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-   -   question about altering a Letus (https://www.dvinfo.net/forum/alternative-imaging-methods/101198-question-about-altering-letus.html)

Wes Powell August 12th, 2007 08:15 PM

question about altering a Letus
 
So I might get a Letus35 and I was wondering if they use a macro or a achromat lens (still new to this so I could be sounding stupid). So my question is I want to use it on a HDV camera.....is there anyway to take out the achromat or macro that is in it and replace it with a better one?

Bob Hart August 12th, 2007 09:38 PM

I am not sure I would want to change what is there optically too much. Quyen has chosen a combination of optics to arrive at a combination which yields an adequate result at a reasonable price point.

The Letus35 flip for Canon XL and JVC HD100 families uses the following path :-

Subject >> SLR camera lens (Nikon or Canon) >> groundglass >> reversed biconvex element (condenser) >> unmounted achromatic dioptre >> Minolta 50mm SLR camera lens for relay with modified mount >> camcorder.

The achromatic dioptre used is unmounted (as in does not have a metal ring around it). Quyen attaches this doublet directly to the front of the Minolta relay lens with a firm compliant adhesive.

You could trim this adhesive away with a sharp pointed knife and replace the dioptre. This however would be the beginning of a slew of troubles. The distances between all optical elements and the groundglass have been determined by the focal characteristics of all those individual pieces of glass.

Your task would be then to shorten or lengthen sections of casework to accommodate those changed distances. This would require remake of some sections which requires good workshop skills or the means to get others to do it for you.

Look through the Ben Winter posts. He has been there - done that.

If you want to see what a Letus35 looks like gutzed out, on the last entry of the Claytons sticky above ion the Letus sub-forum, not the one directly above, there is a link to a clip on YouTube where one is dismantled.

Wes Powell August 12th, 2007 10:27 PM

would getting a basic Letus35 be a bad idea for a HVX200

Bob Hart August 13th, 2007 04:34 AM

Wes.


I can not give you a quality answer regarding the HVX200 as I have not used this camera or the LETUS35FE which I understand is the closest fit to it.

I try to be even-handed when it comes to the various alternative products discussed here but it is a bit difficult as I have no experience with any of the others. Therefore my comments may seem to favour the LETUS35.

If you use the HVX200 at MiniDV resolution you may achieve adequate results with the LETUS35FE because the framing onto the groundglass can be wider than with the Canon/JVC direct relay versions. Apparent resolution is improved.

My own testing of the LETUS35 flip partially dismantled to resemble the FE into a Sony Z1, suggests that with a very good SLR lens, 862 TV lines may be resolvable in ideal circumstances. This is the horizontal resolution suggested by the "B" block of the Lemac chart I used.

Real world conditions are another thing. To achieve best results you will need to light for a film speed of ASA 80 or thereabouts, or relay aperture of about f5.6 and SLR lens aperture set no narrower than f3.5.

You need to be very careful about SLR lens focus and relay lens focus (which is your HVX200's own lens plus achromatic dioptre.) The upside of using a camcorder's own lens for relay is that short burst of autofocus can be used to maintain relay focus and the zoom used for fine framing adjustments.

If you use the HVX200 as a HD camera with the P2 memory cards, then you may find fixed pattern artifacts in your image across bright evenly lit areas of soft focus. If you intend to shoot only for SD distribution or myspace or youtube music videos, the LETUS35 may be adequate.

I understand from past posts that political advertising spots have been shot on the LETUS35 - HVX100 combination and that the client was satisfied.

If you want to sell to HD pay tv or free-to-air broadcast, you may find your product unmarketable.

The LETUS35 remains the only "flip" 35mm film emulative moving groundglass adaptor this side of the MINI35. Other adaptors may yield better results but you have to live with the chore of flipping the image in post.

I understand that the BREVIS may have a flip module available as a retrofit for existing product and as an option for new product quite soon.

Phil Bloom has been achieving marketable product for free-to-air broadcast with the BREVIS, I think into the JVC GY HD250, which has the flip function built-in. You will need to read back through his posts to get the info on this product.

Bob Hart August 13th, 2007 11:40 AM

Footnote To Above Reply
 
I neglected to mention that for relay into the Z1, I used the Century Optics 4+ achromatic dioptre I have used with the long setback version of my own device.

A 7+ via the flip enclosure and bi-convex condenser may be too strong and you may not be able to get the camcorder close enough to focus on the GG even at infinity focus on the camcorder's lens.

As I mentioned above Phil Bloom and Ben Winter have some expereinces in this area.

Steven Dempsey August 13th, 2007 01:31 PM

Wes,

I use a Letus Flip Enhanced with my XHA1 and have gotten spectacular results. The adapter is well capable of rendering a HD-quality image. I don't think there would be any need to change anything.


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