CO 60/4.0 with K4+K5 on front for Hotspot Cure

[Andrea B.]

I made these yesterday with the old Nikon K4 and K5 extension tubes added onto the front of the lens. The BaaderU was added on top of those. I see no evidence of a hot spot with this extension. But more testing is needed because I have read the suggestions from Bjørn's and Enrico's work in hotspot prevention for this lens.

 

Equipment [Nikon D600-broadband + Coastal Optics 60/4.0 + Sunlight + Front Extension Tubes as described]

All conversions & edits were done in Photo Ninja.

Crop & resize for posting was done in Photo Mechanic (whose re-sharpening is just a bit too much on some edges).

It was late afternoon and slightly overcast, so UV had decreased.

 

Visible [f/16 for 1/100" @ ISO-200 with Baader UV/IR-Cut Filter]

 

Visible [black & White]

 

Ultraviolet [f/16 for 8" @ ISO-200 with BaaderU UV-Pass Filter]

It still astounds me just how much texture and surface detail is revealed in UV.

 

Ultraviolet [black & White]

 

Ultraviolet [straight out of Camera]

[nfoto]

An efficient hood for the (Coastal Optics 60 mm f/4 APO) is built in a few seconds.

• Put K4 on front of lens
  
• Put Baader U filter inside the K4. The filter 'crown' (retaining ring with scalloped rim) will rest on a small ledge on the inside towards the rear of the K4.
  
• Put another K4 (or K5) on the first K4 and screw it home. This locks the Baader U in place. Should you find the filter rattles a little too much, put a thin shim inside. I usually don't bother.
  
• For landscapes, no further measures are required. You will have a nice and contrasty image.
  
• For close ups, put something that narrows the opening further on top of the K-rings. This could be anything with 52 mm male threads ending in 40.5 to 42 mm, such as a step ring. If the thread gender doesn't match, use a 'transgender' item such as a male-male 52 mm macro coupler, very cheap on eBay. Whether the narrowing ring ends in male or female threads is not relevant unless you want to add more filters. I have made test shots down to f/45 with this hood setup and there is no trace of a hot spot.
  

Add a K3 and a K2 to the bottom of the filter cell if you wish to have a quick-release of the filter(s).

 

One would expect such an expensive lens to be delivered with an efficient hood, but strangely enough this is not the case. However, most camera tinkers, and that applies in particular to UV shooters, tend to have bins with odds and ends floating around. Besides, the K-ring sets should be considered mandatory any way. They literally are the 'Lego brick' equivalent.