Nikon's New 300mm f/4 Looks Impressive
- Thread starter Rob Bye
- Start date
Whiskeyman
Senior Member
Seconded!
No, a 300mm lens is a 300mm lens, it's a fixed mathematical value. A 300mm lens on an FX sensor gives the field of view equivalent of a 450mm lens on a full frame camera. Depth of field is also greater on a smaller sensor, which is part of the reason people will state that an aperture factor should be applied, as well.
Here's another video from Tony Northrup that explains all off this much better than I could:
https://www.youtube.com/watch?v=f5zN6NVx-hY
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The whole "equivalence" thing is kinda' silly. It should just be obvious to a serious photographer that you will get a narrower field of view with a crop sensor camera, and greater depth of field, than the same focal length lens provides on a full frame camera. People who buy point and shoots that they use a couple of times a year really don't care about the numbers, do they? I dunno', maybe they do and that's why the marketing people came out with all the 35mm film lens equivalents. 
Whiskeyman
Senior Member
The whole "equivalence" thing is kinda' silly. It should just be obvious to a serious photographer that you will get a narrower field of view with a crop sensor camera, and greater depth of field, than the same focal length lens provides on a full frame camera. People who buy point and shoots that they use a couple of times a year really don't care about the numbers, do they? I dunno', maybe they do and that's why the marketing people came out with all the 35mm film lens equivalents.
Woody,
Depth of field is a function of many things, however, sensor size does not matter for any particular lens focal length. It is only when a smaller sensor is coupled with a shorter lens (smaller focal length) and the scene of both cameras match, that you'll have an increased depth of field on the crop sensor camera, all other things being equal. If the cameras are side by side, with the same focal length lens and same subject, the depth of field will be the same for both cameras. It is when the cameras are moved relative to one another, and the sensor images are matched, that the depth of field increases.
WM
Whiskeyman
Senior Member
Whiskeyman
Senior Member
This isn't always the case. Lenses are designed for many things, and one of the characteristics of any particular lens design is the image circle. In many lenses designed for crop sensor applications, the image size isn't as large as the image circle of those designed for full-frame sensor. However, on some DX lenses, the image circle will cover most, if not all, of the FX sensor, albeit with typically poor image quality outside the center of the image, corresponding to the sensor size it was designed for.
An exaggerated example of this would be the image circles of a particular focal length lenses for 35mm format and large format lenses. The designed image circle for a 300 mm lens designed for a 4"x5" or 8"x10" view camera has to be much greater than that of the lenses we use on our 35mm format size cameras. This is one of the factors that make the lenses for the larger format cameras more expensive.
WM
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There is a little more. Sensor size (and its resulting necessary magnification to print size) determines Circle of Confusion (the size of the out of focus point source... a fuzziness factor), which certainly is a factor of depth of field... how large that circle can be magnified in the print before it is a visible problem. The first thing a DOF calculator asks is sensor size.
Sensor size and focal length is all that determines angle of view, simple trig. The lens just has to project a circle large enough to cover the sensor. I think you are just saying the wrong lens can be a limiting factor. Don't use the wrong lens.
The whole "equivalence" thing is kinda' silly. It should just be obvious to a serious photographer that you will get a narrower field of view with a crop sensor camera, and greater depth of field, than the same focal length lens provides on a full frame camera. People who buy point and shoots that they use a couple of times a year really don't care about the numbers, do they? I dunno', maybe they do and that's why the marketing people came out with all the 35mm film lens equivalents.
All of that is true, but those of us with decades of 35mm experience simply just know what a 24mm lens will do, or 200mm lens, etc. What we don't know is what these newfangled little cameras will do, and Equivalent focal length provides that answer. I assume that is its ONLY purpose. At least it is all that it does. We could compute for other sensor sizes, but Equivalent as stated says 35mm film.
No, not at all.
I think that "Equivalence" thing has confused the issue. A 300mm focal length remains the same whether it was designed for a 3x4mm sensor of a cell phone or for a 8"x10" large format camera. What changes is the Image Circle which for a 3x4mm sensor need not be more than 5mm dia, but has to be at least 30mm for DX, 45mm for FF, 85mm for MF and 330mm for an 8"x10".
What a larger Image Circle entails is more glass in front and a more complicated design, hence more cost. That is why a lens designed for a particular sensor size (and a given maximum aperture) is the least cost option.
As has been said a number of times is that as you decrease the sensor size only FOV changes. As smaller sensors are denser, you get more details, which gives us the "magnification".
What a larger Image Circle entails is more glass in front and a more complicated design, hence more cost. That is why a lens designed for a particular sensor size (and a given maximum aperture) is the least cost option.
As has been said a number of times is that as you decrease the sensor size only FOV changes. As smaller sensors are denser, you get more details, which gives us the "magnification".
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Bengt Nyman
Senior Member
Trying to summarize the above discussion including essential facts while avoiding common misconceptions is probably a dangerous task, but I will try.
1. All 300mm lenses (as an example) have the same physical, optical focal length of 300mm, whether designed for format 1, FF or larger.
2. All 300mm lenses are NOT designed with the same FoV (Field of View) but are designed so that the image circle covers the native sensor diagonal.
3. Using a non-native lens, the result is determined by the size of the image circle in relation to the sensor diagonal.
4. If the image circle is larger than the sensor diagonal (FX lens on DX body) the image sensor will crop the image, throwing away some image, some light and aperture, and part of the capability of the lens.
5. If the above cropped image contains more pixels than doing the same amount of post cropping of that image captured in Full Frame, you might have a quality image that looks like it was taken with a longer lens.
6. The optimum is always to use native combinations of camera and lens, when available.
1. All 300mm lenses (as an example) have the same physical, optical focal length of 300mm, whether designed for format 1, FF or larger.
2. All 300mm lenses are NOT designed with the same FoV (Field of View) but are designed so that the image circle covers the native sensor diagonal.
3. Using a non-native lens, the result is determined by the size of the image circle in relation to the sensor diagonal.
4. If the image circle is larger than the sensor diagonal (FX lens on DX body) the image sensor will crop the image, throwing away some image, some light and aperture, and part of the capability of the lens.
5. If the above cropped image contains more pixels than doing the same amount of post cropping of that image captured in Full Frame, you might have a quality image that looks like it was taken with a longer lens.
6. The optimum is always to use native combinations of camera and lens, when available.
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This isn't always true. The optimum is always to use the "best" lens for any given cam which isn't necessarily a lens designed for that same format.
Here's an example:
The 35mm f/1.8 DX vs the 35mm f/1.8 FX on the D7100
Nikon AF-S DX Nikkor 35mm f/1.8G on Nikon D7100 versus Nikon AF-S NIKKOR 35mm f/1.8G ED on Nikon D7100 - Side by side lens comparison - DxOMark
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The focal length of any lens is simply what it is... At any one zoom setting, it can have only one focal length. Which is the distance behind it where that lens focuses. No matter which body you put it on, the lens does not change.
What might change is the sensor size in that body. The sensor size captures the "field of view" that is seen behind the lens. A smaller field of view on a smaller sensor can make it "look as if" it had been a longer lens on a larger sensor, but of course the lens is always still the same lens. The smaller sensor simply "crops" that view smaller, "as if it were" the view from a longer lens on a larger sensor (hence crop factor, hence equivalent focal length).
See Camera Sensor Crop Factor and Equivalent Lens Focal Length
What might change is the sensor size in that body. The sensor size captures the "field of view" that is seen behind the lens. A smaller field of view on a smaller sensor can make it "look as if" it had been a longer lens on a larger sensor, but of course the lens is always still the same lens. The smaller sensor simply "crops" that view smaller, "as if it were" the view from a longer lens on a larger sensor (hence crop factor, hence equivalent focal length).
See Camera Sensor Crop Factor and Equivalent Lens Focal Length
Bengt Nyman
Senior Member
No. However, if you value certain characteristics no matter size, weight and three times the price, yes, then there are always personal choices which do not fit a generalized and somewhat compromised optimum, including a balanced range of variables.
They've been producing FX lenses for an eternity so there's a load of FX for every DX, and FX is held to a higher standard, which all results in plenty FX outperforming DX. Not to mention you'll never see DX versions of some lenses.
Everyone has to make up their own mind how much they prefer to invest in a lens and what they expect for that money. There are plenty of lenses better than mine but I'm simply not willing to invest the difference in money for that increase in performance.
Everyone has to make up their own mind how much they prefer to invest in a lens and what they expect for that money. There are plenty of lenses better than mine but I'm simply not willing to invest the difference in money for that increase in performance.
I think I'm the only one here that shoots the lens. About every shot of me I posted in bird, insects and portraits that shows 300mm in the EXIF is shot with the lens.
RocketCowboy
Senior Member
I'll start a GoFundMe or Kickstarter program to help get me one so I can post a few samples.