Letus streaks

D

dlee_ultra

Member
I'm noticing a bunch of diagnol streaks on the GG of my letus extreme. On the Letus forum, several people have seen the same thing. I've tried keeping the f-stops on the camera & lens between 2.4 - 4. One person on the forum had the motor & GG replaced but still no fix. Here's his test shot that looks like what I'm getting:

http://www.vimeo.com/1031057

Anyone else see this & has actually found a solution? I guess I'll have to submit a support ticket but wondering if there's a real solution for it.
 
First off, it looks like you have something on the Condensor. Youll notice on the lower left side of your frame, there is a dark spec. This looks like dust on the piece of glass behind the GG.

Also, You should not be seeing the GG THAT much at F4. At F5.6 i would expect it to be that visible, but nothing below.
 
If you've got calipers, a toothpick, and some guts, you should open up your LEX, take off the GG and look at the condenser.

Honestly, I'd email your video to Hien and see what he says. Little things like that (dust on the condenser) made me grow a pair and disassemble my LEX entirely. It was a nerve-racking 50 minute round trip, but it saved my shoot.
 
my LEX footage looks just like that even after cleaning the condenser. I am using a 2.8 canon FD zoom lens and I get that same effect no matter what I do.
 
neil, the condensor issue was due to the black dot i saw on the footage, not the streaking.

the streaking looks like hes stopping his lens down, or that his vibration isn't doing the GG justice.
 
I know what your saying papa about the black dot, what i was trying to say is that my LEX with my 2.8 zoom lens at wide open makes streaks just like dlee's. I myself have not been able to get rid of the streaking problem. I haven't tried any prime lenses yet only zooms so it could just be my lens.
 
i am getting these streaks, but only on pretty well exposed subjects and certain colors are they really apparent. i took it apart and used some condensed air for cleaning and to no avail, but i am going to continue experimenting
 
Someone on the Letus forum suggested applying hot glue around the tip of the motor shaft similar to what's shown here:

http://web.mac.com/stevecahill/Steve_Cahills_Blog/Blog/Entries/2008/1/6_Letus_Autopsy_1.html

Instead of applying glue, I put a small amount of silly putty around the tip of the motor shaft. Most of the streaks went away, although I still see some grain from the GG; so I get that "as if I'm looking outside through a window" look. I'll try experimenting more on the weekend. Maybe more silly putty will work better.

To look at the motion pattern of the GG, it was also suggested to speed up the shutter. I used 1/500 and noticed the pattern was more of a diagonal back & forth motion before the putty. Is the circular pattern the ideal pattern for all vibrating GG?

I'd like to know if anyone else can get better results. Be careful not to put glue/putty on the front tip of the shaft. When I did, it stuck to the clear screen between the GG and lens mount. Lucky I was using putty instead of glue. Keep it to the side like the picture.
 
What Streaks??

What Streaks??

I do not have the best computer monitor available to me at the present time. But to me these posted clip images look terrific!!! I am struggling to find any streaks. Is there another way to describe what I should look for?
 
Last edited:
I think dlee is onto something about the GG's motion. It seems more lateral than circular. I can't imagine why the motor would favor a specific direction, but there are lots of things I'm unable to imagine :)

Time to call Hien, methinks.
 
Good call on the hot glue Im going to try that tonight and see if it helps. I have a shoot this weekend and would really like to be able to use my LEX.
 
perhaps it is just me, but through the explanations, i am still curious to know what the glue does at the end of the motor?
 
The glue is enough to change how the motor affects the vibration. Think of it as this: hold you arm out straight & make small circles w/ it. Now hold a coffee cup by the handle w/ the same arm & do the same thing. Your muscles had to adjust to keep doing circles. The muscles are the GG.

If you, like tex098, don't see the streaks, consider yourself one of the lucky ones. Tex098, see the video from the initial post.
 
The glue will add weight to the hammer that rotates on the motor. Hopefully making the grain spin in a fast circular motion instead of the side to side streaking motion.
 
dlee_ultra said:
If you, like tex098, don't see the streaks, consider yourself one of the lucky ones. Tex098, see the video from the initial post.
Click to expand...

Well, I acutally have a different brand adapter. I just meant that while viewing the posted clips, I don't see any streaks on my computer monitor. But I have watched them again and I think I see what you are talking about.
 
I fixed this on my letus last night by taking the front tube off and just slightly touching the GG and rotating it a little and figiting with it until the streaks went away.

The reason why those streaks happen is the GG isn't rotating in a circle when it vibrates, its going in an oval pattern. To check point the camera at something very bright and turn the shutter way way way up like up to 1/1400 or so until you can actually watch the GG rotating. If its not a circle you'll get streaks.

BE CAREFUL THOUGH not to push the GG in or pull it out or your focus will be thrown on all your lenses. Its in a sweet spot, be careful not to move it.

BTW I had to take apart my letus on set a while ago a number of times in 5hrs before we shot...nervewracking and I was sweating and the GG is a PAIN to put back on (and if its off it messes up your focus), but we got it. Still 5hrs of sweat and tears......ugh.
 
KyleProhaska said:
BTW I had to take apart my letus on set a while ago a number of times in 5hrs before we shot...nervewracking and I was sweating and the GG is a PAIN to put back on (and if its off it messes up your focus), but we got it. Still 5hrs of sweat and tears......ugh.
Click to expand...

FIVE HOURS? Geeze, hope you had a lunch break. The first time I took mine off to clean the condenser I clocked in at just under an hour. I nearly crapped myself when I pulled the first GG post on accident...luckily that was supposed to happen. Using a toothpick is the best way to get those GG posts back in.

As mentioned elsewhere, the GG is supposed to measure 7.5mm from the condenser platform. It's worth grabbing the calipers and making sure you're dead on.
 
You must log in or register to reply here.
Back
Top