50mm f/1.8 AF-S versus 50mm f/1.8 "D"
- Thread starter Mike D90
- Start date
Sure you do. You get about 18mm's worth of focal length, and approximately 76° FOV of view.... exactly as per Nikon's specifications.
Ok, lets look at this another way. I want to see everything, using a DX lens on a DX camera, that I would see if using an FX camera lens on an FX camera, while standing on the same spot or same distance from subject with either.
Since it crops the image to a DX specific size, regardless of lens used, that is impossible without going to an even wider angle lens or stepping way back.
I just wonder why they didn't, or can't, make a DX lens that will reduce the full image onto a smaller projected image circle yet yield the same field of view as if used on an uncropped sensor.
I certainly do not understand optics so maybe I am an absolute idiot here.
Since it crops the image to a DX specific size, regardless of lens used, that is impossible without going to an even wider angle lens or stepping way back.
I just wonder why they didn't, or can't, make a DX lens that will reduce the full image onto a smaller projected image circle yet yield the same field of view as if used on an uncropped sensor.
I certainly do not understand optics so maybe I am an absolute idiot here.
In order to project the same image onto the smaller DX sensor as what an FX sensor would 'see', one would need to change the focal length of the lens in order to achieve the desired result.
Don't use focal length to compare the two lenses.... use the Field of View spec instead. Or just use the 1.5x crop factor math instead.
Take a look at the specs for your cell phone camera. Chances are, it's around 4mm, and it's due to the very small sensor inside. Put an actual 50mm lens on it and most people won't be able to hold it still enough to get an image without blurring.
A point-n-shoot camera has a slightly larger sensor, so an 8mm lens would be the same as a 50mm on an FX body.
At the other end of the scale... medium format. 50mm is a wide-angle on them. 4x5 view camera? 50mm is an wide-angle. Pull out an 8x10 view, and 50mm is incredibly wide.
Companies do make converters that will reduce the image circle, effectively reducing the focal length- but it also reduces the back-focus of the lens. It will work on mirrorless cameras, but not on an SLR as the optics would interfere with the mirror. It is the same idea as a Tele-converter. A Teleconverter increases focal length and increases back-focus. The "Wide-Converter" relies on the camera body having a small flange-to-sensor distance.
Reducing the image circle does not change the focal length of the lens. It changes the eFOV just like a cropped sensor does. Are you referring to the adapters that will let you use lenses designed for cameras with longer lens registration distances on bodies with shorter lens registration distance. Like using an Olympus OM lens on a micro four/thirds camera? If the adapter has optics in it it will change the focal length of the setup but not the focal length of the lens. Just like a TC.
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See, I do not understand the way optics work obviously. Just to me, my common sense wants to tell me that 50mm on a DX camera should yield the same FOV as a 50mm on an FX camera. Or, if it doesn't, there should be a way to manufacture a lens that does that.
It would just make it so much simpler to me to be able to stand next to a buddy, that uses an FX camera and I a DX camera and lens, and both of us take the exact same image. I know the DX image would be smaller but I thought it should contain the exact same "framing".
Sheeesh, this is making me crazy.
I guess I didn't understand focal length and its difference in FOV. No, I do not want any converters that do anything.
I guess to be very specific, using the adapter changes the effective focal length of the combined lens. You could also change the spacing between elements in a lens to change the focal length, or add auxiliary lenses to change the effective focal length of the combined optics. I turned a Canon 50/0.95 RF lens into a 35/1.2 retro-focus wide-angle lens for the Nikon F using large negative elements in front of the lens and an extension tube in back. I was not going to nit-pick for a conversation at this level, the OP posted a question- I tried to keep the answer simple. The "wide-converter" reduces the image circle, which increases the effective aperture as well. Nikon made a DSLR in the 1990s with built in reduction optics that sat at the image plane of the lens, it reduced/projected the image to a 2/3" sensor. Nikon rated the ISO of the sensor much higher than it's native rating to compensate for the increase in brightness of the image circle.
For the OP- get a 35/1.8 DX lens. That will get close to using a 50mm lens on a FX body.
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For anyone that really wants to get a basic understanding of photographic optics pick up this book. http://www.amazon.com/Science-Curio...keywords=science+for+the+curious+photographer
Whiskeyman
Senior Member
The reduction in field of view may not be quite that pronounced with some lenses. I can't remember which DX lens it was, but its projection was almost as large as that of a regular full frame lens. The image quality showed strong degradation towards the perimeter, though. But that won't matter as an FX camera body will detect the DX lens and only produce an image size corresponding to a DX camera.
Look at it this way: Focal length has to do with how big your subject appears in your image. All other things equal, longer focal length= bigger subject size.
Field of view has to do with how much around the subject you can fit into the image. All other things equal, a shorter lens focal length shows more of a scene than a longer focal length lens. And FX camera with an FX lens can show more of a scene than a DX format camera can.
Visit a camera shop and have them show you two cameras (one DX format, one FX) with the same focal length lens on it. (The lens must be an FX lens if only one is used.) Pay attention to the outer boundaries of the scene in the viewfinder, and then switch to the other format body, paying attention to the boundaries again. There's a great demonstration on field of view on different format cameras.
There, clear as mud, isn't it!:confusion:
WM
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35mm f/1.8 DX will cover the FX sensor.
Incorrect. The camera can be set up that way, but it's a simple Menu item to change. You can set it up to detect DX lenses and record DX frames, or record DX or FX frames regardless of what lens is attached.
I have both. When you see the IQ of the D compared to a kit lens, the G is almost the same improvement over the D.
I see this all the time. What is IQ? Image Quality?
Comparing this "D" lens to which kit lens? I wasn't thinking there is a 50mm kit lens.
And the G lens is that much improvement over a D lens??
Yes..... IQ = Image Quality.
Kit lens, as in 18-55, 18-105, etc.
And yes, the G is much better than the D.
Whiskeyman
Senior Member
I stand corrected in that there are other possibilities.
Whiskeyman
Senior Member
Almost guaranteed to teach you a lesson.
I sold a car three weeks ago, having purchased an upgrade. Now I'm wishing that I had kept the one I sold. Only good thing about it is that the car I now have is a much nicer model.
Oh well, we learn. (Or we repeat our mistakes over and over!)