Micro 4/3, Super 35, DSLR and the impact on traditional Pro Camcorders.
I was asked by one of this blogs readers about my thoughts on this. It’s certainly a subject that I have spent a lot of time thinking about. Traditionally broadcast and television professionals have used large and bulky cameras that use 3 sensors arranged around a prism to capture the 3 primary colours. The 3 chip design gives excellent colour reproduction, full resolution images of the very highest quality. It’s not however without it’s problems. First its expensive matching 3 sensors and accurately placing them on a high precision prism made from very exotic glass. That prism also introduces image artefacts that have to be dealt with by careful electronic processing. The lenses that have to work with these thick prisms also require very careful design.
Single sensor colour cameras are not something new. I had a couple of old tube cameras that produced colour pictures from a single tube. Until recently, single chip designs were always regarded as inferior to multi-chip designs. However the rise of digital stills photography forced manufacturers to really improve the technologies used to generate a colour image from a single sensor. Sony’s F35 camera used to shoot movies and high end productions is a single chip design with a special RGB pixel matrix. The most common method used is by a single sensor is a bayer mask which places a colour filter array in front of the individual pixels on the sensor. Bayer sensors now rival 3 chip designs in most respects. There is still some leakage of colours between adjacent pixels and the colour separation is not as precise as with a prism, but in most applications these issues are extremely hard to spot and the stills pictures coming from DSLR’s speak for themselves.
A couple of years ago Canon really shook things up by adding video capabilities to some of their DSLR’s. Even now (at the time of writing at least) these are far from perfect as they are at the end of the day high resolution stills cameras so there are some serious compromises to the way video is done. But the Canons do show what can be done with a low cost single chip camera using interchangeable lenses. The shallow depth of field offered by the large near 35mm size sensors (video cams are normally 2/3?, 1/2? or smaller) can be very pleasing and the lack of a prism makes it easier to use a wide range of lenses. So far I have not seen a DSLR or other stills camera with video that I would swap for a current pro 3 chip camera, but I can see the appeal and the possible benefits. Indeed I have used a Canon DSLR on a couple of shoots as a B camera to get very shallow DoF footage.
Sony’s new NEX-VG10 consumer camcorder was launched a couple of weeks ago. It has the shape and ergonomics of a camcorder but with the sensor and lenses of a 4/3? stills camera. I liked it a lot, but there is no zoom rocker and for day to day pro use it’s not what I’m looking for. Panasonic and Sony both have professional large sensor cameras in the pipelines and it’s these that could really shake things up.
While shallow DoF is often desirable in narrative work, for TV news and fast action its not so desirable. When you are shooting the unexpected or something thats moving about a lot you need to have some leeway in focus. So for many applications a big sensor is not suitable. I dread to think what TV news would look like if it was all shot with DSLR’s!
Having said that a good video camera using a big sensor would be a nice piece of kit to have for those projects where controlling the DoF is beneficial.
What I am hoping is that someone will be clever enough to bring out a camera with a 35mm (or thereabouts) sized sensor that has enough resolution to allow it to be used with DSLR (or 4/3) stills camera lenses but also be windowed down and provided with an adapter to take 2/3? broadcast lenses without adding a focal length increase. This means that the sensor needs to be around 8 to 10 Mega Pixels so that when windowed down use just the center 2/3? and it still has around 3 million active pixels to give 1920×1080 resolution (you need more pixels than resolution with a bayer mask). This creates a problem though when you use the full sensor as the readout of the sensor will have to be very clever to avoid the aliasing issues that plague the current DSLR’s as you will have too much resolution when you use the full sensor. Maybe it will come with lens adapters that will have to incorporate optical low pass filters to give the correct response for each type of lens.
A camera like this would, if designed right dramatically change the industry. It would have a considerable impact on the sales of traditional pro video cameras as one camera could be used for everything from movie production to TV news. By using a single sensor (possibly a DSLR sensor) the cost of the camera should be lower than a 3 chip design. If it has a 10 MP sensor then it could also be made 3D capable through the use of a 3D lens like the 4/3? ones announced by Panasonic. These are exciting time we live in. I think the revolution is just around the corner. Having said all of this, I think it’s also fair to point out while you and I are clearly interested in the cutting edge (or bleeding edge) there are an awful lot of producers and production companies that are not, preferring traditional, tried and tested methods. It takes them years to change and adapt, just look at how long tape is hanging on! So the days of the full size 2/3? camera are not over yet, but those of us that like to ride the latest technology wave have great things to look forward to.
IMPORTANT UPATE REGARDING NOISE AND SENSITIVITY: See section highlighted in red below.
Hi all. Well I have got a Canon XF305E for the afternoon. Wish it was longer, but they are like hens teeth. I’m going to be writing and updating this as I go, so please keep coming back for the latest updates and post a comment if there is anything you want me to specifically look at.
Out of the box, first impressions are that it is big. 20% bigger than an EX1. The body is dominated by the very large lens which also has a sensor of some kind to the left of the lens barrel. I assume this is to do with the autofocus system. I hope so as it would make Matte Box use very difficult.
Overall it feels very well made although there are a few bits that could be better. It’s possible to put a battery in the battery compartment incorrectly so that the camera will work unless you knock it and bump it, then the battery connection is lost. You really need to have the camera down on a flat surface to be sure the battery goes in right. In addition there is a pair of really heath robinson looking springs at the back of the battery compartment. Considering this is about the most expensive camcorder in it’s class you don’t expect cheap and nasty springs like the ones fitted in the battery compartment.
They look like an after thought.
Incorrectly inserted Battery
The flap that covers the battery feels cheap and plasticky compared to the rest of the camera body and I would be worried about this breaking off at some point. However if it does break there is a separate battery catch that holds the battery in place.
Looking at the lens my first point of confusion came when I pressed the zoom rocker and nothing happened. I turned the calibrated zoom ring on the lens and the lens zoomed in and out, but the rocker did nothing. So I looked for the zoom servo switch. I didn’t find one but did find the “Zoom – Rocker – Ring” switch. Switched it from ring to rocker, pressed the rocker and the zoom works…….. but….. now the zoom ring does not turn or move, so you can have one or the other but not both. The iris ring has no markings and is of the round and round servo variety so you need to look at the (very nice) LCD screen to see where the iris is set, the same for the zoom when set to rocker.
The focus system is not that dissimilar to an EX with both calibrated manual and non calibrated manual/auto operation. On an EX you slide the focus ring forwards and backwards to switch from full manual to servo control. On the XF305 you have to take your hand off the focus ring to operate a small push button that allows you to rotate the lens body to switch between manual and servo. It’s not quite as convenient as the EX but is easy enough to do. There is a problem with this however. If you set the manual focus ring at say infinity, then switch to the servo/manual/auto focus and use that, when you switch back to full manual the lens will return to the last position you set the focus to. OK, fine, that’s the same as an EX1R, BUT on the XF305 you can’t see the focus scale in the focus window when you are set to servo/auto so you have no idea what the focus is going to do when you switch modes unless you can remember where you last set the manual focus.
Just like an EX1 when you hand hold the camera it’s bulk puts a fair bit of strain on the wrist as it want’s to fall forwards and to the left. There is no adjustable hand grip rotation and the record start stop button is a little low down for my thumb. The hand grip is also quite small and angular. I think the EX1R is a lot more comfortable to hold.
If your using the XF305 on a tripod there is only a single 1/4? threaded hole in a small plate on the bottom of the camera, much like the original EX1, so don’t overload it or you may end up breaking the plate. Perhaps Curtis at Juiced Designs will do a strengthening plate for the XF305. Do camera designers not read forums and look at what happens to cameras when used in the field?
Behind the hand grip there is an array of BNC connectors for SDi, video out, Genlock and timcode. Full marks for using proper BNC connectors here. Behind these are a whole bunch of floppy cheap plastic covers over HDMI, USB, headphone, AV, remote and mini component connectors.
In use the large LCD screen is clear and easy to see. It flips out from under the handle on both sides of the camera which is really neat.
The multi-coloured graphics all over the screen do make it a little cluttered but these can be easily turned off. The XF305 can also display waveform monitor and vectorscope plus a 3 zone waveform monitor all of which are very useful tools to have (LCD screen only, not rear VF). While looking at the LCD I realised that just like the EX1 the microphone and in this case the LCD as well, stick out beyond the end of the lens. Why do camera manufacturers do this? It makes fitting and using a Matte Box so difficult. Doh! Having the LCD screen so far forwards could present problems for Matte Box users.
Where the EX1 and EX3 have picture profiles the XF305 like most pro Canon cameras has a number of “Custom Picture” memories. There are 6 preset memories for you to dial in your own looks plus “Video C”, “Cine V” and “Cine F” setups. The Cine V setup was really soft and Cine F just had a quite flat look, however I didnt really have time to explore these fully. I did try Alan Roberts recommended settings and these are very nice and I would recommend them as a good starting point for really making the XF305 sing. Within the CP settings you can choose from 4 standard gamma curves and 2 cine style gamma curves. The Matrix is fully adjustable so it should be easy to roll your own custom looks. Another setting tucked away in the CP menu is the noise reduction. The XF305 has some very clever noise reduction that is clearly doing a good job of controlling the noise that is normally be associated with a small sensor camera. You can choose between Automatic nose reduction and 8 steps of reduction. If set to 8 however the noise reduction is very hard and the resolution drops way down.
The pictures from the XF305 are very good. At 0db they are quite similar overall to those from an EX1. They do have a different colorimetry to Sony’s camera’s (which I always find a little yellow) and are pleasing to look at. Clearly the lens is very good, CA is well controlled but there is some quite obvious barrel distortion between fully wide and 6mm, but it’s no worse than an EX1R and really to be expected from a camera at this price point.
I also found some noticeable softening in the corners fully wide which appears to be worse on the left side of the image than the right.
When I was looking at the lens distortion I was zooming in and out using the zoom rocker, then I went to turn the zoom ring just to tweak the zoom and of course nothing happened. This zoom rocker or zoom ring, but not both way of operation really sucks.. am I missing something here? While on the subject of the zoom rocker I was asked about how it was with slow creeping zooms. Well it’s very good. I did find that you have to press the rocker a long way past the center point before anything happens, but once the zoom starts to operate you can get a slow creeping zoom. But to then go from the creeping zoom smoothly to a faster zoom is tricky as a tiny bit more pressure on the rocker leads to a rapid increase in zoom speed. It seems that there is a very large dead area where the zoom rocker does nothing and then all the action takes place in the last few millimeters of its travel. It almost feels like the zoom speed is in steps, not entirely variable. I’m sure it’s not and with practice perhaps I could master it, but it’s a little touchy. The EX1R isn’t perfect either. The zoom rocker can be a bit twitchy when trying to do a creeping zoom, but in this case I prefer the EX1R zoom over the Canon. If you do choose to use the zoom ring to control the zoom there is some serious lag between turning the zoom ring and the zoom happening. For slow zooms this may not be an issue, but crash zooms are very difficult to execute. The iris ring also as some lag which makes fine tweaking of exposure a little harder than it should be. The last couple of years I have become so used to the EX1 and EX3 lens with its great feel and proper zoom and iris rings that this is a real let down. Overall I think that optically the Canon lens as a small edge over the EX lens, there is less CA and a greater zoom range. But ergonomically I much prefer the EX1R lens.
Latitude is very similar at 0db between both cameras, I couldn’t really see much of a difference either way. UPDATE There are some differences in image sharpness and noise however. Please see this clip (Vimeo or YouTube) for some examples, generally Vimeo is better quality.
If anything the Canon 305 at first glance appears a little sharper than the EX1R, but looking closer and examining the footage as well as resolution chart results shows very similar resolution from both cameras. However the XF305 pictures contain a lot of quite visible, very fine noise that’s constantly buzzing around at all brightness levels. This very fine noise is easily mistaken for extra picture detail, which it is not.
It’s really interesting to look at side by side comparisons of the EX and XF footage. With the same clip, trees and foliage from the XF appear to be more detailed, but step through the footage frame by frame and you see the XF foliage is actually full of this fine noise compared to the EX foliage, this makes it appear sharper as it adds a fake “texture” to the foliage. But I can’t actually see any extra real detail in the XF foliage. Taking the same clip and looking at the parked car, again the XF shows a lot of noise, but in this case you can clearly see the car is a little softer in the XF footage than the EX. These differences are not so much down to resolution differences, but down to noise and noise reduction working in slightly different ways in the two cameras plus differences in the detail settings.
Turn up the gain on both cameras to +12db and the difference is even more striking. Click on the image to the left to view it full frame or look at the clip I have prepared (Vimeo or YouTube). I find the fine, busy, noise from the XF305 a lot more objectionable than the more blocky noise that the EX1R generates. The XF305 also shows some black speckles similar to those found on the Panasonic HPX301. Given that the XF305 is using small 1/3? sensors this kind of performance is not really unexpected. The XF305 probably has the best front end of any 1/3? camera currently on the market, but controlling noise on small sensors is harder to do than with large sensors and IMHO it still doesn’t perform as well as the EX’s with their larger sensors.
In addition the EX1R’s larger sensor helps it capture more light making it 1.5 stops more sensitive than the XF305. So in low light you will tend to use more gain with the 305 than with an EX. It has been pointed out that the XF305 lens is about half a stop faster than the EX lens which does help the 305 little, but if low light performance is important to you do choose wisely. You can increase the noise reduction on the XF305 to combat the noise but this also softens the picture, especially when used at the higher settings. If you download the raw footage you can zoom in and see the differences for yourself.
The differences are small, but they are there. The Canon is noisier looking while the Sony appears a little softer, but I’m not convinced that it is, I thinks it the XF’s noise giving the impression of a sharper image by adding texture to many surfaces. I personally would take the cleaner image as you can more with this in post production.
I also shot some clips with the XF305 and a NanoFlash as well as the EX1R and a NanoFlash. At 50Mb/s it was very hard to tell any difference between the XF305 and 305/NanoFlash recording, which is what you would expect. If anything the NanoFlash footage may be just a tiny bit less blocky. Comparing the XF305 at 50Mb/s and EX1R/NanoFlash at 50Mb/s the EX footage was quite a bit cleaner with less mosquito noise and macro blocking. If you click on the side by side image on the right you can view it full screen. Look at how much cleaner the EX footage is, but also look carefully at the brickwork. I can tell you that in the moving video clip the bushes in the XF305 clip are full of fine noise, on the frame grab this looks like fine detail, but it’s not.
The EX footage recorded on to the NanoFlash at 50Mb/s is cleaner with less macro blocking and mosquito noise, this is probably due to the very fine noise from the 305 stressing the codec harder than the low frequency noise from the EX. At 100Mb/s the EX1R looked really good indeed. The test footage was shot at 25P and even though the XF305 is recording at 50Mb/s 4:2:2 against the EX1R’s 35Mb/s 4:2:0 the visible difference in the rushes is negligible.
The rear viewfinder on the XF305 is a bit better than the rear finder on the EX1R. It’s bigger and I found it very nice to use, however I could not get the waveform monitors etc to appear in the rear finder, only the LCD screen. The menus are logically laid out, I didn’t find them as straight forward to use as the EX menu’s but then I have been using EX’s for some years now so it could just be a case of them being different to what I’m used to.
So what do I think? Well the XF305 is a very good camcorder. It produces very pleasing images recorded at 50Mb/s 4:2:2. Is it better than an EX1R? Well I don’t think that overall it is. Is the EX1R better then? On it’s own, no, but with a NanoFlash, yes. There are bits of both cameras that I like and dislike. The EX1R is nicer to hold and more compact, it has a better zoom rocker and record switch. The XF305 has a better zoom range and less CA (Chromatic aberration) but I would not enjoy the way you have to choose between the zoom rocker OR zoom ring and can’t have both. The 305?s zoom and iris rings are a little sluggish to respond and the iris has no calibrated markings so you have to rely on the viewfinder or LCD. The 305?s LCD is really very good and I like the way you can flip it out either side. The EX1R’s rear finder, while perfectly useable is not as good as the one on the XF305. The picture quality from both cameras is very good. Different…. but good. The 305 has a slight edge on it’s out of the box look but it is visibly more noisy than the EX1R and it’s easy to confuse the very busy fine noise that appears across the whole image as fine detail. The EX can be dialled in to give great pictures too. As a side note with the EX going in to the Picture Profiles and increasing frequency to +40 helps sharpen up the foliage in the EX pictures. Both cameras have some noise in the images, at 0db I think the EX has the visual edge and looks cleaner, at higher gain levels above +6db the XF305 noise becomes more and more objectionable compared to the EX1R. At 0db the XF305?s fine noise is stressing the codec a little. An EX1R recording to a NanoFlash at 50Mb/s produces a much cleaner image with less mosquito noise and macro blocking.
If your thinking of buying either it’s a tough choice. The XF305 has genlock and timecode in, which the EX1R does not have. For that you need to get an EX3 which is more expensive, but then you can also change the lens. I certainly don’t see any reason to swap my EX’s for 305?s and the similarly priced EX1/NanoFlash combo is an extremely powerful tool offering the benefits of dual record, HD and SD recording as well as higher bit rates. In addition NanoFlash 50Mb/s files are compatible with the XDCAM HD optical disc system, which the Canon files are not. The XF305 has smaller sensors than the EX1 so controlling depth of field will be a little harder, also you will get image softening due to diffraction effects about a stop sooner with the 305 but this may or may not be important to you.
Pictures: Sony (cleaner, less noise)
Workflow: Sony (Because it’s faster (with SxS) more mature and you have backwards compatibility with Optical Disc XDCAM HD) Canon XF305 and Sony EX1R side by side tests from Ingenious TV on Vimeo.
UPDATE: I had a play with one today. It’s actually really good, although it’s very strange holding a small video camera that doesn’t have a zoom control. Click the link: nex-clips to download raw NEX-VG10 (MTS) clips straight from the camera. See end of post for brief hands on info.
So, Sony have launched a new APS-C camcorder. The NEX-VG10 comes from the consumer side of Sony and is based on the APS-C sensor used in the new NEX-5 and NEX-3 Sony Alpha stills cameras launched a few months ago. Compared to a full frame 35mm sensor APS-C is about 1.5x smaller, but still significantly larger than the sensors found in the majority of video cameras. It is designed as a video camera with a familiar video camera look and shape to it. There is a fold out 3? LCD screen on the left side and video style viewfinder at the rear. It records full 1920×1080 HD video using AVCHD at 24Mb/s so it should look pretty good. It also takes still images at “near DSLR quality” thanks to the high resolution 14.2 megapixel sensor. In some respects this is a little disappointing as it means that the sensor will not have an optical low pass filter tailored for video. Without this, in the past, it has meant that the video produced by stills cameras tend to suffer from aliasing and other image degrading effects caused by trying to cram too much resolution into a 1920×1080 video frame or by the sub sampling of the sensor. Lets hope the Sony engineers have done a good processing job getting the footage off the sensor down to HD video. It records 25P (Pal version) or 30P (US version) recoded in an interlace stream to give maximum compatibility. You can use a variety of recording media including Memory Sticks and SD/SDHC cards. On the handle there is a rather strange looking array of 4 microphones in a shock and vibration isolating mount for recording surround sound audio. In addition there is a 3.5mm socket for an external microphone as well as a 3.5mm headphone socket. The camcorder is supplied with a 18 to 200mm optically stabilised f3.5-f5.6 zoom lens that attaches using Sony’s E mount system. This has a very short back focus distance and it will be easy to convert this to take a wide range of other mounts such as Canon via already available low cost adapter rings. Sony will be making an E mount to Alpha A mount for Alpha (and Minolta?) lenses. The supplied lens is a bit disappointing as really for those super shallow DoF shots you want a fast lens and f3.5 is not what I would call fast, but it does offer a useful 11x zoom range. Autofocus can operate while your shooting if you need it.
With a US street price of around $2000USD it represents good value for money, provided it performs. Video that I have seen from the NEX5 cameras looks very good but I have not seen what the aliasing performance is like, after all this is again a sensor optimised for high resolution stills and not video. It’s also important to note that this is not the camera that Sony showed at NAB, so who knows when we may or may not see that. The NEX-VG10 is an interesting looking camera and it surprisingly looks like it will beat the Panasonic AG-AF100 to market as the first low cost 35mm (ish) sensor camcorder. The big question is what will the pictures be like?
HANDS ON: I managed to get a brief play with one today. First off it’s very small and light, but with the supplied lens makes it quite front heavy. The LCD is clear and easy to see, however I did find focusing tricky with the LCD but I did not have time to see if there was any kind of focus assist system or peaking control. With the supplied lens you turn the forward ring to zoom and rear ring to focus. It was quite stiff turning the zoom ring and very difficult to do in shot zooms as you tend to twist the whole camera as you rotate the zoom ring. As well as the focus ring on the lens there is a dial behind the LCD screen that controls many functions including menu navigation, but this is also marked as a focus control. It was very strange holding a camcorder but not having any kind of zoom control. The menu system is quite logically laid out and easy to find your way around. I did shoot some clips with it and could see no signs of any aliasing which is very promising indeed. As expected it had pleasing shallow DoF but the low light performance was disappointing as it didn’t seem to perform as well as I had hoped. In some respects this may be an advantage as it helps get a shallow DoF. It also has to be remembered that the stock lens is only f3.5 compared to the f1.9 of a EX camcorder, so overall low light performance may not be as bad as it appeared. The pictures look very promising, it’s not a particularly expensive camcorder and for video, ergonomically it’s much better than a DSLR. I’m sure this will be popular with those that are seeking the filmic look.
I’ve spend a couple of days putting a PMW-320 through it’s paces. The 320 is the latest addition to the XDCAM EX line up. It’s very much like the PMW-350 which I reviewed in depth last year, the principle difference is the sensor size. The PMW-350 is 2/3? while the PMW-320 is 1/2?. The camera can be purchased with or without a lens, the supplied lens is a Fujinon 16×5.8mm HD lens that has both autofocus and manual focus. The lens mount is Sony’s standard 1/2? hot shoe bayonet, so owners of DSR300? or PDW-350?s etc can use their lenses directly on the PMW-320. As with the 350 the lens that comes with the 320 is pretty good. Nice and sharp and with a good feel to it considering the cost. It does however suffer from flare under harsh lighting and this can soften the picture a little. A good lens shade or matte box with flags would really help this lens.
Externally the 320 and 350 are almost identical. The give aways are the rubber strip under the handle, EXMOR badge on the side and lens mount ring are dark blue on the 320, black on the 350. Off the shelf the stock PMW-320 actually has more features than the 350. SD is included as standard and it can output to both HDSDi and HDMI at the same time. Buttons and switches are the same on both camera as is the excellent high resolution colour viewfinder. On switching on and looking through the menus they appear to be the same as the 350, no there surprise really, so just like the 350 instead of the pictureprofiles and Cinegammas found on the EX1R and EX3 we have Scene Files and Hypergammas more like a PDW-700 or other high end Sony cameras. Talking of the EX1R and EX3, there has been a little confusion over the sensors used in the 320. At first I got the impression that the 320 used new sensors, but I was told at NAB that was not the case and the 320 has the same sensors as the EX1R/EX3. So I was somewhat surprised when I started looking at the images from the 320 to see less noise and a different looking picture.
On the PMW-320 there is a wider range of camera adjustments compared to an EX1R. For example as well as detail settings there is also a section for adjusting the Aperture correction which can also sharpen and soften the look of the camera by boosting high frequencies. Out of the box I didn’t think the 320 was quite as sharp as my EX3. But after a few minutes on the bench and with a few tweaks to the detail and aperture settings the camera was looking very good indeed (detail -8, aperture +20). While not a quiet as the PMW-350 the 320 does appear to have less noise than an EX1 or EX3. It’s not a big difference, but every little helps. My guess there is additional signal processing going on to reduce the noise.
The use of scene files for the PMW-320 and PictureProfiles on the EX1 does make it harder to match the cameras if your using non-standard settings. It can be done, but it takes a little more work.
The power consumption of the 320 is, once again remarkably low. I was powering it with a 95Wh battery and it lasted most of the day. There are no fans to make noise and it’s very light yet well balanced. The big question on my mind when I heard about it was, why buy a 320 when you can get an EX3 for a lot less or a PMW-350 which has amazing image quality for another £2k to £3k. Well obviously the form factor is very different from an EX3. The 320 is a full shoulder mount camera, complete with slot for a radio mic that runs on V-Lock batteries. The EX3 is a semi-shoulder handy-cam running on small batteries. Both will take 1/2? interchangeable lenses, so no great difference there. But as well as the form factor, which can be very important, the PMW-320 also adds SD recording and HDMI output. There is also the small improvement in image quality to consider. I like the 320, not as much as I like the PMW-350, but it is a fair bit cheaper so could prove to be very attractive for those on a tight budget that want the shoulder mount form factor as well as those that may already have nice 1/2? lenses on their PDW-350?s or 355?s.
Click on the images below to see the full frame images. The small noise improvement is difficult to see in a frame grab. It’s more noticeable in a video clip.
Another thing that you must consider when looking at sensor size is something called “Diffraction Limiting”. For Standard Definition this is not as big a problem as it is for HD. With HD it is a big issue.
Basically the problem is that light doesn’t always travel in straight lines. When a beam of light passes over a sharp edge it gets bent, this is called diffraction. So when the light passes through the lens of a camera the light around the edge of the iris ring gets bent and this means that some of the light hitting the sensor is slightly de-focussed. The smaller you make the iris the greater the percentage of diffracted light with respect to non diffracted light. Eventually the amount of diffracted and thus de-focussed light will become large enough to start to soften the image.
With a very small sensor even a tiny amount of diffraction will bend the light enough to fall on the pixel adjacent to the one it’s supposed to be focussed on. With a bigger sensor and bigger pixels the amount of diffraction required to bend the light to the next pixel is greater. In addition the small lenses on cameras with small sensors means the iris will be smaller.
In practice, this means that an HD camera with 1/3? sensors will noticeably soften if it is more stopped down (closed) more than f5.6, 1/2? cameras more than f8 and 2/3? f11. This is one of the reasons why most pro level cameras have adjustable ND filters. The ND filter acts like a pair of sunglasses cutting down the amount of light entering the lens and as a result allowing you to use a wider iris setting. This softening happens with both HD and SD cameras, the difference is that with the low resolution of SD it was much less noticeable.
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 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.
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.
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.
One of the things that really caught my eye at NAB was Sony’s new PVM-740 field monitor. This is one of the first professional monitors to use OLED technology (Organic Light Emitting Diode). Traditional LCD screens work by using a backlight that has a liquid crystal panel in front of it. When a charge is applied to the liquid crystals they change the polarisation of the light passing through them, this light then passes through a second polariser and between them they vary the amount of light passing through the panel to the viewer (If you have ever seen a VariND filter or tried twisting one polarising filter relative to another you can see how this works). While on the whole this works reasonably well there are some issues with this technology. The first is that the liquid crystals never fully block the passage of all the light, so black is never truly black, some light always seeps through. In addition brightness is limited to that of the backlight and the light is attenuated as it has to pass through the crystals and polariser. In addition if the backlight is too bright then the blacks get brighter too which limits the overall contrast range. Another issue is that LCD’s take time to change state from on to off and off to on. This leads to lag and smear with fast motion or high refresh rates. While a lot of money has been spent over the years developing LCD technology and there are some excellent LCD monitors available, these issues still exist and LCD performance still lags behind that of CRT’s.
Enter OLED. Organic Light Emitting Diode displays use a grid of light emitting devices, each pixel is a separate emitter, so when it’s off, it’s truly off. This means that blacks are completely black. When the emitter is on the light it emits is not passing through a polariser or crystal so it’s brightness is not diminished, this means that whites are really bright. In addition you can switch an LED on and off pretty much instantly so there is no lag or smearing. When you see the new Sony PVM-740 OLED monitor side by side with a similar LCD monitor the difference is striking! It’s like looking through a window, the image is clear and crisp, blacks are… well.. black and whites are bright and sparkle. The pictures from the PVM-740 are much more like the images you would expect to get from a top spec CRT monitor, yet the 740 is light weight, compact and uses less power. It should also be more robust and will not be affected by magnetic fields like a CRT monitor.
You really need to see this monitor in the flesh to appreciate the images it produces.
Well one of the big NAB announcements was the intention by Sony to release a compact 35mm equipped camera. A prototype unit was briefly shown at the press event but little details were given. I’ve been trying to find out more but Sony are being very tight lipped. It was announced that it will be available prior to next NAB, so that means that there is likely to be some other launch event in, at my guess 6 to 8 months time, of course there may be more news before then. Last year Sony announced the PMW-350 at Satis which this year is October 19th/20th, so I would expect more news by then. What I would say is that the prototype appears to be more than just a simple mock up as it shows some new switch and control designs that I’ve not seen on a Sony camera before. It has also been stated that this new unit is just part of Sony’s 35mm road map so perhaps there will be more than one new camera. As for pricing, well all that Sony will say is “affordable”. My guess is it will be in the XDCAM EX1 price area depending on lens options. If it uses DSLR lenses and can be purchased without a lens, my guess is that it would be cheaper than an EX but more expensive than a Canon 5DMk2, my guess would be £4k.
So what features can we expect to get? The sensor should have large pixels so it should be good in low light and offer high dynamic range. As it has a 35mm sensor I expect it will shoot 24P, 25P, 30P plus I would hope over-cranking at up to 60fps. It would be really nice if it did 1080P60. It should have decent audio controls and it’s going to need a really, really good viewfinder. I would imagine that you will have a number of different lens options via some form of adapter, possibly being supplied with a Sony Alpha lens mount. The prototype was shown with a PL mount lens and very few users will be able to afford to use them, so there will have to be a lower cost option.
These are exciting times. In the next 12 months we will see a huge change in the tools available for video production. The new 35mm and 4/3? cameras from Sony, Panasonic and Canon will change the way TV is made forever. They won’t be ideal for some applications such as news or run and gun, where you don’t want the focus problems that a big sensor will bring, but for drama, documentary and low budget movies I think we will see a dramayic change in the way things are done.
Until a couple of years ago CMOS sensors were definitely the underdog, they tended to be very noisy due to electrical noise generated the on chip by the readout circuits and A/D converters. In addition they lacked sensitivity due to the electronics on the face of the chip leaving less room for the light sensitive parts. Today, on chip noise reduction has made it possible to produce CMOS sensors with very low noise and micro lenses and better design has mitigated most of the sensitivity problems. In terms of a static image there is very little difference between a CMOS sensor and a CCD sensor. Dynamic range is remarkably similar (both types of sensor use essentially the same light gathering methods), in some respects CMOS has the edge as they are less prone to overload issues. CCD’s are very expensive to manufacture as the way they are read out requires near lossless transfer of minute charges through a thousand or more (for HD) memory cells. The first pixel to be read passes down through over 1000 memory cells, if it was to loose 5% of it’s charge in each cell, the signal would be seriously reduced by the time it left the chip. The last pixel to be read out only passes through one memory cell, so it would be less degraded, this variation could ruin an image making it uneven. Although there is more electronics on a CMOS sensor, as each pixel is read directly a small amount of loss in the transfer is acceptable as each pixel would have a similar amount of loss. So the chips are easier to make as although the design is more complex, it is less demanding and most semiconductor plants can make CMOS sensors while CCD needs much more specialised production methods. Yes, CMOS sensors are more prone to motion artifacts as the sensor is scanned from top to bottom, one pixel at a time (A CCD is read in it’s entirety just about instantaneously). This means that as you pan, at the start of the pan the top of the sensor is being read and as the pan progresses the scan moves down the chip. This can make things appear to lean over and it’s known as skew. The severity of the skew is dependent on the readout speed of the chip. Stills cameras and mobile phone cameras suffer from terrible skew as they typically have very slow readout speeds, the sensors used in an EX have a much higher readout speed and in most real world situations skew is not an issue. However there may be some circumstances where skew can cause problems but my experience is that these are few and far between. The other issue is Flash Banding. Again this is caused by the CMOS scan system. As a flash gun or strobe light is of very short duration compared to the CMOS scan it can appear that only part of the frame is illuminated by the flash of light. You can reduce the impact of Flash Banding by shooting at the slowest possible shutter speed (for example shooting 25P or 24P with no shutter) but it is impossible to completely eliminate. When I shoot lightning and thunderstorms I often use a 2 frame shutter, shooting this way I get very few partial bolts of lightning, maybe 1 in 50. If you shoot interlace then you can use the Flash Band removal tool in Sony’s Clip Browser software to eliminate flash gun problems. CMOS sensors are becoming much more common in high end cameras. Arri’s new Alexa film replacement camera uses a CMOS sensor rated at 800asa with 13 stops of latitude. Red uses CMOS as does SI2K. Slumdog Millionaire (SI2K) was the first electronically shot film to get an Oscar for cinematography, so certainly CMOS has come a long way in recent years. CMOS is here to stay, it will almost certainly make bigger and bigger inroads at higher levels. Read speeds will increase and skew etc will become less of an issue. IMHO skew is not an issue to loose sleep over with the EX’s anyway. I shoot all sorts from hurricanes and tornadoes to fast jets and race cars. I have yet to come across a shot spoilt by skew, generally motion blur tends to mask any skew long before it gets noticeable. If you shoot press conferences or red carpet events where flash guns will be going off, then you may prefer a CCD camera as this is harder to deal with, but the EXs are such good value for the money and bring many other advantages such as lower power and less weight that you have to look at the bigger picture and ask what you expect from your budget.
Click on the link above to download a set of my latest scenefiles. Un-zip and copy to the root of an SxS card, the in the file menu load the files.
These are mainly matrix tweeks. neut2 is one I like that gives rich primary colours while still reasonably true to life. Cine1 is a sudo filmic look Film1 is meant to emulate well saturated film stock DSC-1 is based on Chroma-Du-Monde chart for accurate daylight color Neut is my first matrix tweak for a less green look and warmer skin tones.
Camera setup, reviews, tutorials and information for pro camcorder users from Alister Chapman.