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The Sony PXW-X70. Sometimes good things come in small packages!

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The new Sony PXW-X70 XDCAM camcorder.
The new Sony PXW-X70 XDCAM camcorder.

Initial Thoughts.

As the owner of a Sony AX100, which is a really great little 4K and HD camcorder I wasn’t really all that excited when I saw the first prototype of the X70 at Broadcast Asia back in June. You see in the past Sony have done this many times, taken a high end consumer camcorder, updated the firmware, added a handle and then sold it for a higher price as a pro camcorder.  In the past, there has in reality been little difference between the cheaper consumer model and the more expensive pro version.

The handgrip on the Sony PXW-X70
The handgrip on the Sony PXW-X70

The PXW-X70 is different. This is much more than an AX100 with new firmware. For a start the body of the camera is quite different. The right hand side of the X70 is quite different to the AX100. It has a much fatter hand grip. This makes the camera much easier to hold comfortably for long periods. It also makes space for a full size HDSDI output and a full size HDMI output. But the differences don’t stop there.

On the top of the hand grip there is a large assignable button that is normally set to act as a control for the focus magnification function. This button falls immediately under your index finger when your shooting. In front of this is a new larger and easier to use zoom rocker and then in front of that is another assignable button, this one set as a one push auto iris button – very nice!

The back of the handgrip and the small joystick.
The back of the handgrip and the small joystick.

At the back of the handle there is a small joystick that ends up under your thumb (just where it needs to be). This joystick can be used to navigate through the cameras menu system. So, without taking your hand out of the hand grip you can check focus, zoom in and out, set your exposure and go through the menu system. If only it was this easy on all of Sony’s cameras! Ergonomically this camera is really good, especially when you consider how small it is.

The camera has a nice 12x stabilised, optical zoom lens, behind which sits a 1 inch 20 megapixel sensor. In video mode about 14 million pixels are used, so even in 4K (there will be a paid 4K upgrade option next year) there are more pixels than needed for full resolution. Rather than let this extra resolution go to waste you can activate Sony’s “clear image zoom” function that works seamlessly with the optical zoom to give you a 24x zoom range in HD.

Frame grab from PXW-X70. Click on the image to see the full size frame.
Frame grab from PXW-X70. Click on the image to see the full size frame.

The clear image zoom really is remarkably transparent. If you look hard enough at the image, on a big screen, when it’s zoomed all the way in you can just about discern a very slight softness to the image, but frankly I don’t think this is any worse than the softness you might see from a compact optical 24x zoom. It certainly doesn’t look electronic and unless you have side by side, with and without test clips I don’t think you would know that the clear image zoom has been used.

If 24x is not enough there is also a further digital extender, controlled by a button on the right side of the lens that doubles the digital zoom. This you can see, the image is a little degraded at 48x, but it’s not terrible, might be handy for a breaking news story where you can’t get close to the subject.

The left side of the PXW-X70
The left side of the PXW-X70

As well as the optical stabiliser in the lens the camera also has a switchable electronic stabiliser. The active steadyshot is very effective at smoothing out even the shakiest of hands. But it does tend to hang on or grab hold of the image a bit. So when you do deliberately move the camera it tends to try to stabilise the scene until it can no longer correct for the cameras movement at which point the scene is suddenly released and starts to move. If your using a tripod you definitely want to just use the standard steadyshot and not the active mode.

Dual SD card slots on the PXw-X70
Dual SD card slots on the PXw-X70

The pictures are recorded using either XAVC, AVCHD or standard definition DV to SD cards. For XAVC you must use SDXC cards, but these are cheap and readily available these days. There are two card slots and you can choose between relay record where the camera will switch from slot A to slot B once A is full, or you can make two simultaneous recordings on both cards at the same time. This gives an instant backup if you need it.

XAVC HD RECORDING:

The XAVC HD recordings are 10 bit 422 long GoP at 50Mb/s, 35Mb/s or 25Mb/s. The quality of the 50Mb/s recordings is amazing with no compression artefacts that I can see (there must be some, I just can’t see them). Even the 25Mb/s recordings look really good. You can shoot at up to 60fps in 60i mode and 50fps in 50i mode. In 60i mode you also have 24fps.

Frame grab form the PXW-X70, click on the image to see full size.
Frame grab form the PXW-X70, click on the image to see full size.

Considering this is a highly compact, single chip camera the images it produces are really very good. They don’t have that typical small sensor camera look. The pictures are remarkably noise free at 0db and largely free of artefacts. I tend to find that small handycams often suffer from what I would describe as “busy” pictures. Pictures where  perhaps there is a lot of added sharpening or where the pixels are read in special ways to make a sharp picture. This makes edges slightly flickery and gives the pictures a tell tale small sensor look. The X70 with it’s big sensor and abundance of pixels just doesn’t have this “busy” look.

Train sitting in station. Frame grab from PXW-X70
Train sitting in station. Frame grab from PXW-X70

The pictures really look like they come from a pro camera. Occasionally very fine, high contrast details like white text on a black background can look a little busy, but this is very minor. Dynamic range is quite respectable, it’s not as good as a PMW-300, but not too bad for a compact handycam (I estimate about 10 to 11 stops of DR).

One thing I did find with this camera is that because there is so little noise and the codec is so good, you could quite comfortably shoot about a stop darker than you would normally and then just bring the image up a bit in post. Shooting a little darker helps the camera handle bright highlights and then in post you can just bring up the shadows and mid tones with a simple colour correction to give a nice exposure. I wish I had realised this when I shot the demo video. I would have exposed a little on the dark side and then tweaked the shots in post. There’s so little noise at 0db and so few artefacts that the image holds up to this really well. If your using auto exposure you can set an exposure offset to allow for this in the menu.

PXW-X70 without the top handle fitted.
PXW-X70 without the top handle fitted.

The X70 is pretty sensitive and 9db of gain is quite useable, so shooting indoors in a typical home or at a wedding venue without extra lights should be no problem. Ramp it up to +33db and it see’s better in the dark than I do, but there is a fair bit of noise at +33db.

As well as being generally rather sensitive the PXW-X70 also has a nightshot mode that bypasses the cameras IR filter and includes a switchable infra-red light, so you can shoot in total darkness if you want.

To see what you are shooting there is a 3.5″ LCD panel. This panel is higher resolution than the one on the AX100 and gives a sharp and pretty accurate image. On the back of the camera there is a small OLED viewfinder. This little OLED is pretty good. It has great contrast and is pretty sharp for a small finder. It’s a great feature on bright sunny days when the LCD can become harder to see.

CRISP, SHARP IMAGES:

The HD images are crisp and sharp without any obvious sharpening, almost certainly a result of having a 4K ready sensor. The lack of obvious detail correction helps give the pictures a pleasing, more filmic look. The camera has picture profiles so if you want you can soften or sharpen the images if you choose. As well as detail and aperture controls there are also controls for gamma (standard, still, Cinematone1, Cinematone2, ITU709) and color. The color controls are similar to those on the FS700 where you can adjust the saturation as well as R, G, B, C, M, Y and K brightness. In addition there is a choice of 6 different preset color modes plus black and white.

PXW-X70 auto/manual switch.
PXW-X70 auto/manual switch.

The camera can be controlled either fully automatically or fully manual as well as various in between modes. There is a switch on the back of the camera to switch between auto and manual. In manual you can control the iris, shutter and gain by pressing one of three buttons along the bottom edge of the camera and the using a small wheel just below the lens to set what you have selected. In practice this actually works quite well. There is another button for white balance control on the side of the camera with the usual presets plus auto white balance. Just under the Manual/Auto switch there is a selector for the built in ND filters. I recently purchased a A7s DSLR type camera and I had forgotten what a fiddle it can be to use a camera that doesn’t have built in ND’s. So it’s really good to see proper ND filters on the PXW-X70 as they really help you manage your depth of field.

On the lens there is a single large control ring that can be used to focus the lens or to act as a manual zoom ring. The focus is responsive and although I don’t normally like round and round servo focus rings this one wasn’t too bad.

The zoom/focus ring on the PXW-X70.
The zoom/focus ring on the PXW-X70.

There really is so much to this camera that it would take a small book to go through all the features. For example there’s the touch screen LCD that can be used for touch to focus or touch to expose where you just touch the part of the screen you want to expose or focus on. There’s a full set of exposure and focus aids including peaking, histogram, zebras etc.

On the top of the camera you have Sony’s new MI shoe (Multi-Interface) for connecting accessories like the supplied handle with XLR audio inputs. The supplied detachable handle is really well made and very secure when attached. One small note is that by default when you attach the handle to the MI-shoe the camera switches to XLR audio automatically by default. So if you don’t actually have a mic connected to the handle you won’t have any audio as the internal mic gets shut off. You have to go in to the audio section of the menu to enable the internal mic if you want to use the handle but want to use the built in mic.

If you want to do time-lapse or slow stuff down the camera has S&Q motion that goes from 1fps to 60fps at 1920×1080.

The camera has WiFi and NFC and allows remote control via Content Browser Mobile and simply touching an NFC enabled phone or tablet against the side of the camera will pair the camera with the phone or tablet. In the future following a firmware update you will be able to use the camera to stream your content live via U-stream.

Finally – build quality. It’s really well made. It feels nice and solid, it feels like it will really last. Don’t tell Sony, but I dropped the camera from waist hight while I was using it. It survived, no problem at all.

Sony's new baby XDCAM camcorder, the PXW-X70.
Sony’s new baby XDCAM camcorder, the PXW-X70.

In conclusion: This is a nice little camera. It’s very easy to operate. The picture quality is very good for such a compact camera, the only thing that lets it down just a bit is the highlight handling. But the camera is so clean that you can afford to expose a little lower to compensate for this. Since shooting the demo video I have been playing with the picture profiles to help with the highlight exposure and I found that bringing up the black gamma really helps as it lifts the mid range allowing you to expose slightly lower.

The large sensor, combined with the switchable built in ND filters gives you much greater control over the depth of field than normally possible with a compact handycam.

I think you have to remember that this is a small camera. It isn’t a PXW-X180 and it never will be, but if your budget is tight and you want an easy to use compact camera this could be the one for you. I think it would be a good fit as a “B” camera or for use in lower budget corporate productions. In addition the PXW-X70 would be a good camera to give to PA’s and producers or to hand off to inexperienced shooters for fly-on-the-wall productions.

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Why gain is bad for your dynamic range.

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One way to reduce the noise in a video camera image is to reduce the cameras gain. One way to increase the brightness of the image is to add 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 adding or removing gain reduces the cameras dynamic range as it will artificially clip or limit your low key or high key parts of the image. The maximum illumination level that a camera can capture is limited by the sensor or the gamma curves that the camera has. The black level or darkest part of the image is the point where the actual image signal compared to the sensor noise level is high enough to allow you to see some actual picture information (also known as noise floor). So the dynamic range of the camera is normally the range between the sensors noise floor and recording or sensor clipping point.

To maximise the cameras dynamic range the designers will have carefully set the nominal zero db gain point (native ISO) so that the noise floor is at or very close to black and the peak recording level is reached at the point where the sensor itself starts to clip.

The gain of the camera controls the video output and recording 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 clipping or gamma curve mapping) 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 without (in most cases) any change to the over exposure range, so overall the total dynamic range is reduced.

When you add gain the reverse happens. Generally how far the sensor can see into the shadows is limited by the sensors noise floor. Add 6db of gain and you will make the darkest parts of the image brighter by 6db, but you will also raise the noise level by the same amount. So while you do end up with brighter shadow details you can’t actually see any more picture information because the noise level has increased by the same amount. At the top end as the brightest sensor output is mapped to the maximum recording level at 0db, when you add gain this pushes the recording level beyond what can be recorded, so you loose 6db off the top end of your recordings because the recordings and output clips 6db earlier. So positive gain maintains the same shadow range but reduces the highlight recording range by 6db.

However you use it gain tends to reduce your dynamic range. Adding gain to cope with poor lighting tends to be the lesser of the two evils as generally if your struggling for light then overexposure and blown out highlights is often the last of your worries.

Negative gain is sometimes used in camera to try to reduce noise, but the reality is that you are loosing dynamic range. Really a better solution would be to expose just a tiny bit brighter and then bring your levels down a bit in post production.

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The practicalities of fast run and gun shooting with a large sensor camera.

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Supercell-panoramaWell I’ve just returned home from NAB and a week of Tornado Chasing in the USA. For the Tornado chasing I was shooting in 4K using my Sony F5. I’ve shot run and gun with my F3 and FS700 in the past when shooting air-shows and similar events. But this was very different. Tornado chasing is potentially dangerous. You often only have seconds  to grab a shot which involves leaping out of a car, quickly setting up a tripod and camera and then framing and exposing the shot. You often only have time for one 30 second shot before you have to jump back into the car and move on out ahead of the storm. All of this my be happening in very strong winds and rain. The storms I chased last week had inflow winds rushing into them at 50+ MPH.

The key to shooting any thing fast moving, like this, is having whatever camera kit your using well configured. You need to be able to find the crucial controls for exposure and focus quickly and easily. You need to have a way of measuring and judging exposure and focus accurately. In addition you need a zoom lens that will allow you to get the kinds of shots you need, there’s no time to swap lenses!

For my storm chasing shoot I used the Sony F5 with R5 recorder. This was fitted with a Micron bridge plate as well as a Micron top cheese plate and “Manhandle”. Instead of the Sony viewfinder I used an Alphatron viewfinder as this has a waveform display for exposure. My general purpose lens was a Sigma 18-200mm f3.5-f6.5 stabilised lens with a Canon mount. To control the iris I used a MTF Effect iris control box. For weather protection a CamRade F5/F55 Wetsuit. The tripod I used for this shoot was a Miller 15 head with a set of Carbon Fibre Solo legs.

Storm chasing with a PMW-F5
Storm chasing with a PMW-F5

Overall I was pleased with the way this setup worked. The F5’s ergonomics really help as the logical layout makes it simple to use. The 18-200mm lens is OK. I wish it was faster for shooting in low light but for the daytime and dusk shots, f3.5 (at the wide end) is OK. The F5 is so sensitive that it copes well even with this slow lens. The CamRade wetsuit is excellent. Plenty of clear windows so you can see the camera controls and a well tailored yet loose fit that allows you to get easy access to the camera controls. I’ve used Miller Solo legs before and when you need portability they can’t be beaten. The are not quite as stable as twin tube legged tripods, but for this role they are an excellent fit. The Miller 15 head was also just right. Not too big and bulky, not too small. The fluid motion of the head is really smooth.

Storm Chasing in the USA with the PMW-F5
Storm Chasing in the USA with the PMW-F5

So what didn’t work? Well I used the Element Technica Micron bridge plate. I really like the Micron bridge plate as it allows you to re-balance the camera on the tripod very quickly. But it’s not really designed for quick release, it’s a little tricky to line up the bridge plate with the dovetail so I ended up removing and re-fitting the camera via the tripod plate which again is not ideal. The Micron Bridge plate is not really designed for this type of application, when I go back storm chasing in May I’ll be using a  baseplate that locks into a VCT-14 quick release plate, not sure which one yet, so I have some investigating to do.  The VCT-14 is not nearly as stable or as solid as the Micron, but for this application speed is of the essence and I’m prepared to sacrifice a little bit of stability. The Micron bridge plate is better suited to film style shooting and in that role is fantastic, it’s just not the right tool for this job.

Rainbow under a severe thunderstorm.
Rainbow under a severe thunderstorm.

The MTF-Effect unit is needed to control the aperture of the Canon mount lens, it also powers the optical image stabiliser. But it’s a large square box. I had it mounted on the top of the camera, not in the best place. I need to look at where to mount the box. I’m actually considering re-housing the unit in a custom made hand grip so I can use it to hold the camera with my left hand and have iris control via a thumbwheel. I also want to power it from one of the camera’s auxiliary outputs rather than using the AA batteries internally. The other option is the more expensive Optitek lens mount which I’m hoping to try out soon.  I’m also getting a different lens. The Sigma was fine, but I’m going to get a Sigma 18-250mm (15x) f3.5-f6.5 for a bit more telephoto reach. The other option I could have used is my MTF B4 adapter and a 2/3″ broadcast zoom, but for 4K the Tamron will have better resolution than an HD lens. If I was just shooting HD then the broadcast lens would probably be the best option. After dark I swapped to my Sigma 24-70mm f2.8 for general purpose shooting and this worked well in low light but with the loss of telephoto reach, I need to look into a fast long lens but these tend to be expensive. If you have deep enough pockets the lens to get would probably be the Fujinon Cabrio 19-90 T2.9, but sadly at the moment my budget is blown and my pockets are just not that deep. The Cabrio is very similar to an ENG broadcast lens in that it has a servo zoom, but it’s PL mount and very high resolution. Another lens option would be the Canon CN-E30-105mm T2.8, but overall there isn’t a great deal of choice when it comes down to getting a big zoom range and large aperture at the same time, in a hand-held package. If I was working with a full crew then I would consider using a much larger lens like the Arri Alura 18-80 or Angenieux Optimo 24-290, but then this is no longer what I would consider run and gun and would require an assistant to set up the tripod while I bring out the camera.

A Supercell thunderstorm looking like a flying saucer.
A Supercell thunderstorm looking like a flying saucer.

From an operating point of view one thing I had to do was to keep reminding myself to double check focus. If you think focus is critical in HD, then it’s super critical for 4K. Thunderstorms are horrid things to try and focus on as they are low contrast and soft looking. I had to use a lot of peaking as well as the 1:1 pixel function of the Alphatron viewfinder, one of the neat things about the Alphatron is that peaking continues to work even in the 1:1 zoom mode. As I was shooting raw and using the cameras Cine EI mode to make exposure simpler I turned on the Look Up Tables on the HDSDI outputs and used the P1 LUT. I then exposed using the waveform monitor keeping my highlights (for example the brighter clouds) at or lower than 100%. On checking the raw footage back this looks to have worked well. Quite a few shots needed grading down by 1 to 1.5 stops, but this is not an issue as there is so much dynamic range that the highlights are still fine and you get a cleaner, less noisy image. When shooting raw with the F5 and F55 cameras I’d rather grade down than up. These cameras behave much more like  film cameras due to the massive dynamic range and raw recording, so a little bit of overexposure doesn’t hurt the images as it would when shooting with standard gammas or even log. Grading down (bringing levels down) results in lower noise and a cleaner image.

Frame grab from the F5 of a Supercell storm with a grey funnel cloud beneath.
Frame grab from the F5 of a Supercell storm with a grey funnel cloud beneath.

So you can run and gun in an intense fast moving environment with a large sensor camera. It’s not as easy as with a 2/3″ or 1/2″ camera. You have to take a little more time double checking your focus. The F5 is so sensitive that using a F3.5-F6.5 lens is not a huge  problem. A typical 1/2″ camera (EX1, PMW-200) is rated at about 300 ISO and has an f1.8 lens. The F5 in Cine EI mode is 2000 ISO, almost 3 stops more sensitive. So when you put an f3.5 lens on, the F5 ends up performing better in low light, even at f6.5 it’s only effectively one stop less sensitive. For this kind of subject matter you don’t want to be at f1.8 – f2.8 with a super 35mm sensor anyway as the storm scenes and shots involved work better with a deep focus range rather than a shallow one.

Having watched the footage from the shoot back in HD on a large screen monitor I am delighted with the quality of the footage. Even in HD it has better clarity than I have seen in any of my previous storm footage. This is I believe down to the use of a 4K sensor and the very low noise levels. I’d love to see the 4K material on a 4K monitor. It certainly looks good on my Mac’s retina display. Hopefully I’ll get back out on the plains and prairies of Tornado Alley later in May for some more storm chasing. Anyone want to join me?

 

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Camrade CB Single III Camera Bag.

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I was asked by my good friend Rene of Camrade to take a look at some of their new products. So over the next couple of weeks I’ll be looking at the CB Single III camera bag, the PMW F3 rain cover and a new PL lens adapter for the Sony FS100. First I’m going to take a look at the camera bag.

Camrade CB Single III

I’ve had Camrade bags before and they have always lasted well, standing up to the knocks and bumps that go along with lugging kit all over the place. I was in the market for a new bag for one of my PMW-F3’s, so I was sent the CB Single III bag. From the outside this is a functional looking bag with a large mesh pocket on one side and further external pockets on the other side and at one end. It has a nice well padded chunky carry strap that is comfortable to use.

Inside the Camrade CB Single III

The top of the bag opens up with a dual zipper system that gives you completely un hindered access to the bags interior. This is great for run and gun where you may need to quickly grab the camera from the bag and you don’t want to have to squeeze it out through a small opening. The interior of the bag has various dividers that are secured by velcro, so you can customise the layout to suit your needs. One of the dividers forms a clever storage box to one side of the bag. I’ve found this particularly useful with the F3 as I can safely store my Genus 4×4 Matte Box and a couple of DSLR lenses in here.

Opening the storage compartment shows moveable dividers

Then my batteries, other bits and bobs and the rain cover fit comfortably in the end compartments. This bag really works well with the F3 alloying you to get a complete basic shooting kit into one bag without the bag being too big or bulky.

It’s not perhaps the most fancy or sophisticated of bags, but in terms of practicality and functionality it works very well indeed. There is a strap in the main compartment to hold the camera secure if your really going to be bouncing it around. The base and sides of the bag are all semi ridged and have a good layer of shock absorbing foam in them. With one of these bags typically costing a very affordable $200 it really does represent good value for money.

My thanks to Rene for the sample bag. http://www.camrade.com/products-page/video/cambags/cb-single-iii1

In my next post I’ll look at the nice rain cover that Camrade make for the F3.

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Focal length conversion factor should apply to the camera not the lens.

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I was asked in some post comments whether the a 50mm PL mount lens would give a wider picture than a 50mm DSLR lens. This confusion comes about I believe because of all the talk about focal length conversion factors. I don’t think this concept is well understood by some people as the implication is that somehow the lens is changing when its used on different cameras, when in fact it’s the camera that is different, not the lens.

It is important to understand that a 50mm lens will always be a 50mm lens. That is it’s focal length. It is determined by the shape of the glass elements and no matter what camera you put it on it will still be a 50mm lens. A 50mm DSLR lens has the same focal length as a 50mm PL mount and as a 50mm 2/3″ broadcast lens. In addition the lens focuses a set distance behind the rear element, agin the distance between the rear element and where it focuses does not change when it’s put on different cameras, so an adapter or spacer must be used to keep the designed distance between the lens and sensor, this distance is called the “flange back”.

The key thing is that it’s not the lens or it’s focal length that changes when you swap between different cameras. It is the size of the sensor that changes.

Imagine a projector shining an image on a screen so that the picture fills the screen. The projector is our “lens”. Without changing anything on the projector what happens if you move the screen closer or further away from the projector? The image projected on the screen will go in and out of focus, so that’s not good, we must keep the projector to screen distance constant, just like the lens to sensor distance (flange back) for any given lens remains constant.

What happens if we make the screen smaller? Well the image remains the same size but we see less of it as some of the image falls of the edge of the screen. If our projected picture was that of a wide landscape then on the reduced screen size what would now be seen would not appear less wide as we are now only seeing the middle part of the picture. The width of the view would be decreased, in other words the FIELD OF VIEW HAS NARROWED. The focal length has not changed.

This is what is happening inside cameras with different size sensors, the lens isn’t changing, just how much of the lenses projected image is falling on or off the sensor.

So the multiplication factor should be considered more accurately as being applied to the camera, not the lens and the multiplication factor changes the field of view, not the focal length.

So whether it is a PL mount lens, a Nikon or Canon DSLR lens or a Fujinon video lens, if it’s a 50mm lens then it’s a 50mm lens and the focal length is the same for all. However the field of view (width and height of the viewed image) will depend on the size of the sensor. So a 50mm PL lens will give the same field of view as a 50mm DSLR lens (no matter what camera the lens was designed for) on the same video camera.

The only other thing to consider is that lenses are designed to work with certain sizes of sensor. A lens designed for a full frame 35mm sensor will completely cover that size of sensor as well as any sensor smaller than that. On the other hand a 2/3? broadcast lens will only cover a 2/3? sensor, so if you try to use it on a larger sensor the image will not fill the frame.
The sensors in the Sony F3 and FS100 are “Super 35mm”. That is about the same size as APS-C. So lenses designed for Full frame 35mm can be used as well as lenses designed for 35mm cine film (35mm PL) and lenses designed for APS-C DSLR’s such as the Nikon DX series and Canon EF-S.

See also http://www.abelcine.com/fov/

 

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Focal length conversion factor should apply to the camera not the lens.

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I was asked in some post comments whether the a 50mm PL mount lens would give a wider picture than a 50mm DSLR lens. This confusion comes about I believe because of all the talk about focal length conversion factors. I don’t think this concept is well understood by some people as the implication is that somehow the lens is changing when its used on different cameras, when in fact it’s the camera that is different, not the lens.

It is important to understand that a 50mm lens will always be a 50mm lens. That is it’s focal length. It is determined by the shape of the glass elements and no matter what camera you put it on it will still be a 50mm lens. A 50mm DSLR lens has the same focal length as a 50mm PL mount and as a 50mm 2/3″ broadcast lens. In addition the lens focuses a set distance behind the rear element, agin the distance between the rear element and where it focuses does not change when it’s put on different cameras, so an adapter or spacer must be used to keep the designed distance between the lens and sensor, this distance is called the “flange back”.

The key thing is that it’s not the lens or it’s focal length that changes when you swap between different cameras. It is the size of the sensor that changes.

Imagine a projector shining an image on a screen so that the picture fills the screen. The projector is our “lens”. Without changing anything on the projector what happens if you move the screen closer or further away from the projector? The image projected on the screen will go in and out of focus, so that’s not good, we must keep the projector to screen distance constant, just like the lens to sensor distance (flange back) for any given lens remains constant.

What happens if we make the screen smaller? Well the image remains the same size but we see less of it as some of the image falls of the edge of the screen. If our projected picture was that of a wide landscape then on the reduced screen size what would now be seen would not appear less wide as we are now only seeing the middle part of the picture. The width of the view would be decreased, in other words the FIELD OF VIEW HAS NARROWED. The focal length has not changed.

This is what is happening inside cameras with different size sensors, the lens isn’t changing, just how much of the lenses projected image is falling on or off the sensor.

So the multiplication factor should be considered more accurately as being applied to the camera, not the lens and the multiplication factor changes the field of view, not the focal length.

So whether it is a PL mount lens, a Nikon or Canon DSLR lens or a Fujinon video lens, if it’s a 50mm lens then it’s a 50mm lens and the focal length is the same for all. However the field of view (width and height of the viewed image) will depend on the size of the sensor. So a 50mm PL lens will give the same field of view as a 50mm DSLR lens (no matter what camera the lens was designed for) on the same video camera.

The only other thing to consider is that lenses are designed to work with certain sizes of sensor. A lens designed for a full frame 35mm sensor will completely cover that size of sensor as well as any sensor smaller than that. On the other hand a 2/3? broadcast lens will only cover a 2/3? sensor, so if you try to use it on a larger sensor the image will not fill the frame.
The sensors in the Sony F3 and FS100 are “Super 35mm”. That is about the same size as APS-C. So lenses designed for Full frame 35mm can be used as well as lenses designed for 35mm cine film (35mm PL) and lenses designed for APS-C DSLR’s such as the Nikon DX series and Canon EF-S.

See also http://www.abelcine.com/fov/

 

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Sony NEX-3 Love this stills camera!

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This isn’t really a review and it’s not about video. On the way out here to the US, I did a little bit of Christmas shopping picking up a Sony NEX-3 APS-C camera at the airport for my wife. When I got the opportunity to do some sightseeing in New York I decided to take the NEX along and you know what I’m really impressed. The camera is reasonably small, pocket sized yet behaves much more like a DSLR. In fact I think for a holiday camera or travel camera in some respects it’s better. It’s very straight forward to use, fast and responsive. But the feature I like the most is the Panorama mode that combines a sequence of frames into a seamless panorama. The video is pretty good too, although if your buying one for video the slightly more expensive NEX-5 would be better as that one does 1920×1080 while the NEX-3 is 720P. I can’t wait to use the NEX to take panoramic photographs of the Arctic in January or the storms and tornadoes when I go storm chasing next year. Ah.. one small problem, this is supposed to be a Christmas present for my wife, not a new toy for me. Hmmmm might have to get another one on the way home!

New York Panorama taken with NEX3

-3

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Shooting Snow and other bright scenes.

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Well winter is upon us. The north of the UK is seeing some pretty heavy snow fall and it’s due to spread south through the week. I regularly make trips to Norway and Iceland in the winter to shoot the Northern Lights (email me if you want to come) so I am used to shooting in the snow. It can be very difficult. Not only do you have to deal with the cold but also difficult exposure.

First off it’s vital to protect your equipment and investment from the cold weather. A good camera cover is essential, I use Kata covers on my cameras. If you don’t have a proper cover at the very least use a bin liner or other bag to wrap up your camera. If you have a sewing machine you could always use some fleece or waterproof material to make your own cover. If snow is actually falling, it will end up on your lens and probably melt. Most regular lens cloths just smear any water around the lens, leaving you with a blurred image. I find that the best cloth to use in wet conditions is a chamois (shammy) leather. Normally available in car accessory shops these are soft, absorbent leather cloths. Buy a large one, cut it into a couple of smaller pieces, then give it a good wash and you have a couple of excellent lens cloths that will work when wet and won’t damage your lens.

Exposing for snow is tricky. You want it to look bright, but you don’t want to overexpose. If your camera has zebras set them to 95 to 100%. This way you will get a zebra pattern on the snow as it starts to over expose. You also want your snow to look white, so do a manual white balance using clean snow as your white. Don’t however do this at dawn or near sunset as this will remove the orange light normally found at the ends of the day. In these cases it is best to use preset white set to around 5,600k. Don’t use cinegammas or hypergammas with bright snow scenes. They are OK for dull or overcast days, provided you do some grading in post, but on bright days because large areas of your snow scene will be up over 70 to 80% exposure you will end up with a very flat looking image as your snow will be in the compressed part of the exposure curve. You may want to consider using a little bit of negative black gamma to put a bit more contrast into the image.

If the sun is shining, yes I know this may not happen often in the UK, but if it is then the overall brightness of your scene may be very high. Remember to try to avoid stopping down your lens with the iris too far. With 1/3? sensor cameras you should aim to stay more open than f5.6, with 1/2? more than f8 and 2/3? more than f11. You may need to use the cameras built in ND filters or external ND filters to achieve this. Perhaps even a variable ND like the Genus ND Fader. You need to do this to avoid diffraction limiting, which softens the image if the iris is stopped down too much and is particulary noticeable with HD camcorders.

Finally at the end of your day of shooting remember that your camera will be cold. If you take it in to a warm environment (car, house, office) condensation will form both on the outside and on the inside. This moisture can damage the delicate electronics in a camcorder so leave the camera turned off until it has warmed up and ensure it is completely dry before packing it away. This is particularly important if you store your camera in any kind of waterproof case as moisture may remain trapped inside the case leading to long term damage. It is a good idea to keep sachets of silica gel in your camera case to absorb any such moisture. In the arctic and very cold environments the condensation may freeze covering the camera in ice and making it un-useable. In these extreme situations sometimes it is better to leave the camera in the cold rather than repeatedly warming it up and cooling it down.

Have fun, don’t get too cold, oh…  and keep some chemical hand warmers handy to help stop the lens fogging and to keep your fingers from freezing.

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Why Is Sensor Size Important: Part 1.

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Over the next few posts I’m going to look at why sensor size is important. In most situations larger camera sensors will out perform small sensors. Now that is an over simplified statement as there are many things that effect sensor performance, including continuing improvements in the technologies used, but if you take two current day sensors of similar resolution and one is larger than the other, the larger one will usually outperform the smaller one. Not only will the sensors themselves perform differently but other factors come in to play such as lens design and resolution, diffraction limiting and depth of field, I’ll look at those in subsequent posts, for today I’m just going to look at the actual sensor itself.

Pixel Size:

Pixel size is everything. If you have two sensors with 1920×1080 pixels and one is a 1/3? sensor and the other is a 1/2? sensor then the pixels themselves on the larger 1/2? sensor will be bigger. Bigger pixels will almost always perform better than smaller pixels. Why? Think of a pixel as a bucket that captures photons of light. If you relate that to a bucket that captures water, consider what happens if you put two buckets out in the rain. A large bucket with a large opening will capture more rain than a small bucket.

Small pixels capture less light each

Bigger pixels capture more light each.

It’s the same with the pixels on a CMOS or CCD sensor, the larger the pixel, the more light it will capture, so the more sensitive it will be. Taking that analogy a step further if the buckets are both of the same depth the large bucket will be able to hold more water before it overflows. It’s the same with pixels, a big pixel can store more charge of electrons before it overflows (photons of light get converted into electrical charge within the pixel). This increases the dynamic range of the sensor as a large pixel will be able to hold a bigger charge before overflowing than a small pixel.

Noise:

All the electronics within a sensor generate electrical noise. In a sensor with big pixels which is capturing more photons of light per pixel than a smaller sensor, the ratio of light captured to electrical noise is better, so the noise is less visible in the final image, in addition the heat generated in a sensor will increase the amount of unwanted noise. A big sensor will dissipate any heat better than a small sensor, so once again the big sensor will normally have a further noise advantage.

So as you can see, in most cases a large sensor has several electronic advantages over a smaller one. In the next post I will look at some of the optical advantages.

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Why Is Sensor Size Important: Part 1.

Leave a comment


Over the next few posts I’m going to look at why sensor size is important. In most situations larger camera sensors will out perform small sensors. Now that is an over simplified statement as there are many things that effect sensor performance, including continuing improvements in the technologies used, but if you take two current day sensors of similar resolution and one is larger than the other, the larger one will usually outperform the smaller one. Not only will the sensors themselves perform differently but other factors come in to play such as lens design and resolution, diffraction limiting and depth of field, I’ll look at those in subsequent posts, for today I’m just going to look at the actual sensor itself.

Pixel Size:

Pixel size is everything. If you have two sensors with 1920×1080 pixels and one is a 1/3? sensor and the other is a 1/2? sensor then the pixels themselves on the larger 1/2? sensor will be bigger. Bigger pixels will almost always perform better than smaller pixels. Why? Think of a pixel as a bucket that captures photons of light. If you relate that to a bucket that captures water, consider what happens if you put two buckets out in the rain. A large bucket with a large opening will capture more rain than a small bucket.

Small pixels capture less light each

Bigger pixels capture more light each.

It’s the same with the pixels on a CMOS or CCD sensor, the larger the pixel, the more light it will capture, so the more sensitive it will be. Taking that analogy a step further if the buckets are both of the same depth the large bucket will be able to hold more water before it overflows. It’s the same with pixels, a big pixel can store more charge of electrons before it overflows (photons of light get converted into electrical charge within the pixel). This increases the dynamic range of the sensor as a large pixel will be able to hold a bigger charge before overflowing than a small pixel.

Noise:

All the electronics within a sensor generate electrical noise. In a sensor with big pixels which is capturing more photons of light per pixel than a smaller sensor, the ratio of light captured to electrical noise is better, so the noise is less visible in the final image, in addition the heat generated in a sensor will increase the amount of unwanted noise. A big sensor will dissipate any heat better than a small sensor, so once again the big sensor will normally have a further noise advantage.

So as you can see, in most cases a large sensor has several electronic advantages over a smaller one. In the next post I will look at some of the optical advantages.