Central Hot Spot With Old Nikkor Telephotos . . . Is There A Fix?

[jhinkey]

I've noticed that with my 600/5.6 ED-IF AIS, 400/5.6 ED AI and 300/4.5 ED AI (both non-IF versions) that I can get a central "hot spot" that is over and above natural lens vignetting.  Even if fully stopped down I get a slight central hot spot in illumination that is impossible to remove with the vignette removal tools in ACR.

Is this central hot spot due to a slight IR or UV contamination?  Has anyone else run into this?

I know I can create a custom lens profile to counteract this, but if it's a UV or IR issue I may be able to put an IR/UV cut filter in front of these and hopefully resolve the issue.  These IRUV cut filters are not inexpensive, so I wanted to consult the group wisdom on this.

I will try to take some test photos to show you what I'm talking about, but in the mean time let me know if you have already run into this.

Thanks!

John

[Roland Vink]

I have the AI 400/5.6 ED (not IF) and have never noticed a central hot-spot, but I've never particularly looked for it either...

[longzoom]

6 years(about) ago I had almost the same issue with my old 600 on D3 body. The sensor was oiled. I cleaned it, issue was resolved. Good luck!  LZ

[jhinkey]

It's subtle, but annoyingly there, like in this image (that's been corrected a bit in ACR):



It could just be that these lenses just don't have a light falloff curve that's correctable by canned vignette curves.

Need a clear blue sky for a test background . . .

- John

[Akira]

So long as you use D200, D2X or anything newer bodies (except for some entry level models like D40), there shouldn't be any problem caused by UV or IR contamination, simply because they have efficient UV/IR cut filters in front of the sensor and thus are virtually immune to the contamination from these spectrum ranges.

The hotspot should be caused by other reasons like the flare caused by the internal reflections, fogged lens elements, smeared sensors, etc.

[Akira]

It's subtle, but annoyingly there, like in this image (that's been corrected a bit in ACR):

It could just be that these lenses just don't have a light falloff curve that's correctable by canned vignette curves.

Need a clear blue sky for a test background . . .

- John

I used Ai200/4.0 with D750, and ACR indicated that there is no correction data for the NEF yielded by the "genuine" combo.  The same may go with your MF Nikkor lenses.

[jhinkey]

I used Ai200/4.0 with D750, and ACR indicated that there is no correction data for the NEF yielded by the "genuine" combo.  The same may go with your MF Nikkor lenses.

Of course ACR doesn't have a pre-existing vignette curve for any of these old lenses, but their manual correction tool has to assume some kind of a basic curve shape/profile that you modify - if your vignette has a different basic profile shape you have no hope for correcting it no matter what settings you use.

Let me make some test images with my A7RII and D800 and compare . . .

[Bjørn Rørslett]

I found a hot spot with my 1200/112 ED-IF on the D3 some years ago. Turned out the 122 mm filter in front of the lens was the culprit and once it was removed, the hot spot disappeared completely.

If you don't use the front filter, try removing the small filter in the filter drawer instead to see if the situation improves.

[Erik Lund]

It's subtle, but annoyingly there, like in this image (that's been corrected a bit in ACR):



It could just be that these lenses just don't have a light falloff curve that's correctable by canned vignette curves.

Need a clear blue sky for a test background . . .

- John

This looks very strange! but to get to the bottom of this, you should post images without corrections,,, or it's impossible to tell what is wrong,,, I doubt the lenses are causing this - I would guess some setting in camera and/or software is causing this,,,