Homemade 35mm -- Edited Copy for Reading

[Cosmin Rotaru]

Chris, I own a GL2 (actualy the XM2 PAL version). It is imposible to zoom and focus on a 35/24mm rectangle without a close up lens. For this purpose I've used a philatelic lens.
I have another philatelic lens between the 35mm lens and the GG. Very close (aclmoest in touch) with the GG. This removes the vigneting on the GG.
http://www.utdallas.edu/library/special/wprl.gif

[Chris Black]

So the question remains. Can you get the GG close enough to the lens of the gl2 (without zooming) to eliminate the vignetting?

Chris

[Agus Casse]

you need a magnifying glass from the GG to the DV camera.

[Aaron Koolen]

Ok, Cosmin said he used a magnifier between 35mm and GG, and Agus said between GG and camera. Which is correct? I would think that Agus' is correct cause if you magnify the 35mm image won't you lose some of the DOF?

Couple more things. Have people had more success with the GG near the lens, or near the DV camera. People seem to be doing different things here too. I would have thought you'd have to have the GG the same distance as a 35mm image place to get the correct DOF, otherwise you'll be getting more or less than real 35mm.

And, couldn't you just build a long adapter so that the GL2 can focus on the plane or is that still not possible?

Aaron

[Jim Lafferty]

<<<-- Originally posted by Aaron Koolen : ...couldn't you just build a long adapter so that the GL2 can focus on the plane or is that still not possible?

Aaron -->>>

Possibly - but why would you want to? I can't imagine a benefit of a larger, more unwieldy setup.

On further note of the magnifying glass situation - larger magnifying glasses (i.e. those that match or exceed the 58mm diameter of the GL1/GL2's lens) are insignificant in their magnification power. To get a 3 or 4x magnifier, you need to either: go down in diameter (unacceptable as you will get considerable vignetting); or spend upwards of $100, with no guarantee that the lens will work appropriately (and a lot of work and a bit of risk to figure it out in the end.)

The macro zooms from Century Optics are your best bet, though they do up the cost of your adapter considerably. Be sure to get the +7 adapter, though, as this puts lens placement within 3 inches of the subject possible. +2 puts your lens 10" out. You can then use the macro function separate of your Agus35, too.

- jim

[Jon Yurek]

Couple more things. Have people had more success with the GG near the lens, or near the DV camera. People seem to be doing different things here too. I would have thought you'd have to have the GG the same distance as a 35mm image place to get the correct DOF, otherwise you'll be getting more or less than real 35mm.

People are putting the GG in different places because that's where they are focusing the image, that's all. It doesn't really matter where the GG goes in the adapter as long as you can get the SLR lens to focus on the GG and the DV camera to focus onto the GG. You may want to do it so that focusing would be more like properly focusing an SLR lens for the right distances, and that would take more work than the simple ad hoc solution that some people are likely taking here.

And, couldn't you just build a long adapter so that the GL2 can focus on the plane or is that still not possible?

Of course, but the longer you make it the more unwieldly it will become and the less likely you are to be able to use it handheld anymore. Also, it will be harder to keep it aligned properly unless you have supports.

[Agus Casse]

Ok, i will clear this doubts for once and for all..


The magnifying glass goes between the GG and the DV camera, and the GG has to be as close as possible to the DV camera until there is no vigneting.

Dont get confuse, and the best way to solve it is to find a cheap wide conversion lens, and take the first lens that indeed maginfy and a lot... that will cost ya like 35 bucks... dont find and expensive one and also you dont need one that have the exactly the same diameter, cause you zoom half way in (my camera case), so you can find a cheap wide conversion lens for any cheap dv camera, and just use the part that you need.

Keep it simple, and you will get better results :)

[Luke Andrews]

OK i'm jumping in I have a done a "dry" test; frosted glass, nikon lens, XL1 and a cardboard box. No fresnel or mag glass. No moving parts I want to get a feel for everything before I move on. It really works I'll have some stills later.
My main question is, in the mini35 what all is handled in the relay lens section? How are they over coming the 7.2x magnification of 35mm lenses and 1/3" CCD's? what could we use in place of this my goal is to replace the 16X lens of my XL1 to reduce the amount of glass the image is coming thru.

great jorb Agus, when are you posting your plans?

Luke

[Rob Lohman]

Well, this design basically depends on the camera lens being
in place. The XL1 is a difficult camera if you want to remove the
lens because you will have to replace it by a "relay" lens.

The 7.2x magnification is gone because the image is projected
onto the ground glass (the CD) instead of on the CCD directly.

[J. Clayton Stansberry]

<<<-- Originally posted by Agus Casse : Ok, i will clear this doubts for once and for all..
Dont get confuse, and the best way to solve it is to find a cheap wide conversion lens, and take the first lens that indeed maginfy and a lot... that will cost ya like 35 bucks... dont find and expensive one and also you dont need one that have the exactly the same diameter, cause you zoom half way in (my camera case), so you can find a cheap wide conversion lens for any cheap dv camera, and just use the part that you need.
-->>>

Agus,

Just to be clear, when you say "wide conversion lens" you are talking about a Macro lens? And, you don't have to connect it directly to the camera? Could you explain this....because I think that would be a great way to connect it - put on the macro lens and there you go!?!

Thanks,
Clay

[Spencer Houck]

<<<-- Originally posted by J. Clayton Stansberry :
Just to be clear, when you say "wide conversion lens" you are talking about a Macro lens?
Thanks,
Clay -->>>

What Agus means is that inexpensive Wide Angle lenses have a separate Macro lens attatched. Simply buy a cheap combo, and discard the Wide Angle portion, and you have a Macro lens all by it self. SEE:
http://cgi.ebay.com/ws/eBayISAPI.dll...category=29964

As you can see in the description and photo is states "With Macro". You can see the ring on the bottom of the lens that reads MACRO.

Hope this helps,
Spence

[Luke Andrews]

OK more discussion on the XL-1 conversion.
if the 7.2x magnification is no longer an issue then would it be possible to get say a xl1 to nikon adapter and a good macro lens for your relay? What other issues would need addressed from the GG back to the CCD. Is the relay also flipping the image or is this handled by mirrors inside the unit.

Thanks everyone keep up the good work.
Luke

[Bob Hart]

To test your relay lens options, take your camcorder along to the place you intend to get your relay/close-up/macro lens from and ask to be able to test one.

Take with you also, a test card or probably better, a translucent panel, with a frame drawn on it, the same size and shape as the 35mm image frame. On this frame there should be drawn a grid of parallel black lines, horizontal and vertical, at least eight each of even spacing, thickness and opacity.

Look for in the pattern of lines :-

1. Distortion. ((II)) = barrel distortion ))II(( = pincushion distortion.

2. Variations in sharpness across image, most likely to be apparent in corners or sides.

3. Variations in color across image.

Retailers, if co-operative at all, may only allow you limited instore testing opportunities of the quick and hand-held variety with a salesperson impatiently hovering.

If you are going to be handholding something that does not fit your camera, up to your camera lens to test it, cut yourself a short straight length of wood for a jig, with several holes bored down a straight centreline marked on it. This is to mount your camcorder on at one end so that you can hold the added lens and image target in a steady relationship with the camera lens by bracing down onto the wood or even sit the object on it if it won't fall over. You'll some small scraps of ply or cardboard for packing so you can get it centred vertically.

Also improvised testing itself may introduce an unequal distortion or variation of focus across the image. This will be apparent on one side or upper or lower edge of your test image.
Deficiencies in your intended lens setup will most likely be equally represented in quarters of of your test image provided your added lens is centred on the centre axis of your cameras own lens system.

There is a caveat to all my babble here. With some camcorders, the centres of the tripod mount hole, and centre axis of the lens system do not co-incide. With some camcorders, the centre axis of the lens system does not fall in the centre of the CCD array. This may be due to design or variations in build quality. With my PD150 (PAL), the lens centre axis and tripod mount are off-centre by about 6mm. The tripod hole cannot be used as a centre reference. My PD150 lens centre axis is also offset slightly to the right as viewed in the recovered image (to the left in reality).

Some of the Iraq night-vision images framed wide for best subjective resolution (circular image inside the frame) have the same offset my own tests showed, so it may be a characteristic of the camera.

For the same reason I had to dress the left side of the optical path through a 16:9 adaptor to eliminate left edge cropping on fully wide.

This is probably a lot of useless info for most. Feel free to add to, criticise and correct where necessary.

[Ryan Henry]

I also thought about using something instead of or on the CD. I work in a theater and we have plenty of gels laying around as well as diffusion.

Gels are cheap to purchase and I thought either Rosco or Lee made a solid sheet version, but I can't find it right now. The diffusion comes in different strengths and patterns and is quite consistent.

If you contact a theater supply store you can request a (usually free) swatch book containing small samples of different gels, diffusions, etc.

[Kieran Clayton]

<<<-- Originally posted by Luke Andrews : OK more discussion on the XL-1 conversion.
if the 7.2x magnification is no longer an issue then would it be possible to get say a xl1 to nikon adapter and a good macro lens for your relay? What other issues would need addressed from the GG back to the CCD. Is the relay also flipping the image or is this handled by mirrors inside the unit.

Thanks everyone keep up the good work.
Luke -->>

Yeah I suppose you could, but it would be cheaper just to get some form of close-up adapter I imagine.

Also if you have an XL1 you can just turn the viewfinder upside down by mounting it backwards, if you see what I mean.. It's not ideal, but it's cheaper than any other solution and there's no loss in image quality.

kieran