asymmetric lateral chromatic aberration with N 200-500

I am a long time film user, with.a primary interest in birding.

 

I just purchased a D7200 (just couldn't rationalize the D500), but the main piece was the 200-500/5.6 while it was on special. The lens seems to live up to its reputation in the center of the frame, but there's one thing that I just can't understand. While testing, I noted strong purple fringe at the left side of the frame associated with a high contrast vertically oriented object. Minimal LaCA is seen on the right.

 

I do not see this effect with more "normally" oriented objects, but I assume that it still there, just hidden. Do you think that this is a lens defect? I can return/exchange through January.

 

Many thanks for the anticipated advice.

Asymmetrical corner-to-corner variation of sharpness or fringing is an almost surefire sign of de-centring.

 

A couple more tests you can do:

(1) Take a shot of something with detail in the frame corners, noting the framing - set the lens on MF so that the focus doesn't change between shots. Then turn the camera upside-down and take a second shot with the exact same framing. If the corner/edge sharpness varies between shots, then the lens is decentred. That's comparing the same subject areas between upright and inverted images BTW.

 

(2) Set the lens wide open and point it at an evenly-lit white surface. Overexpose by 2.7 to 3 stops over the meter reading and check the 'blinkies'. With a well-centred lens you'll see a central circular over exposed patch blinking away. If the circle is off-centre, that's another good indication of decentring.

 

Obvious failure of the above checks should call for a return or adjustment of the lens. Some Nikon zooms allow for 'easy' centring correction by a service technician. It requires a specialist rig though.

Edited December 27, 2018 by rodeo_joe|1

Thanks for the suggestions. I will give them a try this weekend, weather permitting, and report my findings.

Asymmetrical corner-to-corner variation of sharpness or fringing is an almost surefire sign of de-centering.

As he says....

Well, that was interesting, informative, and tiring. I had a bit of a learning curve to contend with, since this is my first foray into digital.

 

Testing was done as follows: VR off, tripod on, mirror lockup on, with IR release. Accuracy of focus was verified at each tested focal length/aperture. For the record, AF was spot on. Images were taken as NEF (14 bit) -> DNG -> photoshop, with default parameters. Multiple exposures were made at each setting, and the best selected to avoid issues from vibration.

 

I could not directly demonstrate meaning decentering, no matter what I tried. The blinking (which uses vignetting as a proxy for decentering) was very hard to induce, I think this was becuase of only a small amount of vignetting on a DX body.

 

Color fringing at vertical high contrast edges was narrower, but more intese in the left side of the frame vs the right. I would say that is due to very minor decentering (not unexpected, given the complexity of the design and low price). This was most pronounced at 500mm, f8. I also borrowed a friend's 70-300 dx vr lens. Although I can't diable vr, it too exhibited the asymmetric lateral CA. Coincidence? Some peculiarity of my camera?

 

At 500/5.6, images were sharp in the center, but with a fair amount of lost contrast (spherical aberration?). Contrast improved with each reduction in aperture, with no further improvement by f8. To illustrate, assume a 10 pixel wide sharp line at f8. At 5.6, this would look like a definite 4 pixel line, with 3 pixels of gradual smudge on either side. However, even wide open, I could resolve 1/8 inch high contrast objects (bleck letters on white background)toward the edges of the frame, at the length of a football field, The loss of contrast, once I became aware of it, was a showstopper; I had planned to use the lens wide open.

 

The lens is packed up and going back. Not sure what to do next. Don't want the expense of the 500pf.

 

Take home messages for me:

1. My copy of the 200-500 is superb, if one can live with f8. I do not know if this is representative; based on the reviews. Unfortunately, the price has gone back up, so I will not be getting another copy to try.

2. The 70-300 dx vr is an incredibly nice lens for the money. I wish I had purchased the D7200 with the kit lenses now. And they say that the FX is even better? Can anyone give their personal experience?

3. Pixel peeping can be unhealthy. I will avoid it like the plague.

Also, the D7200 is a steal at the current price of US$700!

Sorry to hear those lens woes. The edges and corners sound disgusting considering you were using it on a DX camera.

 

It seems as if there's no decent telezoom that exceeds 300mm to be had at an 'affordable' price. I have an old Sigma 135-400mm lens that's halfway decent. Worth the cheap price I paid for it used, but I wouldn't say it was worth buying new - or whatever its current replacement is.

 

However, I recently bought a Mamiya 645 to Nikon adapter and started using my old M645 Mamiya Sekor lenses on the D7200. Wow! Some of those lenses are just incredibly sharp on digital.

 

I was especially knocked out by the 300mm f/5.6 Mamiya-Sekor C. It beats any prime 300mm lens I've ever used that's designed for 35mm cameras. There's zero fringing and it's sharp right into the corners. It's also fairly light and compact for a medium format lens.

 

I've owned it for years, but this is the first time I've tried it on a digital camera. Damn! I wish I'd discovered how good it was years ago.

 

All of which set me wondering: If Mamiya could produce such a stunning lens, and one that wasn't very expensive when new back in the late1970s, then why the **** couldn't any of the 35mm camera makers equal it since, and at a sensible price?

 

My advice. Find one and snap it up before word gets around. Even including the price of an M645 adapter it'll be a bargain. Fully manual of course, but really magnificent optically.

Edited January 21, 2019 by rodeo_joe|1

That's an interesting suggestion. I was hoping for an AF solution for birds...

Too bad the focusing screen is not geared to MF.

It seems as if there's no decent telezoom that exceeds 300mm to be had at an 'affordable' price

The Sigma 60-600mm is pretty darned good from 100 - 600mm. It's about the same price as a brand new N 200-500mm was.

 

The N200-500mm is soft beyond 420mm.

 

Nikon Nikkor AF-S 200–500 mm f/5.6E ED VR review - Image resolution - LensTip.com

 

Testing anything at 500mm on it is going to be unsatifying!

If you can live with not zooming.... 300 f/4 with a TC14E yields a 420mm f/5.6. A lot of performance at a reasonable price.

The current 300 f/4 is relatively small and light, and has VR. The older one (AF-S 300mm f/4D) is quite affordable now though, and is optically fine, though not the fastest focussing lens.