I have a Nikon D750 that is now giving a circular image when using my Nikon 18-300 DX VR lens. It was fine before. Why has this occurred and what do I need to do to fix it?
The 18-300 DX VR is a DX lens, as its name says.
DX, by Nikon, is the acronym for APS-C format.
The D750 is an FX body (FX by Nikon means full-frame).
So you are trying to use an APS-C lens on a full-frame body. DX lenses have a smaller image circle which likely doesn't cover the entire FX sensor size, thus producing a circular image on the D750.
Most likely, you were using this lens on your D750 in APS-C crop mode. This means you changed your D750 image area to APS-C instead of the default full-frame (FX) mode.
You can read here for more information.
You can either:
- Manually set the image area to DX
- Enable Auto DX crop which will leave the default image area on FX (or whatever you set it to) and automatically switch to DX mode when a DX lens is mounted
From the D750 manual, page 111:
Automatic Crop Selection To automatically select a DX crop when a DX lens is attached, select On for Image area > Auto DX crop in the shooting menus (p. 310, 318). The image area selected in the shooting menus or with the camera controls will be used only when a non-DX lens is attached. Select Off to use the currently-selected image area with all lenses.