dont get this lens stuff.. i want a 35mm like my 18-200mm vr II at 35m

Started Nov 6, 2012 | Discussions thread
Dennis
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Re: dont get this lens stuff.. i want a 35mm like my 18-200mm vr II at 35m
In reply to MPA1, Nov 8, 2012

MPA1 wrote:

If I have a scene with 4 points in on a planar line to the camera, A, B, C & D and a 35mm FX lens has A & D at the left and right edges respectively, the same 35mm lens on a DX body might have B & C at the left and right edges.

OK, so something like:

A --- B --------------- C --- D

Right ?

If I put a DX marked 35 on the DX camera, will A&D then be back at the left and right (assuming no change in camera position) or not?

No.  The DX 35mm and the FX 35mm are equal; the DX 35mm just projects a smaller image circle (allowing the lens to be made smaller, lighter, cheaper) and would vignette on the FX camera.

NOTE: You would also get the same results putting a medium format 35mm lens on either camera (the medium format lens would show you A-D on FF or B-C on APS-C).

If not, the lens (IMV) is not delivering the image a 35mm 'should' deliver and should either be manufactured at 23.3 and then marked DX 35 or it should be marked 52 not 35.

Sure it is; it's only your expectation that's wrong.  Think about it: if you were to label a DX lens whose focal length is 35mm as 23mm because it gives you the same FOV as a 35mm lens on FX, what do you do with a 35mm FX lens that you want to use on DX ?  Label it as a 23/35 ? For that matter, you *can* use a DX lens on FX ... it just vignettes heavily.  So you do label it as a 23/35V ?  (For 35mm with vignetting ?)

What about the Nikon 1 ?  (CX format with a 2.8X crop factor).  The 35mm lens used on CX gives you the same FOV as a 98mm lens does on FF.  You can use a dedicated CX 35mm lens (I guess there isn't one at this point) or a DX 35mm lens or an FX 35mm lens.

I guess I am one of those people for whom angle of view is what pops into my head when you say "35mm lens" rather than magnification - in my mind, 35mm equates to a specific 'wideness' rather than a specific magnification.

I think that's probably true for a lot of people, but not everybody uses FF and people learn what FOV they get from a given lens for the format they're using.  You know 35mm is slightly wide.  For me, 35mm is "tight normal".  For the CX user, 35mm is portrait tele.

None of this is new to digital.  In film days, an 80mm might be normal for a medium format user while a 150mm is a short portrait tele.  A 90mm lens is a wide angle on a 4x5 view camera.  And some of those film photographers would switch between formats without needing their lenses to be labelled with 35mm equivalents.

- Dennis

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