Canon HD Cinestyle Prime Lenses Are Well Received By Cameramen

The following is an extract from an article by John Keedwell, a freelance lighting cameraman, which we have been allowed to publish with the kind permission of Zerb Magazine.

The first impression of the lenses was that they are very impressively built bits of kit and rather substantial too! The great quality of the finishing and the robust nature of the build are immediately very apparent, and they ultimately have the feel of a quality set of lenses which would be very at home on any 35mm film shoot. They have a standard mount so would fit on most everyday Digi beta cameras, but this would be rather an overkill as the normal camera chips simply could not resolve all the detail that the lenses were capable of.

There are 5 primes in the complete set from Canon: 5mm, 9mm, 14mm, 24mm and the 35mm. The aperture marks are in T- stops as opposed to f-stops, which is great to see. T-stops are a far more accurate method of measuring the light actually being transmitted to the imaging devices by that particular lens (hence the "T" designation). F-stop aperture marks are based on a theoretical mathematical formula which when transferred to different lenses can sometimes be inaccurate up to a full f-stop error.

This inaccuracy is actually much more likely with zoom lenses as they have a more complex series of different glass elements that move around inside to give the different focal lengths. These glass elements can combine together to decrease the actual transmission factor of the light passing through the lens quite considerably at different focal lengths. Prime lenses by their nature dont have the design compromises that zoom lenses have but its always more comforting to have a lens marked in true T- stops nevertheless. A lens with T-stops is crucial when swapping lenses and trying to match scenes that have already been shot.

All of the lenses apart from the 5mm lens have a maximum open aperture of T1.5, with the 5mm being a T1.7 lens. All of them stop down to T16 and there is a C position on each lens that completely caps the lens. All have geared teeth rings around the barrel to mesh with standard follow-focus units. There is also a small bar that can be screwed on each lens if it is used without a follow-focus unit. The focus distances are conventionally marked in bright green fluorescent paint as is Canon customary style and white markings are used for all other of the indications such as the aperture markings; back focus lines and all other manufacturers markings. The actual iris blades within the lenses are an 8-blade design that makes the aperture very circular and uniform in appearance at most apertures. This makes highlights more circular and is a very welcome design aspect over some other lenses that have fewer blades. The lenses all internally focus, so there is no racking forward or back of the front element when doing extreme focus pulls.

Canon has apparently gone to great lengths with these lenses to carefully control the colour characteristics to have a consistent colour temperature throughout the range. Quite simply this means if you swap lenses the colour
balance and contrast should stay the same. This is vital on a shoot where you may be swapping lenses constantly throughout a scene.

Testing
Rather than sit the cameras on a test bench to film some resolution charts then have them examined professionally to get some resolution figures, they were examined in more common encounters that may cause challenges on a shoot. This gives more of a feel as to how the lenses will behave in real life, which is what ultimately matters. We didnt have the time or resources to do an exhaustive test of every possible scenario for a weeks shooting on many different lighting situations.

The lenses were reviewed on a Sony 24P F-900 HD camera supplied by Top-Teks in Harefield. First of all the lenses need to be assessed for any "breathing" when focussing. This is a fault that again normally shows up on some zoom lenses more often as the optics are much more complicated to manufacture. The lenses were focussed right through their range from close focus to infinity to see if they change apparent focal length at all when focussing. It can manifest itself as a very noticeable slight zooming effec when doing a big focus change. This is a very undesirable effect that makes any focus-pull far more obvious to the viewer, and so makes the audience more aware of the film making process. Prime lenses (by their very nature) do not tend to have the same design limitations and compromises as a zoom lens, so are much less likely to have this happen. These HD Canon lenses were fantastic in this respect, and do not "breathe" to any discernable degree when racked right through the range, so in this area they passed the test with flying colours.

The lenses and HD F900 camera were then taken outside in the sun and some testing was done without using a matte box (intentionally) to see if they caught flare or any other nasties. On watching the camera test tape back on the HD monitor no flares or other nasties were spotted at all. The lenses then went through tests to see how they handle bright highlights on water and by being pointed directly at the sun to check for any aperture characteristics too. The lenses performed very well with no hint of flare or chromatic changes on the highlights even when pointed straight at bright highlights. Out of focus highlights were very circular, which was very
pleasing to see.

Interior testing was done under a mixed variety of available fluorescent light, to see how they stood up to the most unflattering lights around! A circular fluorescent work light was illuminating a technician, so the camera was pointed straight at him and the source. No flare whatsoever and reasonably natural looking colours, even though the light fixture was right there in the shot. It was obviously a bland flat light on the subject, and literally the worst light quality in the world, but gave acceptable results under the circumstances.