Cutting/removing the lens off a HVX ?

[Dennis Hingsberg]

Matt, I think it can be done but I will definitely need some help and these forums are a great start.

I need to study the design of the relay lens from my PS Technik which takes the image from the screen of the mini35 to the CCD of my XL2. A well designed relay lens is where I will need to start.

I've read of some people using an F1.4 50mm in reverse as a relay lens, but I'm looking for less loss if possible. Remember, my goal is to have a 35mm adapter projecting the image directly on the camera CCD with a complete light loss total equal to the original stock lens (f1.6 for HVX, slightly more than 1 stop).

The "ground glass" portion I'm not too concerned about. These days we've got people like Dennis Wood (creator of the Brevis) with vibrating gg systems that produce incredible results with HD cameras with losses at about 1/2 stop. The technology is out there to harness I just need to figure out the best way to bring it all together.

For starters I would probably not worry too much about finding a way to attach the 35mm adapter directly to the camera. At the beginning I might just use a rail system could easily be used to mount the 35mm lens, 35mm gg system, relay lens, and HVX camera (without lens). This might require some fine tuning to get the distances accurate.

I also have been emailing Daniel Schaumberger of http://www.jetsetmodels.info/holders.htm who builds gg holders for 35mm adapters, he's offered to help me if he can with any construction or milling work I may need. He also knows a lot about 35mm adapters in general.

In the meantime I'm trying to get hold of someone now who's put their HVX up on the market. I'll need that too : )

[Matt Burton]

I would be more concerned about the electronic implications of removing the lens system from the HVX.
With focus and iris directly controled by the lens who knows what will happen when the two are seperated from the camera.
If only somebaody could test it out on perhaps a damaged camera on it's last legs. Surly panasonic have some near death reterns that are filling up a bin somewhere.
If we could get the ok on the electronics front I would be willing to beta test the mod with my camera.
-matt

[Colin Mounier]

Dennis, nice idea but or better: Have you read the threads about "chromatic" problems the XH1's owners have when they use an other lens? I tryed a non"HD" zoom on a Varicam, The flare inside the lens, the color franges according to the lens figure, even a sharp line of contrast between sun and shadow...there were too many factors to realy do a picture with it. But i would love to hear a solution.

[Dave F. Nelson]

Originally Posted by Dennis Hingsberg

Has anyone here tried or have any experience removing the stock lens from a HVX? Anyone gone that far in taking one apart that they could provide testament to it's ease or difficulty? Any manuals or such would be highly appreciated.

I'm looking at designing a 35mm mod for HVX cameras that will yield an overall brighter setup compared to traditional methods.

In theory the mod could provide an effective light "gain" of 2 stops when using 35mm setup.

This would effectively mean you could bet back to the cameras original working ASA. (ie. approx 400 for the HVX) Currently with most 35mm add-on adapters you end up with an approximate working ASA of 100, or between 50 and 60 once you throw a 35mm lens into the equation.

This is impractical for most film style lighting setups, particularly indoor.

If you don't understand the relationship between ASA, f stops and shutter speeds? Here's a really good read: http://www.uscoles.com/fstop.htm

To my way of thinking, you would be money ahead if you sold your HVX, bought a Canon XL-H1 or a JVC HD100/110, removed the stock lens and installed a mini35 with a relay lens. You could also use a Letus35 with a relay lens with either the Canon or JVC to save money over the mini35.

You would get the gain you wanted when you removed the stock lens and replaced it with a relay lens. You would have no CA problems, and you would also be able to put the camcorder back together and sell it when you were done using it.

You could also test it before you made the plunge to see if it worked for your application, rather than getting a hack saw out and destroying a perfectly good HVX on a lark.

Just my humble opinion.

[Dennis Hingsberg]

Hi Colin,

The idea is to use a relay lens to take the 35mm image projected onto a gg (ground glass) directly to the CCD block of the HVX. I don't intend on using alternative lenses directly on the CCD block of the HVX.

Hi Dave,

I've definitely considered the mini35 on the JVC or Canon however the mini35 loses 2 (or more) stops of light which takes the working ASA of the camera down from 400 to 100. Add a 35mm lens and at 1 f-stop you go from 100 ASA to 50 ASA. This is an impractical working ASA for lighting interior scenes and yields way to much depth of field to the point where the DOF is much too obvious.

A good gg will only lose .5 stop of light, combined with a relay lens I might only lose another 1/2 to full stop. If you think about this it puts me at f1 to f1.4 total light loss - basically the same as when shooting with the HVX stock lens.


Other idea:
I also intend on flipping the CCD block of the HVX so in that sense no flip mechanism is required in the 35mm adapter. This would prevent the image from being up and having to be flipped in post.

Yes all this renders an HVX useless for regular work but I truly believe this would be the ulitmate 35mm digital camera (next to RED of course) due to the overall size and light gain. The HVX body only is 7 inches in length - yet so much power on-board.

I'm still looking for an HVX to buy and starting to research relay lenses.

[Barry Gribble]

Dennis,

GG directly on the CCU sounds interesting... have you done that with a cheaper camera? It seems like something you could start working the kinks out with anything.

Good luck.

[Barry Gribble]

Dennis,

GG directly on the CCU sounds interesting... have you done that with a cheaper camera? It seems like something you could start working the kinks out with anything.

Good luck.

[Dennis Hingsberg]

Barry,

I haven't tried anything with a cheaper camera yet, but likely a good idea. I do however own an XL2 where obviously the lens comes off and I can do some limited testing in terms of testing some good relay lens designs.

I found archives on DVinfo actually from when the XL1 was big news and people were trying to do the very same thing. In most cases 24mm or 50mm SLR lenses were being used as a relay lens combined with "close up" kits to focus on very close gg screens. Problem is if the 24mm or 50mm lens is rated at f1.4 then I'm no better off shooting through the stock HVX lens which is also rated around there (once you zoom in a little).

The idea is a relay lens design with virtually no light loss. That's basically where I am with my idea so far... just finding out as much as possible about relay lens design and alternative relay lens design methods.

The goal was to add 2 stops of light gain to the equation, half of which is easily accomplished by not needing the stock HVX lens.

We'll see what happens and where my progress lands me.

[Ken Hodson]

For experimentation I would recommend a JVC HD1 or 10. The form factor and resolution are much the same. Especially the consumer version HD1(no XLR and high edge enhancement) can be found used for a good price (under $1000?)

Along the same lines I would recommend doing an advanced search selecting the "JVC HD1/10" forum with the keywords " ground glass". I would also try "35mm".
This topic was discussed at extensive lengths back in the day by the first batch of prosumer HD enthusiasts. I seem to recall issues with ground glass and the high resolution not working out.

Check these out for starters. Hope they help.

http://www.dvinfo.net/conf/showthrea...t=ground+glass

http://www.dvinfo.net/conf/showthrea...threadid=30235

[Dennis Hingsberg]

Thanks Ken, I will check out those links.

[Ryan Damm]

Hey Dennis -

Love the ambition. Hope you don't think I'm too forward, but I wanted to comment on the notion of light 'efficiency.'

Most people making 35mm adapters treat f/# as an algebraic variable that can just be manipulated to tell you your total light loss. I find it far more valuable to think of f/# more like numerical aperture -- roughly, a mathematical expression that describes the size of the cone of light in an system.

When you use a scattering plate, you're basically re-randomizing that cone of light. That's why people have noticed a (roughly) algebraic relationship between various lens elements.

In a non-scattering system, though, you don't just start with some arbitrary amount of light and subtract from that total with each element. Properly, you diverge or converge ray bundles, and depending on their total angular displacement you can either increase or decrease the f-number with various attachments (though in practice they usually decrease it).

In a scattering system, the precise scattering properties of your scattering medium (typically ground glass) matter a lot. Since most people are using 35mm still lenses (that is, non-telecentric lenses, like 3-chip video camera lenses), the incident rays on the ground glass aren't perpendicular except on-axis.

The ground glass re-randomizes some of that light, so the rays that are pointing away from your second (relay) lens get scattered back towards the camera.

Note that the numerical speed of your relay system does not guarantee that you'll get all that light. If the scattering properties of your ground glass yield perfect scattering, you'd actually require an (impossible) f/0 relay lens to capture 'all' the light.

In practice, the scattering will send some light off axis and allow some through unscattered. Better relay lenses use field lenses or condenser lenses to redirect the outer ray bundles so they're more perpendicular to the scattering medium. The idea, I think, is that this will even out the hot-spot: the hot spot results from incomplete scattering, and some unscattered light goes straight into the camera lens. Off-axis, that unscattered light is simply lost.

Ironically, aerial lenses Panavision's Frazier and Hylen lens systems do exactly what 35mm adapters are trying to do, but without any scattering plate at all.

As it turns out, you don't need to scatter the light in order to create an image from a 35mm lens. The image is always there. If it doesn't actually strike a physical surface, the rays continue unimpeded. They can then be collected just like a normal image. If your relay system is large and fast enough, you can theoretically capture all of the light (minus scattering and reflection at glass/air interfaces, of course).

Just for fun, if you've got a 35mm adapter, try getting it focused, setting everything up, then removing the ground glass completely.

If your condenser lenses are strong enough, the rays should be bent directly into your second camera. No hot spot, no scattering. Maximum light efficiency. You should be able to record the aerial image directly onto your camera.

Or am I missing something?

[Ryan Damm]

I forgot about the optical invariant. Never mind; it probably wouldn't work without scattering (only because the rear lens would have to operate at a truly ridiculous f-number, to the point where it would have pretty shallow DOF on its own).

I am curious to know what these rigs look like without the scattering plate, though - my guess is you get some properties of the taking lens and some of the rear lens - diffraction patterns, for example - but probably not the DOF.

I'd try it myself, but my XL1s was stolen last week. It was part of a medium-format rig (image plane 75mm x 50 mm, fiber optic plate, dual PCX condenser).

[Bob Hart]

They work in aerial image mode and the Sony autofocus works as well within limits. I regularly use mine with the GG removed for adapting telephoto lenses to the camera.

You lose the shallow depth of field and have to zoom in furthur to get inside the vignette of long lenses.

If you have time to waste in a search on YouTube for videos by "agus35monk" and look for "The Tiger is 75 years young", you will find footage shot on a Z1P with Agus35 with groundglass removed.

[Thomas Barthle Jr.]

I remember reading that the CCD block on the HVX shifts forward and backward to help with macro focusing. They were saying you could focus all the way to the front of the lense. I'm sorry I can't remember who "they" are, but make sure to take this into consideration, as it will effect the distance to the gg. This is my only concern. Good Luck!

Cheers.

[Sven Fleck]

I know someone who has experience with that cutting thing:

http://www.mgm.com/hannibal/home-flash.html