Thursday, March 24, 2011

A lens is a lens is a lens

Over the past few months I have been learning a lot about lens' and quality.  In the past as far as video is concerned people buying cameras where mainly concerned with the feturs and quality a video camera, but totally neglect the lens as a part of the equation.  And I totally and completely understand this mentality.  Why?  because for decades camera companies made us choose between crap image quality in comparison to a more crapy image quality.  So consumers like my self are forced to buy in to CCD image sensor size that was smaller then an 8mm film image. Even george lucas' star wars episode 1 $100,000 camera that was a 1/2 inch did not even come close to the normal focal length 8mm film had.



American cinematographer September '99 Archives Phantom Camerawork

    Carrying that depth was crucial, and required the deeper stop. If there were no bluescreens, we could work comfortably at a T2.8 or less.

    The reason why they needed more depth is because the image size was way smaller then a full frame image on 35mm film.

    If you talk to any real cinematographer they are often less concerned with the camera and more concerned with the lenses.  In fact,  the camera has no effect on the quality of the image only the lens has an effect on the captured image.  No matter how you look at it we seem to be working backwards as far as technology is concerned.  Red and Canon pioneered the way for inexpensive Digital cameras comparable to that of the film image then.  We are now part of an ara that redefines the way we produce movies and content.  And we are not limited to the old system.  In fact,  watching many of the 80's films movie makers where more concerned about story then any fancy effects.  If you watched them you might find how simple the camera setups where.  So now that we don't have to worry about our bank and we can fit all of our gear in one back pack what is the issue.  There should be no excuse now for why we can't make a movie.  In fact, I do own a canon 60D and I have a lap top and I have a back back to put that stuff in.  Every thing is there even my lite tripod.  and with the advent of Magic lantern

    http://magiclantern.wikia.com/wiki/Magic_Lantern_Firmware_Wiki

    we now can capture at 60 (mbps) or more.  So now Filmmakers have no more excuse to the limitations of the camera but rather the limitations of there lens quality and build.  I remember the bigest reason why I ended up buying the Canon 60D was because I saw that the canon xha1 Panasonic Pro 16X9 Anamorphic Lens Adaptor was $800 and I compared that to the DSLRs later and found out that its not worth putting cheap conversion glass on a lens when I can buy a camera for the same price that is the canon T2i at the time which was under 900 with the lens Panasonic Pro 16X9 Anamorphic Lens Adaptor is $800.  So the choice was crappy glass on a lens or great camera and good lens.  The choice was obvious.  However I would never sell my XHA1 because I still need a work camera that shoots on tape.  Last thing I need is a corrupted card that I shot my clients event on.  Not saying that cards are not great but they are more prone to fail considerably.  But back to the lens topic.  So the point I am trying to make is that when you take the capturing format out of the equation you are left with the lens.  Great thing about lenses is that you can re use them that is if camera companies don't change there mounts.  Last thing you need is adapters.

    Some of the biggest problems in lenses is distortion and vignetting


    this is what lens distortion looks like

    Distortion free

    imageBarel distortion

    Pincushion distortion

    Complex distortion


    What is lens distortion?

    another problem in lens' is Chromatic aberrations also known as Fringing.



    Lateral chromatic aberrationDxO Optics Pro Correction


    this is what vignetting looks like 


    Optical Vignetting

    Optical vignetting is caused by the addition of multiple lens elements, such as a telephoto lens, a macro lens, a wide angle lens, etc. Each additional lens piece, by continuing to refract the incoming light, also works to narrow the effective lens opening by which light enters the image sensor. This is an inherent element of lens design, made conspicuous by increasing the amount of refraction and thus vignetting that occurs. The vignetting that occurs as a result of this tends to be subtle and gradual.

    The solution? Well, be careful with what lens elements you buy! Optical vignetting is more likely to occur with cheaper, less well-made lenses, but this is only a generalization. Research different lens elements carefully before purchase lest you make an unpleasant discovery regarding excessive optical vignetting later.



    Breathing (lens)
    From Wikipedia, the free encyclopedia

    Breathing refers to when a lens' optics change the apparent focal length slightly when shifting the mechanical focus. Some (often more expensive) lenses are designed to lessen the degree this effect. Lens breathing does not prevent one from racking focus or following focus with this lens, but it lessens the desirability of any type of focus adjustment, since it noticeably changes the perspective and composition of the shot.  Not to be confused with the suction and expulsion of air from within the lens as its internal volume changes.

    When searching for the right lens, these are all elements to consider when figuring out what to buy.  Hence is why it is so expensive to buy a good quality lens because because good quality lens is precisely engineered to reduce or eliminate these optical issues.  Also remember Better glass is typically more sharper, but also more expensive.  Cheap glass is usually soft and produces color fringing.  

    Prime lens have a huge advantage because there is less moving parts hence no zoom, less glass and wider aperture settings.  The draw back is you need Varinging lens with different focal lengths, which means you need more lens to buy and carry around.  also when you use prime lens you also will find your self changing lens often during a shoot.  Changing lenses often takes up valuable production time and you run the risk of dirtying the image sensor or film gate and even the back of the lens will get a bit dusty.  Dust in the camera is inevitable regardless if you have the lens on all the time but it is more of a problem if you are constantly exposing your camera gate to the elements.  Always remember to bring a can of air with you to every shoot and no do not blow on the lens or gate. First you will never get all the dust off by blowing on it.  a can of air can do a much better job. 2, the humidity of your breath can make things worse but not always. Usually a simple brush for lenses and a can of air will work.  

    The typical bull head approach to shooting is to go from one extreem to another with the lens' aperture and focal length. All lenses have a sweet spot.  Typically, the best way to achieve the maximum sharpness your lens can generate is by adjusting the aperture to F5.6 - F8.  Adjusting your aperture on an open setting like F1.2 - F3.5 will cause strong Chromatic aberrations aka fringing and softening of the image a little.  The same for the extreem smaller aperture such as F22-F36.  No matter what lens you get you have to take in to consideration the boundaries you have.  If you have an intentional look you are going for, use the rules to your advantage but keep in mind the benefits and draw back of your lens settings.   Same goes for lens distortion.  The wider the lens the more distorted the image will appear.  Your image sensor size will determine the strength of the focal length.  So on a 16mm film a wide lens may be a 10mm lens, but on 35mm film wide would be a 20mm lens.  So be aware of the look you are going for and know your limitations when it comes to selecting the focal length for your shot.

    Ok so now that I ranted a little about lens problems I wanted to talk about the best lens kit to have for your cropped sensor or your Full frame sensor.  Honestly I would never buy a lens built for an APS-c camera because it means there is less image aria and your FF sensor will see all sorts of issue as described above.  Plus you can't take full advantage of the sweet spot of the lens if you have a cropped sensor.

    These are the lenses that are on my wish list.

    The Tokina 11-16mm F2.8
    Tokina 11-16mm f/2.8 AT-X116 Pro DX for Nikon AF
    the Tokina lens is actually used by cinematographers on the arri camera and the lens is modified to fit the camera.  So you know you are getting a good lens if it is used for even the big budget films.  This lens also is good because this lens is designed to reduce the amount of distortion found in other wide lenses.  

    I chose this lens Cause I am cheap and its a sharp pice of glass. However this lens has been known to break easy even with normal use. but for the price I think its a good start to the kit. Canon EF 50mm f/1.8 II Camera Lens




      Canon EF 85mm f1.2L II USM Lens for Canon DSLR Cameras
    Canon EF 85mm f1.2L II USM Lens for Canon DSLR Cameras

    Its expensive at 2k but the best lens out there to date as far as image quality.  But if your on a budgit and need a good set you can go with this 85mm.

    Canon EF 85mm f/1.8 USM Medium Telephoto Lens for Canon SLR Cameras
    Canon EF 85mm f/1.8 USM Medium Telephoto Lens for Canon SLR Cameras
    Haven't tested it out but from what I read it is built like an L, color and saturation comparable to an L with out the red stripe. Just has some elements and features that are missing, but does not effect the image quality.  So for $420 vs 2k I think this is a more budget option without the loss of quality.   


    So those are really the only 3 lenses I would get as a solid lens pack.  It has your wide, normal, and long lens.  I am sure you can add the 

    Canon EF 70-200mm f/4L USM Telephoto Zoom Lens for Canon SLR Cameras

    Canon EF 70-200mm f/4L USM Telephoto Zoom Lens for Canon SLR Cameras

    Not a bad pricing probably more worth it down the line.

    Now if you are some one like me who Just can't afford the lens I would not worry and stick with the kit lens your canon comes with.  I have a Canon EF-S 18-135mm f/3.5-5.6 IS UD Standard Zoom Lens for Canon Digital SLR Cameras It works fine and it comes with the camera.  For movie making it works but it doesn't hurt to have good glass.  So if you are in a position where you can't get the best of the best then don't.  Shoot with what you have because at the end of the day you are telling a story not trying to impress some over paid critic.

    By
    Robert Sawin








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