Redrock M2 and the A1

S

scenedirector

Well-known member
Okay, I haven't gotten a straight answer about this yet. Some say you need a spacer, some say you don't.

I can't get a sharp focus with the entire screen filled with the image, rather than the motor in the M2 housing unless the A1 is pulled away from the housing further than the rubber hood will allow.

Can someone give DETAILED instructions, i.e. what zoom number, how far from the housing, all that good stuff in how to get this rig operational.

Any help would be greatley appreciated! Thanks!
 
here's what i've found playing with the m2/a1 off and on for a little while. some lenses, like my FL primes, don't require a spacer. with my zoom set at 69 and my focus at 0.3, there is no vignetting and i can get a nice, sharp picture. on the other hand, some of my FD primes and zooms need a spacer. the exact numbers seem to vary going from lens to lens. to cover all the lenses i have, i've started using a spacer. 1/2" should be more than enough (tho i've been using a 1 1/2" spacer recently to do an in-camera crop of a circular fisheye). you'll want the shortest spacer you can get away with -- because the a1 lens, like most zoom lenses, is variable aperture, so the more you zoom, the less light gets to the camera.

needless to say, setting backfocus is key. take the 35mm lens off the m2, point the setup to an area with some variation in light, close the iris a bit so the cam isn't blasted with light, and use the focus assist tools, particlularly peaking, and an external hd monitor to get the ground glass in focus. then attach the widest 35mm lens you own to the m2. even if you were nicely focused on the ground glass, the image may look a little soft when it shouldn't be. make the minor focus adjustment on your a1 until your focus is perfect. once your focus and zoom are good to go, use your zoom and focus presets to save them. that way, in case of an accidental bump, perfect focus and zoom are only a click and push away.

hope that helps.

EDIT: i should add i've been using the HD achromat. i would guess that there would be some variation in the settings between the SD achromat and HD achromat, but the procedure for setting backfocus is the same.
 
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hi there!

we're playing around with our g1 and the m2 for two days now. we're using the HD achromat, nikon lenses and a marshall monitor.

the m2 and the g1 are close to each other, the rubber fits very well. we had to shim the g1 about 3mm up to get a nice "centered" picture on the m2's ground glass.
the focus of the g1 is nearly at its closest. we're zoomed in about the half way i think.
i dont know if this is normal but we have to close the g1's iris to 9,5 which is the last step before its fully closed. otherwhise we can't get a sharp image even when stepping down on the nikor or pulling its focus.
i've to add that we were only shooting in our test environment yet with a few lights set up. tomorrow we'll be doing the first outdoor tests in hopefully bright sunligt.

would be cool if other a1/g1 - M2 users could provide some information about their setup. its interesting how different they are. sry for my bad english, im from europe. :)

greets,
cya
 
stopping down to f9.5 is not normal and is basically telling us that you are not able to focus at the right distance for how far you need to zoom in. By stopping down that much you are making your focus plane able to focus sharply on the ground glass, but you should be able to focus on the glass without having to stop down that much. It sounds like you may need a spacer tube.
 
"I can't get a sharp focus with the entire screen filled with the image, rather than the motor in the M2 housing unless the A1 is pulled away from the housing further than the rubber hood will allow."

Yeah, I'm having to distance the camera with the HD achromat just beyond the rubber hood. I'm not worrying too much about it at the moment since I just wrap some black gaffer tape around it to cover the small gap.
 
thx for the info!
when we started testing we had the g1 at about 1,5cm distance to the rubber hood. at that distance we were able to focus on the ground glass, but the iris was at f9,5 too.
seems like we have to move back even further and need a spacer tube. the problem is that if the m2 is that far away and we move the camera, the whole rig is shaking. so does the picture we get from the m2's gg.
we didn't hear anything about that yet, so it may have been the result of poor balancing. Chris Santucci's rig seems to work properly. we're using redrock's rails and follow focus.
we're a little confused now because in early posts people were telling that they put their m2's very close to the camera. they didnt say anything about problems with the iris of their a1/g1.

maybe somebody with a nice working setup could post a picture of his rig. so that we get an idea of where things should go.
we'll do some more testing tomorrow. today it was way too foggy for shooting outside.

cya
 
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"when we started testing we had the g1 at about 1,5cm distance to the rubber hood. at that distance we were able to focus on the ground glass, but the iris was at f9,5 too."

As already mentioned here, you definitely SHOULD be able to focus on the GG with a wide open iris. If you can't, you have something not set right. Fifteen millimeters sounds a bit far I'd say. It sounds like you need to find the right combination of focal length, and camera placement to get the distance to where you can focus on the GG correctly.
 
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