Technical aspects of the AFS 300mm f/4 E PF lens

[Øivind Tøien]

The result with the 300mm PF and extension gave a huge hotspot, not usable as predicted.

Interestingly I find no hotspot with my 300PF mounted on PN-11, with or without TC-14E between the lens and PN-11, there is almost no light falloff at all. But then I could only test at nominal f/4 and on a DX sensor. At what aperture did you notice the hotspot? Vis. light or IR?

"Just read the description on DPR, they are missing a crucial point in the description of how to modify the TC to make it work properly..."

So what is the crucial point? A stepwise description here would be much appreciated.

[Bjørn Rørslett]

The 300 PF does hot spot in IR on its own (D5300).

Please guys, if you want to discuss issues and questions relating to the 300 PF, open a new thread under Lens Talk for that purpose. I then can move over relevant posts from this thread.

[Erik Lund]

Mixed light, about 1.8 meters - The point is; the lens optics is carefully designed for a specific flange to sensor distance, with IF floating elements moving the optics around in the lens, it would require more than a miracle for any long extension to work for this kind of lens. IMHO

[Øivind Tøien]

This thread was opened for technical discussions of the  AFS 300mm f/4 E PF lens, like consequences of E-aperture, possible solutions for use with extension tubes, IR issues, focus and VR performance etc. Content was moved here where it is more appropriate.

[Øivind Tøien]

Mixed light, about 1.8 meters - The point is; the lens optics is carefully designed for a specific flange to sensor distance, with IF floating elements moving the optics around in the lens, it would require more than a miracle for any long extension to work for this kind of lens. IMHO

Oviously my experience on a DX sensor differs. Wide open with PN-11 only similar light falloff is seen as in regular use.  Below thumnail captures at roughly  1m (close focus), 1.5 and 2.5m (furthest focus), and this result is regardless of color temperature (indoor light and PC screen).  Same with IR, no hotspot with PN 11 or lens used naked, close or far (previouly posted). But again only wide open possible with PN11 or my D40x.



Thus it is an important question: How much did you stop down before the hotspot showed? (Any filter attached?) For instance if there is a hopeless hotspot at f/8 in visible light with converted TC-20E extension tube, it isn't really much point for me to get it for the 300PF as I already have a chipped PN-11 for my 105/4.

Only focus set to closest distance on the lens gives optimal results with PN-11, but then they are good to excellent, and in particular considering that the lens could only be used wide open. (Sorry for the boring test subject, which incidentally came with the unused monetary gift that allowed me to buy the lens    ;  I tend to be given teddy bears because of my professional work with hibernating bears).

300PF/PN-11 at close focus wide open (whole frame)



300PF/TC14E/PN-11 at close focus wide open  (whole frame)


300PF/TC14E/PN-11 scale at close focus wide open (whole frame, all with D5100)

[Øivind Tøien]

It is worth noting that the firmware update for D750 that was just released is listed to improve VR performance. Several dpreview members have reported an improvement with the 300PF on the D750: http://www.dpreview.com/forums/post/56843370

Repeated handheld tests I performed last night with 300PF on my D5100 at about 3 m distance did show a very slight (only seen at 100% view) but variable vertical only blur component in 1/100-1/200s range compared to repeated captures at 1/20 - 1/60s  that were more consistent and somewhat crisper on average. At 1/15 s it was harder to get quite as consistent results, but then the blur was more random in all directions with the less successful captures. While this is a far too subtle effect (tripod use with VR off without mirror up and inadequate exposure delay can create a lot more blur) to be called a defect, one can wonder if there will be firmware updates for other bodies that can further improve the VR performance in this range.

Edit: While some dpreview members reported improvement with D750 after firmware upgrade, one or two claimed it did not make things better for them. The image example posted had at least of a whole magnitude more vertical blurring than the little remnants I describe above. But then it is very hard to judge anything like this from single posted example images, one need the impressions provided by repeated tests. The after working fix images do not have less blur than the results I get with D5100 at these speeds, so again what I described in the above paragraph is nitpicking. It is rather remarkable that it is possible to get consistent results at 1/20s.

[Bjørn Rørslett]

Must go through my field notes again, but from memory the IR hotspot with the 300 PF on my IR-modified D5300 commenced around f/8.

[Øivind Tøien]

Thanks. What about visible light; at which aperture did the hot spot start to show up with the TC-20E modified extension tube?

[Erik Lund]

Wide open...

[Øivind Tøien]

Thanks, Erik, I think you perhaps just saved me from spending $100 or so on a used TC-20E.
The difference to my results with PN-11 is interesting. Could there be internal reflections in the modified TC-20E? (Could be fixed by adding flocking?) Or is there some sample variation at play (could be confirmed by testing that copy of the lens on PN-11)? Or is the extension with TC-20E longer, and thus changing  the properties? I just tried testing the latter by adding a 12mm Kenko tube to PN-11, but still no hot spot. Or perhaps there cold be some differences as to how the lens interacts with different bodies and sensors.

[Erik Lund]

Yes internal flocking - I really just don't like the rendering... I did a couple of images more with the D3X and the 300mm PF works nicely in some shots with the TC-20E glass less 52.26mm extension for a few images.
VR works AF works I still get from time to time a strange rendering and what I call hot spot seems to get much worse stopped down...

So why not use the Micro Nikkor 105mm 4 Ais it feels at home with this combination Or a 200mm Micro Nikkor if you need more distance.

[Erik Lund]

BTW, the tip removing connection on contact #10 on the lens side on the glass less TC-20E works very nicely, Any AF or chipped lens now reports a real focal length and the wide open aperture value.

VR and AF is retained although the AF tends too overshoot, Doesn't matter since I will mainly use it for MF.
Thanks1

[Øivind Tøien]

Erik, thanks for further information.
The inspiration to use a 300/4 for macro like purposes partly comes from the late Ronny Gaulbert's excellent images. His Pbase account is gone, but there are some images here:
http://www.photoportfolios.net/portfolio/pf.cgi?a=up&pi=RONNIE
and here:
http://photo.net/photodb/user?user_id=522962
Bug images here:
http://photo.net/photodb/folder?folder_id=263165

I think what is gained is an even more pronounced subject isolation due to the larger magnification of the background, but pretty much the same depth of field at the same scale as shorter lenses. For hunting dragon flies and other skittish subject, the long working distance is convenient. It is possible that a TC-14E is enough to get to the right scale with a little cropping. Ronney Gaulbert used AFS 300/4 ED (non-VR) with PN-11 on a D200 and sometimes an additional  shorter extension tube. He typically stopped the lens down quite a bit, shot with tripod in early morning using pretty long shutter speeds, for instance one of my favorites, the Robbber Fly image was captured at 3 seconds @ f/16, ISO-100; great subject isolation in spite of a quite stopped down lens.

Regarding strange rendering with 300PF and the glass-less TC-20E, perhaps turn VR off?


 

[Erik Lund]

The first test images was without VR.

I think a TC-14E is too short to give much for a 300mm.

Well, I have the extension tube now and will use it from time to time - lets see if I grow to like it with some use.

[Øivind Tøien]

TC-14E as TC, not glass-less.