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Object movie rig
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Graham Stabler



Joined: 20 Dec 2007
Posts: 209
Location: Swindon, UK

PostPosted: Wed Apr 16, 2008 6:45 am    Post subject: Reply with quote

Harold Gough wrote:

A relay lens seem to be more or less the opposite of a teleconverter. The former maintains the image size, whereas the latter magnifies it. Also, some relay lenses invert the image, not helful in photography.
Harold


Only a 1:1 relay lens will maintain an image size. It seems that a teleconverter is essentially a 2:1 relay lens, it relays the image from one place to the other while magnifying it.

My Nikon microscope has a X5 relay lens in it for use polaroid, I think you use a 2.5 when using 35mm and I use a 0.5 or 07X for my digital.

Graham
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puzzledpaul



Joined: 06 Aug 2006
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PostPosted: Wed Apr 16, 2008 7:23 am    Post subject: Reply with quote

Just curious - is the construction of a 3D computer model likely to be part of this project?

pp
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Graham Stabler



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PostPosted: Wed Apr 16, 2008 7:28 am    Post subject: Reply with quote

Not from these images but in general yes. I can't say too much until we publish stuff.

Graham
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Harold Gough



Joined: 09 Mar 2008
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PostPosted: Wed Apr 16, 2008 7:43 am    Post subject: Reply with quote

Graham Stabler wrote:
Harold Gough wrote:

A relay lens seem to be more or less the opposite of a teleconverter. The former maintains the image size, whereas the latter magnifies it. Also, some relay lenses invert the image, not helful in photography.
Harold


Only a 1:1 relay lens will maintain an image size. It seems that a teleconverter is essentially a 2:1 relay lens, it relays the image from one place to the other while magnifying it.

My Nikon microscope has a X5 relay lens in it for use polaroid, I think you use a 2.5 when using 35mm and I use a 0.5 or 07X for my digital.

Graham


Interesting. What I found on the internet seemed to be concerned with the 1:1 relays. It makes sense to call a lens a 'relay' lens if it passes on the work done by another, modifying, at most, the magnification.

I don't know where this leads us when some teleconverters are flat field and others are not.

Harold
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rjlittlefield
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Joined: 01 Aug 2006
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PostPosted: Wed Apr 16, 2008 8:23 am    Post subject: Reply with quote

Harold Gough wrote:
...when some teleconverters are flat field and others are not.

Flatness of field is not critical when stacking. All it means is that instead of focusing throughout a flat slab, you end up focusing throughout a slightly curved one. For a single image, the geometry of the reconstructed image is not even changed, only the zone of sharp focus. If you shoot for a full 3D reconstruction, then you have to back out the curvature, but that's straightforward.

Graham Stabler wrote:
It seems that a teleconverter is essentially a 2:1 relay lens, it relays the image from one place to the other while magnifying it.

Correct. And the lens comes in a mechanical mount such that the new place where the image focuses has the same relationship to the new mounting flange as the old image did to the old mounting flange. That's what lets you insert the teleconverter without completely messing up the camera's focus.

--Rik
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Harold Gough



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PostPosted: Wed Apr 16, 2008 8:38 am    Post subject: Reply with quote

I was not suggesting that flatness of field was critical. In fact the additional cost of such an optic would be wasted in typical (?) macro images, in which the subject is central, less important material surrounding it. I was just identifying a point of discussion as to where a teleconverter might differ from a relay lens, if it does.

Harold
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Charles Krebs



Joined: 01 Aug 2006
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PostPosted: Wed Apr 16, 2008 12:10 pm    Post subject: Reply with quote

Graham,
Quote:
While running last night I started to wonder if a teleconverter would work but I wasn't sure because although I know you can increase the magnification of a macro lens I wasn't sure if they were essentially a 2X relay lens, I find photographic speak frustrating sometimes...


I know what you mean. In the microscope world, the terms "relay lens", "photo eyepiece", "projection eyepiece" are often used interchangeably, but can also refer to very different optics. It is probably futile to expect this to change. Wink

Generically, I think of a "relay lens" as an optical way to move the location of a "real image" (one that could be seen on a "screen" if one were placed at that image's location in space), to a different location. While doing so, it may (or may not!) change the magnification --either up or down. One reason this may be done is to "size" the image to fit on a specific film/sensor format (which would be your case with a 10X microscope objective and a 24x36mm sensor). In photomicrography, this is the norm. The image formed by a microscope objective hasn't changed much over the years... about 20-25mm in diameter. But this same image has been used on film/sensors as large as 8x10 inches to as tiny as 2.7x3.68mm (1/4" sensor)! It is essential that the objective's image be "sized" or "mapped" to fit the camera's format.

You might glean more info on this here:
http://krebsmicro.com/relayDSLR/relay_micro.xls
http://krebsmicro.com/relayDSLR/relayoptics1.html

In the case of a teleconverter used "conventionally" in general photography, it is to provide a "magnified" view, as if a lens of longer focal were used.

So with this terminology, the context of usage is important. Even then, it can be confusing since different people mean different things with the same words.
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Graham Stabler



Joined: 20 Dec 2007
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Location: Swindon, UK

PostPosted: Wed Apr 16, 2008 4:25 pm    Post subject: Reply with quote

One way I think a teleconverter does differ from the basic relay lens is that the input image plane is behind the first element or within it, so it is a virtual image plane.

Anyway they will do the same thing in the end, hopefully!

Graham
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Graham Stabler



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PostPosted: Thu Apr 24, 2008 4:56 pm    Post subject: Reply with quote

Just got the Nikon bellows and extension kit today and I am very pleased. If you take the focusing part off the basic bellows there is no real way of mounting it however the extension kit comes with a sturdy base with three threaded holes in the bottom. I can use that with the standard bellows or with the standard plus extension. I probably won't need the latter mind you.




Also have the enlarger lens, step-up ring+reversing ring, RMS-t-mount-nikon adapter and dual fibre lighting.

Drawings are submitted for the mechanics now so things are coming together.

Graham
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augusthouse



Joined: 16 Sep 2006
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Location: New South Wales Australia

PostPosted: Thu Apr 24, 2008 8:52 pm    Post subject: Reply with quote

Graham,

What will the 'sturdy' base of the PB-6E be attached to? It makes sense to me to do this in regard to the bellows for support and levels.
You are losing course focusing capability by switching bases. Course focusing wouldn't be used for the stacks anyway; but I was just wondering what your main focus mechanism will be for focus stacks.

Craig
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puzzledpaul



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PostPosted: Fri Apr 25, 2008 1:28 am    Post subject: Reply with quote

<< If you take the focusing part off the basic bellows there is no real way of mounting it >>

I have no experience with Nikon bellows - but I've been using other makes as the basis of focussing rails for a few yrs (in the field - not stacking setups)

Assuming you're prepared to lose coarse focussing and you want to minimise overall height, then there's a couple of other possibilities that'd be worth considering - imo.

The Nikon bellows appears to have blanking plates (presumably in tapped holes?) at both ends ... couldn't these be used as main 'tie down' points ... together with clamping plates on the lower dovetail?

If you don't mind working on / modifying the item - then remove the racks and drill / tap a couple (or more) holes through / into the rail. If this is similar size to a Canon auto bellows, then 6mm threaded holes will be completely blanked by the rack ... should you wish to sell the bellows afterwards.

If not bothered about this ... then the narrowest part of the cross-section is approx 17mm ... which'd give you even more possibilities for (greater dia) blind tapped holes from the underside (assuming top scale breakthrough is undesirable Smile )

I've taken the latter route - so I can have holes where I want them to be Smile

pp
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Graham Stabler



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PostPosted: Fri Apr 25, 2008 3:56 am    Post subject: Reply with quote

Craig, see first post, Kaiser copy stand.

Paul, of course there are ways to modify or create a mount but as-is the threaded ends you spotted are the only ways to trivially mount something and not a very good way. If I was going all out I would have just made a dove tail clamp like the extension has but as I got the extension it is not needed.

Keeping the rack has the added advantage that I can mount something to the old focuser potentially to hold lighting or a diffuser or some such.

Graham

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puzzledpaul



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PostPosted: Fri Apr 25, 2008 7:30 am    Post subject: Reply with quote

<< not a very good way >>

On their own, yes ... but with additional clamping plates (as mentioned) ... then for the loads involved, it'd be more than adequate.

Using the existing extension is obviously a straightforward solution - but this adds height to the overall assy - clamping direct onto the undersurface of the bellows rail (one way or another) doesn't.

pp
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Graham Stabler



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PostPosted: Fri Apr 25, 2008 3:54 pm    Post subject: Reply with quote

I was re-making my origional point, to trivially mount it all you have are the end holes, adding extra clamps (and something for those to mount to) is what I would call a non-trivial solution in the strictest sense of trivial.

Of course I have to make an adapter anyway to mount it to the enlarger so it is all a matter of degree but it's nice to have one less thing to design and I can live with a few cm overhang especially as it allows the mounting of both rails if I decide to use the extension.

Graham
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Graham Stabler



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PostPosted: Fri May 09, 2008 2:54 am    Post subject: Reply with quote

The camera just arrived, it looks lovely. What I didn't realize is that the lower half of the camera is machined from a solid block.

What an amazingly expensive webcam it is Smile

I will try to takes some images but you will have to bare with me as I have very little time right now.

Graham
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