’s like a TV station transmitting an SD TV show on an HD channel. The channel might call itself an HD channel, but the content is still SD even if it has been upscaled to fill in all the missing bits.

Now don’t get me wrong, I’m not saying that there won’t be advantages to getting the 4:4:4 output option. By reading as much information as possible from the sensor, prior to compression there should be an improvement over the 4:2:2 HDSDi output, but it won’t be the same as the 4:4:4 output from an F35 where there is a pixel for every colour sample, but then the price of the F3 isn’t the same as the F35 either!

What is ISO and how does it compare to gain?

With more and more people using 35mm size sensors, more of the old traditional filming styles and techniques are trickling down from the high end to lower and lower production levels. This is a good thing as it often involves slowing down the pace of the shoot and more time being taken over each shot. One of the key things with film is that you can’t see the actual exposure on a monitor as you can with a video camera. A good video assist system will help, but at the end of the day exposure for film is set by using a light meter to measure the light levels within the scene and then you calculate the optimum exposure using the films ISO rating.
So what exactly is an ISO rating?

Well it is a measure of sensitivity. It tells you how sensitive the film is to light, or in the case of a digital stills or video camera how sensitive the sensor is to light. Every time you double the ISO number you are looking at doubling the sensitivity. So ISO 200 is twice as sensitive as ISO 100. ISO 1600 is twice as sensitive as ISO 800 etc.
Now one very important thing to remember is that ISO is a measure of sensitivity ONLY. It does not tell you how noisy the pictures are or how much grain there is.  So you could have two cameras rated at 800 ISO but one may have a lot more noise than the other. It’s important to remember this because if you are trying, for example, to shoot in low light you may have a choice of two cameras. Both rated with a native sensitivity of 800 ISO but one has twice as much noise as the other. This would mean that you could use gain (or an increased ISO) on the less noisy camera and get greater sensitivity, but with a final picture that is no more noisy than the noisier camera.
How does this relate to video cameras?

Well most video camera don’t have an ISO rating, although if you search online you can often find someone that has worked out an equivalent ISO rating. The EX1 is rated around 360 ISO. The sensitivity of a video camera is adjusted by adding or reducing electronic gain, for example +3db, +9db etc. Every 6db of gain you add, doubles the sensitivity of the camera. So taking an EX1 (360 ISO) if you add 6db of gain you double the sensitivity and you double the ISO to 720 ISO, but you also double the amount of noise.
Now lets compare two cameras. The already mentioned EX1 rated at approx 360 ISO and the PMW-350 rated at approx 600 ISO. As you can see from the numbers the 350 is already almost twice as sensitive as the EX1 at 0db gain. But when you also look at the noise figures for the cameras, EX1 at 54db and 350 at 59db we can see that the 350 has almost half as much noise as the EX1. In practice what this means is that if we add +6db gain to the 350 we add +6db of noise so that brings the noise level 53db, very close to the EX1. So for the same amount of noise the 350 is between 3 and 4 times as sensitive as the EX1.
Does your head hurt yet?
There is also a good correlation between sensitivity and iris setting or f-stop. Each f stop represents a doubling or halving of the amount of light going through the lens. So 1 f-stop is equal to 6db of gain, which is equal to a doubling (or halving) of the ISO. You may also hear another term in film circles and that is the T-stop. A T stop is a measured f-stop, it includes not only the light restriction created by the iris but also any losses in the lens. Each element in a lens will lead to a reduction in light and T stops take this into account.

So there you go. The key thing to take away is that ISO (and even the 0db gain setting on a video camera) tells you nothing about the amount of noise in the image. Ultimately it is the noise in the image that determines how much light you need in order to get a decent picture, not the ISO number.

Softening Faces and Skin Tone.

XDCAM cameras have Sony’s Skin Tone Detail Correction system included in the picture profiles. By turning this on you can point the camera at a face (or any other coloured object) and select the hue you want to treat. By using the phase and saturation controls you can adjust the exact hue and hue range that will be treated. Then you can turn the detail level up and down for the selected range.

It works but is a little fiddly to set. I don’t normally use it, instead preferring to shoot with slightly reduce detail level settings overall and then adding a diffusion filter in post production using Magic Bullet or similar. Another option would be to use a diffusion filter or similar on the camera, I like the Tiffen Gold Diffusion/FX for faces. If your budget won’t stretch to that then don’t forget that you can always stretch a very fine mess net over the lens such as a stocking for a pleasing diffusion effect. Again tricky to get just right, if the mesh is too big you’ll see it, too small and you completely blur the image.

The relationship between White Balance and the Matrix.

So… you want to change the look of the colour in your pictures but are not sure how to do it. One of the first things that you need to understand is the relationship between white balance and the colour matrix. They are two very different things, with two different jobs. As it’s name applies white balance is designed to ensure that whites with the image are white, even when shooting under lighting of different colour temperatures. When you shoot indoors under tungsten lights (you know, the one the EU have decided you can no longer buy) the light is very orange. When you shoot outside under sunlight the light is very blue. Our eyes adjust for this very well, so we barely notice the difference, but an electronic video camera is very sensitive to these changes. When you point a video camera at a white or grey card and do a manual white balance, what happens is that the camera adjusts the gain of the red, blue and green channels to minimise the amount of colour in areas of white (or grey) so that they do in fact appear white, ie with no colour. So the important thing to remember is that white balance is trying to eliminate colour in whites and greys.

The Matrix however deals purely with saturated parts of the image or areas where there is colour. It works be defining the ratio of how each colour is mixed with it’s complimentary colours. So changing the white balance does not alter the matrix and changing the matrix does not alter the white balance (whites will still be white). What changing the matrix will do is change the hue of the image, so you could make greens look bluer for example or reds more green.

So if you want to make your pictures look warmer (more orange or red) overall, then you would do this by offsetting the white balance, as in a warm picture your whites would appear warmer if they are slightly orange. This could be done electronically by adding an offset to the colour temperature settings or by using a warming card, which is a very slightly blue card. If you want to make the reds richer in your pictures then you would use the matrix as this allows you to make the reds stronger relative to the other colours, while whites stay white.