Tom K 66

If I am purchasing a Nikon DX 50mm lens for my nikon D7200, I believe the field of view is 75mm. If this is correct why doesn't the manufacturer label it a 75 mm lens?
If I purchase an FX 50mm lens and use it on my DX camera is the field of view also 75mm? Direct answers to these questions may clear up this confusion for me. Thanks in advance

Pablo8 Loc: Nottingham UK.

I cannot answer for the lens manufacturers, regarding question one. But in answer to question two, yes, the FOV coverage will be that of a 75mm lens. The lens however will have the attributes of a 50mm lens. Other posters may give more complicated answers. I keep it short and sweet (KISS).

tradio Loc: Oxford, Ohio

#1 It's a 50mm lens with the effects of a 75mm lens because it's on a DX camera.
#2 yes

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Your understanding is 100% correct.

Either lens sill have the same angle of view as a 75mm on a full frame camera. But depth of field will be that of a 50mm lens, which is shallower at the same distance. If you move back to provide a similar composition, moving back will increase the distance and the resulting depth of field will be greater. This is a source of great confusion.

JMCPHD Loc: Maine

The focal length of a lens is a physical characteristic of the lens. Manufactures of lenses label the lens with a number which is close to the actual physical focal length, probably rounding to the nearest whole number. Focal length dosen't change when used on cameras with different sensor sizes. The image however does change with the with the size of the sensor. What many of us may think is the expected view from a particular focal length lens is based on the image on film from what were called 35 mm film cameras. The image would be different if used on a camera with a different size film. Full frame cameras, which Nikon calls Fx have a sensor that is essentially the same as the area of film exposed in 35 mm SLR cameras. The field of view is narrower in longer lenses and with a smaller sensor the FOV covers more of the sensor yielding an image similar to what would be produced on a by a longer lens on a larger sensor.

dandi Loc: near Seattle, WA

Nikon does not make DX 50mm lens. All 50mm lenses from Nikon are FX.

BebuLamar

May I ask did you use a 35mm camera or a full frame digital camera before?

deer2ker Loc: Nashville, TN

I have a 35mm and 50mm for my D5500 and although the 35mm has the focal length of the "nifty fifty" in FX mode, I still prefer the 50mm.

Tom K 66

I used a Minolta SRT 101 back in the day.

Tom K 66

It was a hypothetical question in an attempt to clear up my confusion. I still do not understand if a DX lens is for a DX camera, why not label the lens for the effective field of view.

BebuLamar

If that you want then the lens must be labelled as 43 degree FOV for the FX lens and 32 degree FOV for the DX lens but both must be labelled as 50mm focal length.

mwsilvers Loc: Central New Jersey

Manufacturers do not label a 50mm DX as a 75 mm lens because it is not. It is a 50 mm lens. What gives the images from your camera an angle of view similar to 75mm is the smaller size of your camera's sensor and has nothing to do with the lens. You could mount a 50mm FX lens on you camera and the field of view would be identical to the DX lens.

The difference between a DX and FX lens is about something called the image circle. The image circle is the size of the area of light that hits the sensor. DX lenses are manufactured specifically for DX cameras and have smaller image circles to match the smaller sensors of cameras like yours. This makes then more inexpensive to manufacture and lighter in weight.

FX lenses have a larger image circle than the sensor in your camera requires so the outer portions of an FX lens on your camera effectively go used. If conversely you put a DX lens on an FX body that does not have a DX mode, the edges of your images nay vignette badly since the image circle of a DX lens is too small to cover an entire FX sensor.

All this focal length confusion in simply because we are trying to compare specs between two different types of cameras, and it all comes down to sensor size. The additional fact that two different types of lenses are made to cover these different sensor sizes just adds to the confusion. But remember a 50mm lens is always a 5Omm lens, regardlessess of the lens design or the camera it's mounted on.

srt101fan

dandi Loc: near Seattle, WA

I think you understand it according to your original post. It’s not about the lens, because lens is the lens, it does not change. But mostly about the sensor size. The same lens will act differently depending on the sensor size. On a Full frame camera the lens will give you more shallow depth of field. It’s a lot more to that, but I don’t worry about it too much.

BebuLamar

If you read this brochure then you will know that focal length and field of view are 2 different things.
http://www.galerie-photo.com/manuels/nikkor-lenses-for-large-format%20cameras.pdf