SGPro Focus Issues - Backfocus? Collimation?

M

msolid

Active member
I am a noob to this whole adapter thing and I recently shot my first film class project with the SGPro. I wanted to ask you a question about my footage. I noticed that certain portions appear to be out of focus.

In the screenshots that I'm attaching, the woman's hair is especially out of focus and so is the man's back of his head. I was wondering if this is just normal shallow depth of field in your opinion or if you think that there may be other issues coming into play. Did I not properly setup my SGPro? Backfocus, collimation issues?

I am using a DVX100B, SGPro Rev 3, Brevis flip and a Nikkor 28mm 2.8. I had the DVX at 2.8 and the 28mm lens at 2.8.

I'd appreciate any advice on this issue. Thanks in advance.
 

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Last edited:
Nothing looks in focus in those pictures.
Make sure you are focused on the GG.
also, looks like you should zoom in a bit more.
 
I can't tell very much from these photos either. The compression makes it really hard to see. You said you are using a brevis Flip on the SGpro ? Have you tried to use the regular tube that comes with it to see if that eliminate your problem ?
 
SilverWolf said:
I can't tell very much from these photos either. The compression makes it really hard to see. You said you are using a brevis Flip on the SGpro ? Have you tried to use the regular tube that comes with it to see if that eliminate your problem ?
Click to expand...

Wayne emailed me back and said that it's a problem with the achromat on the Brevis flip not being optimized for use with the SGPro adapter. So I guess I'll forget about using the flip and try using scopebox with the image flipped. Thanks for your help.
 
Matty_g said:
Nothing looks in focus in those pictures.
Make sure you are focused on the GG.
also, looks like you should zoom in a bit more.
Click to expand...

How can you tell from these pics that I haven't zoomed in enough? Is it the vignetting or is there something else in the image that makes you say that? I'm just asking because I'd like to know what to watch out for in the future.

I zoomed in pretty far (I think it was Z95 on my DVX). How far in do you go when you use the SGPro with your HVX?
 
Actually, Leonard Levy had the SGpro working very well with our flip. There's a thread over in our forum with his findings. We've also had a few M2 folks using it.

Cheers,
Dennis Wood.
 
msolid has explained to me in his PM that he has edge to edge sharpness issues (with 35mm lens removed, GG stationary to focus on the GG grain). With the centre in focus the edges will be out of focus. This is means that the achromat is simply not optimized for this setup and distance.
 
Our flip/achromat system is optimized to an image within a given target range from the flip exit face...and with the M2, and GS, you should be in range. If there's a long lead tube attached to your unit, remove it (see Lenny's illustrations). Two other things to check:

1. Is the flip properly aligned with the camera? In other words, with just the flip attached (no adapter) the image coming through the flip unit should show the edges vertical and horizontal relative to the camera's frame. Now attach the adapter and make sure the XY adjust is done. Our flip has two XY adjustement points....check our Video University for clips on how to do this effectively.

2. With no 35 lens attached, focus so the right edge of the frame is in focus. Assuming field focus curvature is there (and I don't believe with our flip and this camera you'll see this), if the SG spinning disc is perfectly aligned, the left edge will be in focus too. If the spinning disc is not perfectly aligned perpendicular to the optical plane, the right edge will be in focus, but nothing else will be. Post up a frame grab if you can with the right edge in sharp focus, then one with the center in sharp focus (unit off). Repeat with the unit on. Should be a snap to diagnose this.

3. Make sure your 35mm lens mount is collimated correctly to the SG spinning disc...46.5mm for Nikon lenses.

Give us a call during the week (9 to 5 EST) if you need more assisance :-)

Cheers,
Dennis.
 
I've used the Brevis flip on every adapter (except Letus obviously) with good results. I never did Rez charts or anything scientific but I can say that it was not soft and had no issue mounting to the adapters.

Simple step-up/down rings did the job (but try to use as few as possible).

Heres a link to an SG-Brevis and Redrock-Brevis music video we shot a few months ago. Not exactly great online stream quality but actual video was very acceptable for broadcast:
http://www.mtv.com/videos/blowing-trees/235008/the-day-the-world-left-me.jhtml#artist=2578442
 
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