35mm 1.8 DX or 50mm 1.8 FX

35mm 1.8 DX or 50mm 1.8 FX for a D5100

The wife has green lighted me to purchase one of these two lenses. Without dispute they both appear to be great lenses but I have been unable to get one question answered from all my research.

For the purpose of my question I will use numbers easier to work with.

The DX lens is made to pass through an image of 3/4" that matches the size of the 3/4" (cropped) sensor. The FX lens lets through an image of 1" but the sensor is only 3/4" so the outer 1/4" is physically cropped off. Understanding this what I want to know is the optical image that comes through to my eyepiece going to show me for than what can be imaged (FX) or will the image in the optical viewfinder match what will actually be photographed (DX) and not show the additional 1/4" that will be cropped out due to sensor size?

I will eventually go to FX so I'm thinking I would like to do an FX lens. However, if the view I see in the viewfinder will be cropped out in part by the sensor that would make my pictures inconsistent. I do understand that the DX lens will go on an FX body and the camera will shoot in DX mode.

I may be wrong about this... but you have to figure that DX lenses are made to work with APS-C sensors. These are cropped sensors which are not sized up in 35mm.
Now using a lens made for an FX/Full Frame body will not end up being cropped but will be increased by 1.5x. This means that being used on an APS-C sensor the lens will be viewed as a 75mm (1.5x 50mm) lens, whereas the 35mm DX will stay as described since it is optimized for an APS-C sized sensor.

I may not be explaining myself well but the question is will the viewfinder show what will be captured as a picture or will the FX lens through my viewfinder show me more than what will be captured by the sensor.

Moab - I think I might know what you are trying to explain but without the flowery explanation, here is my answer.

Using your D5100 regardless if you use an FX or DX lens, your camera will record whatever you see on your view finder or LCD if you are using live view. Your current camera will not record what you might see in a FX camera since it doesn't have the full frame sensor.

So, if you buy the Nikon 35mm f1.8G DX lens now, you will have a similar field of view once you have a FX camera and a FX compatible lens such as the 50mm f1.8G.

Buy the Nikon 35mm f1.8G for now and sell it once you shift to FX including your D5100 if that is something that you would like to consider.

D600 with 50mm f1.8G is a good combination.

You answered what I was asking - what I will see in the viewfinder. Thank you.

Correct me if I'm wrong but doesn't the image get to the viewfinder via de mirror, then prism? If so, then it should show exactly what will land on the sensor, notice there will be extra image around the mirror, prism and sensor.


There is no place like 127.0.0.1

Moab Man said:

I may not be explaining myself well but the question is will the viewfinder show what will be captured as a picture or will the FX lens through my viewfinder show me more than what will be captured by the sensor.

Click to expand...

An FX lens on your DX camera will capture the same image you see in your viewfinder with the exact same dimensions. The viewfinder is looking thru the lens by way of mirrors and the light that's hitting the mirror and reflecting up though the viewfinder is the exact same light that your sensor will "see".

Perfect. Another affirmation. Thank you.

Just for clarification, some DSLR cameras do not have a 100% view finder coverage such as the Nikon D700 and D5100 which has an approx. 95% coverage; therefor, the recorded final image will be slightly wider compared to what you see on the view finder.

You will get the more accurate framing based on what is displayed on the LCD in liveview mode.

Get the FX as it will not affect your D5100 pictures at all but you will be able to use it if you move up to DX. Your field of view with the 50mm on the FX will be greater than when fitted to the DX. Now to throw a spanner in Hogan says the 50mm DX will cover the full frame of an FX camera.
Clearly you are going the route of having a bag of lenses and a bad back rather than just buying an 18-200 zoom

First of all, 50mm f1.8 G is DX lens, not FX. The old one, 50mm f1.8 D is made for film and FX.
Second, either you use FX or DX lens with your D5100 you will get the same FOV, just with FX lens you will be using only cropped center of the glass, so in theory you will have better quality, but in practice it may be different story.
Third, your D5100 will not auto focus with 50mm f1.8 D lens, so if you want 50mm lens you should go for DX 50mm f1.8 G, unless you want to focus manually.
And fourth, no matter your lens is designated as DX or FX, on a cropped sensor camera you have 1.5x magnification/crop factor, so if you use 35mm lens it will be almost the same as 50mm on full frame camera, 50mm on DX will be 75mm on DX, and so on.

It depends of your needs, but on a DX camera 35mm lens is far more usable than 50mm, my advice is to begin with 35mm, and then later add 50mm to your lens collection.
As for FX and DX, I would still buy a DX 50mm f1.8 G, because it is better wide open than the old one, but more expensive and with little bit more distortion.

alfaholic said:

First of all, 50mm f1.8 G is DX lens, not FX. The old one, 50mm f1.8 D is made for film and FX.

Click to expand...

I don't think your affirmation is right. The 50 1.8 G IS a FX lens. At least according to this.

The 50mm f/1.8G is a FX lens
The 35mm f/1.8G is a DX lens

Both lenses will 'suffer' from the crop factor of the APS-C sensor on your D5100;
35mm effectively becomes 52.5mm
50mm effectively becomes 75mm.

As already stated, what you see in your D5100 viewfinder is going to be 95% of what will be recorded, unless you use LiveView.

If you're unsure as to which to purchase based on focal lengths, may I offer the following advice based on my personal situation with these lenses.
First of all, set your 18-55mm at ~35mm then at ~50mm and see what the difference is between the two.
If that doesn't help matters, then consider future purchases. A lot of people will say, buy both as they are both cracking lenses for the price you will pay, but what I personally found was that the 35mm was to close to the 50mm to warrant both in my arsenal.
With that in mind I am looking at the FX 28mm f/1.8G instead of the 35mm, and whilst not owning a FX camera, I am quite particular about loving the fact that I would be using the centre of the FX lens on my DX body and thereby getting the sweet spot of the lens

Marcel said:

I don't think your affirmation is right. The 50 1.8 G IS a FX lens. At least according to this.

Click to expand...

I was wondering where "alfaholic" got his information. It is definitely a misinformation.

You will find this usefull ...all the nikon lenses and serial nos

Nikon Lens Serial Nos

Without all the techno bable, i can say that i do not regret trading in my 50 for a 35. The 35 1.8 is a sweet little lens. What is great about, is the fact that nothing on the outside moves - except the focus ring if you want to manual focus. All the movement happens inside the lens, unlike the 50 where the barrel would go in and out. It comes with a hood, pouch, front and rear caps.

Marcel said:

I don't think your affirmation is right. The 50 1.8 G IS a FX lens. At least according to this.

Click to expand...

Yes, you are right. My mistake. :redface-new:

I agree, 28mm + 50mm is nice combination, but 3 times more expensive than 35mm + 50 mm.
For my photography there is a big difference between 35mm and 50mm, outdoor is very similar, but I am often indoor so I need that wider FOV.
Again, 28mm on DX body is not wide enough for architecture or landscapes, for example Tokina 11-16mm costs the same but an be very useful for some.

I also agree it is nice to have FX lens on a DX body, but my 35mm f1.8 G is much better wide open than FX 50mm f1.8 D.
Every rule has an exception. Or two...

I think the biggest problem beginners have is to find what they are most interested in photographing, and then according to that choose the glass.
Usually those two comes at the same time, so you can not choose by your self, you always need someone to tell you where to look...

AC016 said:

... unlike the 50 where the barrel would go in and out.

Click to expand...

As far as I'm aware the 50mm f/1.8G does not have a barrel on it, and it certainly doesn't go in and out

§am said:

As far as I'm aware the 50mm f/1.8G does not have a barrel on it, and it certainly doesn't go in and out

Click to expand...

I was talking about the 50 1.8D, in which the inside barrel does move in and out like a little zoom.

I have to ask why not a 35mm lens FX? If the intent is an normal prime... then the 35mm lens is more appropriate on a DX body (or 28mm or 24mm).... but if you do upgrade to a FX body, then a 35mm FX would make the most sense (now and then). Also, just a comment on the bag of lenses versus zooms in general. Primes are generally sharper, faster, and lighter, and I would argue better for the photographer. I used to shoot a 18-200mm, it is a good lens and not too heavy, but I would choose a 24mm, 50mm and 85mm over that any day. Typically as you get better camera bodies and lenses, you end up with very heavy FX zooms, and suddenly zoom weight is an issue (even just two). In general carrying two or three primes versus zooms, primes are going to take up less space and be a lot lighter than one or two good zooms. I probably have a dozen primes, I carefully choose what I am going to need before I go, not carry everything I own. Also, in the DX world where you will be handicapped on light sensitivity over the equivalent FX body, primes offer better light gathering ability. Anyway, I just wanted to reinforce the good aspects of the direction you are heading and suggest a wider angle FX lens as a possibility. JD