Infinity focus - what is right

[lahnet]

I am having some problems regarding infinity.

I have been sanding a adaptor, and I would like to hear your option. Have I gone to far or am I still not there.

The lens is Super-Takumar 50mm 1.4 and the 2 pictures are just some snapshots from my garden. Things to look at is the blue rope and the blue traffic sign i the back. There is about 20 meters to the blue rope.

Shoot at f1.4 for testing reasons.

Link to Flickr because I think full size is necessary.
http://www.flickr.com/photos/lahnet/sets/72157601583153930/

[Orio]

Not easy to tell for sure as the Tak is quite flaring. It looks correct however.
Maybe try to repeat the test stopping down a half-stop, that should be enough to remove most of the flaring while not significantly changing the DOF.

Also adviseable to make another test with a different M42 lens.

[Ballu]

To me, its perfect.. I can see the crossing sign and read the number plater (OJ--, I think).

[peterqd]

These pictures worry me slightly. My S-Tak 1.4/50 is quite a lot sharper and has less flare wide open. Is it possible you have a loose element or maybe one that's reversed? My copy was fairly soft too until I realised there was a loose lens retaining ring.

I'm also curious why you need to sand the adapter. Could the problem be because on this lens the large the rear element protrudes beyond the mount quite a lot when the lens is at infinity?

[lahnet]

You can see the focus point move further away from picture 1 to 2. Because of that I think is fair to conclude the sanding is necessary....or?

I will try to shoot more pictures tomorrow using this Takumar and a Pancolar 50mm/1.8.

I am thinking to shoot these test pictures using f2 settings on bots lenses.

[peterqd]

[lahnet]

peterqd: I can see the problem when using the adapter in the piture. Thank you for making me aware of this.

However the adaptor I use is not that type and is is impossible that this is the reason.

The need for sanding adaptors to reach infinity is quite common on Minolta and Sony DSLR.
If someone would like to read more:
http://dyxum.com/dforum/forum_posts.asp?TID=3714

I NOW have uploaded more pictures and would like you all to take a look and tell me if infinity is as good as possible.
http://www.flickr.com/photos/lahnet/sets/72157601583153930/detail/
A tripod has been used, all pics. are untouched and have the same WB.

Pictures shoot using Super-Takumar 50/1.4 : at f1.4 - 2.8 - 8
Carl Zeiss Pancolar 50/1.8 : at f1.8 - 2.8 - 8

I think i am ok but.... maybe not.

Btw. the Tak seem a little sharper than the Zeiss.

[peterqd]

Ah. Thanks, I didn't know about this problem with M42/Minolta adapters. It's surprising they're so inaccurate, is there a reason or are they just poorly made?

The focus looks fine to me at f8 but I'm not sure about the 2.8 shots. It might not be a bad idea to take a little more off the thickness than you need. I actually prefer it if the lens goes slightly past infinity - I don't trust every adapter to work perfectly with every lens, and if I can't focus past infinity I don't know for sure whether I could achieve better focus when I hit the stop. But you also have the strength of the adapter to think about!

[lahnet]

I guess they just are poorly made