Eeeee, what's this?!!?

[apaflo]

Originally Posted by wildmaven

Okay, I had time to play today. Here are the results:

Any chance you could rent or borrow a 50mm f/1.4G lens for a day and repeat that test with it?

[wildmaven]

Originally Posted by scoundrel1728

What is being imaged here? In other words, what is your setup and what (besides the central spot) are we looking at? Is this the blue channel only or is it a composite of all three channels converted to monochrome? If it is a composite, what kind of a composite is it? And why is each image lighter at the bottom than the top?

I added that info to that reply so others know, too. This was an image of the blue sky. I put the camera on Aperture Priority and then changed the aperture after every shot. The images were converted to black and white so it was easier to see the spot. My only purpose with this was to see at which aperture the spot disappeared. Here in Las Vegas (where I'm visiting), there is a lot of haze on the horizon, which is why it is lighter on the bottom than the top. Manual focus.

Originally Posted by apaflo

Any chance you could rent or borrow a 50mm f/1.4G lens for a day and repeat that test with it?

I don't know anyone in my town who is a photographer and there's no camera store there. Right now, I'm visiting my parents in Las Vegas (my mom had open heart surgery) and my dad doesn't have anything similar. I do want to try it with my 11-16mm lens that I bought recently, though.

[Max@Home]

Originally Posted by wildmaven

I don't know anyone in my town who is a photographer and there's no camera store there. Right now, I'm visiting my parents in Las Vegas (my mom had open heart surgery) and my dad doesn't have anything similar.

(1st: wishing your mother a speedy recovery )

AFAIK lensrentals.com ships rented lenses to the entire USA

I do want to try it with my 11-16mm lens that I bought recently, though.

what's stopping you ?

...€0.02...

Kindest regards!

Max@Home

[wildmaven]

Originally Posted by Max@Home

(1st: wishing your mother a speedy recovery )

<3 Thanks!

AFAIK lensrentals.com ships rented lenses to the entire USA

I have to wait until I get home, then I'll look into it. Not sure if it's really necessary, though.

what's stopping you ?

Time. Maybe after we get back from the hospital this morning. I haven't noticed it on the 11-16mm, though. Just the 50mm.

Or, should I put on my 18-200mm and set it at 50mm and repeat it with that? Hmmmmm....

[Max@Home]

Originally Posted by wildmaven

Or, should I put on my 18-200mm and set it at 50mm and repeat it with that? Hmmmmm....

Testing is knowing

...€0.02...

Kindest regards!

Max@Home

[Ed Shapiro]

Seems to me and this is only an uneducated guess that there is some artifact, defect or damage within the lens or on the sensor that comes into focus when the aperture is stopped down because if the inherent depth of field at such f/stops. This observation is based on the varying size of the spot and the way it virtually disappears at wider apertures. The shape of the spot does no mimic the shape of the diaphragm blades(??) I wonder of this has anything to do with the anti-aliasing filter(??)

Beyond this guess work, I think that Scoundrel's original optical theory is correct. This could be an intrinsic fault in that entire production run of that particular lens. Was that lens originally designed for film cameras?

I look at my old optics book from my academic days and none of the examples of common optical aberrations fit this "spot". The closest ting I see here is an inconsistency of a similar nature that occurs in wide angle lenses whereby a split neutral density is supplied with the lens to correct this problem. Interesting how flare seems to be surrounding the spot.

Wish I can do better.

Ed

[Rense]

I think it is really due to a reflection from the image sensor back to the lens, due to coatings on the sensor.

Could you test the lens on a film camera, the spot should disappear even at high f-stops!

I have the same with old M42 lenses on a digital camera.

[ksgal]

Originally Posted by wildmaven

Okay, I had time to play today. Aperture Priority, manual focus at infinity. Photo of the sky and converted to black and white. Here are the results:

Bottom line is this lens and your camera body are not going to work together, and it is time to think about a replacement. I thought it would go away by F11 but that is just awful! Bummer. Hopefully there is another 50mm that can work and you can acquire.

And wishes to mom on a speedy recovery!

[Ed Shapiro]

M-

Don't worry- I am sure there is a raft of 50mm primes out there that will do the job for you. Main thing now is to look after your Mom and take care of yourself- it's hard on us when the parents become ill.

Take good care! Ed

[O|||||||O]

Is the sensor on the D90 more IR sensitive than typical?

It does look like a hotspot to me, but I've only noticed hotspots when shooting IR.