Sometimes people ask questions on what the difference is between DX and FX lenses. DX and FX are Nikon lingo in specifying different sensor sizes on cameras.
On digital cameras Nikon have traditionally employed what they call DX size sensors. This sensor was originally a CCD type sensor such as the one in the D70 camera and has later been replaced by a CMOS sensor on the later versions such as D200 and later cameras.
Before we all went digital a “normal” prosumer or semi-pro camera was almost always a 135 system camera. This means we had 35 mm film in the camera and the projected image was usually 24×36 mm onto this film. With the invention of the APS-C format sensor which is 23.7 x 15.5 mm in size this format was known as DX. They are all small format cameras.
Because the digital bodies, with the exception of the so called “full frame” bodies, have a much smaller area onto where to project the image from the lens, it is possible to make cheaper and lighter lenses by sacrificing the area outside the sensor. The result is a special line of lenses called “DX” lenses.
Canon, Sigma, Tamron, Tokina… they all have their own respective way of denoting lenses that are “optimized” for digital DX format cameras. But what happens if you mount a DX lens on to an FX body and start taking pictures?
In the worst case you would get completely black corners. Because the “full frame” sensors are bigger parts of them may fall completely outside the projected image by the sensor, something that would lead to black corners.
In many cases it would not be so dramatic but instead you would see some vignetting, the falloff in light in the corners and in all cases you can be pretty certain that sharpness, chromatic aberration and so on will not be very good in the corners of the picture.
Here is a demonstration of the difference and why it may be difficult to use DX lenses onto the new types of digital cameras with larger sensors, results will vary depending on the actual lens, some DX lenses work better but never as well as a lens actually designed for FX format cameras.
This picture shows an extreme case of vignetting where the image from the lens fails to cover the whole sensor of the camera. This can happen for example with extre wide-angle lenses designed for DX cameras and mounted onto FX bodies.
This is a more normal result of what most DX lenses would produce on FX bodied cameras, the falloff is more graduated and could still be useful.
Here is the lens used on a DX format camera. Note how the crop factor of the camera "crops away" all the vignetting of the lens.
By not having to design lenses for the full FX format the manufacturers can make do with smaller lenses, this means they can be lighter (good for hiking photography) and they can be made cheaper.
How about using FX lenses onto DX cameras then?
That works exceptionally well! Because of the crop factor the DX body will use only the best part of the lens, usually the middle of the picture is sharper and more defined than the edges and if the edges are cropped away because of the smaller sensor you will have excellent sharpness all the way out in the corners of the picture!
So there are definitely advantages to the DX type bodies, that should not be forgotten!
Tags: APS-C, chromatic aberration, conrer cut, difference, dx, format, full format, fx, lenses, projection, sharpness, vignetting
I found this very helpful in understanding the differences between the types of lenses. Thanks, Sarah
Thank you very much Sarah for the nice words!
Thanks for making the difference understandable.
De nada! I am happy you got good information from it!
Excellent article. Thanks very much. First time on your site but will be delving further to build up my knowledge base. Thanks again.
That’s great, thank you for your input!
Thank you for your article. I am going digital soon & have several Nikon lenses. Great to have this info. I’ll keep it in mind for D3 & D700
Happy to be of service of course!
Then one must take into account that a lens designated for FX cameras when used on DX cameras, the focal length is actually 1.5x’s greater. In other words, a 100mm, whether AF or MF would be the equivalent to a 150mm lens when used on a DX camera. Am I making the correct in assuming this or am I still out to lunch?
Goose: The focal length does not change with the sensor size. But the angle of view does or the field of view. Since most small picture cameras used to be 135-systems with a negative imprint that was somewhere 24/36 mm on the long side then for people who are used to these cameras it makes sense to calculate the “equivalent” lens for such a system to get an idea of the field of view covered.
On the other hand if you are used to a medium sized camera then you might want to convert the digital “crop factor” to that format instead it depends on what you are comparing to. Personally I don’t convert the focal lengths at all, and the reason for this is that other aspects such as telecompression stays the same no matter what the sensor size is.
But to answer your question, a 100 mm AF/MF lens on a modern digital would be perceived as the equivalent of a 150 mm when mounted on a DX body. The “crop factor” of nikons DX cameras are about 1.5x meaning if you are using a 150 mm lens on a FX format camera or analogue 35-mm system you would get a very similar field of view.
I would not worry too much, the lenses are still very useful and the “elongation” you get from the crop factor is only a problem when using the more extreme wide angled lenses (< 24 mm) since they do not look as wide any more on the DX bodies. Therefore there is a range of DX ultra-wide lenses to cover this, generally in the 10-20 mm range (equivalent to 15-30 mm) but they won’t fit an FX camera for the same reason.
Thanks. Your explanation is the first one I’ve seen that has a photo showing a DX lens on a full frame camera. I would love to go up to a full frame camera but the thought of replacing ALL my DX lenses is way too costly.
Very good discussion. Much helpful for me to compare “AF-S DX Zoom-Nikkor 12-24mm” and “AF-S NIKKOR 24mm”. I am trying to get one for my D300. I think I’d go for the first one for the DX factor. Any more hint would be appreciated.
A very helpful and easy reading discussion. Thank you very much Sarah
Thanks so much for this clarification! I searched for hours to understand why a DX lens would still have a 1.5x crop factor when used on a DX camera. I *thought* the DX lens was changing the focal length such that it was focusing all of the front glass element onto the smaller DX sensor. After reading your article it is apparent that the DX lenses are not changing the focal length, but rather, only using high quality components to cover the smaller area. So the projected image circle is still theoretically the same as an FX or 35mm lens, but the useable area is designed to be the size of the DX sensor.
That is absolutetly correct, although since the DX lens do not have to cover such a large area the circle of light it produces can also be smaller by making the lens barrel smaller in diameter which is another factor lessening the weight and the cost of the lens.
Thank you very much for best information
How does the crop factor affect the DX lens on DX body? Does it mean I have to add 1.5 of DX lens and 1.5 of sensor from DX body to have 3x crop factor from a nikon lens on nikon camera? Please help. Thanks
Brian: The crop factor only means the camera has a smaller sensor than a standard 35 mm camera does. The lenses have therefore been adapted to this fact and therefore won’t cover the full sensor on a full sensored body. That’s all. The crop factor is a function of how much smaller the sensor in the DX camera is compared to the sensor or rather film in a standard 35 mm camera.
Crop factor for most Nikon bodies of DX type is 1,5.
Very helpful, thanks.
I’m still a little fuzzy as to what this all means on the output side of the equation. Basically Large Format offers photographers with more ‘photograph’ to work with, whereas DX is like wearing blinders? You only get a portion of the image that a FX offers? Is that right? So basically Large Format is just giving you more to work with, like the old 120 negatives [or 4 x 5's] did as compared to a standard 35mm negative. Yes?
Yes you are correct. It also affects some other things such as Depth of Field and other interesting properties but in essence, a wider sensor means a more wide angle image for the same focal length of lens.
But this article is actually about what happens when you take a lens that is specifically designed for the DX line of cameras and put it on an FX camera. That is another business because the circle of light falling from the lens may not cover fully the sensor chip on the FX camera and thus produce, in some cases extremely, bad vignetting when you are photographing.
Hi. I am thinking of buying a Nikor 28mm-300mm FX glass for my DX body D90 Nikon. Is that a good idea?
It would work well, but if you have a DX body you might want to consider the 18-200 for that wide angle which I really like. If you rather have more zoom the 28-300 will definitely work well on your DX as well.
Hi,
I recently bought a Nikon D5100 D-SLR and its a DX-Body. Can I buy FX lens for the same? I am interested in bird photography. Will an FX Lens suffice for this work, If so, can you please suggest me which one to buy.
Thanks,
Guna
Sure you can, it will work very well. A lot of people love the trusty 80-200 as an all purpose general tele lens. For bird watching you might want something longer (and more expensive) with still f/2,8 aperture.
Very helpful article and brillianlty demosntrated too…thanks!
Wanted one more help, taking that Crop Factor in account a 70-300 FX would actually be delivering 55-200 DX or so images. Isn’t? But that would be crispier, as you suggested.
I am unable to decide upon between above two for my D5000.
Eh, no it is the other way around.
A DX 55-200 lens on a DX body would give you the same field of view as a 80-300 FX lens on an FX body would.
A FX 70-300 lens on a DX body gives you the same field of view as a 105-450.
Putting a DX lens on an FX body produces veignetting, sometimes very extreme and can reduce the image to a circle with very limied field ov view because the projected image from the lens will not entirely cover the senson on the FX body.
Hi,
I am planning to buy a Nikon FX lens for a DX body, i read somewhere that it does not work the way we want and you should not use the FX lens on the DX bodies. But what i read here is totally a differnt perception. Please advise should i go for a FX lens on DX body or not. if you have an image with this combination that will be great for me to understand
Hi, please tell me which lens and I can give you some more advice. In general it is not a problem, actually FX lenses on a DX body uses only the “sweet spot” of the lens meaning that you get a very sharp, nice picture generally.
But tell me which lens you want to buy and which camera to use it on and I can tell you more about if the combination is okay. You should also check if your body need AF-S lenses to autofocus or if it can use AF lenses (mechanical focussing).
Thank you so much for posting this information….it helped me understand so much better..
now I know to buy a fucking fx instead of that piece of shit dx camera.
Now i know how a woman feels when she goes out on a date, gets the guy into bed…gets all worked up…only to find out that he has a tiny pea sized cock.
May I know why FX body (which has bigger sensor) with 80-300 FX lens is unable to cover more area than area covered in DX 55-200 lens in DX body (which has smaller senser) ?
I am not certain I understand your problem Sudhakar?
Hi, thank you for all the information its very useful.
I have a Nikon D200 with this lenses DX 10-24 f/3.5-4.5, DX 17-55 f/2.8, VR Zoom 80-400 f/4.5-5.6 ED, and a 600mm f/4G ED VR.
I am interested in a new body and considering the D3S but because its FX I don’t know if the lenses I have can be used. properly. Or do you recommend another body? I am going on Photo Safari next year.
You will likely have to change your lenses when you get a FX body. All lenses that says “DX” on their model will have some kind of trouble on the FX body. How severe is difficult to say, but generally they might not cover the full sensor meaning you will have to re-crop your images after and will get some serious veignetting and soft corners.
Photo safaris are difficult because it takes time to change lenses. Ideally you would like a wide-to-normal zoom on one body and a telephoto lens on another. But it may be difficult (and heavy). So my compromise is that I am using a “superzoom” lens while moving. This lens goes from 18-200 mm and I then have the possibility to capture most of what is put in front of me without losing any time.
When stopping to study something at a distance, I change to a better quality telephoto lens. When I want to take in the scenery I put the wide angle lens on the camera. And sometimes I use the nifty fifty (AF 50/1.8G) to take panoramas with. It is lovely for this purpose.