Large Sensor Cameras - Everything that you need to know
There is such a selection of large screen cameras now, all promising to achieve the elusive ‘film look’, that it can be hard for film makers to make an informed choice in the selection of choosing the right combination of camera and lenses.
This short article aims to illustrate the main differences between the current range of cameras in order to help you make that choice!
· Large sensor cameras range from the inexpensive Canon EOS 7D, 5D MkII and MkIII plus Nikon D800 and which also include the Panasonic AF-101 and Sony FS-100 at the low end;
· The Sony PMW-F3, Sony NEX FS-700, Canon C300 EOS and C300PL and RED Scarlet in the middle range;
· And the RED EPIC, Sony F-65 and ARRI Alexa at the high end.
So where do they all fit and how should I select the right camera for my production?
What is a large sensor camera?
The size of the digital sensors in large sensor cameras range between 18x14mm (Micro 4/3) and 36x24mm (full frame). These all have a very differing look from conventional video cameras which incorporate sensors which vary from 1/3” (4.6x3.6mm) to 2/3” (8.8mm x 6.6mm).
By virtue of the large sensor, the depth of field perceived for a given focal length lens and iris setting is greatly reduced compared to the conventional video-style look achieved with smaller sensor cameras. See Appendix below.
As a consequence of this, different lenses are required to be used which create larger images in order to cover the larger sensors. A consequence of differing sensor sizes is that the sensor may not ‘see’ the entire image produced by the lens, leading to a variable crop factor. See
You are generally able to choose between using film lenses and DSLR lenses on the range of large sensor cameras with a range of manual and electronic mounts now available – see appendix below.
Broadcast quality or not?
The minimum data recording rate as directed by the EBU and followed by most Broadcasters is the ability to record minimum 50Mb/second in a 4:2:2 colour space with a sensor size of at least ½”. As a consequence of this, as of June 2012, only the following large-sensor cameras satisfy the Broadcast criterion:
· ARRI Alexa, Alexa 4/3 etc
· Sony F-65
· RED Epic, Scarlet and M-X
· Canon C300EOS and C300PL
The important consideration here is that most large sensor cameras outside this list satisfy the criterion as far as image quality output from the camera (as they have appropriate sized sensors and native sensor resolution and colour space) but the recording module and codec does not satisfy the quality conditions.
Happily, the introduction of an external HD recorder, such as NanoFlash, Ki Pro Mini etc (see external recorder article) can very cost-effectively convert non-Broadcast cameras to be Broadcast acceptable by recording the pictures externally. This way, the following cameras have been used successfully for HD Broadcast:
· Sony PMW-F3
· Sony NEX FS-100
· Sony NEX FS-700
· Panasonic AF-101
The conventional DSLR cameras such as Canon EOS 7D and 5D MkII and recently the Nikon D800 have often been used as supplementary cameras for Broadcast, though they do not comply with required specifications and the lack of a ‘clean’ HDMI feed precludes external recorders to be successfully used. The new introduction of the increased data-rate Canon 5D MkIII may allow this to be used for broadcast use but it is presently not passed to do so.
All Broadcasters have their own standards, so always check with the commissioning channel technical specs prior to selecting your camera to ensure that your equipment choices meet with their criterion.
ARRI have made film cameras for many years and they intuitively know from experience what film makers need to shoot comfortably. So the ARRI Alexa is perfectly designed not to have fussy menus and clever functions but simply to quickly and easily power up; select the frame rate; record to solid-state SxS card; plug card into a Mac; open in Final Cut; that’s it!
The interface is very simple and the camera is solid and robust.
The ARRI Alexa is on every TV drama list, so put simply, if everyone could afford it, then we would only stock one camera!
It has a native 3.5K sensor with PL mount compatible with motion picture film lenses but shoots 1920x1080 to internal card in 24p/25p and slow motion up to 120fps in native Prores 422 and 4444 formats, so really easy post production into FCP. ARRI have just released the rather pricy DNxHD options, which is useful if you are using AVID but most are happy to record Prores.
New variants of split camera/recorder solutions (Alexa M); optical viewfinder (Alexa Studio); 4/3 and 16/6 switchable aspect ratio camera (Alexa Plus 4:3) exist now but the basic camera and recording format is the same as the regular Alexa. The Alexa Plus is the same as the original Alexa but offers an integrated lens control function when using C-Motion or ARRI WLCS but makes no difference if operators are using the Preston FIZ3 systems favoured by many focus pullers
For large screen productions, you can now record ARRIRAW externally using CODEX or Gemini which increases the resolution recorded in the enhanced dynamic range format of 2880 x 1620 (16x9 Mode) as well as increasing the dynamic range as well. Also, Adobe CS6 now supports ARRIRAW for easy Post Production!
This is by far RED’s best camera yet and much more reliable and stable than the now infamous RED One. Solid state drives (SSDs) for media capture greatly reduces the possibility of data corruption/
loss and the modular design means that this camera has a very small footprint, so lends itself well for 3D applications and productions where size is a premium.
The original EPIC was called EPIC-M, as it used the Mysterium Sensor shared with the RED M-X has now been upgraded to the Mysterium-X sensor. This is a 14 Megapixel chip (5120x2700 pixels) with 13.5 stops of latitude and up to 18 stops with the HDRx mode (RED calculations) whereby the camera effectively takes a dual exposure and you have the ability to decide how best to take the best information from the fast and the slow exposure at either end of the latitude spectrum.
Best of all is the slow motion capability which is up to 300fps, though be aware that only certain frame-rates are available at particular picture formats, so you can shoot up to 120fps in 5K or up to 300fps in 2K. However, shooting at 2K will introduce a necessary crop factor of around 40%, so for example a 24mm lens will act like a 32mm lens.
Also, you can shoot at various picture sizes from 720 RGB to 5K RAW. In our experience, 5K RAW is not really stable enough to recommend shooting without camera instability but our clients have been very impressed by the very stable performance of this camera when shooting at 4K RAW, so this is what we recommend that you ought to shoot at!
Proxy and RED Workflow
Adobe CS6 now supports RED R3d natively and can be viewed at lower resolution so no proxies will be needed and no need to hire a DIT to be busy transcoding massive files either!
Saying that though, although the RED workflow is now very well established, sometimes the quality of the RED codec is too good for small screen productions and it can sometimes be easier to bypass the on-board record function using RED codec and RED post production route if you are shooting for TV or even the internet!
If this applies to you, then you can record to external recorders onto Compact Flash or SSDs at very high quality in standard codecs.
In English, this means that you can record up to 300fps and immediately play back the material from the camera and record onto an external recorder with no rendering; then insert this media into Final Cut Pro for immediate use with no rendering - very easy! The 'usable proxy' setting allows the camera output to be recorded and include such metadata information such as the clip name and timecode for later online conversion and de-bayering if you want to.
It is important to mention that if you use the above approach for high speed, then since most external recorders do not support high speed, then the high speed material would be laid off as a regular 24 or 25fps slowed down recording and that you will lose the metadata from the RED camera, so this will only be useful if the proxy file is the final version used in post. The advantage though is that it greatly simplifies post production for you.
Sony’s answer to compete with the ARRI Alexa and RED Epic.
The Sony F-65 is a top-end 8K motion picture camera shooting on solid-state SR Memory cards. The performance of the camera can only be described as stunning and the new SR Memory on-board record device allows an incredibly impressive sustained 5Gb/second – fast enough for anything available today or conceivably in the future too!
It uses a 20 Mega pixel 8K CMOS sensor (PL mount only) with a rotary shutter (to remove gello effect) and runs up to 120fps, creates HD/2K or genuine 4K resolution images with a huge colour gamut, outstanding dynamic range, and high sensitivity.
It will also record in a variety of HDCAM SR and RAW codecs including SR-lite, in order to reduce the very hungry data capture rate to a more manageable 220Mb/sec from a maximum of 880Mb/second of 4:4:4 HDCAM SR presently.
In spite of all of the above, it is premium priced product which has yet to find universal acclaim in the TV world for drama and budget features, owing to its high cost.
The RED Scarlet is to all extents and purposes a RED EPIC painted grey with reduced slow motion performance. It shoots 4K RAW the same as EPIC (no full speed 5K offered) but only limited slow motion.
Consequently, this is an excellent choice when you want to shoot large sensor and large format but either don’t need slow motion, else are looking for a second unit when shooting RED EPIC.
As with the RED Epic, you have the choice of using a native PL mount for film lenses or a Canon EOS mount to use Canon EOS DSLR lenses.
Since its release in early 2012, the Canon C300 has received widespread acceptance and acclaim and is a new generation of large sensor cameras suitable for Broadcast documentaries, promos commercials and other genres.
The Canon EOS C300 Digital Cinema Camera comes in 2 flavours. The EOS version allows low cost Canon DSLR lenses to be fitted and used and the PL only version permitting motion picture film lenses to be used. Both models feature an 8.3MP Super 35mm-equivalent CMOS sensor developed specially for the system, a modular design and record to high speed Compact Flash (CF) Cards for ease of use and cost.
Following from Canon’s success with the 5D MkII, this camcorder has the form factor of a supersized DSLR, however all of the problems of the 5D have been fixed with excellent viewfinder, picture and audio monitoring and most importantly a data record rate of the all-important 50Mb/second to satisfy Broadcast capture standards. Since it is clearly aimed solely at digital cinematography, with a total absence of still image capture as well as AF and AE functionality. This means that even when using a Canon EF lens on the C300 EF you won't get the benefit of the lens' auto focus capabilities!
Contrary to expectation, the C300 is a Full HD 1080p camcorder rather than being a 4K device even though its CMOS sensor is actually natively 4K resolution (This pitches it head to head with the Sony PMW-F3).
Rather than the moire-pattern inducing line skipping method employed in the EOS 5D Mark II, the C300 uses a far more video-friendly down-sampling method whereby a group of 4 pixels are sampled and then mapped to each final output pixel.
Interestingly, where the Sony F3L's S-Log option offers the ability to obtain dual-link 4:4:4 output for the ultimate in recording quality, the C300 has built in log capability but only provides a single 8-bit 4:2:2 output via a single HD-SDI connector but don’t be put off by the numbers, this produces truly decent images and has impressed most who have tested it!.
Whether you want to shoot with EOS or film lenses is up to you but our experience with drama has shown that the Canon C-300PL with compatibility to film lenses, makes it a great choice for second unit on Alexa dramas.
The Sony PMW-F3 is last year’s favourite large sensor camera which, as a consequence of its limited 35Mb/second on-board capture, makes it unsuited for Broadcast productions unless you use an external recorder.
However since it shoots with a Super-35 CMOS 1920 sensor, low cost packages available from VMI with HD external recorder still make this a very attractive option for HD acquisition and the easy post production workflow using native XDCAM-EX codec and SxS cards still make this a worthy favourite with programme makers.
One other recent development is the recent release of the S-log option, which offers a ‘flattened’ gamma curve which has the effect of making colours look a little greyer but extends the dynamic range of the camera to a full 13 stops. The other benefit is that you can also record log images in a full 4:4:4 colourspace if using this in conjunction with a Gemini/Cinedeck recorder. In doing so, the PMW-F3/S-log/Gemini/Cinedeck option competes very favourably with RED EPIC, Scarlet and ARRI Alexa, batting well above its weight and cost – not bad for a mid-level camera!
The camera features a proprietary Sony ‘Alpha’ mount, which allows it to be fitted with a Sony zoom. This is a poor lens made by Sony which is not generally stocked by rental companies as it is fairly slow and also expensive. However, since the camera is supplied as standard with a PL adapter, it can fit motion picture film lenses and is easily modified to take Nikon mount and now Canon mount EOS lenses using the latest electronic lens mounts from MTF and Berger.
The PMW-F3 also shoots up to 60fps slow motion but only at 1280x720 using the XDCAM-EX codec.
Sony NEX FS-100
This is Sony’s low 1080 large sensor camera which shares the same capture device as its bigger brother, the PMW-F3. However the native codec of the camera is only AVCHD which is limited to 24Mb/second which does not conform to broadcast specification. However unlike the PMW-F3, you can shoot up to 60p slow motion in 1080 mode, though at only 24Mb/second.
The FS-100 has an E-Mount permits Canon EOS, Nikon ZF and PL motion picture film lenses to be fitted with the relevant adapters.
Also, just like the PMW-F3, you are able to record off-board to external recorder to make this camera Broadcast acceptable, though the absence of an HD-SDI output port means that you are limited to using HDMI only. Our experience is that HDMI is a very unreliable connector which is not suited to reliable camera to an off-board recorder where movement is always a possibility and which will certainly result in data interruption and media corruption. As a consequence, we don’t recommend that the Sony FS-100 is used with an off-board recorder.
The Panasonic AF-101 is a native 1080 camera which features a 4:3" sensor and micro 4/3 lens mount. It is easily adapted to fit either Nikon or Canon EOS mount lenses and can also be adapted to PL mount to fit motion picture film lenses.
Just like the Sony PMW-F3, it features HD-SDI monitoring, industry standard audio inputs and monitoring.
Because it uses a 4/3” APS sensor sensor which is a bit smaller than Super-35, this reduces the image view and creates an approximate 20% image crop. For a comparison compared with PMW-F3, check out the Abel Cine size comparison wizard.
Another ramification of using an APS sensor in place of a Super-35 sensor is that for the same conditions the depth of field is increased. It may be an anathema to most film makers to use a camera which increases the depth of field over others (who always seem to want to reduce depth of field instead of increasing it!), however, this can also can be a positive advantage for the film maker. This is because shooting with a very shallow depth of field can lead to soft focus since the focus point is critical when shooting wide open and so shooting with a slightly smaller sensor and commensurately larger depth of field will mean that the focus point is not so critical, so images are a little more forgiving and your images are more likely to stay in focus!
As with the PMW-F3 and FS-100, the camera imaging electronics conform to Broadcast specification but the recording capture device does not, recording only up to 24Mb/second to AVCHD 4:2:0 in common with the FS-100. Using an inexpensive Ki Pro or NanoFlash external HD recorder converts this into a potent low cost combination that satisfies Broadcasters, works well and shoots very nice pictures and is thus very popular with film makers.
The NEX-FS700 is another strange camera which doesn’t really seem to fit anywhere comfortably. On first inspection, it appears quite wonderful with incredibly effective slow motion at up to 480 per second in 1080 mode or 960 frames per second in 720 mode and a new 4K sensor recording to SD cards but you need to dig a little deeper to work out what is going on…
It shoots AVCHD 25 Mb/s at 1080/25p or 30p, so no Broadcast acquisition on board or in the US frame rates, shoots AVCHD 28 Mb/s at 1080/60p, so still no Broadcast acquisition on board but you can get around this by using an external recorder, such as Ki Pro or NanoFlash.
Then it shoots slow motion but in ramping mode, the data rate is FIXED at 20MB/s! This means that if you shoot at 800 fps (max in 25 frames mode), then you actually record less data than at the regular 25p rate, which is itself not even Broadcast quality. Saying that though, the slow motion is incredibly effective and does record up to 480 per second in 1080 mode (or 960 frames per second in 720 mode) and given that you always have an proportion of allowable non-HD material included in an HD delivery, this makes snippets of slow motion produced by this camera actually quite useful. There is no way to externally record ramped images presently.
The FS-700 also can work in 4K and mode but cannot record 4K on board, so if you wish to shoot 4K, then you need to record using an external 4K recorder. These have yet to materialise until the end of 2012, so we shall see what results…
The FS-700 does have usefully 4 x ND filters built-in which is very good and a S-35 4K brand new sensor which is the generation after the PMW-F3 and FS100; It shoots to SD cards and has a Sony E-mount in common with the Sony FS-100, which is fairly easy to adapt to EOS, ZF and PL mounts.
Canon 5D Mk II
The Canon 5K MkII has become the de-facto standard in DSLR capture for video, as a consequence of its impressively large full frame sensor (36mm x 24mm), which generates a fantastically shallow depth of field effortlessly and is compatibile with low cost Canon EOS DSLR lenses!
However, make no mistake that the limited data record capability to 30Mb/second and H.264 codec, makes this camera non-complaint with Broadcast specifications for HD capture. Also, its maximum 4GB limit for individual scenes makes the 5D MkII unable to shoot sequences of more than about 12 minutes. FInally, the lack of a clean HDMI output makes is also unsuitable for external record.
Shooting on the 5D MkII is not really fun to shoot with either, as there is only a single mini jack socket for stereo audio input and also output, so you have no effective audio monitoring. Picture monitoring is difficult too, as the on board LCD display changes from displaying HD to only SD when you begin shooting and if you plug in an external monitor, then the on board LCD switches off.
Saying that though, the images are great, compatible lenses are cheap and there are workarounds all of these limitations which many are expert in! So, whilst the Canon C300 has taken the majority of 5D MkII production work owing to its superior codec and interface, the 5D MkII still has its place in production and shoots very beautiful pictures with a marvellously shallow DoF with no effort. Be aware of possible vignetting (shading around the extremities of the frame) when using wide angle lenses, as a consequence of the extremely large sensor size which is incompatible with some wide angle DSLR lenses.
Canon 5D Mk III
The Canon 5D MkIII has improved on the 5D MkII in many ways – the record duration has increased from 10 to 29 minutes; the sensor has increased from 21.1 to 22.3 Megapixels and the recording codec peaks at 90Mb/second with a i-frame vbr ( variable bit rate) codec.
Taking these refinements into account, the Canon 5D MkIII is still difficult to use in production, owing to the same audio monitoring limitations and that there is still no HD-SDI output for video monitoring.
Very nice pictures though, compatible with all Canon EOS lenses and a cost effective solution for ‘film-look’ production but if you can afford it, use the Canon C300EOS instead.
The Nikon D800 series DSLR Cameras are also increasingly being used for cinematographic TV Productions and have the advantage of a clean HDMI output, so they can be recorded on external HD recorders satisfactorily but we don’t stock them at VMI.
Types of 35mm Lenses
Motion Picture Lenses
Motion picture lenses have had decades of refinement until they have reached the point today of near perfection!
There is a huge range of lenses which offer excellent optics, robust casings, beautifully smooth mechanics, zero focus breathing etc but the limited numbers for production and high build quality means that they are usually out of reach for budget productions but offer the best performance for motion picture cinematography.
Motion picture film lenses, such as Zeiss CompactPrime/ SuperSpeed/UltraPrime/MasterPrime and Cooke S4i/S5i/Panchro lenses are film lenses with a PL lens mount. A ‘standard set’ would generally include 5 lenses of around the following focal lengths – 18/20mm, 25mm, 32mm, 50mm and 75/85mm. There are many more focal lengths available to supplement the ‘standard set’ from 8mm-300mm.
They are made with extreme precision optics and lens markings and each lens is optimised for optical performance at its focal length.
DSLR stills lenses
Stills lenses are a much lower cost option of lenses than motion picture lenses but because they are built for stills and not motion picture use, there are several compromises to be made. Happily, there are also several solutions too!
If you buy a quality stills prime set such as Nikon or Canon, then you can expect great image quality at a stills price. In contrast, a set of Cookes or UltraPrimes will cost up to £100,000 compared with approximately £5-7,000 for an equivalent set of stills prime lenses.
There are some challenges though to using stills lenses for video work.
Firstly, modern digital SLR cameras tend to be fully automatic and all of the lens controls are operable from the camera. Consequently, over time, the manual functions began to disappear from stills lenses, so that today many lenses available to buy do not have a manual iris ring, which makes them useless for the lens adapters above.
Problems with using stills lenses for large sensor video cameras
There is no focus gear on stills lenses. This means that you can’t drive the focus mechanism with a follow-focus unit. External focus gears can be fitted onto stills lenses or custom modify lenses (like VMI do), which effectively straps a gear onto the outside of the lens to be driven by a follow focus unit. The downside to doing this is that the focus adjustment of small lenses means you have a smaller amount of adjustment of the focus ring over the entire range of the lens compared with a film lens. In other words, your focus puller will find these lenses harder to pull focus than film lenses.
The focus thread runs in the opposite direction to motion picture film lenses, so your focus puller either needs to learn to pull focus in the opposite direction, or alternatively use a follow focus unit with an idler gear, which reverses the motion of the follow focus correct for stills lenses. This correction gear is built in to the ARRI MFF1 follow focus units.
Differing lens diameters meaning standard clip-on matte boxes won't fit, as DSLR lenses use non-standard lens diameters – besides which the lens will not be strong enough to hold a clip-on matte box without putting undue pressure on the lens mount and housing. VMI modify the lens fronts on all stills prime sets, to ensure that they all have a standard 80mm lens front, which is a standard size for matte box donuts.
Stills lenses have Nikon ZF, Canon EOS or other proprietary lens mounts which differ from the conventional Motion Picture PL mount, so you must ensure that the camera mount is compatible with the lens mount.
Happily, most mounts are available now for most large sensor cameras to allow most lens/camera combinations. However, be aware that Canon EOS lenses are designed to have the iris controlled from the camera body, so as a rule, do NOT include a manual iris ring. If you plan to use these lenses with a manual camera (non Canon), such as Sony PMW-F3 etc without a digital lens conversion ring, then be aware that you will not be able to operate the iris ring and this will remain fully open whilst in use. However, the latest electronic lens mounts with controllers from MTF and Berger, do allow iris control of EOS lenses when using large sensor cameras which do not have native EOS mount and the external controller provided will allow the iris to be driven by the operator to solve this problem. VMI can also supply RED EPIC and RED Scarlet to be fitted with Canon mounts in place of the regular PL mounts to permit the use of Canon EOS lenses and the iris to be controlled from the camera - you can even now use the autofocus function through the camera’s own touch screen interface (though this is a bit clunky!). DSLR mounts are also not as secure as PL motion picture lens mounts or B4 video lens mounts, so be sure to support heavier lenses using a suitable bridge plate/bars system.
Stills lenses are designed for portability, so some lenses ‘breathe’ so when changing the focus of the lens, the image can noticeably resize, resulting in ‘Focus Breathing’.
Stills lenses aren't built to withstand the rigours of motion picture film production, which means that they are built in much more lightweight lens housings. As a result of this, the screws holding a lens together are not designed to withstand the forces applied when using follow focus units etc. If you use a lens control system to control the focus, then the power of the servo units is sufficient to rip the screws of a stills lens apart! The good news is that the Hocus Focus wireless lens control system is designed to work with these lenses without risk.
VMI offer the excellent Zeiss ZF series prime lenses which have fully manual operation and the Canon EOS L-USM prime sets. Both of these sets have received custom modifications to make them work better in video applications.
Even considering all of the above, if you have a low-budget short film and want to narrow the depth of field of your images and are using a low-cost camcorder, then it is still worth considering a set of stills primes to work with your system.
The Zeiss Planar and Distagon design use the same lens arrangements which have been proven in the World-acclaimed Zeiss SuperSpeed, DigiPrime, UltraPrime and MasterPrime lenses.
The ZF series lenses are the same high quality optics re-housed as used in the Zeiss CompactPrime lightweight 35mm lenses, except they cost ¼ of the price!
Both Zeiss ZF and Canon L-USM lenses are high speed professional lenses which are very fast (up to F1.2/1.4) to allow the Cinematographer easier depth of field manipulation.
VMI have modified the lenses to fit a custom follow focus ring which is a larger diameter than the lens, to give the focus-puller a greater range of adjustment.
VMI have also custom-fitted 80mm lens fronts so that the entire set shares a common 80mm lens diameter and can be used with common matte-box donuts for ease of use.
VMI supply the ARRI MFF1 follow-focus unit which includes a reversible gear, so that the direction of rotation is corrected during operation automatically.
These lenses include the commonly available Nikon ZF mount which allows them to be fitted either to Nikon stills lenses or threading adapters for other stills lenses or 35mm lens adapters such as Letus etc.
WHAT AFFECTS THE DEPTH OF FIELD
Effect of Iris on the Depth of Field
Many years ago at school, we made a pinhole camera. This was a magnificent experiment because it illustrated the relationship between depth of field and the size of iris beautifully.
You can make a pinhole camera very easily like this:
Take a cardboard box and cut one side of the box off.
Stick a sheet of tracing paper over the open side with tape.
Make a small hole in the side opposite the tracing paper.
Point the hole towards a window on a bright day
In doing this, you will see a perfectly focussed image (upside down) projected on the tracing paper.
What this illustrates is:
An infinitely small iris (hole) has an infinite depth of field, since the entire image will be in focus.
It also illustrates why the quality of lens of a very small iris is not at all important, since you have no more basic lens than just a hole and this can deliver perfect pictures!
Taking this argument a stage further, explains how mini DV cameras equipped with very basic, very cheap lenses, can produce excellent images on sunny days – since in a well-lit environment, you will shoot with a very small iris.
Contrary to this example is what happens when you shoot in low light. In low light, you must open the iris considerably and in doing so, the depth of field becomes much shallower. Poor quality lenses struggle when used in these testing conditions.
A practical example of this is a glasses-wearers difficulty whilst driving at night. The short-sighted nature of the person means that his/her eye lenses are slightly imperfect, or rather his/her lenses are slightly imperfect. Driving at night in low light conditions causes the irises to be wide-open to let in maximum light and the wide iris causes the depth of field to be very shallow. With the imperfect nature of the lenses, these challenging conditions cause the viewers sight be blurred when the irises are wide-open, yet during the day these same eyes give perfectly focussed images.
This also explains why mini DV camcorders equipped with cheap lenses shoot lovely images during the day, yet give soft images when shooting in drama-type situations in low light with a wide-open iris.
It also helps to explain why DoPs are so passionate about lenses because they perform well in all situations and why really great lenses are so reassuringly expensive!
THE EFFECT OF SENSOR SIZE
The Size of Sensor and effect on image size
The size of the sensor will affect the image angle of view, so that a 25mm Prime lens will look different if viewed on a variety of image formats.
Thus a 25mm lens will have a mid shot when used on 35mm film (HDTV 1.78:1 16:9 aspect ratio), close up on HD Camcorders and big close up on smaller semi-professional, 'prosumer' camcorders such as EX-3 and Z1 etc which have 1/2" sensors and 1/4" sensors respectively.
This explains therefore why if you mount an HD lens onto a ½? camcorder (such as Sony PDW-F355) without an optically corrected mount, that a wide angle acts like a telephoto and why the focal lengths of wide angle lenses of ½? lenses are always smaller than those used for 2/3" lenses.
Here is a useful sensor size chart:
For 1/3-inch CCDs: H = 4.8 mm, V = 3.6 mm
For 1/2-inch CCDs: H = 6.4 mm, V = 4.8 mm
For 2/3-inch CCDs: H = 8.8 mm, V = 6.6 mm
For 1-inch CCDs: H = 12.7 mm, V = 9.5 mm
Conversion of focal lengths between camera formats
Even though lenses are designed to work with different negative and sensor sizes, the convention is that lenses are still referred to by their focal lengths and/or also their zoom ratios in the case of zoom lenses.
A very useful trick to know is that to convert 35mm focal lengths to 2/3", just divide by 2.5 and to convert Super16 to 2/3", divide by 1.6.
Thus a 25mm PL mount film lens has the same field of view as a 10mm 2/3" lens.
The same lens in Super16 has an equivalent focal length of 16mm and has the same field of view as a 10mm 2/3" lens.
Size of Sensor and the effect of Depth of Field
The size of the sensor also greatly influences the Depth of Field.
Simply, the larger the sensor or negative, the narrower is the depth of field.
The ubiquitous 'film-look' has a shallow depth of field and is called this because this is easy to perform when shooting on a 35mm negative. As the size of the negative or digital sensor is reduced, so the depth of field commensurately increases for the equivalent shot and the same iris settings.
Thus, a Broadcast HD Camcorder with a 2/3" CCD sensor under the same conditions has a larger depth of field than a 35mm camera and an HDV prosumer camera with a 1/3" CCD has a larger depth of field still.
This also explains why miniDV Camcorders always shoot beautiful images with loads of depth of field and why a shallow depth of field is almost impossible to achieve without using a 35mm adapter.
The larger the sensor (or negative), the shallower is the depth of field for given conditions.
Alexa/ PMW-F3/Canon C300/ RED Epic cameras have a 35mm-sized CMOS sensor which uses the same lenses as 35mm and these use a conventional motion-picture film lens PL mount as standard; Of these 3 groups, this is the largest sensor size and for the same conditions achieves the shallowest depth of field.
Broadcast HD Camcorders, such as the Sony PDW-F800, Panasonic Varicam and others have a 2/3" CCD blocks and use 2/3" B4 lenses. There is a wide range of lenses available for this lens mount including Standard Definition and High Definition lightweight ENG lenses and cine-style cinematography lenses plus film lens adapters.
'Prosumer' cameras use sensors smaller than this including 1/3? and ½” CCD or CMOS sensors.
VMI June 2012