Everything you wanted to know about the Letus Extreme and were too afraid to ask

It sounds to me that your noticing what I have, which is I suspect that the achromats used in these adapters all have their sweet spots for good corner to center focusing. Its makes the whole business pretty complicated.

Its certainly a combination of
1. distance from achromat to the screen
2. Zoom focal length on the video lens
3. The size of the image (related to the zoom length) (be it Academy or SLR full frame (Vistavision)
3. The Focus distance on the video lens (also a function of 2 & 3)
4. The video camera itself and its lens. This can alter many parts of the equation and its why dennis has different screens for different video cameras.

I wonder if an adapter that has great sharpness at Vistavision can maintain that while zooming into Academy. If not is an adapter that looks great with say Vistavision Nikkors going to look as good with Zeiss Academy cine lenses and vice versa?

That's a good question for the adapter makers. Dennis?


BTW - Rather than comparing the field of view of a Nikkor to a Red image that was posted somewhere why not compare it to a real SLR. I found the redrock to pretty similar and suspect the Brevis is likewise. close.
 
Hey there and thanks for your answers.

I've been a AC only once on a film shoot (you really earn your money...), so measuring is still essential to me and I guess for everyone who's neither very talented in that or just not long enough expirienced...

So at least markings would be great, does anyone know, when the put these marks on the adapter?

Ryan E. Walters said:
but my Nikon lens marking are very close to being right on (They are only a couple of inches off from the measured distance.).
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This sounded a bit shocking to me, a couple of inches is quite a lot, specially in with higher focal lenses (you knwo the story)...

But I may not have understood you correctly.

BTW: Ryan, thanks for the nice adapter review, though my picky questions I still like the adapter very much :)

Max
 
MaxZenk said:
Hey there and thanks for your answers.

I've been a AC only once on a film shoot (you really earn your money...), so measuring is still essential to me and I guess for everyone who's neither very talented in that or just not long enough expirienced...

So at least markings would be great, does anyone know, when the put these marks on the adapter?



This sounded a bit shocking to me, a couple of inches is quite a lot, specially in with higher focal lenses (you knwo the story)...

But I may not have understood you correctly.

BTW: Ryan, thanks for the nice adapter review, though my picky questions I still like the adapter very much :)

Max
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Yes having the markings off by a couple of inches is a big deal if you are only going by the markings. There are a couple of solutions to this (Which I've used before in AC work that I have done with SLR lenses.)

1. Put a piece of spike tape (1/4" tape) around the measurement markings and mark the lens yourself with the correct measurements.

or

2. Adjust the adpater until the measurements line up correctly. (I haven't tried this yet with the Letus Extreme. But with teh M2 I found it easier and quicker to just do #1)

Something else to keep in mind is that using an SLR lens is VERY different then using a cinema lens. Cinema lenses are beautifully made and are made for this kind of work, and SLR lenses are not. The first thing that you will notice with the SLR lens is that they turn differently then the cinema lens. This is a bigger deal if you've gotten used to the cinema lens, as you have to adjust your thinking to the "new" way the lens turns. Secondly, a cinema lens is very smooth and even in it operation- this is not always the case with SLR lenses. Which makes operating them a different experience then the cinema lenses. Thirdly, the SLR lens markings are spaced out differently then the cinema lenses- again they were developed for different applications, so the lens markings on an SLR are not always helpful anyway, and you'll have to make some of your own marks. And lastly, on an SLR you do not have the fine control of the exposure that you do on a cinema lens. On a cinema lens you can fine tune your exposures, while on most SLR's you are either at one stop or at another. A close exception to this are the SLR lenses from Zeiss- when I've used them, they are the closet to feeling like a cinema lens that I have experienced- they are still SLR, and still have some of the issues I just mentioned, just not as extreme.

Anyway, all that to say that when you are using a 35mm adapter with non-cinema lenses there are a bunch of additional changes and differences that you have to adapt for anyway so figuring out a solution to the markings is just an additional one for me. After using a set of prime cinema lenses it is hard to go back to the SLR lenses.... I'd really like ot get a set of Zeiss super speeds ..... :)
 
Lenilenapi said:
It sounds to me that your noticing what I have, which is I suspect that the achromats used in these adapters all have their sweet spots for good corner to center focusing. Its makes the whole business pretty complicated.
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Yeah, there definately seems to be a sweet spot alright.

Lenilenapi said:
BTW - Rather than comparing the field of view of a Nikkor to a Red image that was posted somewhere why not compare it to a real SLR. I found the redrock to pretty similar and suspect the Brevis is likewise. close.
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The RED test was more for people who are wanting to get the same field of view as a cinema lens, that was the point of that "test".
 
Yes having the markings off by a couple of inches is a big deal if you are only going by the markings
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Furthermore, if the marks are off (presuming you're measuring from the focal plane) then that means infinity is probably off too; meaning the lens won't focus to infinity.

If you're measuring from the front of the lens, the marks will definitely be off; film camera lenses are designed to be measured from the focal plane, not the front of the lens. But if you're measuring from the front of the lens, and the distance marks don't correlate with what the tape says, then you either have a bum/miscalibrated lens, or your collimation is off. If the collimation is off, you probably won't be able to get a sharp image when the lens is focused at infinity.
 
Barry is correct and frankly of the 4 adapters I have had, the back focus was off on 3 of them so that's not very good odds. Your lens should focus at infinity just as you hit the end of its travel. If it doesn't you are off. A good check also is to try a zoom lens. If your backfocus is off it will not track the focus properly as yous zoom from telephoto to wideangle (assuming you have a good zoom lens which is another story.) Same as setting backfous on a professional video lens.

If your back focus is correct your footage markings should be correct also, but Ryan is right, SLR l;enses are not designed for focus pulling and the markings may not be as precise nor are they spaced well for good pulling. Unfortunately as fabulous as these adapters can be , ata certain point you get what you pay for.

Lenny Levy
 
Barry_Green said:
Furthermore, if the marks are off (presuming you're measuring from the focal plane) then that means infinity is probably off too; meaning the lens won't focus to infinity. ... If the collimation is off, you probably won't be able to get a sharp image when the lens is focused at infinity.
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Yep- that is a good point indeed. (Although for wide shots where I need to get to infinity I've just been using the stock HVX lens, as it gives me a wider field of view anyway.)
 
Lenilenapi said:
Unfortunately as fabulous as these adapters can be , ata certain point you get what you pay for.

Lenny Levy
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This is especially ture when it comes to the glass you are putting infront of the adapter- I highly recommend getting a great lens(es)- they will last you longer then the camera.
 
The 35mm lens backfocus has nothing to to do with whether the backfocus of the adapter is set correctly for your videocamera.

The second half of that set-up guide is for 35mm lenses. Actually I don't think its quite complete enough because its stops where it tells you to do the fine adjustments.
They have a different method than I use . Don't know if there's is better or worse. i don't think I would trust the focus marks on my lens to set to though because that seems kind of a vague mark. Mabe I'm wrong though. I have been setting mine so that infinity is reached at the end of my focus barrell - so I can't go past it.
I'm not sure if that's neccessarily correct though and I should research it because I seem to remember that sometimes lenses are designed to go a touch past infinity, but that seems like a bad idea in our work.

I double check it with a number of lenses and especially with a zoom lens to make sure focus tracks from wide to tele. So far it seems to work.
Make sure your 35mm lens iris is wide open. Doesn't matter what the video camera is set for.

Lenny Levy
 
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trudd said:
Sorry if this has been covered, but..

How would one go about setting the backfocus properly on the Letus Extreme?
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We set the backfocus before we send the adapter to you. We also took into consideration different kinds of mounts so there is no need to change the back focus for each lens each time you change the mount.

Thanks
 
Is it easily user adjustable if for some reason it gets off or comes that way.
I ask this because in each of my cases previously the backfocus was supposed to have been set at the shop.

i don't mean to question your competence, just hoping that a simple adjustment is available to the user.

- lenny levy
 
Yes, we will walk you thru the process on the phone to adjust it depending on which way it is off. Pretty easy though.

Thanks,

Hien
 
hienle said:
We set the backfocus before we send the adapter to you. We also took into consideration different kinds of mounts so there is no need to change the back focus for each lens each time you change the mount.

Thanks
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:dankk2: That's great to hear. Looking forward to getting my Letus Extreme! I've got a shoot next weekend so here's to keeping my fingers crossed (ordered on 9/24)...

Thanks to the Le brothers for developing such a promising product.
 
hienle said:
We set the backfocus before we send the adapter to you. We also took into consideration different kinds of mounts so there is no need to change the back focus for each lens each time you change the mount.

Thanks
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It would be nice if you could give the rough measurement or marking for each lens mount when one wants to buy an extra different lens mount and change them when using difference brands with the Extreme. I will be buying an extra Canon EOS lens mount when I order an Extreme with Nikon mount.

I used to have a WDR35pro , a Brevis with both of them a FD mount and a Nikon mount. The Nikon mount is further away to the G.G then the FD mount. But then not all my Nikon Lens have the same back focus lengh, So It is still up to the individual to keep a record of thier lenses back focus measurement with each different adapter. The difference ranges between 0.1mm to 1mm of my Nikon lenses. It might not be alot, but it makes the difference between a sharp image through out or not espsecially in HD. That is why a good an accurate Vernier Calliper is a tool to have when one uses 35mm adapters.

No one adapter will shoot perfectly out from the box. It also depend on the lenses you have and how you set up the back focusing of that adapter to your lens.

I'm sure that most adapters out on the market gives very sharp images. But it is those that allows you to fine tune to your lenses that makes the differences (Brevis has the micro collimation). That is why we have so many footage from different people looking off focus while using the same adpater as those who show us sharp images. I always blame the camera operator (which is me) that the image is lousy. Give Barry Green or Macgregor a small HV10 and they will still do better then me with a HVX.
 
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Ryan E. Walters said:
Also, I was not able to get the image edge sharp 100% like it is in the center
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Thanks for posting Ryan.
I'm not used with HVX/XH-A1, but with my DVX+M2+Nikons edge to edge sharpness is absolutely there and usable, unlike that on your comparison. Is this simply because we're talking HD instead of SD?

Ryan E. Walters said:
and an even bigger difference when compared to the M2 pix.
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Well, again I would prefer the lower res on the center of you're M2 grab, but all over the sensor (as I achieve), instead of a higher res only in the center.

(that's not for a "mine adapter is better then yours". I'm just looking for finer adapters and finer picture and my english is too poor to let me explain as I'd like)
Cheers
 
David, If your individual Nikon's are not collimated the same , my guess is they should be sent to a repairperson. Nikon cameras are designed for professionals to be able to use interchangeable lenses. There should be a standard distance for Nikon backfocus and all lenses should adhere to that.

Maybe i'm expecting too much here. in quality control. With cine lenses I guess there should have been the same standard but in rental houses they always have to check lenses every time they go out. I do remember differences there. Seems to me we used to use some kind of shims for adjustment, but I honestly can't remember what we did.
Lenny
 
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