Advice on attaching camera to a B&L Balplan Trinocular

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ScottH
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Advice on attaching camera to a B&L Balplan Trinocular

Post by ScottH »

I just scored an Older Bausch and Lomb Balplan for next to nothing. It has really pleasing visual views so I thought I might attempt some photomicrography with the trinocular head but I am having a hard time figuring out what I need to purchase. Has anyone been down this road before me ? I would like to attach a DSLR to the trinocular and it appears that I do not need any corrective optics to do this.

Thanks

Scott Hogsten

Charles Krebs
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Post by Charles Krebs »

Scott,

Personally I am not familiar with B&L scopes, but many of the principles of using a camera on a trinocular tube are fairly universal.

There are two basic approaches... projection and the afocal method. The first thing I would want to find out is the location of the "intermediate" image in the trinocular tube when the image is in focus through the viewing eyepieces.

See if this discussion is helpful at all:
http://www.krebsmicro.com/pdf/trinoc_a3.pdf

What size is the camera sensor? A photo of the trinocular head would be helpful as well.

ScottH
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Post by ScottH »

Thanks Charles I read your paper and it confirms some of my thinking. Now on to your question camera wise either a d7000 or a d200 I have both bodies available, so Nikon DX sensor. I don't currently have a phototube and there is a lot of room to play with so I can likely get the camera to the focal plane. I've looked on ebay but I can't be sure the phototubes are for Balplans. The Balplan is an infinity system and I suspect I would get less than optimal result if I put a finite phototube on there. It appears the opening for the phototube in the trinocular is 28.5 mm. Here are some photos of the head and the body of the scope. I should also add that I have a lathe and milling machine and I'm quite handy with them so I can make anything mechanical.

Image
Image
Image

Charles Krebs
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Post by Charles Krebs »

Chances are you have seen these pages, but in case not:
http://lrak.net/secret/Balplan/balplan/ ... on_10.html
http://lrak.net/secret/Balplan/balplan/index.html

If it is an "infinity" system the tube lens should be in the base of the trinocular head inside the dovetail that attaches to the microscope stand. (At least that is where it has been in all the infinity microscopes I have looked at. But as I mentioned I have no familiarity with this model). If so, that means that there is no need for a "tube lens" in the trinocular tube.

If the "tube lens" is in the base of the head, then no additional optics are actually necessary unless:
1) You can't physically place the camera at the correct height to place the intermediate image on the sensor

2) You wish to "re-size" the intermediate to make a better fit onto the camera sensor.

To see what options are available to you I would try the following:
Set up the microscope and focus on a detailed high contrast subject. Leave the focus at this setting. Then hold the camera body (no lens attached) over the trinocular tube and move it up and down to see if it is possible to get the sensor at the plane of the intermediate image (an in-focus image in the camera body simultaneously with the viewing eyepieces).

If it is possible to position the camera so the the in-camera image is in focus, you then need to decide what approach to take. You can either "direct project" with no intervening optics (just an empty tube of appropriate length), or you can come up with an optical arrangement that would "magnify" the intermediate image about 1.5X to make it "fit" the sensor out to the corners.

If possible, direct projection is definitely worth considering. I would try that first (use the D7000). You may need to crop the pictures if the objectives can't "cover" the APS-C size format with adequate image quality, but you won't know until you try it. (Step up the tube diameter after the connection to the head, at least wide enough so that if the objectives are capable of producing the larger image you do not "mechanically" vignette the image with a narrow tube.

Even if you do find you need to crop the images using "direct projection", the overall quality will not suffer (even if you have the Apochromats made for the Balplan) using the 16Mp D7000.

If direct projection is not possible then you will need to come up with an optical solution to project the intermediate image into the camera body. In this case you would probably want about a 1.5X magnification.

Pau
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Post by Pau »

Charles Krebs wrote: If the "tube lens" is in the base of the head, then no additional optics are actually necessary unless:
1) You can't physically place the camera at the correct height to place the intermediate image on the sensor

2) You wish to "re-size" the intermediate to make a better fit onto the camera sensor.
I would add a comment about complemetary corrections.

Many microscopes do not correct all the objective optical aberrations at the objective itself but do some complementary correctios at the tube lens or at the eyepice. I don't know anything about yours, but if that complementary corrections are needed and done at the eyepiece, direct projection will deliver poor image quality at the periphery.

If the microscope is bundled with its original eyepieces as it seems, you can have a first indication looking through them at a white background: corrective eyepieces show an orangeish halo just at the image limit, like you can see here at the first picture:
http://www.photomacrography.net/forum/v ... 911#122911
Pau

ScottH
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Post by ScottH »

Got a chance to spend some time with this and unfortunately the image forms about 5 mm inside the trinocular head. So I'm going to have to find something to reach down there and bring the image up to the camera. The eyepieces don't seem to be correcting for color however they may be correcting for some slight pin cushion distortion. I can get a picture by removing the head completely and holding the camera over the microscope and other than the pincushion the images aren't half bad.

That said I have a spare eyepiece (appears to match scope as well) so could I create a mount to locate the spare eyepiece above the trinocular port then project to the camera above ?

Scott

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Post by rjlittlefield »

ScottH wrote:That said I have a spare eyepiece (appears to match scope as well) so could I create a mount to locate the spare eyepiece above the trinocular port then project to the camera above ?
Yes, this could work very well using a variation of the "afocal" method as suggested by Charles.

You would mount the spare eyepiece so that it is parfocal with the regular eyepieces when you look through by eye. Then position your camera with an ordinary lens focused at infinity to look through the eyepiece.

There are many threads in the forum discussing this approach and especially what sort of lens you need on the camera. Just search on "afocal" as a keyword.

--Rik

ScottH
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Post by ScottH »

Rik thanks for the tip on the correct search word. I had a chance to play a bit more and by juggling parts, eyepieces, and the camera ( would have been nice to have three arms today) I got the image of some onion skin below. Given that is a crappy slide, everything was moving around, and absolutely nothing was on the optical axis it is promising. I did crop the image slightly to remove a large dust bunny and some nastiness on the slide.

Thanks for pointing me in the right direction.

Image

rjlittlefield
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Post by rjlittlefield »

This looks like a great start.

By the way, one of the advantages of the afocal method is that it's very resistant to linear movements of the camera with respect to the scope. This means you can decouple camera from scope and you don't need to be terribly concerned about rigidity of the camera mount.

Optically, it's just like pointing the camera across the street, looking through a hole that's the size and location of the eyepiece exit pupil. As long as the camera doesn't tip and doesn't move away from the hole, it doesn't matter if the camera happens to move around a little.

--Rik

Charles Krebs
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Post by Charles Krebs »

The Balplan is an infinity system
I would like to attach a DSLR to the trinocular and it appears that I do not need any corrective optics to do this.
Got a chance to spend some time with this and unfortunately the image forms about 5 mm inside the trinocular head
Something odd here. (At least based on the photo you posted showing no tube at all on the trinocular port.) Are you accounting for the ~46mm depth of a Nikon SLR body (lens mount to sensor)?

Are you sure this is an "infinity" system. I have photos of B&L objectives that were "finite" as they were clearly marked "160/0.17", but they could have come from an earlier model. What have you seen that tells you it is an infinity system and that it does not need corrective optics?

ScottH
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Joined: Sun Feb 07, 2010 12:38 pm

Post by ScottH »

>>Something odd here. (At least based on the photo you posted showing no tube at all on the trinocular port.) Are you accounting for the ~46mm depth of a Nikon SLR body (lens mount to sensor)?


Charles not sure what you are asking. I could not get an image to form above the trinocular port. Removing the head and playing around I could get an image by moving the camera lower than the top of the trinocular port, the camera was almost resting on top of the microscope body. So I am estimating that the focus point is below the top of the trinocular port by 3-5mm. The factory camera adapter appears to have a lens at about this point.


>>Are you sure this is an "infinity" system. I have photos of B&L objectives that were "finite" as they were clearly marked "160/0.17", but they could have come from an earlier model. What have you seen that tells you it is an infinity system and that it does not need corrective optics?

This gets a little more murky, Balplans are definitely odd ducks I can't find anything that explicitly says this in an infinity system just a lot of anecdotal evidence that points to this being an infinity system. I've spent a bunch of time on the internet researching and there just isn't much documentation available. The objectives are unmarked in anyway on the Balplans other than the B&L Name, Magnification, Cover slip, and the type of objective plan, achromat, phase, etc. The 160mm B&L objectives do not work in the scope (been there, done that). I also could not get one of the B&Ls to form an image on a 170mm Lecia SM-Lux. There is a lens in the stand between the objective turret and the field stop that you can see in the photo of the stand. I can't tell much about the lens itself it appears to be a cemented double or triplet.

Scott

Charles Krebs
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Post by Charles Krebs »

Removing the head and playing around I could get an image by moving the camera lower than the top of the trinocular port, the camera was almost resting on top of the microscope body. So I am estimating that the focus point is below the top of the trinocular port by 3-5mm. The factory camera adapter appears to have a lens at about this point.
Scott... I added the bold type to your quote above. Based on what you say, it sure does seem like there is something optical missing from the trinocular port. Sorry I can't offer more in the way of suggestions, but I don't know what is going on here. :smt017 :smt102

ScottH
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Post by ScottH »

I wanted to post something I just learned in case someone comes along later. There's definitely another lens assembly that is required. I took things apart and there is a lens inside the trinocular head. You can see it where is at in this image.

http://lrak.net/secret/Balplan/balplan/ ... _3_5-2.jpg

It's difficult to measure exactly but that lens is about where I am getting the camera to come to focus with the head removed. So I do think I may need to find a real Bausch and Lomb camera adapter. This probably also applies to someone trying to use any of these objectives on a camera.

Scott Hogsten

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