Advice needed on focusing

[pikapig]

Thankful that the forum is up and running.

Had this question that is bothering me for awhile. I noticed that when i focus my lens on my camera and viewing thru the center focusing patch in the view finder, at infinity, the focusing don seems to be aligned. in fact, i need to readjust back by roughly 1-2mm thereabout from infinity to get the correct alignment. Is this normal or is there a correction required? Or is the infinity referring to a very very far distance? I tried using the focus on 2 blocks away...n it still show this prob.

This happen to all my lens.
but so far, i do not notice any out of focus to the pictures i have taken.

 

[pegasus21]

This is probably focusing beyond infinity ie negative focus i think. This is to allow for slightly badly manufactured bodies so that they can achieve focus at infinity.

Correct me if I'm wrong about this.

Anyway I'm not sure if this is normal or abnormal.

 

[jonmanjiro]

Do all your lenses have the same amount of misalignment in the same direction? If so, your camera needs a slight adjustment.

If the double image lines up perfectly just before the lens's infinity position, and then goes slightly out of alignment when the lens is focused all the way to the infinity position, you've got slight front focusing. If the double image doesn't quite line up even when the lens is focused to the infinity position, you've got slightly back focusing. I wouldn't worry about slight front focusing, but slight back focusing might show up if you shoot for example a Nokton 50/1.5 af f/1.5 and minimum focus distance.

Edited to add: 2 blocks is probably not far enough away. With my Zeiss Ikons, I need to find an antenna or something at least 1km away to check infinity adjustment.

 

[pikapig]

Hi pegasus thanks

Hi Jon, thanks for the help, its front focusing issue then. Let me try it with all my lens tonight again at a further away distance. U might be correct that 2 blocks might not be too far away.

 

[pegasus21]

I learnt something today. Thanks jon

 

[jonmanjiro]

There's currently a thread over at RFF about exactly this problem. Worth checking out! Link is below:

http://www.rangefinderforum.com/forums/showthread.php?t=102961