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Old December 14th, 2005, 01:50 PM   #1
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Support Your Local.....Letus

Using the Letus35A in conjunction with a smaller 28mm or 50mm lens has been relatively shake free on set for the past couple of days. But using th big 105mm lens has been a different story, pulling focus has been a nightmare with shaky shots unavoidable. Especially annoying in tracking shots (with big or small lenses) where the lens shakes, rattles n rolls due to the Nikon mount having barely any bayonet left, requiring duct tape to stop them hitting the floor.

I took a quick break from shooting today to go pick this up from the post office:

Manfrotto 293, At 25 for a brand new example it seems a steal when compared to the pricier rod support systems. Of course the rod systems have their place for FF gear and whatnot but for me, now, this does the job just great.

To aid in supporting the lens I have the "V" under the lens pushing it up into the mount. The strap tightens leaving the lens fixed in position, but free to change focus. If I had mounts I would position the support under the Letus itself so I could change and lenses without loosening the support system.

The length is very adjustable and sturdy metal construction mean the support is weighty and does not bend at all.

When I picked my Z1 up the other day I ran out to get something to put it in for the shoot. A padded Stanley toolbox for 15 does the job just great.

A Lowepro Computrekker pLus AW is on the way next week, but the hard weatherproof case means I will probably prefer taking this on a chaotic set.

Just needs some more padding and it's complete.

Hope thats of use to some of you, Regards,

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Old December 14th, 2005, 07:28 PM   #2
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Good thinking! Light, elegant and necessary. Something to remember.
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Old December 22nd, 2005, 09:47 AM   #3
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Great solution Anthony, thanks for sharing those pictures with us :)

The Cavision MiniDV Rods Support is not very pricey, but it's been out of stock for a while now...

One thing though... I have a Manfrotto 701RC head with the quick-release plate. How would that work? I guess I'd "quick-release" the whole thing... And it seems there's another quick-release plate included on top of the support itself. That makes it two :P

thanks again,

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Old December 22nd, 2005, 01:04 PM   #4
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You're very welcome Lucas,

That is precisely what I have been doing with a Manfrotto 503, very quick and simple. The quick release plate of the Manfrotto screws into the bottom of the support which in turn has a quick release mechanism.

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Old December 22nd, 2005, 07:45 PM   #5
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Your Nikon Mount. Is this real Nikon or a copy? The real Nikon has a diaphragm spring which goes behind the mount ring and exerts positive pressure on the lens to keep it accurately against the mount face and thus at correct distance from the focal plane.

There is a clearance machined in back of the Nikon mount for this spring but the spring requires clearances for the bows to be made in the face of the case on which you fit the lens mount.

Having the latchpin is nice but the spring is sufficient on its own to retain the lens, especially the low friction autofocus types.

It is a small matter of marking and digging the clearances out freehand with a dremel or similar, or using a small mill if you are handy and have one.

Until you secure that lens you are going to have an unremitting headache. You will also find that 28mm may be softer than it should be. Whilst wides seem to have an inherently greater apparent depth of field, they also seem to be less forgiving of the backfocus being wrong.

I find that just the minute distortion introduced by tightening down the back cover of the case of my own design is enough to put the backfocus off. The cover and backfocus adjustment uses the same pillar bolts.
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Old December 23rd, 2005, 02:22 AM   #6
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The Nikon mount is a copy, a plastic circle with three protruding "fins" or blades underwhich the nikon "fins" slide. That is all there is...or was. Now there is just a circular hole with nothing for the Nikon fins to slide under. The plastic is very soft and the slightest irregularity in placing the nikon lens shaves off any plastic. I dont have a genuine nikon mount to compare it to, but I was thinking if worse comes to worse buy a cheap M42 to Nikon metal adapter and screw/glue it to the Letus so atleast have metal mounts.

To behonest it would be best to ask Quyen about his nikon mounts, but I do know there is certainly no spring mechanism to be found.

The 28mm certainly has given me headaches. To achieve focus I have to zoom out on the camera a touch more that I would on the 50 or 105mm lenses, giving me a LOT of visible ground glass in the image and requiring me to zoom in by around 12% in post :\

Thanks for your input, the letus is due to go back to Quyen this week so I will hope to have some of these problems addressed while its in his hands.

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Old December 23rd, 2005, 06:16 AM   #7
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Anthony how's it working out?
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Old December 23rd, 2005, 06:33 AM   #8
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I am using a f1.8 28mm Nikon Mount Sigma lens. It is a little soft wide-open anyway but I found with very careful setting of the backfocus, I could bring it in just that little bit sharper.

The Nikon F style lens mount can be had as a replacement part. Fortunately for me, there has been another unrelated prototype development going on here in Western Australia, so all the mounts I have wanted plus spring and screws have been available as stock has been maintained for the other buyer.

I too went the path of the plastic mount. It certainly was very convenient but I encountered the very same problem. The lugs on the lenses have sharp corners which have been made even sharper by the time one gets them secondhand by the very act of them being fitted and removed. They shave the plastic off fairly quickly.

If you install a genuine Nikon mount and the original plastic mount is not removeable, ie., part of the case itself, you may have to move the groundglass forward if this is possible or the portion of the case the mount fits onto backwards towards the groundglass if the the groundglass is not moveable.

In my case I cannot set it by measurement with a vernier because I can only access the front of the groundglass which is the clear side so fine adjustment has to be by the look and see method using the camera.

As you correctly suggest, only Quyen can give you the correct information on this subject.

I was not going to bother fitting a metal mount and got by through putting slivers of masking tape on back of the lugs to pack the clearance out. That is until I dropped one of the lenses, my nice one too. Fortunately I was able to catch it on my foot and boot it off onto the grass.

Since I made the improvement, I have been kicking myself for not having done so sooner, as it is one more thing I no longer have to keep in mind. The added workload with the AGUS in terms of keeping focus and maintaining relay framing already gets in the way of spontaneous or instinctual work.

Another concern with using the 28mm lens wide is that its sharpness may well go off at its widest aperture. It is a pretty severe test we put these still-camera lenses to.

The other aspect is that MiniDV resolution is not so great in dealing with fine background textural detail anyway and much of the use of the 28mm is going to frame a lot of it, which makes focus using the standard viewfinder or LCD pretty difficult at best.

In highly controlled tests, I can come up to the resolution of MiniDV as 530 TV lines and I think better than, but in the real world the results are often inferior. Where these things shine, is with the portrait style setups through the narrow lenses.

Some of the cheaper or worn lenses can introduce shake even if everything else is tight anyway.
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Old December 23rd, 2005, 07:49 AM   #9
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Hi Yasser,

crazy time of year....hectic for sure. A few little problems my end. Bought a Dell 2405FPW 24" HD hour after ordering my 2500 laptop decides it would like a new motherboard...hrmph...I have an amd 64 3000 machine here but it refuses to work with HDV so its an HDV-less xmas for me. On a brighter note the monitor is stunnnnnnnnnning, highly recommended if you are shooting HDV. Only problem is its soo big you can really see all the errors in your footage. Z1 + Letus not looking so hot in full res :\ (think grain....lots of grain)


Thanks again for your detailed response. Adjusting the GG position in the letus requires some fiddling and removal of glue but its not an option for changing the lenses in the midst of a shoot, though I do keep the hot glue gun handy at all times. Installing a genuine nikon mount could be done quite easily i think, would require some dremeling of the plastic mount to counter sink it, so its at the same level as the plastic fins. Food for thought...cheers mate!
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Old December 23rd, 2005, 09:34 PM   #10
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Once you get the backfocus at best for the 28mm lens, ie., sharpest at infinity and wide-open, all the other lenses should be spot on if they are themselves correct.

The lens has to be sharpest at the infinity position on the focus ring against a far far distant subject. If the image goes sharp at a point past infinity if the control ring will over-travel or goes sharp on a faraway target before infinity on the focus ring, this is not ideal, at least not on my combination.

As for dremelling the case, if you use the spring (recommended as the lens will still turn in the mount without it), as well as there having to be the thickness of the metal mount to be allowed for, you will need another 0.5mm to 1.0mm for the three clearances around the bows on the spring.

I tapped threads into the plastic case of my appliance for the 4 small mount screws and also glued the mount to the case.

Depending on the plastic used, you may have to buy in some longer small screws with small nuts to go on the ends.

These have to be countersunk as the lens mount face must be able to pass over the heads which cannot stick out. A polyproplene plastic will not grip threads and the glue will come unstuck.

As far as I recall and perhaps somebody else here might like to confirm, the flange (contact face of lens to mount) to focal plane (ground glass surface) distance for the Nikon F is 46.5mm.

I just managed to get the .jpgs to open and display on my system. Looking at the tripod, it may be a little light-on for long lenses to be steady. I eventually went to overkill and use a big old hickory legged Miller for the long lenses.

If the friction on your tripod is having to be set hard to hold the weight of the combination from falling forwards as it looks to be, you are going to get bounce the moment you disturb the front lens.

A rear counterweight or re-positioning to bring the whole thing back into balance will help as the loading on the tripod legs will become more vertical than lateral. If the disturbance to your images is most evident in a vertical direction and less so in a horizontal direction, balancing will definitely help.

For ground-to-air aviation shots with a 50mm - 500mm Sigma, even the Miller is shaky unless that balancing is done.
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