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1.5 Crop factor question.

dx fx crop factor

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6 replies to this topic

#1
Jmuir

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I have a Nikon D5500 which is a DX format. I had a 18-300mm DX lens but still wanted more zoom. I read that using a FX lens on a DX camera would effectvly make a 300mm lens act like a 450mm lens due to the crop factor involved with 35mm sensors and full frame sensors. So I bought a 28-300mm FX lens excited to try out the greater zoom power. I compared the two lenses by taking pictures with both at full zoom of the same object from the same possition. I assumed the FX lense would have greater zoom. It did not. In fact the two pictures were identical. I switched lenses back and forth testing them. I could tell no difference between each lens in terms of zoom. So is it a myth? Am I doing soemthing wrong? Is there a setting I need to adjust? Why did'nt the FX lense zoomed at 300mm look more like 450mm?
Thanks for any help/input/education.

#2
Wayben

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Your DX lens gets the crop factor also, giving it the same angle of view as a 27-450 mm lens.  Unfortunately, it doesn't matter whether you use  an FX or DX lens, on a DX format camera the crop factor applies to both.

 

Hopefully, it's not too late to return the 28-300.



#3
Jmuir

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So there is no difference between a DX lens and a FX lens when used on a DX body? That is what I am seeing but that certainly is not what everyone says.

#4
dcbear78

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So there is no difference between a DX lens and a FX lens when used on a DX body? That is what I am seeing but that certainly is not what everyone says.

 

No. No difference on a DX camera. Focal lengths are always the same, regardless of the size of sensor (or film in olden days) behind it. The only difference the sensor size makes is how much of the image is recorded.

 

Here is an example of the same focal length and the different parts that would be captured. This is example is using a FX capable lens....

nikondxandfx.jpg

 

 

The difference is with a DX specific lens, it actually also produces a smaller image. It does this to reduce costs. So what would happen with a DX lens, on an FX camera would record a wider image than the lens is projecting onto the sensor. And this is what you would get...

02_ImageCircle_DX_FX.jpg

 

This can all get really confusing, but really it makes absolutely no difference unless you are swapping between a FX and a DX camera regularly. If all you use is a DX camera then you will never know any difference.



#5
Jmuir

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OK. So if I get the gist of it here it really makes no difference whether I use a DX or FX lens on a DX body. They both will give the same result (assuming all other specs are the same, which in the case of the 18-300 and 28-300 lenses they are speced nearly the same). I was Interested in the 28-300 because so many things I read told me that the 28-300 would behave more like a 42-450mm lens on my DX camera. Sounds like that it just not true. I would like a wider angle, but not worth the hassle if all I am gaining is 10mm (the difference between 18mm and 28mm). If they are the same I'll stick with the 28-300 which could come in handy if I upgrade to a full frame camera some day.

#6
Wayben

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On your DX body the DX lens gives the field of view of a 27-450mm lens.  Your FX lens will give the field of view of a 42-450 lens.  The smaller DX sensor doesn't change the focal length of the lens, but due to it's smaller size gives the smaller field of view.  You can look at it as the DX sensor cropping the center out of an FX sensor's image.

 

Hope that helps.



#7
Jmuir

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Thanks. I'll hang onto my 28-300 lens in the event that I want to upgrade to FX.