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Old May 17th, 2009, 08:11 PM   #1
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Rented Ultimate, have questions

Hello. I rented an Ultimate this weekend to see if a 35mm adapter fits into my workflow and stylistic goals. The weather was not cooperative; therefore, I did not get as much hands-on time as I would have liked. I have a few questions. They are not specific to the Ultimate; that's was the only Letus the shop rents.

1) I want to confirm the general strategy for exposure control. I was coached by the rental shop to control exposure with the camera by using ND filters to limit light in overexposure situations and add gain in underexposed scenes when extra light is not available. They adivised against adjusting the camera's iris from f4.0. Is this consitent with other peoples' approach?

2) Do you ever touch the zoom on the camera once you've lined up the edges of the GG? I was coached to leave it at Z75.

3) How do you control dust? I didn't have an issue but the shop suggested I have some canned air handy. I must be old school, but I was once told never to spray canned air onto an optical surface for fear you might get some propellant on the glass or blast the dust into the lens/ground glass. Any thoughts on this?

4) How do you cart all this stuff around? The rental shop gave me the use of the Zacuto DOF lined Storm case. My goodness, my two children could live in there! Does anyone know of a backpack that will hold the EX1 with Letus rig attached plus 2 or 3 Nikons?

All in all, it's a wonderful device. I completely understand now why a follow focus rig is important and the need for beaucoup light when shooting indoors.

Thanks
Bob
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Old May 18th, 2009, 08:19 AM   #2
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1) "Technically" this is correct, but I don't know anyone who uses this technique. Everyone I've talked to (including myself) using both the 35mm lens iris and the video camera's iris to control exposure and DOF. I say "technically" they are correct, because the sweet spot of most lenses is around f/4.0. So if you want the absolute best quality picture, you should leave the video camera's iris set around f/4.0. But in real-world use, I've never been able to tell the difference, and having the ability to open/close the iris on the video camera to get the look you want is virtually a necessity. NOTE: Letus includes an iris on their rely lenses just for this reason.

2) On my EX3 I set it somewhere between Z68 and Z70. I've read about people (Philip Bloom) that actually zoom with the video camera's zoom, while they are using an adaptor. But honestly, I've never tried it. I just put a piece of gaffers tape that covers both the zoom and the focus to lock them in place.

3) This is a problem. I haven't found a solution for it yet that works well for me. I've never liked using canned air. I purchased a "blub" that you squeeze and it blows out air to blow any dust off your lenses and the GG. It's not perfect, but it gives more control than canned air.

4) I use a Zacuto DOF Storm case to haul the rig around. You're right, it's HUGE. But it has wheels and has worked out well for the type of projects we do. Go to Philip Bloom's site to look for a back pack style case. I'm pretty sure he's had success with one for his EX1 rig.

The amount of light needed to shoot indoors is a bit of a problem. This has been my only complaint with shooting with an adaptor. But a solution is coming in the form of the Letus relay for the EX3. It will bring back almost 2 full stops. Too bad it's so expensive though. ($4200)
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Old May 18th, 2009, 09:03 AM   #3
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Philip Bloom is pretty much the more well known Letus Ultimate/EX1 and EX3 guru and perhaps your best on-line mentor. He and some others who post here do this for a living and do a lot of travelling into some difficult places.


In the meantime until someone responds, here are a few comments. Defer to Phil's recommendations if mine conflict.

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1) I want to confirm the general strategy for exposure control. I was coached by the rental shop to control exposure with the camera by using ND filters to limit light in overexposure situations and add gain in underexposed scenes when extra light is not available. They adivised against adjusting the camera's iris from f4.0. Is this consitent with other peoples' approach?
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I endorse the shop's recommendation for exposure control. An iris of f4 seems to be accepted as the sweet spot for the EX1, adaptor fitted or imaging direct-to-camera. If you do not have quite a few hours up on groundglass adaptors, it will be best to stay inside known performance limits for predictable results.

My own checks confirm this as about the best setting. The explanation is a bit involved so will not go into it. Just take it on faith.

My personal preference would be to open up the camcorder iris before dialling in more than 3db gain. Gain noise can cause an apparent softer image by loading the mpeg2 codec. Doing it my way however, also introduces a risk of a softer image in two ways.

(a) You are no longer in the sweet zone of the camcorder lens. You are no longer in the sweet zone of the combination of the camcorder's internal lens system and the relay lens.

(b) Because the depth-of-field of the camcorder lens itself is now also shallower, the focus of the camcorder onto the groundglass must be vigilently monitored, shot-to-shot. (You set your relay focus with the camcorder lens wide-open in any event.)

I may seem a bit obsessive in this following comment. - I very frequently use a large Siemens star on a A4 sized (US letter sized) when setting up.

I prefer to use a resolution chart with blocks of fine lines to set up a relay for a camera like a JVC GY-HD100 with a Mini35-400.

The Siemens chart I use it to quickly check relay focus if in doubt but pressed for time as well as the more common method of focusing onto the groundglass (sandpaper) texture, which takes a little longer to do properly.

The peaking and focus assist functions of the EX1 are my best friends for checking relay focus onto the groundglass and focus of the objective lens onto the groundglass.

If I want to do a focus follow and time permits, I will mark the Nikon lens barrel with a china pencil for each end of the focus excursion.

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2) Do you ever touch the zoom on the camera once you've lined up the edges of the GG? I was coached to leave it at Z75.
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Again I endorse the vendor's recommendation. The EX1 that I have access to does not have an underscan viewfinder mode like the older Z1/FX1 cameras.

Therefore unless you have an underscan monitor to refer to, you cannot know if you are picking up an edge of the optical path.

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3) How do you control dust? I didn't have an issue but the shop suggested I have some canned air handy. I must be old school, but I was once told never to spray canned air onto an optical surface for fear you might get some propellant on the glass or blast the dust into the lens/ground glass. Any thoughts on this?
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You and the rental vendor have valid points.

The Letus prism path is pretty much sealed these days against entry of dust. The only place I can think of in the optical path where unlikely dust intrusion would introduce a new blemish would be on the condensor behind the groundglass.

The front glass behind the Nikon lenses is not at any focal plane so specks of dust are not likely to degrade your image. I think you are safe blasting bits of dust off that.

I would have some reservations about using canned air on the groundglass disk. Because this is in an enclosure, it is unlkely to become contaminated by environmental dust to the extent it is noticeable. For your purposes and it being a rental item, this is not a user-serviceable part. If you have problem there take it back to the vendor.

The spinning disk of the Ultimate is another best friend. Disks tend not to show dust or will throw specks off. Introduced liquids are another matter. A broad area stain will introduce a flickering artifact, maybe a streaking artifact as well.

Fortunately you should not get such a stain on the groundglass in normal sensible use. Stay out of the rain and do not freeze and then rapidly thaw the adaptor and you should be fine.

The only other and very unlikely source for a stain on the disk might be if someone has lubed the disk bearing and some oil comes out and runs out over the groundglass. This will appear as radial lines when the groundglass is stopped and as a flicker artifact in motion.


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4) How do you cart all this stuff around? The rental shop gave me the use of the Zacuto DOF lined Storm case. My goodness, my two children could live in there! Does anyone know of a backpack that will hold the EX1 with Letus rig attached plus 2 or 3 Nikons?
"""""""""""""""""""""""""""""""""""""""""""""""""""""

My personal preference is to have two cases, one for the camera/adaptor, one for the lenses, mattebox and accessories. I also prefer to transport the camera and adaptor separated in a solid case, then assemble/test close to the location the day/night before.

If you have to cart the assembly around in a soft backpack to wild and remote places over rough trails, I would make a strong plywood halfbox with at least three contoured padded support ribs for parts of the camera/adaptor which rest in the halfbox. (I suspect you would not be using the Letus in this circumstance but sticking with the bare camera, however who knows? The Nikon lenses give you some amazing creative options.)

Add velcroes to stop it from moving around and and maybe a tripod screwhole in the halfbox bottom to lock the assembly to the plywood. To lose some weight, cut a bunch of large holesaw circles out of the plywood. You can afford to lose the narrow plank.

More important to keep the broad piece and the ribs, maybe use a thicker piece of plywood if there is no narrow plank.

Without this added "spine", the actions of bending one's body while wearing the backpack might introduce bending stresses to the adaptor/camcorder junction. Best not to transport the combination with a Nikon lens attached. In violent events, the unsupported mass of the lens will have leverage over the camera/adaptor junction.

If you must have the Nikon lens fitted for ready-use, then the plywood must also extend beyond the Nikon lens. Because of variation in lens sizes, it is not practical to make a support rib for the lens unless you decide to transport with one single lens fitted for ready use. In that case, make the extra contoured rib.

Depending on how well you want to protect it and retain the use of the backpack, you might use soft clothing stuffed in around the combination.


Other users may prefer to pack the assembly loosely and let it take its chances. There are however some sharp corners on the camera/adaptor rails assembly which over time may give you some localised chafes and bruises through the backpack and if you take a tumble it might crack one or two of your ribs.
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Old May 18th, 2009, 05:20 PM   #4
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Thanks for the comprehensive answers
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