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DSLR Adapter And Other Questions

 
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Mitch640



Joined: 15 Aug 2010
Posts: 2137

PostPosted: Fri Aug 27, 2010 11:23 am    Post subject: DSLR Adapter And Other Questions Reply with quote

Today, my cheap E-Bay camera adapter came in the mail. It does fit my Canon MkIII and it does fit over the trinocular tube. But I had to focus using live view on the camera, as it was nowhere close to in sync with the ocular view. Also, I got some really bad yellow tint that I could not clean up in CS3. I am still waiting for the dedicated USB camera to arrive, supposedly a guaranteed delivery by 3pm. Wink

This shot is full frame, and I was wondering what the bright ring is from?
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rjlittlefield
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Joined: 01 Aug 2006
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PostPosted: Fri Aug 27, 2010 6:55 pm    Post subject: Reply with quote

The bright ring is undoubtedly an internal reflection.

Remove the camera and look by eye into the adapter. Probably there is a shiny ring reflecting stray light that would otherwise be directed outside the frame. You need to mask that ring or cover it with some non-reflecting paint or flocking.

Rarely an internal reflection can involve the sensor itself, but in my limited experience those are not nearly so well defined as this one.

The yellow tint is just a problem of color balance. It looks like you had the camera set on daylight or flash, while the microscope's illumination is incandescent. This sort of problem is very difficult to fix once the image is committed to JPEG. With microscope illumination, if you want really accurate color it's generally best to do a "custom white balance" from a blank field. Often auto white balance will do a good job too, but some cameras are not willing to make enough correction, especially if you have the scope brightness turned below maximum so the light is even more yellow than full power incandescent.

--Rik
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Mitch640



Joined: 15 Aug 2010
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PostPosted: Sat Aug 28, 2010 12:19 am    Post subject: Reply with quote

Thanks Rik. I was comming around to the reflection inside the tube part. What else could it be when you think about it. LOL. As for the yellow, I did some later shots, while tethered to EOS Utility, and using AWB and shooting in RAW. When I opened them in CS3, I just hit the Auto adjust button and it adjusted them to the proper, or close to proper white balance on it's own. For the next test, I will try incandescent setting to start with and see how that works. Like everything else, it's a matter of trial and error. Smile
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Mitch640



Joined: 15 Aug 2010
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PostPosted: Sat Aug 28, 2010 4:34 am    Post subject: Reply with quote

I found the reflection problem. There is a C-mount adapter tube that is part of the overall adjustable adapter that came with the scope. It is some kind of bright silver finishing process on the metal itself. When assembled, you can look down the tube from the bottom end and see a ridge of that bright metal. Since it is from the bottom, I assume the ring of light is from glare/flare off the little ledge of bright metal being reflected around the tube. The ridge itself is not visible to the camera sensor.
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Charles Krebs



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PostPosted: Sat Aug 28, 2010 10:36 am    Post subject: Reply with quote

Regardless of the camera you use, you will want to use a consistent light level intensity setting when taking pictures (even if you have some success with "raw" files). The tungsten-halogen bulbs... if that's what you have... will photograph nicely at 3200k, but only at the correct "brightness" (voltage) setting. At a lower level the color temperature drops quickly and you're battling yellow to deep red pictures. At higher settings they get too blue for a 3200K balance. (And you are providing too much voltage to the lamp which will lower it's life expectancy).

Quote:
But I had to focus using live view on the camera, as it was nowhere close to in sync with the ocular view
If you simply attach a SLR camera body to a trinocular tube (no other optics involved) you will almost certainly be positioning the sensor quite distant (too far) from the image formed by the objective. As a result it will never focus the same as the eyepieces (i.e. "parfocal"). You will then need "re-focus" by moving the objective much closer to the subject to attain focus in the camera. This is not only a nuisance, but is not good microscopy technique. Microscope objectives are designed to be used at a very specific working distance. If you change that too much, you can seriously degrade image quality. Generally it's not a major issue at lower powers with low or modest NA's (numerical apertures), but gets progressively more noticeable as NA increases.
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Mitch640



Joined: 15 Aug 2010
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PostPosted: Sat Aug 28, 2010 10:45 am    Post subject: Reply with quote

Quote:
You will then need "re-focus" by moving the objective much closer to the subject to attain focus in the camera.

That's exactly what happened. I think there is supposed to be a lens of some kind in the adapter, which didn't come with one. There is some kind of little lens in the trinocular tube, below the adapter, but it can't be removed. The image above is certainly not the quality I expected or see from other people, so something isn't right. And I am still waiting for my dedicated scope camera to arrive, supposedly today by 3pm. I am sceptical though.
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Charles Krebs



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PostPosted: Sat Aug 28, 2010 12:35 pm    Post subject: Reply with quote

In a different thread I recently posted this:

You can't just attach a camera to the trinocular tube without some consideration where the actual image that is formed by the microscope optics is located. Then you can approach it a few different ways...

1) direct projection (very often not possible because of physical constraints)

2) via a projection eyepiece in the trinocular tube (no lens on camera)

2) with a "regular" eyepiece in the trinocular tube and a suitable lens on the camera body ("afocal method").

With all these methods the positioning and spacing of the components its pretty important.


The real image created by the objective is (usually) located 10mm down from the edge of the eyepiece tube. (And also 10mm down from the edge of many trinocular tubes). Incidentally, this image is referred to as the "intermediate" image in microscopy. So if you consider the three approaches mentioned above...

1) The physical constraint normally encountered is that there is simply no way to get the SLR camera sensor at that location in space! (Unless the trinocular tube is removable or you cut it off. Even then, a DSLR has a body depth of about 45mm, so it still may not be possible).

This is what you experienced above. The camera sensor was much higher than the intermediate image produced when the viewing eyepieces were in focus. So you needed to "shift" the location of the intermediate upwards toward the camera, which was accomplished by moving the objective closer to the subject. (But as mentioned earlier, this made the viewing image terribly out of focus, and "upset" the optical design parameters of the objective.

2) Some manufacturers made/make "projection" type eyepieces. These are inserted into the trinocular tube. They "pick up" the real image that is located in the trinocular tube, and project it to form another real image some distance above, and usually magnify (or reduce) the intermediate image to some degree. With proper adapters a camera body can then be positioned above this projection eyepiece so that the newly created "real" image coincides with the camera sensor. **

3) A "regular" eyepiece is inserted into the trinocular tube. It should be in focus at the same time as the binocular viewing eyepieces. Then, a camera with an attached lens (focused at "infinity") is located directly over the trinocular eyepiece. This works well but (for reasons too long to discuss here now) it can be tricky to get a camera lens that can be positioned close enough to the eyepiece to get a full image with no vignetting.

** A "regular" viewing eyepiece can be used as a "projection" eyepiece if it is elevated in the trinocular tube (about 5-10mm often works out OK). Image quality may be variable, and I would generally suspect it is a little lower than when using a manufacturers designed projection eyepiece... if one was available.

The goal should be to have the camera and eyepieces "parfocal" ... or at least very close, and with a quality "optical" connection to the camera. This is both from a simple operational consideration as well as an image quality one. If the manufacturer of your microscope makes the requisite components and they are used as intended this will (should!?!) be the case. If you get a "generic" adapter or need to press other components into service they were not intended for (such as "elevating" a viewing eyepiece for projection) you usually lose the "plug-and-play" aspect. Then, you'll often need to make spacing and mounting adjustments and modifications to set things up nicely.
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Mitch640



Joined: 15 Aug 2010
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PostPosted: Sat Aug 28, 2010 1:00 pm    Post subject: Reply with quote

What your saying is what I saw. However, there is some kind of lens just inside the trinocular head when you unscrew the dust cover. This lens does not come out. I don't see being able to drop anything into the trinocular tube. Also, the hole is much, much bigger than my ocular lenses. It must be the 30mm C-mount thread. The scope came with an extender that screws into the dust cover threads, and it is even adjustable, but it's as long as my hand is wide, maybe 4 inches or so. The top end has that silver tube I mentioned above, and that is 23mm size, I think, not good with the EU measurments. Smile

However, all this may be moot. My dedicated 10Mp video USB camera arrived an hour ago. And it does have a couple of small lemses with it. I shall return after I give it a try and give a breakdown on what I brok, er, achieved with this new gear. Wink
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Charles Krebs



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PostPosted: Sat Aug 28, 2010 1:36 pm    Post subject: Reply with quote

Yes... let us know.


Quote:
The scope came with an extender that screws into the dust cover threads, and it is even adjustable, but it's as long as my hand is wide, maybe 4 inches or so. The top end has that silver tube I mentioned above, and that is 23mm size


It sounds like the your trinoc head came with a removable tube. Wouldn't be a bad idea to have a picture of what you have or at least a model description.
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Mitch640



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PostPosted: Sat Aug 28, 2010 2:10 pm    Post subject: Reply with quote

I can do that. I have just installed the video drivers and software, and have the camera on the trinoc head for a test run. After that, I'll get some stills of the adapter area and tubes they sent. But, first things first. LOL
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Mitch640



Joined: 15 Aug 2010
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PostPosted: Mon Aug 30, 2010 9:19 am    Post subject: Reply with quote

I haven't forgotten to get pics, I am down to just one lens for the 1D3, having sold all my birding lenses. It's not got a wide enough field to shoot the scope, without moving to to the other room, and I have been busy adjusting the new video camera, waiting on some M-Nu and otherwise just looking at bugs through the scope. They call that learning, I call it fun. Smile

I did go out and buy a can of flat black, which I am going to try and spray inside the adapter tubes today, if I can find my roll of masking tape. That might work better than M-Nu, which is still in shipping.
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