NikonGear'23

Gear Talk => Lens Talk => Topic started by: Tristin on March 12, 2016, 23:30:20

Title: Infinity focus adjustment
Post by: Tristin on March 12, 2016, 23:30:20

I recently dissembled my Nikkor 105mm 1.8 and had to take apart the focus ring to clean a helicoid.  This meant putting it back together as closely as it was prior as I could, since it sets the infinity focus.  Today I tested it out.  Aiming at a radio tower probably around 8 miles away on a tripod with magnified liveview, I set the lens at f/1.8 and found that it was focusing in just a bit before the lenses infinity hard stop, hitting the infinity hard stop threw it out of focus somewhat.  I have two questions.

Was this a good testing method? 

Does my result entail any performance degradation I am unaware of?  I am assuming I am losing a bit of close focusing distance, but I am just guessing.

Title: Re: Infinity focus adjustment
Post by: pluton on March 13, 2016, 07:45:50

I have used this method with my "Scotch Tape Infinty" lenses, the 135/2 Ais and 84/1.4 Ais.  As I recall, the taped rings were directly under the rubber focusing grip, so easy off, easy on.
 If it's the same on your 105/1.8, remove the tape, adjust infinity, and replace the tape. 
The nice thing about the Scotch tape lenses is that you can go back and re-adjust infinity without taking it to a shop.

Title: Re: Infinity focus adjustment
Post by: Erik Lund on March 13, 2016, 16:31:15

Quote from: Tristin on March 12, 2016, 23:30:20

,,,, found that it was focusing in just a bit before the lenses infinity hard stop, hitting the infinity hard stop threw it out of focus somewhat.....

How much is a bit on the scale on the lens,,,

ED lenses focus past infinity so does many other lenses,,,

Title: Re: Infinity focus adjustment
Post by: richardHaw on March 13, 2016, 16:44:41

i was told that this focusing pas infinity by a bit thing was done on purpose to accommodate glass expansion when the glass is hot under the sun  :o :o :o

you can change that easily by adjusting the numbers and then taping it back  ::)

on series E lenses and many 80's Zoom-Nikkors, it's another story.

Title: Re: Infinity focus adjustment
Post by: Erik Lund on March 13, 2016, 16:59:25

Quote from: richardHaw on March 13, 2016, 16:44:41

i was told that this focusing pas infinity by a bit thing was done on purpose to accommodate glass expansion when the glass is hot under the sun  :o :o :o

Yes it is, for ED glass.

Title: Re: Infinity focus adjustment
Post by: Akira on March 13, 2016, 18:15:15

Ais 105/1.8 doesn't use ED glasses and should have the infinity stop right at the infinity...

Title: Re: Infinity focus adjustment
Post by: simsurace on March 13, 2016, 20:27:44

Doesn't non-ED glass also expand?

Title: Re: Infinity focus adjustment
Post by: Erik Lund on March 13, 2016, 21:07:33

Not to a point where its a problem.