Confused about DX lenses on a FF or mirrorless camera

I have a Nikon 7500 and a bunch of specialty DX lenses. I've been thinking about upgrading to full-frame or mirrorless at some point, so I've been reading up on lens compatibility.

 

I'm a little confused about what I'm reading (and have read some contradictory claims). I hoped somebody might clarify for me:

 

If I used a DX lens like a Samyang 8mm, Tokina 11-16mm, Nikon 35mm, Nikon 18-140, or Nikon 70-300mm on a Nikon full frame:

• Would I get the same photo view as I would on my Nikon 7500? (i.e. the cropped sensor view)
  
• Would the megapixel quality be the same, less, or greater than on my Nikon 7500?
  
• Would vignetting occur on all DX lenses, or just certain lenses at certain focal lengths?
  

If I used a DX lens like a Samyang 8mm, Tokina 11-16mm, Nikon 35mm, Nikon 18-140, or Nikon 70-300mm on a Nikon mirrorless with converter:

• Would I get the same photo view as I would on my Nikon 7500? (i.e. the cropped sensor view)
  
• Would the megapixel quality be the same, less, or greater than on my Nikon 7500?
  
• Would vignetting occur on all DX lenses, or just certain lenses at certain focal lengths?
  

Any help would be greatly appreciated!

Would I get the same photo view as I would on my Nikon 7500? (i.e. the cropped sensor view)

 

Yes, if DX crop mode is in effect. By default, Nikon's FX DSLRs will automatically enter DX crop mode when you mount a DX lens. In this mode, the image is captured from a central, APS-C-sized area of the sensor. The outer parts of the sensor do not participate in the image. As a result, the angle of view you wind up with is exactly the same as if you had used the same lens on a DX body.

 

You can disable automatic DX crop in the camera's Shooting menu, under Image area. When this is disabled, you can set the image area to any available one, including FX. This will increase the angle of view of subsequent images.

 

Would the megapixel quality be the same, less, or greater than on my Nikon 7500?

 

Assuming you're in DX crop mode, most FX sensors will give you fewer megapixels than if you were using the D7500. This is because their pixel density is lower. For example, the 24-MP D750 will give you about 10 MP in DX crop. Only the D850 has the same pixel density as the D7500, resulting in the same number of pixels in DX mode as a D7500.

 

Would vignetting occur on all DX lenses, or just certain lenses at certain focal lengths?

 

In DX crop mode, no additional vignetting will occur besides what you'd get on a DX sensor anyway. In FX crop mode, most DX lenses will not only vignette severely but even show a black circle at the perimeter of the image to varying degrees, because they project an image circle that is too small to cover the sensor. There are some DX lenses that are well known for covering the FX sensor pretty well, such as the 35mm f/1.8G DX. I don't have a list of lenses with such coverage, and yes, for zooms it will vary with the focal length. (I do know that the AF-P 18-55mm covers the FX sensor pretty well starting at 28mm.)

 

All of these answers also apply to use on full-frame Z bodies with the FTZ adapter, with one exception: The Z cameras will not allow you to exit DX crop mode when a DX lens is mounted.

Full frame is full frame, it does not matter dSLR or mirrorless, it is still a 24x36mm sensor.

 

#1, no.

100mm lens / 35mm DX normal lens = 2.9x magnification

100mm / 50mm FX normal lens = 2x magnification. Same lens on a FX camera will give you less magnification and a wider view.

 

#2

That depends on WHICH FX camera you select.

A D750 at 24MP has essentially the same resolution as your D7500, but a D850 at 36MP has more resolution, and a Z7 at 47MP even more resolution.

 

#3 The DX lens will generally (but not always) have a smaller image circle than the FX lens.

This means that on a FX camera, the image will be vignetted in the corners, so your usable image rectangle will be smaller.

This seems to be lens specific, some do, some don't, some will have vignetting at one end of the range and less/none at the other end, some will wide open and less as you close down.

 

THIS is one of the major concerns of upgrading from DX to FX; that you likely have to replace ALL your DX lenses with FX lenses.

 

 

If you run a FX camera in DX mode, why even upgrade to FX?

You are not getting the use of the entire FX sensor, which to me is the reason for going from DX to FX.

Edited March 31, 2020 by Gary Naka

Why are you considering upgrading to FX?

 

If it is Image Quality, consider this.

MOST DX cameras are limited by the lens, not the camera.

I have the same 18-140 as you. When I used the 70-200/4, I was surprised at how MUCH better the image was.

At the same focal length, I could see more details in the image shot with the 70-200.

This told me that the DX camera was capable of a lot more quality, but could not deliver it, because of lenses that did not have the optical quality to match the sensor.

So put some GOOD glass on your D7500, and you may not have to upgrade.

Nikon DX lenses are designed to cover the DX, i.e. 16x24mm, frame. In certain focal lengths, some of the DX lenses may appear to cover the entire FX, 24x36mm, frame, but image quality outside of the 16x24mm area may be fairly poor, and it gets worse farther away from the center of the frame.

 

On Nikon FX DSLRs, there are photographer selectable options on how to treat FX and DX lenses. Essentially there are three options:

1. Always capture the entire FX frame and let it vignet and the quality degrade toward the edges
   
2. Always capture the DX frame
   
3. Auto switch between capture FX or DX, depending on the type of lens mounted, FX or DX.
   

On Nikon Z mirrorless bodies, the Z50 is DX to begin with. On the FX Z6 and Z7, they will force the DX crop if you mount a DX lens. I.e. the third option above. The Z6 and Z7 will not capture the entire FX frame when you mount a DX lens. Plenty of people have tried to override that restriction, and I am not aware of any way to do so.

 

Incidentally, both the Nikon D850 DSLR and the Z7 mirrorless camera are 47MP. They use similar (but not identical) sensors.

Ooops, I got the D810 and 850 confused.

The 810 is the 36MP camera.

If not obvious by now, I would add to the above that I would consider using DX lenses on an FX camera as a temporary solution only, until you save up enough to buy some dedicated FX lenses to go with your camera, otherwise the drawbacks almost outweigh the benefits.

If not obvious by now, I would add to the above that I would consider using DX lenses on an FX camera as a temporary solution only, until you save up enough to buy some dedicated FX lenses to go with your camera, otherwise the drawbacks almost outweigh the benefits.

 

I wouldn't necessarily say that.

 

I have a couple of wide angle zooms-a 12-24mm f/4(DX), a 10-20mm AI-P DX(the cheap one), and the big 14-24mm f/2.8(FX).

 

The 14-24mm is definitely the best of these, but it's a massive lens that weighs a bunch and can be awkward to use with the big, bulbous front element.

 

The 12-24mm is bad on FX. I don't remember the exact details of where this happens, but I know that the distortion is terrible and it's all but unusable.

 

The 10-20mm is a different story, though. It vignettes at roughly 10-13mm, but at 14-20mm it covers nicely with some geometric distortion that cleans up well. It's a $300 lens that weighs almost nothing, and pairs really well with a lightweight FX SLR like the D600/610 or Df.

I wouldn't necessarily say that.

 

I have a couple of wide angle zooms-a 12-24mm f/4(DX), a 10-20mm AI-P DX(the cheap one), and the big 14-24mm f/2.8(FX).

 

The 14-24mm is definitely the best of these, but it's a massive lens that weighs a bunch and can be awkward to use with the big, bulbous front element.

 

The 12-24mm is bad on FX. I don't remember the exact details of where this happens, but I know that the distortion is terrible and it's all but unusable.

Ben, I have had the 12-24mm/f4 DX and 14-24mm/f2.8 FX since their respective early days for each lens. As far as I am concerned, the 12-24mm/f4 DX is fine on FX only at 24mm, or maybe the 1 or 2mm just before that. As I mentioned above, even though it appears to cover the entire FX frame around 18mm or so, in the sense that there is no more vignetting around the corners, image quality is quite poor outside of the DX area.

 

The 14-24mm/f2.8 is a fine lens, but I also dislike the bulging front element, which is vulnerable when I travel. Even though I have had that lens since 2008, it turns out that I rarely use it. For a few years I thought I just didn't need something as wide as 14mm.

 

To me, the game changer is the mirrorless 14-30mm/f4 S lens in the Z mount. All of a sudden I use 14 to 24mm a lot more for wide landscape and some buildings. The 14-30 S takes regular screw-on filters and normal 82mm lens cap, such that there is no more vulnerable front elements to worry about.

Ben, I have had the 12-24mm/f4 DX and 14-24mm/f2.8 FX since their respective early days for each lens. As far as I am concerned, the 12-24mm/f4 DX is fine on FX only at 24mm, or maybe the 1 or 2mm just before that. As I mentioned above, even though it appears to cover the entire FX frame around 18mm or so, in the sense that there is no more vignetting around the corners, image quality is quite poor outside of the DX area.

 

The 14-24mm/f2.8 is a fine lens, but I also dislike the bulging front element, which is vulnerable when I travel. Even though I have had that lens since 2008, it turns out that I rarely use it. For a few years I thought I just didn't need something as wide as 14mm.

 

To me, the game changer is the mirrorless 14-30mm/f4 S lens in the Z mount. All of a sudden I use 14 to 24mm a lot more for wide landscape and some buildings. The 14-30 S takes regular screw-on filters and normal 82mm lens cap, such that there is no more vulnerable front elements to worry about.

 

Shun, thanks-I couldn't remember the exact details of the 12-24. I still have mine, mostly because it's a bit of a beater that's not worth much, and it's a nice little lens for walking around with older DX cameras that aren't super demanding and where I like the rendition enough to bother with them(looking specifically at the Finepix S5).

 

I'm sure the 14-30mm is a MUCH better lens than the 10-20mm AF-P, but of course those of us still using F mount cameras can't use the former. Your observation about the 14-30mm taking a screw-in filter is something that also applies to the 10-20mm-it takes a 77mm screw-in.

I wouldn't necessarily say that.

 

I hear you, and I understand that there may be specific DX lenses that perform reasonably well on the FX frame, so I'm not at all saying that changing to an FX camera means you have to bin all your DX lenses. Attaching a DX lens occasionally to take a few pictures if you do not have a corresponding FX lens is totally fine, however, I would advise against building a system that has only DX lenses with an FX camera. That is a sure way to miss out on the capabilities and benefits of the FX system.

Attaching a DX lens occasionally to take a few pictures if you do not have a corresponding FX lens is totally fine, however, I would advise against building a system that has only DX lenses with an FX camera.

 

I agree with your basic sentiment that you shouldn't build a an FX system around DX lenses. In my case, I only have a couple of DX lenses, and only two that get used regularly(the 35mm f/1.8 for a few specific tasks on one specific DX camera, and the 10-20mm I mentioned above).

 

With the 10-20mm, though, it's not a question for me of "having" a comparable FX lens. I have the lens that is the benchmark F mount lens for this FL range, the 14-24mm f/2.8. I often choose consciously to leave it at home and carry the DX 10-2mm in its place even when there's not a DX camera to be found in my bag. The reason? The 10-20mm gets me as wide as the 14-24mm, and weighs almost nothing while still working with readily available filters, while the 14-24mm weighs a ton and needs expensive aftermarket filter systems.

 

It's dismissive to say that it's only a good idea "for a few pictures" if you "don't have the corresponding FX lens" when really there are good reasons to use certain DX lenses in an FX kit.

Just for fun I mounted my kit lens from my old D200 on my Z6 using the FTZ adapter. Works just fine, but it's kind of pointless. The resulting DX images are about the same resolution as the D200, 3936 x 2624 for the Z6, vs. 3872 x 2592 for the D200. Sure, the sensor is better and lower noise, but it's no great gain. It might make more sense with a Z7, but if you can afford a Z7 you can probably afford the lenses to go with it. :D

if you can afford a Z7 you can probably afford the lenses to go with it

It's not uncommon to have 3x as much invested in lenses as a camera body.

Newer thread from the same OP on essentially the same topic:

I'm on DX. Should I upgrade to FF or Mirrorless?

 

Please continue the discussion on the newer thread.

Edited October 8, 2020 by ShunCheung