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Shilesh Jani
30-Nov-2003, 12:14
Hello All,

I am fairly new to LF, and have been using my gear with a modicum of sucess. One thing that perplexes me is that I have used the Nikkor M300 mm, f9 lens on both close-up distances (~ 3 feet) and at infinity. My results are much better (tack-sharp) for close-up work. The infinity shots are comparatively soft. What is up with that?

Regards.

Shilesh

Roy Harrington
30-Nov-2003, 13:05
Hi Shilesh,

I've always had very good results with my 300-M so this is surprising. The lens is optimized for longer distances. Are you by chance using a thick lens board that is interfering with the element separation? That lens is physically pretty short and the back element screws down very close to the retaining nut.

Roy

Michael Kadillak
30-Nov-2003, 14:52
My 300 M Nikon is extremely sharp at infinity. If the elements were not in the correct position (spaced) on the lensboard, I believe it would have an adverse optical effect for any shooting situation.

I would verify a series of variables that I feel could be the problem with your 300M. Is you focus position locked down tight? By chance did the camera shake during the exposure? By chance are you using camera movements with your infinity shot? Most novice LF shooters go overboard with movements and that could be your softness.

As accurately as possible, put your front and rear standard parallel to each other and make a real infinity exposure of a far distant subject and I will bet you it is where it should be.

Good Luck!

Shilesh Jani
30-Nov-2003, 15:10
Hello Roy & Michael,

I checked the mount on the lens board and here is what I found. (1) the rear element was slightly loose, (2) I seemed to have screwed on the retaining ring in the wrong orientation, i.e., the radiused end was towards the front of the lens. Either one may have contributed to my problem. Additonally, after proper remounting, I found that the maximum length of the lens is approximately 0.5 mm longer when mounted on my Zone VI Copal 1 lens board than when the lens is unmounted. Does it make sense, though that the lens was screamingly sharp at close distance?

I guess I had better check the mounts on all of my other lenses. Hate to have my shots ruined because of my sloppy mounts.

Thank you for your quick help.

Regards.

Shilesh

CP Goerz
30-Nov-2003, 16:17
Did you re-focus the lens? ;-)

CP Goerz

Guy Boily
30-Nov-2003, 18:09
I had a similar problem when one of my friends was using my G-Clarion 300 f9. I had tack sharp images and his were fuzzy and sometimes downright aweful. I had a soft Nikon cable release and he had a stiff rubber cable. When he pressed on it to release the shutter the front lensboard moved each time. He applying way too much force on the cable. Check that out Guy Boily

Roy Harrington
30-Nov-2003, 20:41
Shilesh, if you are finding the lens longer on the lens board than by itself, this is definitely a no-no. Element spacing is important -- (maybe it's more important at infinity than closeup for this lens design?). The issue with the 300-M sounded a little familiar and now I remember trading that radiused lock nut for a thinner one when I put my 300 on a thickish lensboard. Does the lip on the locknut fit into the hole in the lensboard? When you screw in the back element it should not come in contact with the locknut before bottoming out.

Roy

Shilesh Jani
1-Dec-2003, 06:02
Roy,

You are absolutely right. The back element does indeed come into contact with the lock nuut before bottoming out on the rear element. I am having a machnist grind the lock nut thinner so this does not happen anymore. I checked the rest of my lenes, and they are just fine (phew). Thank you for the tip. I will check for infinity focus before and after the machning just to confirm.

Regards.

Shilesh