New extreme owner lens and use questions
 

I got my Letus extreme a last Friday, and I've been working with it quite a bit. I have a few questions, and hopefully someone give me feedback . I LOVE the look, btw. Thanks, Hien.
1- I've tried my Nikon 50mm 1.8, 85mm 1.4, and a 28mm 2.8, all of which work well. I put on my Nikon 17-55 2.8, and got nowhere. It was an incredibly dark image. I think that the iris closes down when you power down the digital camera, and stays that way when you put it on the extreme. Am I missing something or is this lens unusable on the extreme?

2- I have a wedding on Sunday, and am debating trying out the Letus. i'll still have two other cameras, so it won't be the main rig I'll depend on. Which lens would I better of starting with in order to get some creative shots of the bride, flowers, etc? My only experience is shooting around the house, and I'm not sure what opportunities I'll have. I'll also keep it on tripod.
I'm pretty happy so far, and look forward to putting it to use.
Bruce Yarock
www.yarock.com

Some newer Nikon lenses require you to wedge the little iris lever in back of the mount in the open position for work on an adaptor.

The usual cuplrits for quick and dirty wedges range from bits of toothpicks, shaved down rolled roast skewers, a little tube of insulation stripped from single core eletrical wire, a small piece of rolled up cardboard or paper, a small piece of whipper-snipper (weedwhacker) cutting line.

Bob,
I got an email from Mike stevens at lenses35.com, and he told me that the zoom lenses, like my 17-55 and 70-200 , have auto iris and no manual iris control on the lens itself. Therefore, when you take it off the digital camera, the iris shuts down. So I guess those lenses are out.
Thanks
Bruce yarock
www.yarock.com

It has also been my experience that, regardless of the length of the lens you are using, stopping down much beyond f4 results in too much of the ground glass grain coming through in the final image. I imagine you could stop down further in extremely high light situations, but I've been using the f4 limit as a general rule.

Hi Bob,

Is it a simple easy thing to do? Got dummy-proof pictures illustrating such?

I have a sigma ultra-wide digital lens (the 10-20mm zoom to be exact) for nikon. It would be fantastic if there was indeed an easy way to open and lock the aperture wide, and get it working with the adaptor, without damaging it.

Thanks in advance.

Kevin.


I do not know the Sigma for Nikon 10mm - 20mm zoom. As a digital lens it may only be suitable for a 24mm wide groundglass image. . The Letus models for lens-in-camera style camcorders characteristically enable a wider view of the groundglass than 24mm so you may find some corner brightness falloff or even a vignette onto a groundglass whn using a digital lens. Some Sigma models are optimsed for digital but are also designed to cover a full still-image film frame 36mm wide.

I am a bit apprehensive about advising on how to deal with this lens and concerned that I may send you on a destructive journey.

The Nikon lens I did this to was the 12mm - 24mm f4 zoom.

In back of the lens body is a chrome coloured Nikon mount and inside of that is a little lever which moves in a slot about 7/16" long. There is spring pressure against the lever which keeps the iris in an almost closed position.

If this lever is moved anticlockwise, the iris opens up.

I used a piece of approx 1/8" diameter gray rubber cable insulation stripped from a microphone cable. This I squeezed into the space vacated by the lever when I moved it leftwards to the iris fully open position.

You need to cut it long enough to hit bottom in the hollow it is shoved into so that it does not go right through to the inside and become lost there. It is best you have a long piece, say about 3/4", shove it into the slot and trim it shorter to have about a 1/8" tail sticking out.

The cable insulation scrap I lost when I returned the lens to a camera.

The next wedge I made up was a piece of orange weed trimmer cord. It is not smooth sided but has grooves extruded into it for presumably a better cut.

It is very slightly wider point to point than the slot in the lens but the ridges between the grooves will squash and let you shove it into the slot.

The ridges then conform to the thin metal of the edges of the slot and the piece of cord does not fall out. It can be a devil of a job to remove it later however.

Shortening any wedging piece after you have shoved it into the slot can be awkward. I found the best means for cutting was a jaws style fingernail clipper, not scizzors which twist the wedge piece.

Both these items are lazy and quick fixes on my part, not professional at all.

What I should be doing is making a small rectangular section to fit precisely into the space with a wider head to prevent it from falling through to the inside of the lens rear body and high enough that it will just clear the inside of the 35mm adaptor but will not fall out before it fetches up against an internal surface of the adaptor.

I'll try for a photo but I have not been able to successfully upload a still-image to dvinfo as yet.

Thanks Bob.

I'll have a peep at my 10-20.
A 10mm prime is near impossible to get so it'd be great if there was a good hack.

Cheers.

Took a pic of the 10-20.
There is a pin switch (circled in pic) that appears to open the aperture.

Kevin.

That is it. When you move the lever to the left as viewed from rear of lens it will leave a space. This space is where you put the wedge. For starters just try a piece of thin cereal pack cardboard rolled up tight, approximately 3/8" square. About two and a half folds will be about it.

Before you shove it in, just probe the space to find the depth first with something like an opened out paper clip. You may need to make that cardboard 1/2" x 3/8" but I doubt it will need to be bigger. The lever may creep back past a little but it should not matter.

I think you will find that your lens will vignette on the 10mm end but may widen as you zoom it in. I expect that your lens iris wide-open may be also in the ballpark of f3.5 to f4, going by the size of the rear element.

This may only give you about 1 f-stop of headroom before groundglass artifacts become apparent if they are not already there.

There are modern motion picture primes which go down to 9mm but they are hell expensive and also do not cover much larger an area on the groundglass than the digital lenses as they are designed for the 24mm wide motion picture flm frame.

On the Letus Extreme you may find you achieve just as much field-of-view coverage by using the 14mm f2.8 Nikon prime across a larger groundglass area.

This will yield fewer if any artifacts and sharper resolution through having less magnification of the groundglass, therefore smaller scaling of the groundglass texture relative to the image area seen by the camcorder.

There are older 9.8mm f1.8 Kinoptiks but these tend to be a little soft and flary. They also vignette a full 35mm still-image frame. There are two shots with this lens in this clip :-

http://www.youtube.com/watch?v=kpm72LpoV0k

Another thing you will observe if the 10mm -24mm is a rectilinear lens, is that whilst straight objects like doorframes remain straight, there will be stretching of the image in diagonal directions to the corners.

This can be cool for accentuating motion towards and away from the camera or camera moves themselves.

It may limit your vertical camera positions in a room to about midway high relative to a window frame in the shot and camera tilt set at near level, otherwise it is going to look weird perspectively with window frames taking on an accentuated trapezoid shape.

An example of this accentuated perspective can be seen in this clip shot on Super16 film with a 5.7mm Kinoptik which of course covers a much smaller image than the 35mm film frame but is near the same in field-of-view terms in the Super16mm format as the 9.8mm is to 35mm :-

http://www.youtube.com/watch?v=43KPM55B-FU