Wide Angle Camcorder Lens for CIH? - AVS Forum
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post #1 of 21 Old 09-20-2008, 12:06 PM - Thread Starter
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Assuming that they could be placed close enough to the projector's lens, could a "wide angle" camcorder lens such as Sony's VCL-E07A or their VCLHG0737C (both .7x lenses) work in a CIH setup?
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post #2 of 21 Old 09-20-2008, 10:11 PM
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0.7x as in compression or reduction? If the lens only does this in one direction - typically horizontally, then it should (when reversed) magnify in the same plain.

Typically the math is as follows -
1 x 1.3333333 = 1.3333333 and
1.3333333 x 0.75 = 1 so this should work...

Mark

So provided the lens does not vignet, should work.

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post #3 of 21 Old 09-21-2008, 07:27 AM
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I thought a camcorder lens will not compress in one direction and therefore would work as a zoom lens rather than an anamorphic lens. Are there camcorder lenses that would compress in one direction?
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post #4 of 21 Old 09-21-2008, 07:36 AM
 
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These lenses are not anamorphic and even if they were they would be FAR too small in diameter. Taking lenses are different to projection lenses. If this was a viable alternative don't you think it would have been discovered before now?

Do you need any more reasons why this is a bad idea?

Forget about it. Won't work in a million - make that a billion - years of trying.
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post #5 of 21 Old 09-21-2008, 11:34 AM - Thread Starter
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Quote:
Originally Posted by Aussie Bob View Post

These lenses are not anamorphic and even if they were they would be FAR too small in diameter. Taking lenses are different to projection lenses. If this was a viable alternative don't you think it would have been discovered before now?

Do you need any more reasons why this is a bad idea?

Forget about it. Won't work in a million - make that a billion - years of trying.

If I could get, maybe, one or two more reasons that'd be good. Seriously, though, I searched the threads here for any kind of history of this ever being tried and didn't find a single mention.

I do appreciate the comments, guys -- thank you all! I did some measuring and it does seem that the camcorder add-on lens would fit right up against my projector's lens, so, Mark -- after reading your figures I'm sort of inclined to at least try it. If it doesn't work I should be able to return the thing okay.

Anyhow, thanks again -- I'll report back later.
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post #6 of 21 Old 09-21-2008, 05:58 PM - Thread Starter
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It's officially a bust. I tried a VCL-E07A lens and it just throws unfocused light all over the room. I held a screen scrap up close to the projector for a quick A/B and it looks like the camcorder lens does just magnify the picture. Oh well.

At least now if anybody else gets the same idea they might find this thread and see that it doesn't work.
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post #7 of 21 Old 09-21-2008, 07:42 PM
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Didn't someone actually use a zoom lens and post an image in the official 235 thread?
Have a look at THIS link...
This meant that they didn't actually have to zoom the image, but rather drop it in the light path, then give a quick re-focus...
The key difference between a zoom lens and an anamorphic lens is that the anamorphic lens is only curved in one direction, where the zoom lens will be curved in both. Typically, anamorphic lenses are also concave on the front element, though I have seen one that changed those rules...

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post #8 of 21 Old 09-21-2008, 09:44 PM - Thread Starter
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Quote:
Originally Posted by CAVX View Post

Didn't someone actually use a zoom lens and post an image in the official 235 thread?
Have a look at THIS link...
This meant that they didn't actually have to zoom the image, but rather drop it in the light path, then give a quick re-focus...
The key difference between a zoom lens and an anamorphic lens is that the anamorphic lens is only curved in one direction, where the zoom lens will be curved in both. Typically, anamorphic lenses are also concave on the front element, though I have seen one that changed those rules...

Mark

Nice. Well, that'd make sense, then. I already took back the lens or I might play around with it a bit more. I did try refocusing the projector while the wide-angle lens was in its light path, but it never got even close to clear. I reckon I'll just break down and build a prism lens one of these days . . .

Thanks again for your help!
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post #9 of 21 Old 09-22-2008, 01:26 AM
 
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I didn't think I'd talk you out of it, but there you go.

An ideal anamorphic lens has to have a theoretically infinite focal length, that is, focused beams of light that pass through it do not change their point of focus (i.e. the screen). Infinite focal length lenses are essentially transparent to focus of the projector. The lens you were talking about is basically a quickie add-on for a camcorder. Different principle altogether.

Infinite focal length lenses are made up of a minimum of two elements with a precise relationship between their focal lengths and the distance between them. This distance has to be large (several inches) or else distortions and aberrations will come into play. The larger the distance between the elements, the better the job the lens will do of passing a projected beam unaberrated.

As I said, your lens is a taking lens, not a projection lens.

Also, it is not anamorphic. Only anamorphic lenses are suitable for CIH projection. They are cylindrically curved (curved in only one direction). The Sony lens is spherically curved, not cylindrically curved. In other words, even if the focal length WAS infinite, it would spread the beam in all directions, not simply widen the image horizontally.

Lastly, even if it was anamorphic and possessed infinite focal length, and was otherwise suitable for projection (which it is none of) the expansion ratio would be 1/0.7 = 1.42. You need a 1.33 expander for CIH. You final ratio would have been 1.42 x 1.78 = 2.53. Far too wide.
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post #10 of 21 Old 09-22-2008, 04:37 AM
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Quote:
Originally Posted by Aussie Bob View Post

You final ratio would have been 1.42 x 1.78 = 2.53. Far too wide.

Don't let Vern catch you saying that

Mark

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post #11 of 21 Old 09-22-2008, 08:26 AM - Thread Starter
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Quote:
Originally Posted by Aussie Bob View Post

I didn't think I'd talk you out of it, but there you go.

An ideal anamorphic lens has to have a theoretically infinite focal length, that is, focused beams of light that pass through it do not change their point of focus (i.e. the screen). Infinite focal length lenses are essentially transparent to focus of the projector. The lens you were talking about is basically a quickie add-on for a camcorder. Different principle altogether.

Infinite focal length lenses are made up of a minimum of two elements with a precise relationship between their focal lengths and the distance between them. This distance has to be large (several inches) or else distortions and aberrations will come into play. The larger the distance between the elements, the better the job the lens will do of passing a projected beam unaberrated.

As I said, your lens is a taking lens, not a projection lens.

Also, it is not anamorphic. Only anamorphic lenses are suitable for CIH projection. They are cylindrically curved (curved in only one direction). The Sony lens is spherically curved, not cylindrically curved. In other words, even if the focal length WAS infinite, it would spread the beam in all directions, not simply widen the image horizontally.

Lastly, even if it was anamorphic and possessed infinite focal length, and was otherwise suitable for projection (which it is none of) the expansion ratio would be 1/0.7 = 1.42. You need a 1.33 expander for CIH. You final ratio would have been 1.42 x 1.78 = 2.53. Far too wide.

Well, that all makes perfect sense now! Thanks for the info, AussieBob -- that explains why it didn't work.
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post #12 of 21 Old 09-22-2008, 11:31 AM
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Applesandrice

A wide angle lense will only increase the zoom and will not do any type of anamorphic stretch.

The link that CAVX posted was my old theater. I used a .8x wide angle camera lens to achieve constant height by the zoom method. Basically, my pj didn't have enough native zoom so I zoomed my projector to the max and then used the lens for the rest of the zoom. I had to vertically shift the image as well. It's not the most practical way to do CIH but if your funds are limited, this is a viable option if your pj doesn't have enough zoom. Focus wise though, the Olympus WCON-08B lens was very sharp... sharper than my current UH380.

If your pj doesn't have a threaded lens ring, then devising a mount for a wide angle lens will be challenging.
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post #13 of 21 Old 09-22-2008, 05:43 PM
 
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Well, that all makes perfect sense now! Thanks for the info, AussieBob -- that explains why it didn't work.

Maybe so, but I still doubt it would have stopped him trying. When you look through one of those screw on lens fittings you see something similar to what you'd see when looking through an anamorphic lens, and it looks like it might work. What you are seeing in reality is an image formed on your retina through TWO lenses: one is the lens in your hand, the other is the lens in your eye. Many people forget that.


*************

The formula for a "thin lens" (theoretical, or "paraxial" system) infinite focal length projection lens is as follows:

F1/F2 = Desired expansion,

where:

F1 = focal length of the convex or "positive" lens (entry lens in the case of an anamorphic expander)

F2 = focal length of the concave or "negative" lens (exit lens in the case of an anamorphic expander).

F2 - F1 = D = air gap between the lenses.

For example, a 300mm focal length concave lens (as an exit lens), coupled with a 400mm focal length convex lens (as an entry lens) will give an expansion factor of 400/300 = 1.3333x.

The air gap should be 400-300 = 100mm between the lenses.

I stress this is theoretical only (and somewhat simplified to reduce the need for a longer and more complex explanation) but sufficiently correct for the present purpose. It is based on the "thin lens" forula for calculating the resultant focal length of two lenses combined together and separated by an air gap. This general formula is as follows:

Composite focal length =(F1 x F2)/(F1 + F2 + D)

where the focal length of the concave lens, F2, is expressed as a negative number. Ignoring the value of (F1 x F2) at the moment, it can be seen that:

(F1 + F2 + D) = (300) + (-400) +100 = 0,

Any fraction with 0 as denominator = Infinity, hence this combination, at 100mm separation, will have infinite focal length. (Don't worry that you can't divide by 0, that's only a message computers spit out when things get too hard for them... mathematically speaking, any number divided by 0 is infinity).

The formula takes no account at all of lens shape or aberrations, including geometric, astigmatism or color aberrations. It also takes no account of the two lenses being cylindrically curved, rather than spherically curved, which are the source of many of the familiar aberrations present in anamorphic lenses (if not minimized).

If you flip the order of the lenses, and flip the orientation of the lenses themselves then you will have a 0.75x (300/400) squeeze lens. Rotate it 90 degrees and you will have a vertical squeeze lens.

Iscos and Schneiders follow the basic F1/F2 infinite focal length form, sort of...

The reason why they have focusing adjustments is because a real life anamorphic lens will be somewhat different (although superficially similar) in form to this, and will need adjustments for astigmatism rectification and color correction.

Making a lens that delivers a good image is a VERY big and complex task, but these are some of the basic principles of anamorphics.


*********

So now you know why a single element lens won't work as an anamorphic projection lens...

A single element lens has to be taken as part of a multi-element lens comprising the projection lens itself, plus the add-on lens, both of them with discrete focal lengths. The only way you can get this type of combination to work anamorphically is to make the add-on lens of infinite focal length and cylindrically curved. That way it has no (theoretical) influence on the focus or operation of the prime projection lens.

In the uncurved direction it is basically two flat sheets of glass and therefore of theoretically infinite focal length. In the curved direction it is of infinite focal length due to the physical arrangement and focal lengths of the two lenses used.
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post #14 of 21 Old 09-26-2008, 05:40 AM
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An interesting explanation on fundamentals. thanks.
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post #15 of 21 Old 09-26-2008, 09:19 AM
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What about using something like this http://www.bhphotovideo.com/c/produc...s_Adapter.html
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post #16 of 21 Old 11-19-2008, 06:41 PM
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Quote:
Originally Posted by pocoloco View Post

Applesandrice

A wide angle lense will only increase the zoom and will not do any type of anamorphic stretch.

The link that CAVX posted was my old theater. I used a .8x wide angle camera lens to achieve constant height by the zoom method. Basically, my pj didn't have enough native zoom so I zoomed my projector to the max and then used the lens for the rest of the zoom. I had to vertically shift the image as well. It's not the most practical way to do CIH but if your funds are limited, this is a viable option if your pj doesn't have enough zoom. Focus wise though, the Olympus WCON-08B lens was very sharp... sharper than my current UH380.

If your pj doesn't have a threaded lens ring, then devising a mount for a wide angle lens will be challenging.

pocoloco,

If your WCON-08B was sharper than your UH380...may I ask why you switched? I have a UH380 paired with an Optoma H78. My throw is too short now that I went to a bigger screen and the pincushioning is severe no matter how centered and square to the screen the projector lens is.
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post #17 of 21 Old 04-01-2009, 02:36 PM
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Response is 4 months late but here goes....

My current projector doesn't have vertical shift so I couldn't use the wide angle lens.
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post #18 of 21 Old 04-05-2009, 02:27 PM
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I've got the anamorphic lens for my Panasonic DVX100 DV cinema camera...

Once I've converted my Sony SXRD RPTV into a front projector I am definitely going to try it out...
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post #19 of 21 Old 01-09-2010, 12:35 AM
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Quote:
Originally Posted by sumitagarwal View Post

I've got the anamorphic lens for my Panasonic DVX100 DV cinema camera...

Once I've converted my Sony SXRD RPTV into a front projector I am definitely going to try it out...

Sorry to bring back to life an old thread, but I've been wondering about this myself. If you used an anamorphic lens for a 16x9 camera I wonder how well that would work.
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post #20 of 21 Old 01-12-2010, 06:09 AM
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Originally Posted by TSD444 View Post

If you used an anamorphic lens for a 16x9 camera I wonder how well that would work.

You can't use capture lenses for projection and expect god results as they were not designed for that use.

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post #21 of 21 Old 05-23-2013, 07:59 PM
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