New and clueless, looking for some equipment advice.

Starting out in microscopy? Post images and ask questions relating to the microscope and get answers from our more advanced users on the subject.

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hankbaskett
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Joined: Tue Sep 04, 2012 6:56 am

New and clueless, looking for some equipment advice.

Post by hankbaskett »

Hi,

I am a Geologist, and a (very) amateur photographer. Through my work, I come across a lot of samples that I would like to get some high quality pictures of. I have a Leica MZ6 Stereo microscope that I use to examine samples and cuttings, and I have an Olympus OM-D micro 4/3rds camera that I use for taking pictures.

As I understand it from reading the forums, stereoscopes are less than ideal for taking quality pictures, so I am open to other options besides mating the camera to the scope, but it would be very convenient to use the stereoscope.

I use a 10x eyepiece on the scope, and between 1x and 2.6x on the objective, depending on the sample. I've tried using a prime 40mm lens and simply holding the camera above the eyepiece, but the pictures are not great. I'll attach a sample, maybe my expectations are too high or something.

Thanks for any advice.Image

rjlittlefield
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Post by rjlittlefield »

Hank, welcome aboard! :D

The first thing to do is carefully compare what your camera captured with what you see through the eyepiece.

In a single picture, the camera may be hampered by limited depth of field, whereas your eye can adjust focus to fit different parts of the subject.

So what you're looking to know is whether the sharpest parts of the image contain the same amount of detail that you can see through the eyepieces.

If they do, then apparently the limitation is in the scope optics and we need to get you set up with something sharper.

But if the camera image is everywhere less sharp than what you see through the eyepieces, then obviously there's some loss getting to the camera and with luck that might be fixable.

There are some standard defects that we often see in images captured through eyepieces. This image looks like it has some curvature of field, with the center sharp but all the edges blurred, possibly out of focus. I'm not seeing color fringes (lateral chromatic aberration -- CA), which is good. In the very center of the image I'm seeing some sharp details on a few of the rock pieces.

One reasonable interpretation is that this image is focused just a short distance above almost all the rocks. If that's the only problem, then it's easily fixed by refocusing and by focus stacking.

Be sure to run your comparison with a few different focus settings, so that for sure the camera is seeing well focused subject in some image all across the field.

I have a couple of questions.

1) Is the black circular frame exactly the way the camera captured it, or has that been enhanced in Photoshop or other software?

2) What's the field width in this photograph -- how many mm across the field?

--Rik

Charles Krebs
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Post by Charles Krebs »

Sometimes a large part of the quality photo "problem" using stereo microscopes is that it can be so easy to try to work at magnifications that are simply too high for good resolution given the (generally) modest numerical aperture of the stereo microscope.

Based on the information you have given here this does not seem to be the case in your work.
I use a 10x eyepiece on the scope, and between 1x and 2.6x on the objective, depending on the sample. I've tried using a prime 40mm lens and simply holding the camera above the eyepiece
At the magnifications you mention I would expect to see better results than the example you have provided.

What was the shutter speed used? Is the camera mounted in some way or are you actually "hand-holding" it above the eyepiece? How are you focusing in the camera?

Which objective lens is on the stereo microscope?

Which lens are you using on the camera? I am aware of an Olympus 45mm lens but don't know of a 40mm micro 4/3 lens. For the 17.3mm x 13mm sensor in your camera, a wider focal length (in the 25 to 28mm range) would provide a better match in field size for the view you see through your eyepieces, but that would not explain the softness seen in the sample.

hankbaskett
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Joined: Tue Sep 04, 2012 6:56 am

Post by hankbaskett »

Hi Rik,

The sharpest parts of the image are definitely significantly less sharp than what I can see through the eyepiece. I resized that photograph, because I doubted that your board wanted to take on a 4mb JPEG, but I reposted it here in higher detail: http://www.flickr.com/photos/86803015@N04/7948666010/

Looking back, it was processed in lightroom and I removed a bit of the noise, here's an unprocessed shot (just white balance): http://www.flickr.com/photos/86803015@N04/7948666010/

To answer your questions:

1) It was untouched in photoshop. Not adjusted, cropped or otherwise messed with.

2) I'm not positive, but I'm pretty sure that it was taken at 1x objective, which is just under 21mm diameter on that scope.

hankbaskett
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Joined: Tue Sep 04, 2012 6:56 am

Post by hankbaskett »

Charles Krebs wrote:Sometimes a large part of the quality photo "problem" using stereo microscopes is that it can be so easy to try to work at magnifications that are simply too high for good resolution given the (generally) modest numerical aperture of the stereo microscope.

Based on the information you have given here this does not seem to be the case in your work.
I use a 10x eyepiece on the scope, and between 1x and 2.6x on the objective, depending on the sample. I've tried using a prime 40mm lens and simply holding the camera above the eyepiece
At the magnifications you mention I would expect to see better results than the example you have provided.

What was the shutter speed used? Is the camera mounted in some way or are you actually "hand-holding" it above the eyepiece? How are you focusing in the camera?

Which objective lens is on the stereo microscope?

Which lens are you using on the camera? I am aware of an Olympus 45mm lens but don't know of a 40mm micro 4/3 lens. For the 17.3mm x 13mm sensor in your camera, a wider focal length (in the 25 to 28mm range) would provide a better match in field size for the view you see through your eyepieces, but that would not explain the softness seen in the sample.
Hi Charles, I posted another link to a couple of photos above. The shot in question was at 1/320. I used a tripod and the self- timer. I'm not positive which method I used for those particular shots, but I've tried both auto and manual focusing.

I'm fairly sure that the shot was taken at 1x objective, so 10x magnification. As far as the model, it's this one: http://www.spachoptics.com/10411589_p/l ... 411589.htm

The camera lens is the Panasonic 20mm 1.7 . I always think about them in 35mm terms, so I called it a 40mm. I do have the 45 (90) Olympus lens, and gave it a shot, but the 20mm did a much better job.

Thanks!

Pau
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Post by Pau »

hankbaskett wrote:.... but I've tried both auto and manual focusing
For use "afocal" on the microscope as you do, set the camera lens manually focused at infinite and focus with the microscope ( I don't know how relevant it may be in the results you posted, but is the right method)
Pau

rjlittlefield
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Post by rjlittlefield »

Thanks for the additional information and larger image.

Quite frankly I'm puzzled.

The reason I asked about the circular border is that it looks very clean -- sharp and no color fringes. That border is almost certainly the field stop inside your eyepiece, so the fact that it looks good means that your camera is playing nicely with your eyepiece.

Your setup sounds fine. Afocal at 1/320 second on a tripod and self timer, with no direct connection between microscope and camera, and a mirrorless camera to boot, should be very resistant to vibration. Shooting down an eyepiece is basically just like shooting across the street in that regard.

Looking again at the high res image...

At center of the image, there are a couple of darker pebbles that show tiny bright spots, probably direct reflections of the illumination lamp from small crystal faces that happen to be oriented just right. Those tiny bright spots are not elongated as they would be with motion blur. Some of them are as small as one pixel in a 2048x1536 frame, and none of the small white spots are surrounded by distinct color fringes.

On the other hand, nearby main edges of the pebbles have unsharp edges with color fringes that are consistently blue to the left of a white area and yellow to the right. That same pattern -- blue to the left of white, yellow to the right, persists across the entire image.

This combination of no fringes when sharp but fringed when fuzzy is typical of one type of longitudinal color aberration combined with a consistent focus error.

I'm still thinking that most of the problem shown in this one image is just focus error. You could nail that down with a series of images shot in small increments sweeping through focus, with the camera locked on manual focus at infinity. I emphasize small increments. The camera is much less forgiving of focus errors than your eye is.

Switching gears and thinking about alternatives, 21 mm maximum field width and 21/2.6=8.1 mm minimum field width would be about 0.8X to 2.2X in terms of magnification onto the sensor of your OM-D camera. That range is easy to do using a reversed enlarging lens on bellows, so there are good alternatives available if your scope doesn't work out.

--Rik

Charles Krebs
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Post by Charles Krebs »

Like Rik, with this additional information I'm thinking focus is first place to look more closely.

As Pau mentioned, setting the lens to "infinity" (with camera set to manual focus) and doing the final focus with the microscope is the "proper" way of doing the afocal method. But with the magnifications we're discussing here, is likely not that critical whether final focus is done via camera lens or microscope. (It should be a very minor microscope focus adjustment if camera is set to MF and lens is set at "infinity" focus).

But one way or another very accurate focus is critical. The puzzling part is that with the camera you are using it should be very easy to obtain accurate focus manually (and even AF should be excellent). I am not that familiar with the operation of your camera, but you should be sure that in some of your testing the camera is truly set to "manual focus" and you provide the final fine focus with the microscope while viewing a magnified image on the LCD screen.

Your 10X eyepieces show you a field number of 21mm. With a 20mm lens on your Olympus camera you will be recording a field number of 27mm, hence the circular image showing the aperture in the eyepiece. But this is not a reason for the "softness, it just means you will need to crop the images (or switch to a longer -- 25-28mm -- focal length if you want to avoid the black circle in the camera itself.

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