Nikon's New 300mm f/4 Looks Impressive
- Thread starter Rob Bye
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Bengt Nyman
Senior Member
Thank you aroy, that's correct.
Here are some practical examples where the crop factor may or may not offer an advantage, in case of the lack of a corresponding native lens:
The Nikon 1 uses a sensor with 18 MP and offers a crop factor of 2.7. If you were to crop a 36MP image from an FX camera to the same enlargement you would end up with a 5 MP image.
The Olympus OMD uses a MFT sensor with 16 MP and offers a crop factor of 2.0. If you were to crop a 36MP image from an FX camera to the same enlargement you would end up with a 9 MP image.
The Nikon D7200 uses a DX sensor with 24 MP and offers a crop factor of 1.5. If you crop a 36 MP image from an FX camera to the same enlargement you are left with a 16 MP image.
Assuming that the pixel IQ difference between the FX and the DX sensors is less than 30%, putting the Nikon FX 300mm lens on a D7200 would produce 450mm reach and most likely an image quality superior to cropping an FX image down to the same enlargement retaining only 16 MP. This combo might even tolerate a TC14 reaching 630mm before the IQ would degrade below a cropped 36 MP FX camera image.
Here are some practical examples where the crop factor may or may not offer an advantage, in case of the lack of a corresponding native lens:
The Nikon 1 uses a sensor with 18 MP and offers a crop factor of 2.7. If you were to crop a 36MP image from an FX camera to the same enlargement you would end up with a 5 MP image.
The Olympus OMD uses a MFT sensor with 16 MP and offers a crop factor of 2.0. If you were to crop a 36MP image from an FX camera to the same enlargement you would end up with a 9 MP image.
The Nikon D7200 uses a DX sensor with 24 MP and offers a crop factor of 1.5. If you crop a 36 MP image from an FX camera to the same enlargement you are left with a 16 MP image.
Assuming that the pixel IQ difference between the FX and the DX sensors is less than 30%, putting the Nikon FX 300mm lens on a D7200 would produce 450mm reach and most likely an image quality superior to cropping an FX image down to the same enlargement retaining only 16 MP. This combo might even tolerate a TC14 reaching 630mm before the IQ would degrade below a cropped 36 MP FX camera image.
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Bengt Nyman
Senior Member
Tony is right:
For everyday photography where you can get close enough to your subject: USE 1 SERIES LENSES ON 1 SERIES BODIES, DX LENSES ON DX BODIES, FX LENSES ON FX BODIES, ETC.
For wildlife where you can not get close enough to your subjects AND YOUR CAMERA DOES NOT OFFER A LENS WITH SUFFICIENT REACH, you can put a larger format lens on a smaller format camera to take advantage of the crop factor. Just remember that the smaller format sensors do produce a lower IQ image. That's why DxO insists on testing lenses on cameras for an accurate assessment of the overall IQ expressed in P-MP or perceptual mega pixels.
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lol. How does putting a 300mm Dx lens (55-300) differ from putting a 300mm fx lens(70-300) shooting wildlife? They both will give you the same fov.
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Bengt Nyman
Senior Member
On what camera(s)?
what difference does it make? You say that a dx lens will get you closer than an fx lens being the same focal lenght. I say, horse hockey.
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Well ime lost now,i thought i was saying a FX lens on a crop of any size was a good idea,i also thought thats what the video said,i also thought you said it wasn't,to repeat myself ime lost nowmind you i was only talking wildlife.
When they talk about the aperture change it is also "equivalent aperture" which does not imply the actual aperture or light changes. It simply means that if you'd take the same shot with an FX or DX, the f/1.8 of the FX would be an equivalent f/2.8 on the DX. Now why would that be?
Maybe because you're taking the same shot but at a different distance?
Sorry, I meant you said an Fx lens will get you closer then a Dx lens..Im postingg on my cell phone
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A 35mm DX lens on a DX body has a FoV of 43.50° while a 35mm FX on an FX body has a FoV of 63.50°. That same FX lens on a DX body also has a FoV of 43.50°. It's not the lens that affects the FoV here, it's smaller sensor.
Nikon | Imaging Products | NIKKOR Lens Simulator
Bengt Nyman
Senior Member
J-see, correct.
A 35mm FX lens has an actual, physical, optical focal length of 35mm. This is a true optical measurement. On other formats the advertised focal lengths have been adjusted to mimic the results of an FF camera. An "apparent 35mm DX lens" would not have a physical focal length of 35mm but a physical focal length of 52.5mm, which is why it "becomes" a longer lens when you put it on an FX camera.
You can make the same argument in terms of field of view, but that does not as clearly reveal the truth about actual, physical focal length.
A popular way to look at it is in terms of "crop factor" which unfortunately neither clarifies the physics behind it.
A 35mm FX lens has an actual, physical, optical focal length of 35mm. This is a true optical measurement. On other formats the advertised focal lengths have been adjusted to mimic the results of an FF camera. An "apparent 35mm DX lens" would not have a physical focal length of 35mm but a physical focal length of 52.5mm, which is why it "becomes" a longer lens when you put it on an FX camera.
You can make the same argument in terms of field of view, but that does not as clearly reveal the truth about actual, physical focal length.
A popular way to look at it is in terms of "crop factor" which unfortunately neither clarifies the physics behind it.
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You're saying a 35mm DX is actually a physical 52.mm in disguise? Then why do I get the exact same shot when I use a 35mm FX on my DX?
Bengt Nyman
Senior Member
Yes J-see, 52.5 mm.
That's not very accurate. A 35mm Nikon has an effective focal length of 35mm whether it is a DX or FX format. Only the FoV changes depending the sensor used and the FoV of a 35mm on a DX is roughly the equivalent of a 52mm lens used on an FX.
The effective focal length does not change regardless which Nikon you put the lens on.
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RocketCowboy
Senior Member
Adding to this ...
Using the Nikkor 35mm DX f/1.8 and the Nikkor 35mm f/1.8 FX lens on my D7100 provide the exact same image FOV. There is no difference there.
Using the Nikkor 35mm f/1.8 FX lens on a D6100 provides a wider FOV.
Both results taken from the D7100 are "cropped" ... i.e. they are images contained within the same image pulled from the D610.
Exactly
All lenses are quoted at their full frame (Fx) equivalent focal length. That's the standard.
Bengt Nyman
Senior Member
Agreed. The optical, physical focal length obviously does not change. And actually, the FoV of the lens does not change either. Only cropping, inside or outside the camera, and subsequent enlargement introduces room for misunderstandings.
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Whiskeyman
Senior Member
The whole "equivalence" thing with crop sensor cameras is run-amok marketing BS from the camera manufacturers to convince the buyers of DX cameras that they are getting something special. Another equivalent piece of such mumbo-jumbo would be to say that having a sensor with twice the number of collection cells (pixels) would increase your focal length by 1.414.
An object's size on a camera sensor is the true measure of the focal length of a lens. How soon you run out of room on the sensor, or not, is dependent upon your sensor size.
WM
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