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Publié le par Association TNT

Y'a une occase d'objectifs anamorphique 2.35 sur ebay.

Des Lomo 35mm f2.5 50mm f2 75mm f2...

 

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G
Gauthier
29/04/2007 00:02
ça colle avec la monture qu'on a ? ou alors c'est pour acheter une monture PL ?
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A
Association TNT
29/04/2007 11:38
C'est une PL, et on en a deja une donc voila...<br /> Ca ferait du vrai 2.35, avec en plus le 16/9 de la hd.<br />  <br />  
B
Bérenger B
28/04/2007 12:44
ANAMORPHIC LENSES General Information and AdviceFOCAL LENGTHSThe focal length of anamorphic lenses is different from sherical ones. The anamorphic element changes the horizontal angle of a lens by a factor of 2, but leaves the vertical angle untouched. So in fact you have the characteristics of two focal lenses combined in one. A 50mm anamorphic lens for instance has the vertical angle of a 50mm lens, but the horizontal angle of a 25mm lens. This also influences the depth of field. To be safe one should calculate the depth of field based on the actual focal length of the lens. In the case of the 50mm, one would calculate the depth of field based on a 50mm lens, and not a 25mm lens. This means that a 50mm anamorphic lens, although it covers the same horizontal angle than a 25mm spherical lens, only has half of the depth of field than that spherical 25mm lens.STOP DOWN THE LENSAlmost all the problems, the distortions, chromatic abberations, shallow focus, tricky focus-pulling, can be minimized simply by shooting at a decent stop. Anamorphic lenses have what is known as a "curved field of focus" that works similarly to the curved movie screens in some large Cinerama theatres. This is one reason that one needs to expose these lenses at a deeper stop. If one doesn’t, the curved field will not be covered by depth of field and either the edges or centre of the frame will be soft. The other reason is contrast that translates into apparent sharpness. With more contrast, the image appears cleaner and sharper. Anamorphic lenses look best sharpness and contrast wise when stopped at least 2 stops down. T4 or T5.6 are great anamorphic stops. It is not a good idea to expose deeper than a T11 either. Optically, a lens' performance will deteriorate after that.CHECK THE MINIMUM FOCUS SETTINGA lot of these lenses don't focus closer than 4 feet, some only to 7 feet, unless one can wrangle some closer-focusing lenses. It is a good idea to carry some diopters.THINK ABOUT WHEN TO RACK FOCUSThe breathing is so prominent because of the change in compression, unless one is really stopped down, that one should think carefully about when to rack-focus and when to just hold focus -- don't ping-pong it during a two-shot dialogue scene.WATCH FOR LENS FLARESA little more of a problem than with spherical primes due to the anamorphic element at the front of the lens. On the other hand anamorphic flares can be very nice and be part of the look.TESTINGEach anamorphic lens even of the same series (except the very latest ones) has different characteristics in color, contrast and sharpness. The quality of these older lenses does vary and one needs to test them find the best ones.What to look for in lenses is that they are flat (curved field of focus), contrasty and have as neutral a color as possible. Some are warmer or colder than others. Try to get as many similar millimetres as possible to compare to. Not only project the lenses at the rental house to evaluate these performance variables but shoot a lot of film on a focus chart that has targets all over the field of view. Shoot wide open and stopped down. Also shoot film outside at deep stops to make sure the shutter blades do not vignette the wide format. They shouldn't but the older lenses used to.CAMERA SYSTEMSPanavision used to have the edge over PL mount cameras (ARRIs and Moviecams), because their cameras were designed with anamorphic in mind. The viewfinders on their cameras are switcheable from spherical to anamorphical. ARRI kind of missed the boat on anamorphic in the nineties, because they geared their cameras more towards Super35 and 3 perf. However that problem has been solved with the new Arricams. They now come with an Universal Viewfinder which, just like on Panavision cameras, is switcheable between spherical and anamorphic.  LOMOThese are Russian lenses. It's important to make a distinction between the old square Lomo's, and the newer round Lomo's. They're two completely different designs. The older ones had the anamorphic element in front of the spherical assembly, making them breathe and weave quite a bit. ‘Andrei Rublev’ among others was shot these lenses.The newer round ones have the anamorphic elements in between the spherical assemblies, making them breathe very little. They were manufactured in the 1980s and are very good lenses, although not quite comparable to modern anamorphics like the Hawks or Primos. They are a bit lower in contrast as well. The 100m and 150mm are the 75mm with an extender added at the back. Beware of the newer 35mm, it distorts too much, besides being big and heavy. In fact, it's the one occasion where the nimble old Square 35mm has a slight upper hand. Lomo Round Front AnamorphicsFocal length Stop Min. Focus Weight22mm T3.430mm T3.235mm T2.4 3’3”50mm T2.4 3’3”75mm T2.4 3’3”100mm T3.2150mm T3.4Lomo Square Front AnamorphicsFocal length Stop Min. Focus Weight35mm T2.8 50mm T2.480mm T2.5
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B
Bérenger B
28/04/2007 12:18
Attention pour les focales<br /> 35mm = 35mm en hauteur / 17.5mm en largeur<br /> 50mm = 50mm / 25mm<br /> 80mm = 80mm / 40mm<br />  <br /> Apres il manquerait une longue focale.
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