Because the glass elements in a camera lens are round, lenses project a circular image onto a camera’s sensor plane. This projected image circle must be large enough to cover the rectangular sensor, like so:
Lenses designed for Nikon DX generally project a smaller image circle because they only need to cover the smaller DX sensor. This enables a DX lens to be smaller and lighter, but also means that these lenses are not suitable, by design, for FX cameras. For the Canon ecosystem this law is absolute, as EF-S lenses, designed for a smaller APS-C size sensor, cannot be mounted on full frame EF bodies.
The great thing about Nikon is that they do their best to offer backward compatibility. Mounting DX lenses on FX bodies has always been possible, with the FX DSLR automatically cropping the image frame to only output the area covered by the DX sensor.
Additionally, you can set the camera to output the full FX frame regardless of the mounted lens, by accessing Shooting Menu -> Image Area -> Auto DX crop -> OFF.
You might expect this to spell trouble with DX lenses because of extreme vignetting. Indeed this is what one sees when mounting many types of dedicated DX lens, espsecially zooms, on FX bodies. Here is an example of what you see with a Nikon 18-200mm f/3.5-5.6G DX VR lens on a Nikon FX camera (single frame from a HD video sequence recorded with a Nikon D600):
The bad news is that high quality FX lenses like Nikon’s golden “trinity” are intimidatingly expensive, big and heavy.
The good news is that not all DX lenses behave as you might expect. Two DX lenses that I dearly love are my Nikon 35mm f/1.8G DX and my Tokina 11-16mm f/2.8 AT-X Pro DX. These two represent the best of DX as they are small, fast, light and affordable, yet still perform excellently. What many owners may not know is that both of these lenses cover the full FX frame circle!
Nikon 35mm f/1.8G DX on FX
Until recently, the only fast modern 35mm lens that Nikon offered for FX was the expensive professional 35mm f/1.4G prime. With the recent announcement of the 35mm f/1.8G ED the situation has improved a lot from the affordability perspective. Yet the 35mm f/1.8G DX is the most affordable still, and one of Nikon’s most popular lenses to date – for a reason!
How can you expect it to perform on FX? I was pleasantly surprised. As expected, FX corner performance is nothing to write home about, and some noticeable vignetting is visible. However at larger apertures (larger than F8) the vignetting is bearable. Large aperture prime lenses are often used to draw attention to a single object, and then corner sharpness is seldom crucial. Vignetting may be aesthetically pleasing, and can be corrected to some extent. The center performance remains impressive, as this is what the lens has been designed for.
This little 35mm’s small size makes it unobtrusive and truly portable – especially desirable qualities for street photography. 35mm counts as moderate wide angle on FX which allows for just a bit more flexibility in creating interesting compositions compared to a 50mm “normal” lens.
Here are some examples:
35mm f/1.8G DX at f/1.8 (straight from .NEF – distortion and vignetting not corrected)
35mm f/1.8G DX at f/5.6 (straight from .NEF – distortion and vignetting not corrected)
In my opinion these photographs are quite usable. With some vignetting correction in Adobe Lightroom, the photo at f/2.8 looks as follows – compare it to the supplied photo taken with the large Nikon 24-70mm f/2.8G ED – one of Nikon’s professional FX “trinity” lenses.
Both photographs below were taken at 35mm f/2.8, but which was taken with which lens? At a casual glance these photographs are hard to tell apart – the top photograph was taken with the 35mm f/1.8, while the bottom photograph was taken with the 24-70mm f/2.8.
Even zooming in to 100% pixel-level detail shows little difference, as the corners are out of focus anyway (in both cases, the 35mm f/1.8 is on the left):
Caveat: starting at f/5.6, and especially at longer distances, the smaller image circle does become visible. With decreasing apertures, vignetting increases in the extreme corners. Personally I mainly use fast prime lenses at large to medium apertures, so this need not be a problem. Be aware, however, that in very bright light without using an ND filter this lens will becomes less usable as you will have to resort to smaller apertures. This makes the 35mm f/1.8 DX lens great for street photography, but less so for e.g. studio work where depth of field needs is attained by smaller apertures.
Uncorrected image with focal point at infinity, f/5.6. Here vignetting is already becoming intrusive:
At f/22, vignetting is very clearly defined (just as the dust on my Nikon D600’s sensor):
Uncorrected image with close focal point, f/5.6. At this closer focal distance vignetting is much less pronounced than at infinity, and not as intrusive:
At f/22, vignetting is again clearly defined, but less severe than at longer focal distances:
Tokina 11-16mm f/2.8 AT-X Pro DX
The other lens that I want to talk about is the Tokina 11-16mm f/2.8. Regarded as one of the best ultra-wide-angle lenses for DX, it has the same performance on DX as a 16-24mm f/4.0 lens would have on an FX body. But what happens when you put it on an FX body?
At 11mm the vignetting is rather extreme:
At 15mm the vignetting starts to disappear:
As we zoom in to 16mm, vignetting becomes less and less of an issue, up to the point where there is almost no visible vignetting any more at 16mm f/2.8:
The corners can be improved by stopping down – here the extreme right-hand edge is shown at 15mm f/2.8 (left) versus 15mm f/5.6 (right):
The corner performance is noticeably degraded compared to dedicated FX lenses, but if you are willing to live with this you have a very affordable ultra wide angle lens for an FX camera, usable up to 15mm at an aperture of f/2.8! Keep in mind that the only other lenses that come close are the Tokina 16-28mm f/2.8 Pro FX or the excellent, but much more expensive Nikon 14-24mm f/2.8G ED.
Conclusion
In this post I showed you how to use two very different but popular DX lenses for something they were never meant to do. But against all odds, these lenses are surprisingly adept at their job and will be able to give you great creative potential without adding much in the way of cost. This is especially attractive for amateur photographers taking the leap from DX to FX.
If you can live with the limitations of such a set-up, at least your DX lenses may have some use before you fully move to FX. With them you can still enjoy the better low-light performance, brighter viewfinders and more control over depth of field that FX offers.
Do you know of any other DX lenses that work well on FX? We’d love to hear about it in the comments.
Some examples of the 35mm f/1.8, from the streets of Trento, Italy:
Some examples of the Tokina 11-16mm f/2.8, from the streets of Trento, Italy:
Does the use of a teleconverter increase the focal plane coverage? For instance, a Nikon DX 10-24mm zoom would become a 14-34mm zoom with a 1.4x teleconverter, a really cool zoom range, for cheap money, even including the teleconverter. The 10-24 DX zoom already covers the full FX frame from 15mm and longer. OF course, you lose one stop with a 1.4 converter but the High ISOs available in modern digital cameras make this not much of a problem. Experiment!!!
A teleconverter would increase the coverage (image circle) of the Nikon AF-S DX NIKKOR 10-24mm f/3.5-4.5G ED if one could be attached.
However, its lens construction diagram reveals that the rear of this lens is occupied, leaving no room for the protruding front section of a teleconverter.
photographylife.com/lense…-5-4-5g-ed
I jumped from a DX DSLR (D7500) to FX mirrorless (Z5) and I am able to use my DX lenses with the FTZ attachment. That was a big selling point for me, and the Z5 DX pictures look pretty good, but are lower resolution than the pics from the D7500. I took the same picture at 24mm with an FX and a DX lens and compared them in GIMP and the DX version is a literal crop–it can be overlaid on the FX version and lines up pixel for pixel as if it was cropped (with some slight differences since I was using 2 different lenses). The Z5 spits out 6016×4016 images in FX and 3936×2624 in DX, but the 7500 spits out 5568×3712 images, so the DX images from the Z5 are a little lower resolution than the images from the D7500. I didn’t actually notice any lower quality until I took some 300mm zoom photos with the DX lens on the Z5, so I’m still pretty satisfied, and the lower resolution is a minor disappointment. But unlike the full frame DSLRs, there does not seem to be a way to override auto DX mode on the Z5.
I have been using some vintage manual lenses on the Z5 with adapters which are much dumber than the FTZ (old Pentax lenses with an adapter that has no electronic connections at all), so I decided to see if a non-nikon adapter will let me use the DX lenses in full frame. I ordered one of the F-mount G lens compatible adapters, which has an aperture ring and no electronic connections, so I will give that a try when it arrives in a few days and see if I can squeeze a few more pixels out of my DX lenses. Obviously losing full auto on those lenses to get a slightly larger field of view is a sketchy tradeoff in most situations, but manual mode on the Z5 is actually pretty easy (with vintage lenses designed for manual focus, at least), and if nothing else it will be fun to see how it works.
Maybe in some future upgrade, Nikon will let us turn off the auto DX mode on this camera. It seems (based on the images here) that we could take square pictures with a DX with no problem at all–there’s no reason why we have to be restricted to a 3:2 ratio with the DX if we can squeeze a little more image out of the lens at the top and bottom.
Some Nikon DX lenses, e.g. the AF‑P DX NIKKOR 10‑20mm f/4.5‑5.6G VR, have a rectangular rear baffle (aka flare stop) to reduce lens flare. This baffle also acts as a field stop, such that the lens coverage is little more than the area of a DX sensor.
“set the camera to output the full FX frame regardless of the mounted lens, by accessing Shooting Menu -> Image Area -> Auto DX crop -> OFF.“
Could not find this in the menue of my Z7.
Any other possibility for a using a DX lens uncropped on the full FX sensor of a Z7?
I’ve just downloaded both the Z 7 User Manual and the Z 7 Reference Manual. I can’t find the phrases “Auto DX crop” or just “Auto DX”.
It seems that a mounted DX lens forces the Z 7 into DX crop mode, unless this has been made a menu option in a recent firmware update.
I regret selling my Tokina 12-24mm f4 ATX Pro DX because I loved using it on my D3s in FX mode from 19mm completely vignette free. Maybe I buy another one :-)
What does with the FF sensor area where vignetting occurs (keep black) in comparison to the image area (receiving light) if prolonged use of DX lenses?
What does ***happen*** in terms of possible damage…
Nothing detrimental. Just frame it out – the dark corners.
Ron S
Thanks for your answer
Using a Nikon D750 and selecting 1.2 Crop factor (16mb), the nikkor dx 10-20mm and dx 35mm f/1.8g performance improves and will produce 300+ dpi 11″x14″ prints. If interested in matching mexapixels to print performance, see this Thom Hogan article: www.dslrbodies.com/camer…print.html
Please subscribe me to your site–I was not able to subscribe from your website
I just bought a D750, have a large number of DX lenses for my D7000 incl a Sigma 10-20mm f3.5
I wasn’t aware of the fact that some DX lenses work the way described, and I’m quite excited to try them out tomorrow, disabling the auto crop DX function. I’ve been using Nikons since the late 1970s and have a nice collection of old AI lenses (manual focus, full frame) that work fine on the D750 in Aperture priority, but now I find manual focusing a bit of a pain (yet it didn’t bother me back in the 1980s and 1990s). I was somewhat resigned to the fact that I’d have to use them a lot, rather than the autofocusing DX lenses. The prospect of spending thousands on new FX lenses is a bit depressing, but I’ll buy a few over time. Thank you for writing this great article, it is encouraging. I will likely use the DX lenses on the D750 sometimes, just to clarify, does that give me the 1.5X effect on the FX camera? I think it does.
Yes, with your D750 in auto DX mode, your old DX lenses will have the equivalent focal length & depth of field of a lens that is 1.5 time the stated values on the lens.
Be aware though that the area of the sensor being used will be vastly reduced. There is also to shoot in 1.2x crop mode, which may allow more of your DX lenses to be used.
The following information about the D750 cop mode resolutions is courtesy of Amature Photographer Magazine…
D750 also has a 1.5x DX Crop mode as well as a 1.2x Crop Mode. Utilising the former reduces the image size to 3936×2624 pixels (a resolution of 10.3-million-pixels), whereas the 1.2x crop mode has the effect of reducing the resolution to 16.7 million-pixels from 24.3 million pixels, with a maximum image size of 5008x3336pixels.
Read more at www.amateurphotographer.co.uk/revie…KKylEP4.99
Tokina 50-135 F 2.8 else work at 135 mm
Hi David,
Today I have shot with the DX 35mm f1.8 mounted on my D850. I was blown away by the outstanding image quality of this cheapest Nikon lens.
I did use the vignetting control setting at normal at the D850. That’s all. The was no lens vignetting at all in the images, and the test images are razor sharp after. I performed autofocus finetuning with DX 35mm f1.8 mounted at the D850 and the results where perfect!
I bought the DX 35mm f1.8 years ago with my D7200 but left it most of the time attached to my D7200, which I even use from time to time for my professional work.
Now that I experienced the DX 35mm f1.8 on the D850, I will use this lens as I’m shooting the Milky Way next month to see how it performs.
Hi Raymond,
How was the result of the combination of 35mm DX lens on D850 for Milky Way?