How do you adjust M2 ground glass?

cardmaverick

cardmaverick

Well-known member
I recently started setting up a brand new M2 at work for our HVX. I got everything perfect...except focus on the ground glass. I can get the center of the frame to have sharp focus on the ground glasses grain, but my edges go out of focus. I also have a hard time focusing on far away objects with my 85mm 1.4 Nikkor lens, and well, any of the lenses I tried (all prime 1.4 Nikkors).

After many hours of online searching here, and at the M2 forums, I found people mentioning adjusting the ground glass. My big question is how???

I took it apart and looked at it. Exactly what do I do to adjust it? I see its held on to the motors spindle by a screw and nut. Do I just use pliers to hold the spindle still and unscrew the nut? I'm woried about scratching the glass. And when I get it off, what then? The directions that came with the unit are a bit sparse in this area....any help would be greatly appreciated, and I'm not giving up! I've seen too much awesome footage from this duo to give up now.

Thanks!
 
LOL, I'm doing that too, figured I'd double dip and get as much advice as possible, I even emailed redrocks support. They say in the manual that there is a customer support forum...to bad the link is dead! I emailed redrock asking about how I can get there.
 
You may not have to make any internal adjustments just yet. How close is your achromat to the actual M2 housing? Try adjusting that distance whether further or closer then you are now and see if that makes any difference. If that doesn't do it, then here is the link to the extra tutorials over at redrock: http://www.redrockmicro.com/tutorials/adjustments.htm. if you can't access the customer service forums, it is probably because you arent authorized yet, so PM Brian or one of the other moderators to let them know you don't have access and they should help you out. I'd suggest first adjusting the motor all the way down as that should definitly help to decrease the amount you have to zoom in and will help a little in achieving better edge to edge focus. If you've found that lowering the motor, and adjusting the distance between the achromat and the M2 housing still leaves your image with undeseriably soft edges, then go ahead and make the ground glass adjustment.
 
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I concur with macintosh . Get the distance right and that should solve the center vs. edges issue. it will never be perfect but you should at least be focusing on them at roughly the same time. You should be focused at about F15. This is the M2 back-focus adjustment

The next issue is whether you can fill the farme with the ground glass at Z75 or so. iof not you may need to lower the motor or even offset it a bit.

The last issue is harder. Are your lenses focusing on the grd glss correctly. this is a nikon adapter back-focus distance question.
Your footage ##'s should focus approximately in the right place, zoom lenses should track. Infinty should be accurate etc. all at wide open. if this is way off you have a problem that will be slower to fix.
 
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