Specifications:

• This confirmation  Camera Adapter Ring allows you to use Contax C/Y mount lens on EOS camera
• With this Lens Adapter Ring, your beautiful Contax C/Y lenses (Carl Zeiss Jena, Penta con, Pentax, etc.) can be used on digital or film EOS camera
• Auto focus function
• Precisely made of brass
• This is an original product

Details:

• This lens adapter ring has a beautiful appearance
• Using lenses or filters is a great way to enhance your photographic experience. In order to use lenses with the digital cameras, you must purchase a  Camera Adapter Ring

• With this Mount Adapter Ring, you will be able to add to your camera (model specified above) wide angle, macro, telephoto, fisheye conversion lenses & all different type of filters to increase your photo options

• With this Lens Adapter Ring, you can achieve various effects improving basic photographic capabilities

• This Lens Adapter Ring will allows camera to accept any threaded filter, step-up ring or macro lens

• This Lens Adapter Ring can screw onto the front of your digital camera easily and allow you screw-on lenses or filters

How to Choose Adapter Ring?

• First of all you have to buy the appropriate physical lens adapter required to get your lens attached to your camera. For this you should consult your favourite camera shop . But a number of manufacturers build simple metal ring adapters that let you attach various types of lenses
• If you've got, for example, a lens designed for an old Pentax threaded (screw mount) camera like the Pentax Spotmatic you'll need an adapter for M42 lenses. Same with the new line of Carl Zeiss ZS lenses, which also use M42. If you have a telescope you'll probably need a T-mount adapter, assuming your telescope has the ability to be hooked up to a camera at all. Or if you have a Nikon lens you'll need an adapter that lets you fit Nikon F lenses to your EOS body. Likewise Leica R, Leica Visoflex, Olympus OM, Contax/Yashica RTS, Rollei, and Contax manual focus, or even big Hasselblad, Mamiya 645, Pentacon 66, Pentax 645 and Pentax 6x7 medium format lenses can all be adapted. Microscopes apparently often require C-mount adapters. Tamron built a series of Adaptall II lenses and you can still occasionally find used Adaptall II->EOS adapters around. I have links to some sources for these adapters at the end of the page
• Most adapters are simply metal rings with an EF bayonet on one side; And since the EF mounting ring is larger in diameter than most 35mm SLR lens mounts quite a few lenses can be adapted to the EOS system

Adapter ring compatibility problems and infinity focus

• The most common problem is that of lens registration - the distance from the lens mount to the film plane. It may not be possible to build a lens adapter that gets this distance right for certain lens mount systems
• For example, the back focus distance (distance from the rearmost lens element to the film plane) on EOS cameras is 44mm, but on Leica rangefinder cameras it's 27.8mm. Matching the back focus distance would require a lens mounted deep inside the camera body; not usually an option. In cases such as this you may either have to buy an adapter ring that won't let you achieve infinity focus or you'll have to get an adapter ring which contains one or more glass lens elements and which will inevitably degrade the image quality somewhat. These compensating elements let you achieve focus to infinity, though at the expense of image quality. Contax G, Konica F, Leica M, Minolta MD and Miranda lenses are other lens mounts with back focus distances less than that of Canon EOS
• There is also the case of lenses which have lens register distances very close to that of a true Canon EF lens. Contax/Yashica lenses (45.5mm) and Canon EF lenses (44mm), for example, have only a 1.5mm difference in lens registration, and 1.5 is awfully thin for a metal ring adapter. Such adapters have to be machined to incredibly close tolerances in order for infinity focus to work, which means they can be quite expensive. Cheaper ones often have to be sanded down to maintain infinity focus - but even that is something of a dodgy proposition as you have to sand the surface down accurately from one side to the other, down to a fraction of a millimetre
• Also appears that it isn't possible to make adapter rings that let you mount Pentax K (bayonet mount) lenses on EOS cameras with EF lens mounts. The Pentax K diaphragm coupling lever physically interferes with such a possibility. So you'd have to modify the lens (or the camera) to make such a conversion possible. Note that this does not apply to cameras compatible with the EF-S mount. The design of the EF-S mount, with its smaller mirror box thanks to the 1.6x crop factor, coincidentally permits the use of such lens adapters
• Finally, and this isn't strictly to do with manual focus lenses per se, but you can't use Minolta Vectis or Four Thirds (Olympus, Kodak, Fuji, Sanyo, Sigma, Panasonic and Leica) lenses on EOS cameras. These lenses, in addition to being autofocus lenses, cast very small image circles; much too small to cover the imaging area of EOS cameras. In theory I suppose the Vectis lens design might cover an EF-S sensor, but it would probably be pointlessly expensive to make such an adapter

What is Adapter Rings?

• Adapter Rings allow the adaption of "Series Sized Filters" to your lens. Adapter rings contain two components: an adapter ring and a retaining ring. A Series Sized filter is a glass filter that does not contain filter threads. The Series Filter is held in place between the Adapter ring and the Retaining Ring
• The advantage of this method is utilizing same sized filter on a number of different sized lenses by attaching different sized lens adapters
• Not all lenses are designed with standard filter accessory screw in thread sizes. For these lenses, many of which are very popular, the way to mount a filter is via an adapter ring. A main feature of adapter rings is that you can utilize one size filter with a number of different sized lenses via different adapter rings
• An Adapter ring consists of two parts: an adapter ring and a retaining ring. The non-threaded filter is held in place between the two as you screw the retaining ring into the adapter ring. The adapter ring is than screwed directly into the lens or is mounted to the outside diameter of the lens barrel via a setscrew lock ring adapter
• To stack non-threaded filters, a second retaining ring is required to be threaded into the first retaining ring and the second filter is than held in place between the two
• Adapter rings contain two measuring specifications: 1) the direct screw in size to the lens such as 86mm, 95Cmm, etc / or outside lens diameter to mount a setscrew lock ring and 2) the size of the filter that the adapter wil1 accommodate
• Example: 105Cmm-4-1/2'' screws directly into a lens requiring a 105Cmm accessory size and accepts 4-1/2"round size non-threaded filters
• Example: 124SSLR-138mm features an adapter that set screws over a lens barrel (SSLR) with an outside diameter of 124mm and accepts 138mm round non-threaded filters
• Larger or smaller filters than the designated filter size may also be utilized on lenses via a Step Up or
• Step Down ring. To determine which type ring you need, start with the lens accessory size of your lens and convert it to the desired filter size needed to be used
• Example: A lens featuring a 62mm accessory size with the need to mount a 77mm filter would require a 62mm-77mm Step Up ring
• Example: A lens requiring a 58mm accessory size with the need to mount a 52mm filter would require a 58mm-52mm Step Down ring. It is not suggested to utilize a Step Down ring more than a two-size difference between the lens and filter otherwise lens vignetting may result

Instructions:

• This Adapter Ring allows you to use filters when you have your lens reverse-mounted on your camera body (the front of your lens is facing the mirror of your body). If you have an adapter that allows you to reverse-mount your lens, then you can use this adapter to still use your filters

Package Included:

• 1 x MASSA Contax / Yashica C/Y Lens to Canon EOS Mount Adapter Ring