FX vs DX lenses on APS-C bodies
Sep 24, 2014 19:34:37 #
amehta wrote:
There are no DX zooms with a focal length longer than 55mm at the wide end. There are 55-200mm and 55-300mm DX lenses, but no 100-400mm DX lenses. As far as I know, other DX zooms are 18mm or wider at the wide end, including the typical 18-55mm and the superzoom 18-300mm. The only DX prime beyond 50mm which I know of is the 85mm macro.
Hopefully, the proliferation of Sony's mirrorless APS will change some of this !
Sep 24, 2014 22:11:33 #
sherwinc
Loc: SE Idaho
Ok, I don't believe that using an FX lens on a DX body results in just using the "sweet part" of the lens, the image still uses all of the lens whatever it's type. Every part of a lens contributes to every part of the image cast, it's just that the DX sensor only intercept the middle part of the image created by an FX lens. I don't see why that would necessarily improve the image quality.
Sep 24, 2014 22:44:09 #
sherwinc
Loc: SE Idaho
We often read on this and other forums that one advantage of using a FX lens on DX body is that the image then intercepted by the DX sensor is created by just the center part of the attached FX lens. The fact is that every part of the image created by any lens on any sensor is created by every part of the lens, otherwise it's not a very good lens. To understand, draw a picture of a simple lens, and a subject and a sensor. Light reflected from any point on the subject will radiate out and a small part of it will strike the lens, all of the lens. The lens, unless window glass, will refract this light from wherever it strikes the lens to a spot on the sensor corresponding to the point on the subject. A point at the edge of the subject image that would be recorded on a FX sensor may well be beyond the edge of a DX sensor, in this case, but every part of the lens would still contribute to it.
Sep 24, 2014 22:53:03 #
Sep 24, 2014 22:59:58 #
sherwinabc wrote:
We often read on this and other forums that one ad... (show quote)
You are somewhat correct but not totally.........the center of a lens is the sharpest part and only the central part of the lens contributes to this central image portion. - this is where the light is "less bent" if you will ..... and where the APS coverage is with a FF lens.
Sep 24, 2014 23:03:14 #
imagemeister wrote:
You are somewhat correct but not totally.........the center of a lens is the sharpest part and only the central part of the lens contributes to this central image portion. - this is where the light is "less bent" if you will ..... and where the APS coverage is with a FF lens.
:thumbup: :thumbup:
You are absolutely correct and if you check the Nikon specs they will state this.
Sep 24, 2014 23:12:04 #
SteveR wrote:
One of the advantages of an FX lens on a DX body, is that the center, sweet, portion of the lens projects onto the sensor. It's one reason I like the Nikon 28-300mm on my D7000.
:thumbup: :thumbup: :thumbup: That is exactly why I got the 28-300mm for my D7100. and if I get that D750 I have a starter lens
Sep 24, 2014 23:36:37 #
Sep 25, 2014 00:05:01 #
amehta
Loc: Boston
sherwinabc wrote:
We often read on this and other forums that one ad... (show quote)
Yes, every part of the lens is used to produce the image.
The resulting image, however, is not generally of equal quality, and the best image quality is at the center. So the more precise way to say it would be that the DX sensor uses the "sweet part" of the image circle the FX lens produces.
Sep 25, 2014 00:05:09 #
Going in the same relative direction as the OP, if (when) I upgrade to a FF, like the A99, will I lose the extra 50% reach of the APS-C body (the 105mm f2.8 will be 105mm instead of 157mm?)
Sep 25, 2014 00:07:55 #
amehta
Loc: Boston
sherwinabc wrote:
OK, look at this
http://electronics.howstuffworks.com/camera1.htm
http://electronics.howstuffworks.com/camera1.htm
The question with this is whether the center of the pencil will look better than the point/eraser.
Sep 25, 2014 00:08:52 #
amehta
Loc: Boston
planepics wrote:
Going in the same relative direction as the OP, if (when) I upgrade to a FF, like the A99, will I lose the extra 50% reach of the APS-C body (the 105mm f2.8 will be 105mm instead of 157mm?)
The answer which helps you is "yes".
The correct, obnoxious answer is, "you never had it to lose." :twisted: :lol:
Sep 25, 2014 00:09:59 #
planepics wrote:
Going in the same relative direction as the OP, if (when) I upgrade to a FF, like the A99, will I lose the extra 50% reach of the APS-C body (the 105mm f2.8 will be 105mm instead of 157mm?)
The focal length does not change.
The 105mm lens is still a 105mm lens on your APS-C body.
It will have the equivalent angle of view as a 157.5mm lens on a full frame body because the sensor is smaller on your APS-C camera.
Sep 25, 2014 00:56:31 #
GoofyNewfie wrote:
The focal length does not change.
The 105mm lens is still a 105mm lens on your APS-C body.
It will have the equivalent angle of view as a 157.5mm lens on a full frame body because the sensor is smaller on your APS-C camera.
The 105mm lens is still a 105mm lens on your APS-C body.
It will have the equivalent angle of view as a 157.5mm lens on a full frame body because the sensor is smaller on your APS-C camera.
To put it another way, it will be a cropped and zoomed image that looks the same as if it came from a 157mm lens uncropped on a FF camera.
Sep 25, 2014 03:30:50 #
skiman wrote:
To put it another way, it will be a cropped and zoomed image that looks the same as if it came from a 157mm lens uncropped on a FF camera.
Cropped, not zoomed. Depth of field does not change.
If you want to reply, then register here. Registration is free and your account is created instantly, so you can post right away.