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Alex Nelson

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Alex Nelson last won the day on August 4 2015

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About Alex Nelson

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    Los Angeles
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    Product Engineer/Designer - Duclos Lenses
  1. The easiest way to use it with your camera is to pull the optical cell off its focus threads (which is much easier than it sounds) and attach it to an inexpensive focus helicoid. Another fellow did exactly that with a 75mm Baltar to use it with an EF mount. (http://www.cinematography.com/index.php?showtopic=67913&hl=baltar)
  2. Baltars were sold in virtually every mount used between their release in the late 1930's and the release of the Super Baltars. For the most part, that means Eyemo, Debrie, Mitchell (almost all variations), Cameflex, Wall, etc. I have seen a single 40mm Baltar in Arri standard mount, but I don't think any of the three wider focal lengths (25, 30, 35) would reliably clear a reflex mirror. The 75mm, though, is guaranteed to work with pretty much any reflex system or mount because of its relatively long rear working distance. It also covers full-frame 35mm without issue (as do all Baltars longer than 35mm) and can give you a really pretty image if the glass is in reasonably good condition.
  3. For AC's doing check-outs in rental houses, taping out lenses against the engraved scale is a quick way to catch back-focus issues. If you don't have accurate marks, you might find out too late that your lenses can't hit infinity. There are also many instances where you just have to pull off the marked barrel and there aren't monitors with peaking or wireless focus systems on hand.
  4. The Red Pro Primes were not rehoused still glass. They were designed and developed by the team behind UniqOptics, in California. Kenji Suematsu, who was responsible for the mechanical design, talks about the process (and eventual lawsuit) for a few minutes in this interview: http://archive.densho.org/Core/ArchiveItem.aspx?i=denshovh-skenji-01-0022
  5. Sorry, I should definitely have stressed the safe removal aspect of the process more.
  6. I have an old Bardwell McAlister 2k that had a similar problem. The pinch ring that they used to hold the fresnel in place had a thick asbestos insulation around it that actually made contact with the glass. Most of it had deteriorated or rotted off by time I got it, meaning there was no longer enough pressure to keep everything secured. I carefully removed the rest of the asbestos and wrapped gaff tape around the metal ring instead, as a temporary replacement. I don't know for certain if the 751 had the same asbestos wrap, but it could account for the loose fresnel.
  7. Pointing the eyepiece assembly at something like the moon will tell you if the objective/eyepiece are properly calibrated, but placing a mirror in front of the whole thing with the light source turned on will also tell you if your reticle is calibrated as well.
  8. I apologize, my original instructions were not terribly clear. I have an LED flashlight on my Richter, so I was envisioning taking the whole autocollimator assembly (light source, eyepiece, and objective) into, say, a bathroom and pointing the whole thing at a mirror. The more reasonable method would be to just get a small hand mirror and place it in front of the objective without taking the whole thing off the rails. The rest of the process is the same.
  9. There is an old Jon Fauer promotional/educational video for the Arricam system that featured the same effect. In that case he was showing off the Arricam's ability to ramp the shutter during an iris pull. Of course, that presupposes that the shutter angle changing wouldn't negatively affect the motion in your shot.
  10. The quick and dirty way to check if the reticle is in its place is to mount one of the collimator objectives on the eyepiece and point it at a mirror while looking through (as though collimating a lens). Assuming the objective is properly calibrated, the reticle should look sharp in the eyepiece. If it isn't, then you have to determine whether the other objectives have the same problem. If they all look soft, then the reticle probably needs to be adjusted. If some are sharp and others aren't, then you need to decide which variables to start eliminating.
  11. Swing by Technological Cinevideo Services (TCS) at 45th and 11th. They're relatively small, but they do huge shows (House of Cards, Mr. Robot) and a lot of big independent movies like St. Vincent. It's a very intense place to work, but after a couple of years there, you'll be in a great position to move into the field.
  12. Cine zooms don't usually change focus during zooming unless the back-focus is off. If a lens is properly collimated to the camera, by shimming the mount on either the lens or on the camera, it should hold focus through the full zoom range.
  13. The macro shots look incredible. It's such a clear, creamy lens. Glad you gave it a new life!
  14. Not to stray too far off topic, but why do Australian crews prefer focus scales in feet and inches? I visited Vantage in Paris several months ago, and apparently French camera assistants have the same preference.
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