Is there such a thing as an adapter to fit a FF Lens into APS-C to prevent cropping?
 

I've being here wondering how smart is now, using the 50/1.4 and the 85/1.8 on the 7D now that it will be 1.6x

Is there an adapter to fit the FF lens perfectly in the APS-C so it's possible to preserve the orginal focal length of the lens.

Does that make sense?
Is that a dumb question?

i don't know, it just came to my mind.

Thank you very much.

Short answer is no. But with the right adapter, which will no doubt exist eventually, you could rent cine lenses which would be true to their printed focal lengths. They're too expensive for most people to purchase.

Unfortunately there isn't. It makes sense once you consider the reason why APS-C has that 1.6x factor - the sensor is physically smaller, and no adapter can reduce an EF lens's projection circle to become 'full frame' on an APS-C.

The focal length remains exactly the same on both cameras. What changes is the angle of view.

I'm sure you could adapt many of the 35mm lens adapters that are currently in use on EX1s and all the other little cams, that's no big deal, but what would be the point? You'd be losing so much light that you'd actually get shallower DOF without the adapter. Plus, you are introducing so many horrid artifacts that could be easily avoided.

The focal length of a lenses doesn't change, the angle of view is merely different. You have to learn the equivalent focal length for each format, there are tables that can help you.

Input form for a table of equivalent focal length lenses.

Film people have done this for many years shooting 16mm, Super 16, 35mm and Super 35. You can use a 35mm cine lens on a 16mm film camera, the focal length doesn't change, but you do get a narrower field of view. That's also why 35mm telephoto stills lenses were so great for nature film makers shooting on 16mm & Super 16.

Best thing might be to add a 35mm focal length lens to your set (28mm often tend to be a bit slower).

A thought overnight is that what you require is already available, they're the wide angle adapters that widen a lens' angle of view. Unfortunately, they tend to add barrel distortion and you need to adjust your prime lens to around the closest focus, resulting in a very compressed focusing range; not a good feature if you've got a shallow DOF. They tend to be used mostly with the wider angle lenses.

An optical adapter for the rear to allow you to maintain an angle of view is complex and expensive. An example being the JVC adapter that allows you to use PL mount 16mm film lenses on their 1/3" cameras.

As I mentioned above, best buy another lens.

Yeah, the focal length doesn't change. If you get a 50mm FF lens and a 50mm APS-C lens and put it on a 7D, both will look the same and have the same FOV. But the FF 50mm would look wider on a 5D.