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DX lenses Anonymous
While cruising through Nikon's lens selection the yesterday, I came across a glossary of terms used to describe their lenses. I knew that DX lenses were not meant for 35mm cameras, but are they designed to still give you the actual focal length listed including the sensor crop (so a 10.5DX is still 10.5)?
>> Anonymous
Focal length is equal to what it would be on a 35mm even if it doesn't fit a 35mm.
>> Anonymous
>>100844

But you have to factor in crop factor to that number. It's not accounted for already.
>> Anonymous
A 10.5mm lens is a 10.5mm lens, period, no matter what it's put on. Some lenses project a large enough image to cover a huge 8x10 plate; others only project enough to cover a ~6x~5 point and shoot sensor. Different lengths of lenses produce different fields of view.

"Crop factor" is a convenience while people get used to smaller sensors than the 36x24mm sensors they're used to. It has no technical meaning whatsoever other than, "hey, this sensor is one and a half times bigger than that one! Neato!"
>> Anonymous
a) All SLR lenses have the actual focal distance marked.
b) Unlike Canon EF-S, Nikon DX lenses actually fit on full-frame cameras, they just give massive vignetting in this case.
>> Anonymous
OP here, I guess I didn't word it right, but what I'm trying to get at is if I use a 10.5DX lens on my DX sensor camera, will the image appear (same angles and all) as a 10.5 lens on a 35mm camera, or will it be more like a 16mm angle
>> Anonymous
>>100854
It will produce the same field of view as a 15.75mm lens would fitted to a 35mm film camera.
>> Anonymous
>>100849

All well and good but your statement has no practical use when actually taking pictures. The crop factor idea is here to stay as it's a useful rule of thumb. Arguing against it is stupid.
>> Anonymous
>>100926
I'm not so sure about that. Unless the latest crop of photographers is significantly more stupid than the previous ones, that is. Before digital befell us, nobody needed crop factors for half frame cameras, any of the various medium formats, or any of the various large formats. They just knew that a 60mm lens on 4x5 was extremely wide, slightly wide on 6x6, around normal on 35mm, and telephoto on half frame. There was also never any confusion as to whether or not a 10.5mm lens was really a 10.5mm lens, or if it somehow magically transformed when mounted on different cameras.
>> Anonymous
>>100936

You are being pointlessly pedantic.
>> ac !!VPzQAxYPAMA
>>100936
One difference there is that those different formats didn't, generally, share lenses. Or really even shoot a lot of different formats at the same time. If you shoot Canon, you might often switch between 1.6x crop, 1.3x crop, and full-frame with the same lenses. It just makes it easier if you can normalize the numbers in your head.
>> Butterfly !xlgRMYva6s
>>100950
True for Nikon and Sonyminolta too.

How is focal length found out? Crop has nothing to do with it.
>> heavyweather !4AIf7oXcbA
To actually answer OP's original question:

On a DX body, the 10.5mm fisheye is a full-frame fisheye, meaning you have an image from corner to corner.

On an FX body, it's a circular fisheye, which means it's still a perfectly usable lens. People have been using circular fisheyes for years.

This is by far one of Nikon's coolest lenses. Snap one up if you can.