Welcome to our community

Be a part of something great, join today!

Log in
  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Nikon Mount is askew

danbrazda

danbrazda

Well-known member
Joined
Jan 29, 2008
Messages
208
Reaction score
0
Points
16
Age
66
Location
Richmond, VA
Website
www.vcutvhd.com
I have the Red Nikon mount and all 6 of my nikon lenses show focus falloff on the same side of the frame. I know some of you have had to shim the mount to get it to hold the lenses tighter but has anyone had to shim just one side to compensate for the mount not being flush all the way around?
 
Yes, as Shane said. Something is not allowing your mount to sit flush, and it's probably that you have pinched the i cable somewhere, or perhaps something else is interfering.

Syptom of loose springs are a lens that doesn't feel tight when mounted, not the "focus falloff" you describe.
 
Douglas Underdahl said:
Yes, as Shane said. Something is not allowing your mount to sit flush, and it's probably that you have pinched the i cable somewhere, or perhaps something else is interfering.

Syptom of loose springs are a lens that doesn't feel tight when mounted, not the "focus falloff" you describe.
Click to expand...


Just removed the mount and the iCable is where it should be. In fact, now that I think of it, the Nikon mount has not been removed since it was installed at Red so I guess this shouldn't surprise me. Here's a link to a chart I shot after putting the mount back on. Lens is Nikon 50mm, stop is 5.6.

https://www.box.net/shared/static/1f58s2glz1.tiff

I have done the same test with 6 different lenses and all results are the same. Am I over-reacting?
 
I'm not seeing what you're seeing. Also,I'm pretty sure that those focusing charts were designed to be used independent of each other.
Try shooting a brick wall or a newspaper taped to the wall and open the lens up to its widest, it's hard to see any issues at 5.6.
But,yes, you may be over-reacting.
regards,
Shane.
 
Shane Kelly said:
I'm not seeing what you're seeing. Also,I'm pretty sure that those focusing charts were designed to be used independent of each other.
Try shooting a brick wall or a newspaper taped to the wall and open the lens up to its widest, it's hard to see any issues at 5.6.
But,yes, you may be over-reacting.
regards,
Shane.
Click to expand...

Here's a blowup from mid-frame to frame-left (cam was definitely perpendicular to chart):
 

Attachments

  • 50Type.jpg
    50Type.jpg
    42.6 KB · Views: 0
Could be a lot of different issues.
Too many variables for me to make an educated guess.
Could be the camera, could be the lens, etc...
One question:
If you were to bring the left side into focus, does the right side go out of focus similarly?
 
Matthew Duclos said:
Could be a lot of different issues.
Too many variables for me to make an educated guess.
Could be the camera, could be the lens, etc...
One question:
If you were to bring the left side into focus, does the right side go out of focus similarly?
Click to expand...

Yes Matthew, when I focus on the left 1/3 area of the frame, the right 2/3rds goes soft. I think I can rule out the lenses because I have checked them out on two other cameras and they are sharp everywhere.
 
another simple test

another simple test

Shane Kelly said:
I guess the next thing to check would be to put the PL mount back on and use a PL lens to see if the results are duplicated. The sensor may be out of alignment (if that is possible). Just a thought.
Click to expand...
If you can mount the Nikon mount upside down try putting the lens on and see your results:
If the softness stays the same it means sensor if it reverses it means lens/mount combo.
Optimator makes it really easy to see with the rotating neutral mount:001_tongue:

Edit: Beat you to it, Doug:001_tongue:
 
Dan - remove the Nikon mount, then put it back on upside down. If the results are reversed, then it's the Nikon mount. If the results are the same, then perhaps the sensor is out of alignment . . .
 
I have a set of super speeds with me on Tuesday so I can check the PL Mount then.

But yes, the upside down Nikon Red Mount would be worth a try tomorrow morning. Looking forward to getting a more solid Nikon mount on here (assuming it's not the sensor).
 
Dan,
we had the same problem on a shoot. Couldn´t figure out what it was. Sometimes it happend, sometimes not. Back home I discovered a tilt play of the lens. Got after several advises rubber bushings from Red for the nikon mount. When I was mounting them I discovered that I already had one bushing in one spring feather, which I didn´t see before (tiny and squezed) but not in the others. After all 3 spring feather got there rubber bushings the mount is tight and I don´t have the effect of falloff anymore.
Have a look, maybe you also miss one or two rubber bushings in the spring feathers.


Marc
 
Marc Berger said:
Dan,
we had the same problem on a shoot. Couldn´t figure out what it was. Sometimes it happend, sometimes not. Back home I discovered a tilt play of the lens. Got after several advises rubber bushings from Red for the nikon mount. When I was mounting them I discovered that I already had one bushing in one spring feather, which I didn´t see before (tiny and squezed) but not in the others. After all 3 spring feather got there rubber bushings the mount is tight and I don´t have the effect of falloff anymore.
Have a look, maybe you also miss one or two rubber bushings in the spring feathers.


Marc
Click to expand...

Thanks Marc- I'll check it out in the morning and re-post.
 
OK, I think I've solved it (thanks to Marc). After closer inspection, only 2 of the 3 springs have bushings in them. Getting replacements sent from Red as we speak. Hope I'm not over-confident here but this issue may be history.

Thanks again Marc! Gotta love this forum.
 
Bad news. I swapped out the Nikon mount for the PL mount and did the same test. Exact same results as with the Nikon. Camera will be going back to Red for sensor block test. :crying:
 
OK, now I feel like I'm going crazy. I sent the cam to Red, they were awesome as always and turned it around in less than a week. They said: "We shimmed the camera, took it into repair, and it passed our outbound specifications".

I repeated the exact tests I posted earlier in this thread and the results were identical. Focus falloff cam left side of frame. Help me out guys. Am I nuts? Are my tests somehow flawed? I actually hope they are and there is a simple explanation that I am overlooking.

:crazy:
 
danbrazda said:
OK, now I feel like I'm going crazy. I sent the cam to Red, they were awesome as always and turned it around in less than a week. They said: "We shimmed the camera, took it into repair, and it passed our outbound specifications".

I repeated the exact tests I posted earlier in this thread and the results were identical. Focus falloff cam left side of frame. Help me out guys. Am I nuts? Are my tests somehow flawed? I actually hope they are and there is a simple explanation that I am overlooking.

:crazy:
Click to expand...

If RED says everything is good with the camera, maybe you should have the lens checked out.
 
You must log in or register to reply here.
Back
Top