Question on a 15mm f/3.5 ai-s

[Fons Baerken]

I have a 15mm f/3.5 ais here at my disposition with a rear bajonet filter type A2 attached, when i take the filter out it doesnt focus beyond less than a meter.
Strange, in my opinion the filter should not interfere with the focus just give it a warmer tone?

[Bjørn Rørslett]

That is not correct. As the filter is part of the optical system (by virtue of being in the light pathway) it most definitively will influence focus. Expect a focus shift approx. 1/3 of the filter thickness. Perhaps not much in absolute figure, but for a short focal lens such as the 15 mm, that will throw infinity focus well and truly off, as you already discovered.

[chris dees]

Should't you replace it with a clear filter? As with the 16/2.8 AI-S fisheye.

[Bjørn Rørslett]

There is an L1Bc filter as part of the standard kit for the 15/3.5. Use that filter or do an extra click-white if the A2 is deployed.

The 15/3.5 uses the identical filter kit to the 16/2.8 Fisheye.

[Fons Baerken]

Thanks for the clarification.

[pluton]

Nikon made (makes?) both an L1Bc (very pale magenta "skylight") and an L37c (close to colorless) for that 39 bayonet mount. 

[Bjørn Rørslett]

True, but I think only L1BC was delivered with my 15/16 mm lenses.

L37C is practically worthless in terms of any UV attenuation, but it does serve a purpose in ascertaining the correct focus.

[Fons Baerken]

Searching on the internet the availbility of  these filter sets brought up nope, may have to get a nikkor 16mm fisheye for that ; without the corrective glass element  the minimum focal distance shortens.

[Bjørn Rørslett]

Why not continue to use the A2? in the digital era, correcting w/b is a breeze.

[Bjørn Rørslett]

By the way, the filter set is delivered in a leather pouch labelled CA-2.

[Fons Baerken]

Why not continue to use the A2? in the digital era, correcting w/b is a breeze.

True, driven by curiosity i suppose.

[David H. Hartman]

True, but I think only L1BC was delivered with my 15/16 mm lenses.

L37C is practically worthless in terms of any UV attenuation, but it does serve a purpose in ascertaining the correct focus.

The L1Bc was part of the standard filter set and installed on my 16/2.8 AIS Fisheye.as delivered. If memory serves me the L1Bc is approximately a CC025M filter.

The L37c was an available extra cost option. It doesn't add a yellow tint as it's very close to colorless. The L37c may be hard to find used. I may have had to special order mine.

Dave

[Peter Forsell]

By the way, the filter set is delivered in a leather pouch labelled CA-2.

Yes! That "CA-2" was the magic word. I got curious too and tried to find the filter but couldn't. But with "CA-2" as the search phrase there's plenty of them. This is just a random pick (not in Europe):

http://www.ebay.com/itm/Genuine-Nikon-39mm-Bayonet-Filter-Set-B2-O56-A2-for-13mm-15mm-f-3-5-16mm-f-2-8/322446736554?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140602152332%26meid%3De0aa9e58155a424bb56a58fe91d61978%26pid%3D100011%26rk%3D1%26rkt%3D1%26sd%3D321745333040

[Bjørn Rørslett]

Do note the complete kit should comprise 4 filters.

[Akira]

Those rear filters are still listed in the online catalog of Nikon.  L37C is readily available at some large retailers.