rcdovala

I was playing around with my D600 using an older Tamron 1.4X lens extender from my film days. It is a model MC4. It actually performs better on my digital cameras than it did on my film cameras. And that is primarily due to the fact that digital images can be sharpened which makes what would have been a marginal image on my film cameras an acceptable image on my digital cameras. None of that is surprising. But what is surprising is that when I attached one of my DX lenses to the extender, I discovered that the lens/extender combination allowed for full coverage of the sensor. Initially, I thought that the D600 was in the crop mode but it was not. The next thought that came to my mind was that this was probably an anomaly specific to the lens that I had mounted. But that was not the case either. Every DX lens that I mounted on the extender covered the entire sensor with no vignetting that I could see. I've attached three images as an example. These are not works of art so critiquing is not required. We've had a horrible drought in California and my backyard still has not recovered. Also, the three images have been downsized to make their file size manageable so you'll have to take my word that these images are from the full sensor. What makes this exciting for me is that my Tamron 11-16mm f:2.8 DX wide angle zoom becomes a 15.4-22.4mm f:4.0 lens on my Nikon D600. Has anyone else observed this behavior either with a Tamron extender or any other brand of extender?

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GalaxyCat Loc: Boston, MA

Very nice!

Apaflo Loc: Anchorage, Alaska

It will work exactly the same with any TC using any DX lens on any FX camera.

The way that a TC (a Barlow lens) works is to enlarge the image that is projected on the sensor. Hence a 1.4x TC is exactly the right amount to enlarge a DX size image to match a FX sensor. A 1.7x or 2x TC enlarges the projected image even more and thus will also provide full coverage on the FX sensor, but it will be even larger.

rcdovala

That all makes sense after the fact. But I don't recall this subject being discussed on this forum before. Or if it was, I missed it.

Apaflo Loc: Anchorage, Alaska

Off hand I don't recall ever seeing a discussion of it on UHH, but I may have forgotten it.

rcdovala

I hope that this discussion will benefit someone that has a raft of DX lenses and is using them in crop mode on an FX camera. There are limitations. of course. A zoom lens with an aperture of f:5.6 at the telephoto end effectively becomes an f:8.0 lens and may prove difficult to focus on anything other than in bright, contrasty light. But, it can be a useful tactic for those moving from the DX world into the FX world.

Lance Pearson Loc: Viriginia

the extender moves the objective lens further forward by the length of the extender which allows the captured light to expand to a greater diameter where it now hits the sensor....I believe.

Apaflo Loc: Anchorage, Alaska

That is true for extension tubes, which also change the plane of focus by moving it closer. A teleconverter does not change the focus.

Both project a larger image.