Starting my “career” as a photographer on a Nikon D5600, I quickly built a portfolio of good and less-good glass. One of my favorite lenses was the Sigma 18-35 mm 1.8 DC, and must admit that this lens was one of the reasons why I hesitated to go full frame – it is that good!!
However, someone kind told me that not all is lost. The Nikon F-mount is still the Nikon F-mount and the lens will fit and you will get all the EXIF information still. So what happens if you use the DX lens on an FX camera body?
Limited coverage
As you probably have figured out, the DX lens for the cropped sensor is designed to cover a smaller area than the FX sensor, so when you shoot with the DX lens, you will get vignetting meaning that especially the corners of the picture are darker or pitch black. The lens throws a light intended to cover the DX area comfortably, but when challenged with the FX sensors larger area, the circle cannot cover, and especially the corners are cut off.
However, how much depends on the zoom. The wider you go, the bigger the problem becomes. The first example here is at 35mm, i.e. the most zoom that the Sigma 18-35 mm 1.8 DC can give and as you can see there is some vignetting in the corners:
If you widen the perspective to 22mm (this is not even the widest it will go), you will see that the problems have gotten worse and now more of the corners are cut off:
However, if you study the pictures carefully, you will see that the 22mm has a wider reach than the 35mm despite the vignetting. In the water, top left, there are two buoys and you can see that there is more of the horizon to the left of them in the bottom picture. So although you have to crop the picture in post processing to get something useful, you still get a fairly wide picture using the Sigma 18-35 mm 1.8 DC on a FX body.
So, don’t sell all your DX glass if you decide to go for full frame – you may find that the DX glass is useful on a FX body. But it varies a lot from lens to lens, so the best is if you can test your lenses with the camera body you plan to buy, so you know exactly how useful your DX glass is on the FX frame.
Nikkor AF-S 18-140mm 3.5-5.6 ED DX VR
One of Nikons classic kit lenses is the Nikkor AF-S 18-140mm, and as you can see the vignetting is bad both when zoomed out (18mm) as this shot of a window frame shows:
And it only gets a notch better when zoomed in close – here at 140mm of the same window frame:
If you compare this to the Nikkor AF-S 35mm 1.8G DX, you can see that the vignetting here is much less, actually – I think – hard to see unless you know it is a DX lens on a FX frame:
I think you have to compare it to the 50mm FX equivalent (Nikkor AF 50mm 1.4D) to notice the difference:
So the Nikkor AF-S 35mm 1.8G DX in my mind is highly usable on a FX frame whereas the Nikkor AF-S 35mm 1.8G DX is much less. Finally, lets take a look at another classic kit lens.
Nikkor AF-S 18-55mm 3.5-5.6 G II ED DX
This lens is probably one of the most common kit lenses, and at 18 mm it – not surprisingly – shows the same vignetting as the 18-140mm:
However, at 55 mm there is hardly any vignetting:
So I think this illustrates that you need to test the specific lens you want to put on a FX camera as it is hard to make a conclusion or a guide that applies to all lenses.
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