Does this make sense? Or just an impulse purchase.

[§am]

I think the confusion arises from converting to the 35mm film/FX equivalent.

If you have a 50mm lens on a DX body and you are not likely to ever go to 35mm/FX then IMO there's no need to worry one's self with converting.
However if you were to in the future then use a FX body, then yes you'll notice the difference in your FoV etc, but again IMO within a very short time you'll try and forget the DX limitations

 

[jwstl]

There's the belief that a DX lens has the field of view of the focal length stated when that's not the case. The focal length is the same no matter the size of the sensor because the focal length is distance from the film/sensor and that doesn't change from DX to FX to film. If you want to know the field of view of your lens on DX as it compares to film and FX then you always have to use the conversion no matter what lens you use.

 

[TedG954]

The only thing that makes a DX lens DX is the fact that it's made to cover the smaller sensor which typically results in smaller, lighter lenses. An 11-16 DX lens and an 11-16 FX lens would behave exactly the same on a DX camera: a field of view of 16-24 or so.

There was no mention of an FX 11-16. Introducing FX to this thread is causing the confusion.

 

[jwstl]

There was no mention of an FX 11-16. Introducing FX to this thread is causing the confusion.

It would only confuse you if you didn't understand there's no difference between the 2 in focal length or field or view. My point was it doesn't make a difference if that 11-16 is DX or FX; it still has the crop factor because that is a result of the sensor size and nothing else. I'm sorry if that's confusing you; I don't know how to make it more clear.

 

[TedG954]

It would only confuse you if you didn't understand there's no difference between the 2 in focal length or field or view. My point was it doesn't make a difference if that 11-16 is DX or FX; it still has the crop factor because that is a result of the sensor size and nothing else. I'm sorry if that's confusing you; I don't know how to make it more clear.

Other than declaring your understanding of sensor sizes, what is your point? Why are you even discussing FX and crop factor? Did you even read the original post?

 

[jwstl]

Other than declaring your understanding of sensor sizes, what is your point? Why are you even discussing FX and crop factor? Did you even read the original post?

Some people...

Rick M pointed out that the 11-16 is equal to a 16.5-24 and you then posted this question:

"The Tokina is a DX lens, why wouldn't it be a true 11-16mm on the D5100?"

You asked the question and I tried to be helpful and explain to you why it's not a "true" 11-16. And that's the crop factor. And there is no such thing as "FX crop factor". Every lens on a DX body-like the 5100-has a crop factor. If you think by buying the 11-16 because it's called a DX and using it on the 5100 you are getting the views of an 11-16 lens you are mistaken. But I feel you don't really understand or care to know the answer to your question so I'll move on.
​

 

[TedG954]

So, according to that definition, a DX 18-55 is actually a 27-83mm. And a DX 35 is really a 52mm, a DX 50 is a 75mm, etc.

I wonder why all these lens companies mis-label their products.

OK, so I'm a horse's ass. But if a 35 is 52.5mm, then it should be called a 52.5mm lens.

As stated by jwstl,

There's the belief that a DX lens has the field of view of the focal length stated when that's not the case. The focal length is the same no matter the size of the sensor because the focal length is distance from the film/sensor and that doesn't change from DX to FX to film. If you want to know the field of view of your lens on DX as it compares to film and FX then you always have to use the conversion no matter what lens you use.

So, I may have purchased an 11-16mm for a D5100 believing it would be wider than my 16-35mm on my D800. That would have been a $700 mistake.

I should probably give jwstl a portion of that money. Again, I'm a horse's ass and I apologize.

:disturbed:

 

[BackdoorArts]

Here we go again. There's plenty of clarification on this board already about what the difference between a DX and FX lens is. Perspective is exactly the same, it's the cropping that's different. In other words, a full frame 11-16mm lens will look exactly the same on a D800 and a D5100, but the D5100 photo will only reveal the center 1.5X crop of the photo. The area represented by that crop is the same as what you would get if you used a 18-24mm lens on a full frame camera - but the perspective and distortion generated by the wider lens will not be visually equivalent to a 18-24mm lens.

A 11-16mm DX lens will look the same as an 11-16mm FX lens on a DX camera. On an FX camera the DX lens will only project light on a portion of the sensor, fully covering the 1.5X crop in the center, and then running out somewhere beyond that.

 

[Marcel]

So, I may have purchased an 11-16mm for a D5100 believing it would be wider than my 16-35mm on my D800. That would have been a $700 mistake.

I should probably give jwstl a portion of that money. Again, I'm a horse's ass and I apologize.

:disturbed:

I would not agree with the horse body part section of your post Ted, but you're right about the first part. The 11-16mm on DX would give you the same image crop as if you had a 16-24mm on your D800. So in a way, your 16-35 has more range than the 11-16 on DX.