Roiding The Extreme

[Bob Hart]

I had a furthur short play with the SI2K and the Extreme. Unfortunately, time did not permit me to borrow or cajole the owner into more extensive testing however the initial result is encouraging.

This time the lens used for relay was a 50mm f1.4 Nikon.

With the prism centricity adjustment modification and the condenser port widened, there is no trace of an edge creeping in that I could see. There was also no trace of edge darkening. So there is a little more wider image to be had from the groundglass but the lens choice for relay is not there in the Nikon range.

On a 16mm film camera, at the Super16mm edges, there is a trace of edge vignetting from the condenser port when a 35mm f1.4 Nikon is used for relay so this would defnitely vignette on the SI2K.

If there was such a thing as a 42mm f1.4 lens to be had as a relay, then this might go close to allowing the maximum amount of groundglass image area.

I also mounted it up to the JVC GY-HD111 there with a 35mm f1.4 Nikon lens for relay. It seems to work well enough but I did not study a large image on a monitor, only what I could see on the LCD screen.

[Bob Hart]

This is a frame grab with Nikon 105mm f1.8 lens on the Extreme before the view was widened. The image picks up rivet detail on the wing panels nicely.

Sorry - the upload failed. Seems like I may have clicked the wrong button.

[Bob Hart]

Another try at upload.

[Ted Ramasola]

Bob,

Is this frame from your jvc + 35mm f1.4 relay + extreme + 105mm f1.8 set up?


Ted

[Bob Hart]

Ted.


That frame grab is from a loaner PMW-EX1 on the modified Letus Extreme but before I widened the available view by about another 2mm.

The 105mm f1.8 field-of-view as you will observe, is quite wide as I chased with the EX1 zoom as much of a wide view off the groundglass as I could get.

It is probably about half-way between standard movie and the field-of-view you get with your medium-format adaptor.

I think it is possible to hit the resolution limit of the JVCs with wide groundglass views. I think your medium format may have already done that.

If I get time on the next music gig, I will try the arrangement on Steve Rice's JVC again to get some grabs. I have some fears about capturing from his camera as it took my computer down last time I tried.

[Ted Ramasola]

Bob,

Looking at the footage by extreme you hacked onto the SI2k, I wonder why you have to? What is the sensor size of the SI2k? I thought it was big enough for cinematic DOF?

Another thing, since youre talking about the relay setup, I'm tempted to play around with my set up AGAIN, you mentioned that you have used a 35 or 50mm nikon as a relay for the jvc, what power achromat are you placing infront of the 50? or 35? and whats the distance from the achromat rim to the GG?

I have the cinevate and sgpro achromats, what do you suggest should i use? If i use a 20-40 sigma zoom as relay at the widest setting at 20mm, you think this would be better than the 50mm/35mm relay you tested?

I'm after of several results for this test.

a. a shorter rig set up.
b. to achieve a wider or optimum gg area.
c. an approximate or better image resolved compared to the stock 16x.

if you think its not worth experimenting replacing the 16x with a hack relay please advice if it won't achieve those objectives.


Ted

[Bob Hart]

Hello again Ted.


I wouldn't go hacking just yet. The 50mm on the JVC may take you back to the multiplication factor problem of the Minolta lens on the original direct relay Letus. The SI2K is also a single CMOS sensor, not 3 x sensor prism arrangement so the colour fringing problem is not an issue.

I'll test it some more on Steve's camera and see how it shapes up with a proper test chart.

The Letus achromat is the one for the EX1. It works in combination with a special rectangular shaped condenser lens they have had made up. I'll substitute the 4+ and 7+ Century dioptres from the Agus 35s and see how the size of the image/zoom setting compares.

[Ted Ramasola]

Thanks Bob,

I knew the 50mm had high crop factor as a relay in my first tests, i was apprehensive I was missing something. I had difficulty getting it to record a wide gg area. After fiddling with the combinations, the compromise image i had ended me with a long distance from achromat to gg so much so that the length was the same if i was using the 16x!

I'll wait till you get around to test it again. In the meantime, my life will go back to normal.. hahaha

Thanks again Bpb.


Ted

[Bob Hart]

Ted.


The Sigma zoom I suspect will not be as sharp as the JVC's own zoom lens as a relay.

The prime lenses may only just come up to the sharpness of the JVC's own lens but if they do, then as you require, the whole thing could be shortened.

Another aspect ran past me. I think from memory you are using a HD250 with in-camera flip. The non-flip Brevis and SGPro achromats may be of a higher power than the ones I have used for my own adaptor which were 4+ and 7+.

The Extreme I have been playing around with has the EX1 special achromat which seems to work equally well with the Z1. I think it is in the ballpark of 4+ power. The condenser lens inside the Extreme seems to be fairly powerful. How much this interacts with the achromat, I do not know and would have to pull it apart to find out.

Next time I get hold of Steve Rice's HD100, I'll set it up with the Nikon 35mm, the EX1 achromat and a 60mm x 70mm target and see what happens. My sense is that with only 4+ or so, the non-flip adaptor is still going to be fairly long. If Wayne's or Dennis' achromats are sharp to the edges with your current setup, then the same achromats on a Nikon prime may be okay as the Nikon's front glass is of a smaller diameter and may likely work more inside a sweeter area in centre of the achromats.

[Bob Hart]

Ted.


I forgot to answer your question on why put a 35mm adaptor on the SI2K. I understand that the P+S Technik Pro35 has been used but it is an expensive solution.

I am probably a glutton for punishment but it is for no better reason than it is there to be tried. To achieve similar shallow depth-of-field effects, Super16mm superspeed lenses have to be aquired. With the RED, SI2K and others, there has been a run on these and they are now rare secondhand and expensive. The cupboard on ebay is now quite bare.

I would not use a 35mm adaptor on the SI2K exclusively but only where I wanted the specialty looks of shallow depth-of-field or an exceptionally wide field-of-view like with the 35mm 14mm lenses or the Peleng 8mm fisheye.

As you correctly suggest, the sensible use of Super16mm and good quality 35mm stills primes will be adequate in most cases.

Interestingly, ( I guess this is off-topic) I had another look at the RED post. Their proposed 28K Monstro sensor appears to be purposed to using plate camera lenses. I imagine your back room is full of old plate cameras from past generations at work.

To what purpose one might wonder but my thoughts are that Omni and Imax style immersive theatrical exhibition might make a big comeback if this technology and the means of economically processing and exhibiting the images gets up. Just imagine it in 3D which would be a financial impossibility with film. There is also obvioius military application and I would not be surprised if the 28K became export restricted like much of the infrared imaging technology.

[Bob Hart]

I don't know what is going on but my posts are dumping on first attempt. Here is a quick recall. I'm not writing a second long one.

Tests with a Letus Extreme modified for adjustable centricity and wider groundglass view indicate the following lenses will work as direct relay via the special EX1 achromat.

The lens on front of the Letus was a Nikon f1.4 85mm.

The relay test lenses were mounted to the JVC camera with a Les Bosher Nikon-to-JVC mount adaptor.

The JVC test camera, Les Bosher Nikon-to-JVC mount adaptor, Nikon lenses for relay and Letus Extreme were assembled with care onto the standard Letus rail system. It is not safe for the hardware to be assembled and tested without this support.


Nikon f1.4 50mm. (multiplication factor as with original direct relay).

Nikon f1.4 35mm. (image width roughly comparable with P+S Technik Mini35-400).

Sigma for Nikon f1.8 28mm. (image width roughly comparable with EX1 wide view of unmodified Letus Extreme).

Sigma for Nikon f1.8 20mm. (image width roughly comparable with EX1 wide view of modified Letus Extreme).


The Nikon f1.4 35mm relay image yield, with detail on the JVC set at "normal" suggests an apparent resolution of the "B" block of a Lemac chart which is 862 horizontal lines or better.


This information should not be taken as assurance that these tests can be confidently repeated on your camera and Letus Extreme adaptor without possible damage occurring.

Using these lenses for direct relay should only be regarded as an inferior stopgap until the genuine direct relay lenses from Letus come along.

The 35mm and 50mm lenses have 52mm diameter filter mounts and would require custom bridging rings to mount to the back of the Letus Extreme if they are not available from Letus or their vendors. The Sigma f1.8 28mm has a 62mm filter mount.

The Nikon lenses become longer or shorter when focussed so the Letus front body mount pillar bridgepiece should be loosened on the rails and allowed to slide so the lens movement can happen.

The weight of the Letus Extreme should be supported and not allowed to hang on the relay lenses. The focus movements will otherwise become impossible to adjust.

The Nikon 35mm f1.4 may work as a direct relay on an unmodified Letus Extreme, depending upon how correctly centered in combination, both the camera sensor and the Letus Extreme optical paths happen to be.

I cannot capture from this camera. I will be sending the tape to another JVC owner who may or may not capture and post the footage.

[Bob Hart]

The Nikon f1.4 28mm which has a 72mm diam 0.7mm pitch threaded filter mount with a Les Bosher Nikon-to-JVC adaptor mount will work turnkey from scratch as a relay with the Z1 adaptor ring on an accurately centered Letus Extreme which is also centered internally. As it is an internally focussed lens, the Letus Extreme body can be locked down to the rails.

A groundglass view, wider than motion picture frame is available. With the EX1 achromat, edge to edge focus on the groundglass appears to remain sharp.

The maximum aperture opening of f1.4 is not practically usable. Opening the iris ring that last click introduces a moderately severe "milky" artifact which seems to be some sort of interaction with the camcorder prism splitter as colour separation also occurs when the relay is defocused.

The Nikon f1.4 35mm also behaves the same.


"Normal" detail setting on the camera results in a similar artifact through the Letus on items like chain link fencing as is seen direct-to-camera. This occurs with both the f1.4 35mm as relay and the f1.4 28mm as relay. Detail probably needs to be wound back.

The f1.4 28mm is no longer made and its value is now more than the projected cost of the purposed direct relay lens which is in the works at Letus. Use of it as a relay would be pointlessly extravagant.

If a 62mm diameter filter mount adaptor ring could be made, the Sigma f1.8 28mm lens would be adequate stopgap direct relay if a groundglass view wider than the motion picture frame is required.

This arrangement in conjunction with Paolo Ciccone's Truecolor V3 scene file really looks magic in outdoors lighting. Greens especially are reproduced faithfully.


EDIT. Here is a web address to a very short SD extract from the JVC footage via DVD recorder. The vision is a bit soft and does not reflect the true image for sharpness at all. If you look closely in right half of frame, you may see one of our pestiferous bush flies come through the focus zone in the third shot.

http://exposureroom.com/members/DARA...fa25d62896f0f/

The HDV cannot be captured due to blown firewire port.

[Bob Hart]

Here are some frame grabs also low res from a DVD recording of the JVC - Letus via Nikon direct relay test. They illustrate the comparative view of the groundglass for the same objective lens on front, which was a Nikon f.14 85mm.

The wider lenses may not work successfuly for relay unless the Extreme is accurately mounted and the internal optical path is re-centered. The 20mm begins to pick up an edge from the widened path on the one I have modified for about 2mm wider view of the groundglass.

FOOTNOTE: Sorry I think I broke the uploader. Will try again.

FURTHUR FOOTNOTE: Success. The black bar down the side is an artifact from forcing a recode of composite DVD-Video through AspectHD. The brown margin on left in the parrot feed shots is not an artifact, but the edge of a vertical window blind I had hidden the camera behind. I had hoped to grab a shot of birds fighting but they spotted the camera and shot through. The similar margin on the cricket practice frame was a metal fencepost I was doing pull-focus things with.

[Bob Hart]

During playback of tests conducted today with the Nikon f1.4 28mm lens as relay, it was observed that in bright sunny high contrast outdoors conditions, a severe broad blue CA corona surrounds overblown white objects such as white vehicles and pinpoint highlights, a quite unacceptable artifact.

There is also blue-green blending in tree canopies.

Previous tests yesterday with the Nikon f1.4 35mm lens for relay were conducted in low-contrast overcast lighting conditions which would not have provoked this artifact.

This blue corona was also observed with the 35mm relay at night around headlights as previously mentioned so it is highly likely to occur with the 35mm lens as relay as well.

What a blow. However, this is likely the reason why the wait for a direct relay lens from Letus has been so long. The CA issue would have been waiting in ambush and may not have raised its ugly head until after some money was already spent on custom lenses.

The use of the Nikon lenses for relay of the Letus Extreme may be viable in controlled low contrast lighting conditions but for bright outdoors, especially in the 10am to 4pm zone they will come up short.

Sorry about the initial rush of enthusiasm but this is what R (without the "&D") is all about.

Be patient with the Le brothers and the other vendors on direct relay lenses for the JVC GY-HD*** , Canon XL** camera families and Sony Z7. It is obviously a tough nut to crack. It is certainly something you want to work right.

[Ted Ramasola]

Thanks Bob for quickly adding this last post, I was already raising my hand with the scalpel and taking a deep breath before plunging the knife to severe the stock lens from its body when the computer went DING! -saying a theres a reply to the thread! -I held my hand, lowered the scalpel and read your post urging a stay in my cams execution... he got a timely reprieve.

My life is back to normal for the moment.