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Old August 21st, 2007, 10:13 PM   #1
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upgraded glass in new letus adaptors?

Does anyone know if the upgraded glass is being used in the new letus adaptors? It was mentioned a few months back that they were planning to upgrade but I haven't heard anything since.

And when choosing the nikon locking mount vs nikon and canon swappable metal mount - is there any advantage in weight, convenience etc in getting the nikon only mount over the canon/nikon swap version?

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Old August 22nd, 2007, 11:52 AM   #2
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Don't know about the upgraded glass..but when I had the letus...the swappable mount is very light..it looked and felt like hard aluminum vs metal. So weight is not an issue. On my SGpro they use a metal adapter that is heavier. In addition the Letus does not come with a locking pin to hold down your lens vs the SGpro does.
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Old August 22nd, 2007, 10:15 PM   #3
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sent letus a email a while ago asking about the rumor, I received no response. Email them, maybe you'll have better luck.
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Old August 22nd, 2007, 11:25 PM   #4
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I'll send a follow up note as well - see what happens.

thanks for the replies. : )
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Old August 23rd, 2007, 11:50 PM   #5
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If you already have Nikons, then my personal preference would be to use the dedicated Nikon mount and buy in the Canon dedidcated mount if a Canon lens came along later.

The reversable mount is difficult to maintin in a stable position once the backfocus has been correctly establsihed, partly due to the machining for the Canon lens being in the part of the barrel of the mount where the thumbscrew tightens down.

There is no way to avoid this in a reversable mount in the current layout of the front enclosure and thumbscrew.

The dedicated mount I understand may now have a retracting pin, retention lock system to stop the lens from turning in the mount during focussing and falling out.

The P+S Technik, Les Bosher mounts and a generic Nikon to C-mount adaptor, all use compact springloaded release button designs which are different to the Nikon camera.

Unless you take care to rotate the lens in the mount slightly to take any side loading off the release pin there is a tendency for the pin to bind and fail to retract completely.

The penalty for haste and brutalilty is that the release lever bends and the necessary mechanical movement to retract the pin is lost.

I think the Letus Nikon dedicated mount may now have a similar retracting pin feature. Check with Quyen. If it does, definitely choose the dedicated mount.

The release button may be tricky like the other designs and require patience to operate. There was a discussion thread here on dvinfo on this problem a while back and I gave a lot of bad advice to the user who fortunately discovered the solution with no harm done.

The issue is not the design but the availability of space within the mount to put the retraction system. With the Nikon camera, there was a whole camera body for the designers to play around in.
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Old August 24th, 2007, 08:10 AM   #6
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I haven't bought anything yet so I could go all nikon.

Thanks for the explanation on the mount - that was what I was wondering about - if there was an advantage to just sticking with the nikon mount. I had asked Quyen in a note awhile back but didn't get specific clarification on it.

I'll ask about the retracting pin feature and hopefully get an answer on it.

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Old August 24th, 2007, 12:24 PM   #7
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"Retracting pin" was my definition in my previous post to try for accurate description. "Locking pin" might be more commonly and correctly used.

If you are going to buy in Nikons from scratch, buy only lenses with f1.8 aperture or wider for your Letus35. Sigma gives you some options for Nikon mount as 20mm and 28mm in f1.8. Nikons with f2 may well be okay but I haven't tested them.

If you are ebaying lenses, watch out for some of the older metal barrelled Nikons, Early ones used thorium glass which is mildly radioactive, which deteriorates the glass over time and develops a pale beerbottle warm colour cast. White balance mostly takes care of it but you have to remember to do this with each lens change, a good practice but sometimes not always convenient.

This does not disqualify the lenses which remain otherwise perfectly functional but you do not want to be paying too much for a yellowed lens. Sometimes the vendors post "through the lens" images against coloured backgrounds, not white and this masks the defect.

"Sunning" such discoloured lenses in UV light whilst keeping the black bits wrapped in silver foil to reduce heat for about a week apparently restores their clarity however, this might also aggravate breakdown of the balsamic bond used in older lenses between cemented elements. This also manifests as a yellowish cast.

Last edited by Bob Hart; August 24th, 2007 at 12:52 PM. Reason: added text
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Old August 24th, 2007, 06:30 PM   #8
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Thanks for the tip on the used lenses. Much appreciated. I'm not sure I'd have even known without experience with how a lense should be in decent shape. Sad we have to be so wary!

I was thinking of going for one of the light weight nikkor 50mm to start - more plastic parts but still decent glass inside (this is from what i've read at any rate)

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Old August 25th, 2007, 06:21 AM   #9
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I had a lightweight autofocus Nikon f1.8 85mm and that was the sharpest of any I have used. It is now in a Mini35 kit. Whilst modern lens bodies may be plastic, if they are the retrofocus types where the focussing elements move inside the guts of the lens body and don't snorkel out through the front, I expect they will be okay.

Modern lenses with manually over-rideable autofocus, tend to have very light actions with a shorter throw (arc of movement) of the focus ring. Without frictional damping also found with the longer throw manual lenses, hunting past and back over the sharp image point is a hassle.

If you change the method you use to focus these lenses from the traditional two fingers and rotating wrist from the side to laying your wrist or palm on the camera body behind the lens and working the focus ring as if it is a steering wheel with several fingers resting around it, you will find that focus pulls can be both fast and accurate as you do not shift grip on the focus ring and the intuitiveness of moving an automotive steering wheel translates quickly to the simpler twisting wrist movement controlling the lens.

A downside with some retrofocus designs is that they become good environmental vacuum cleaners and get dusted inside because of the moving elements drawing air in and out.

The cheaper alternative brand plastic bodied prime lenses may be quite sharp but those with moving elements which snorkel in and out through the front, tend to have lots of clearance and will jump your image about during focus pulls. These also tend to be environmental cleaners.

This clearance is a practical necessity when moving plastic on plastic and is not necessarily accompanied by poor optical performance, just not good for motion images.

If you eventually aspire to using a follow focus, the lenses you choose now should be selected also for their ability to have a follow focus gear mounted on them. The older metal-bodied Nikons can be easier to fit up with focus gears.

The adaptor you choose now should have a firm mounting system for the lenses with the locking pin. A remote controlled follow focus does not feel when a lens is turning in its mount or turning the mount itself out of the adaptor.

The firmness is required to keep the lens from rocking in its mount. Even the benchmark P+S Technik Mini35 builders need to lift their game with respect Nikon mounts.

The Mini35 will not let the lens fall out because it has a locking pin, but like all the other alternative adaptor mounts I have seen, there is no effective pre-load system within the mount as with the genuine Nikon mount to compensate for minute clearance variations caused by wear.

On my own home-made device, much of it may be scrap and salvage but the lens mount is genuine Nikon.

If there is no locking pin, the first you know is the loud crack as the lens hits the floor.

If you are lucky, there is a soggy thud and a strange mewling utterance from your camera assistant as the lens bounces off his or her foot across the floor or this curious white wobbling blur as the lens rolls about, well caught by the mattebox bellows after coming loose.

There is a contention that lens sharpness is not overly critical with regard groundglass based image relay adaptors because of the resolution limits imposed by the groundglass. I tend to disagree. A soft image landing on a groundglass is furthur softened and this aspect becomes aggravated if the overall image in "sharp" focus is bright. The outcome is that a groundglass, like intensified night vision, actually multiplies softness in the image in an almost logarithmic fashion.

If say, a pinpoint in an image is 1 micron. It hits a groundglass which has a notional resolving ability of 5 microns due to the size of the pits and humps in the diffusing surface, then the pinpoint the camera sees is 5 microns or maybe more if more than one pit or hump is encountered. If due to lens softness this 1 micron pinpoint is presented to the groundglass as a five micron pinpoint, then potentially it can be presented by the groundglass to the camera as a pinpoint 25 microns or more.

In practical terms it may not seem to matter as the resolution of cameras themselves and the relay optics may not be all that good, but the net effect is that contrast suffers and the apparent sharpness of the image along with it.

Last edited by Bob Hart; August 25th, 2007 at 06:50 AM. Reason: error
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Old August 26th, 2007, 11:26 PM   #10
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Wow, you have an incredible amount of knowledge - you should be teaching this and/or making adaptors for us to buy. : )

I was talking to another A1 camera owner here in Toronto and he said a follow focus is essential if you want to do anything serious with a 35mm adaptor. I'm not even sure if you can add one on with the letus. I know the brevis and redrock etc have ones to purchase.

You have me leaning back to a metal body nikon though, after reading this. I was just thinking lightweight with the nikkor and the fact that they are so short they don't add too much length to the configuration.

I'm still torn on adaptors and which way to go - I was really leaning towards the letus because it comes flipped already without requiring an attachment that adds even more length. It's still at that borderline where you can get away with no rails. At least that seems to be the concensus.

Thanks again for taking the time to post such detailed information. It's much appreciated.

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Old August 27th, 2007, 03:26 AM   #11
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It is a bit of a horses for courses thing with adaptors. To some degree users should shop for the features which best suit their needs.


For turnkey utility right from the word go, you would be better off with the real thing, the current benchmark product Mini35-400, which comes with facility for rods support of accessories built-in. However budget will most likely constrain that impulse.

The Mini35-400 requires some skill and mechanical facility tpo assemble and set up consistent with skills possessed by an experienced cinematographer-videographer.

Secondhand, there might be some Mini35-300s out there.

This is a commercial level device.


In the following comments I may be straying into giving misleading info so read from here with a jaundiced eye. I have not had any hands-on experience with the following products including the Letus model for the A1 and rely entirely on my own recollection of accounts read here at dvinfo.

If there is seen to be any unjust prejudice towards any particular alternative device, I would hope that builder-vendors contibute comment here to correct my comments.

Next down the turnkey-ready ranks would seem to be Dennis Woods' Brevis. This device is a full design from scratch and believed to be built to consistent standards. This however does not flip the image but a flip module to retrofit the existing non-flip model is in the works. Dennis' product is the only which also offers choices of swappable groundglass translucency. Depending upon the user choice of groundglass grade, the resolution and brightness will vary. User accounts published here suggest the resolution is very good. Rods support for mattebox and follow-focus are believed to be options. Groundglass motion is believed to be precise mechanically controlled orbital principle similar to Mini35-400.

Visual product from this device is believed to have been commercially marketted as broadcast documentary.

Regarded as a commercial level device.


Next down the turnkey-ready ranks and maybe equal to the Brevis would seem to be Wayne Kinney's SGPro. This device is a full design from scratch and believed to be built to consistent standards. This device also does not flip the image and no flip module has been proposed by Wayne to my knowledge. Subjectively, the published SGPro images seem to be the sharpest as the largest area of image recovery off the groundglass is used. Rods support for mattebox and follow-focus are believed to be options. Groundglass motion is believed to be precise rotating disk principle similar to Mini35-300. It is regarded as having very good performance in regard to visible artifacts in adverse lighting conditions.

Visual product from this device is believed to have been commercially marketted.

Regarded as a commercial level device.


Next down the turnkey-ready ranks would seem to be Quyen Le's Letus35 models. He offers a choice of devices, some which flip the image, some which don't, some which relay directly to camcorders which have removable lenses, some which relay via a close-up lens attachment to lens-in-camera styles like yours. Resolution from Quyen's devices is a bit of a mixed bag. The direct-relay devices are limited by the cost-effective choice of relay lens to a smaller image area off the groundglass. The models for lens-in-camera types enable a larger image off the groundglass and correspondingly finer scaling of groundglass artifact relative to the image area, therefore potentially sharper image. Quyen's devices are comprised significantly of existing available components with the flip module, front end cover, lens mounts and bridgework to relay lens and relay lens mount being original build and design work. Quyen does well by integrating all these sourced components into his devices however there have been mixed reports as to structural integrity and reliability. All Letus models require some practical enthusiast skills and facility to set up and maintain correctly. There is no fitting for rods support for mattebox and follow-focus and these have to be innovated by the user from available third-party kits. The groundglass motion is free elliptoid. This system is very quiet however can have inferior performance relating to a visible fixed pattern artifact in adverse lighting conditions. The battery pack, with power switch requires some tender care or can be damaged.

Visual product from some versions of this device is believed to have been commercially marketted in the form of music video clips and political advertising spots.

Regarded as entry-level to commercial device depending upon actual model chosen.


Next down the turnkey-ready ranks would seem to be the Redrock M2. This device is the first of the marketed developments of alternative groundglass image relay devices. It does not flip the image and no flip module to my knoweldge is proposed for the near future. Accounts of image quality have varied. At best it has been reported by a U.S. DoP as superior even against the benchmark Mini35. Other users have been less satisfied. This device requires considerable effort to set up and maintain correctly. Once set up and locked down, its performance has been reported as very good. I have not read-up recently on this device. Rods support for mattebox and follow-focus is believed to be available. The current groundglass motion system is unknown to me. The original developments used a precise rotating disk system and Redrock still supply a kit with disk and instruction set for home-build enthusiasts.

I have no knowledge of visual product from this device being marketted but that should not be taken as a suggestion it has not happened. A DoP's published endorsement of this device should not be taken lightly therefore I am encouraged to suggest this is a high entry-level commercial device.


There are several other product developments which I have not covered and I would hope that others will chime in and finish what I have not included.


FOOTNOTE:

P+S Technik have recently released a version of their Mini35 which is called the "compact". This device does not flip the image and is configured to lose only half a stop of light. Rods for mattebox and follow-focus support are attched to the front and are not an integrated part of the total structure as the full Mini35-400.

The groundglass motion system remains a precision mechanically controlled orbital system. This version should lend itself more to agile-portable work with cameras such as the JVC GY HD-250 which has built-in image flip capability.

My initial reaction is that this model may be a response to the alternative adaptors such as the Brevis, M2 and SGPro which confer some conveniences the Mini35-400 does not. This model would seem to be ideal for ENG/EFP camera configurations of the JVC GY HD250 for documentary work such as Phil Bloom's recent projects.

I do not build my devices for sale because they are hand-made from existing common plumbing hardware, available optical accessories, salvaged parts, are thus sub-standard and because any alternative devices potentially infringe existing patents.

I have been discouraged from original intentions of publishing a construction plan kit due to litigation against open-source publishers of free-software by persons who claimed losses through using it. I simply do not have the resources personal and financial to defend such an action.

As for teaching, I have a short guest spot at a local institution of higher learning which gives me a good feeling about the whole thing. I hope my niche skills are up to the task as the students are a keen lot.

Your A1, I understand to be a lightweight camera.

If you want to go now into 35mm groundglass devices for learning and not commercial production straightaway, the path might be initially buy in Quyen's Letus35FE for the time being with an intention of trading up later on.

If you intend to go hand-held, to develop 35mm format film-lensing and compositional skills, then this model may be a good entry-level choice if you have some handyman skills or backup to call upon to set it up, add re-inforcement where needed and perhaps modify the lens mount.

However if you intend to aspire to a higher level of skill including the use of traditional production hardware, follow-focus etc., then you might like to examine waiting or moving up to Dennis's Brevis when his flip module is available.

If it is conveniently close-handy, a day's hire of a Mini35-400 A1 kit for Nikon lenses should not be a deal-killer and would establish for you what expectations you should have of groundglass based relay imaging.

Last edited by Bob Hart; August 27th, 2007 at 03:35 AM. Reason: errors
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