Hi, I have a Nikon D5500. I have been searching for a way to use FX type lenses with the smaller APC-S sensor. I know that you can use them, but they have the crop factor of approximately 1.5 I believe. I have heard of these things called speed boosters and did some research into metabones. What I can't seem to figure out is if there is an adapter from an FX lens to a APC-S sensor on a Nikon body. All I can find is Nikon to Sony-E, or Canon, etc. I cannot seem to find an adapter that simply eliminates the crop factor. I appreciate any advice you all could give me.
As others have said, you don't need any adapter to use FX lenses on a DX body. The only difference that FX vs. DX makes is that an FX lens has a large enough field to cover the larger FX-sized sensor, or a standard frame of 35mm film, while a DX lens has a smaller field, to only cover the smaller sensor of a DX camera.
You can use FX lenses just fine on a DX body. I have several 1970s-vintage lenses, originally for use with my F2, that I routinely use on my D3200.
On the other hand, if you try using a DX lens on an FX body, then you can expect a result something like this:
That was taken using the stock 18-55mm lens that came with my D3200, mounted on my F2, using Tri-X film. Because it's a DX lens, it didn't cover the entire 36×24mm frame of 35mm film.
The one thing that you will want to watch for, in more modern lenses, is that they be designated “AF-S”, “AF-I”, or “AF-P”. These designations indicate a lens that has a built-in focusing motor. Lenses designated only as “AF”, without the “-S”, “-I”, or “-P” do not have a built-in motor, and will only autofocus on camera bodies which provide a focus motor in the body, which the D3x00 and D5x00 bodies do not. You can still use them on your D5500, but you'll have to focus manually.
@Marcel made mention of old non-AI lenses. Nikon claims that non-AI lenses cannot be used on any DSLR other than the DF. My three non-AI lenses, by D3200, and I, very much disagree with Nikon on this point. As far as I know, the only issue that non-AI lenses introduce is that the conflict with the AI coupling on some newer cameras, with the potential to cause damage to that coupling. The DF has an AI coupling that folds up out of the way to allow non-AI lenses to be mounted, as did some of the early “transitional” film SLRS back in the late 1970s and early 1980s, to allow AI lenses to be safely mounted. The D3x00 and D5x00 bodies simply don't have an AI coupling at all, so the issue simply isn't relevant to them. My non-AI lenses work just fine on my D3200, albeit with the very obvious and expected issues that would apply to any non-CPU lens—no exposure metering or autofocus; the camera will only operate in “M” mode and everything has to be set manually.
As for angle of view. a 50mm DX lens will give you the same angle of view on your DX-sized sensor as a 50mm FX lens; but that is approximately the same angle of view that you'd get on an FX sensor or a 35mm film camera using a 75mm lens. Any lens will give a narrower angle of view on a DX sensor than on an FX sensor, because the DX sensor is smaller, and takes in a smaller portion of the image focused by that lens. The “crop factor” that is often cited, and generally given as 1.5 (though 1.55 would be more accurate) describes this relationship. Any lens on a DX sensor gives a field of view about equal to a lens with that focal length multiplied by 1.55 on an FX body. In my picture above, I had the lens zoomed out to 18mm, with it trying, (and failing, because it's a DX lens) to cover an FX-sized frame. On a DX camera, the sensor would be a smaller portion of that image, taking in a narrower field of view, that would be approximately equal to what I would have got on the 35mm frame if I had used a 28mm lens.