Setting up optics.

[GfL]

Right, my microscope has a maximum magnification of 675x , 45x objective, and my camera has an optical zoom of up to 12x and with digital zoom that goes up to 24x.

The focal length of the camera lens is 6.0 - 72 mm

What is the optimal distance that the lens has to be from the eyepiece tube (with eyepiece removed, of course, to obtain the best magnification and resolution?)

I currently use an ad hoc cardboard adapter and am planning to get a laboratory (burette) stand soon. Should the distance between the tube and the lens be sheathed in PVC or something?

Are there any low investment adapter designs available?

Ta.

[Pau]

Right, my microscope has a maximum magnification of 675x , 45x objective, and my camera has an optical zoom of up to 12x and with digital zoom that goes up to 24x.

Forget "digital zoom", it only crops the available image and expand it to more pixels, so no resolution nor any other advantage could be obtained. Be aware that pro cameras doesn't have this feature.

The focal length of the camera lens is 6.0 - 72 mm

This will be a compact "superzoom" camera, usually the more difficult to use with a microscope, in special if the lens is very long

...(with eyepiece removed, of course, to obtain the best magnification and resolution?)

Usually with a fixed lens camera the best way is the afocal setup, i.e. set the objective to manually focus to infinite and take the picture throug the eyepiece, (a wide field eyepiece is recommended)
The optical zoom may be set to the minimum that allows to fill the sensor with the microscope image

I currently use an ad hoc cardboard adapter and am planning to get a laboratory (burette) stand soon. Should the distance between the tube and the lens be sheathed in PVC or something?
Are there any low investment adapter designs available?
Ta.

If you post some images of your setup (both microscope and camera) and of your result, it will be more easy to understand and make comments and advice.

[rjlittlefield]

I see Pau has posted before me. These comments complement his.

GfL, unfortunately your question cannot be answered without more information. I noticed your image posted over in the Microscope gallery, HERE. It sounds like you are using an unusual setup.

As background...

Normally photography through a microscope is done with one of the following setups. The names are not perfectly standardized, but with luck the descriptions will be enough.
1. "Afocal" method. The camera with its normal lens is pointed into the microscope's eyepiece. Essentially the camera just takes the place of a human eyeball.
2. "Direct projection" method. The eyepiece is removed from the microscope, the lens is removed from the camera, and the objective focuses its image directly on the camera's sensor.
3. "Projection eyepiece" method. The lens is removed from the camera and a special eyepiece is placed in the microscope. The special "eyepiece" is not designed to be used with a human eye at all, but rather is a special arrangement of lenses that bends light coming from the objective so that it focuses to form an image at the camera sensor instead of near the top of the eyepiece tube where the objective alone would normally put it.
4. "Optical adapter" method. The camera is used with its normal lens, and additional lenses are used in place of or in addition to the normal eyepiece.
5. "Infinity objective plus telephoto on camera". See discussion HERE and HERE (image 2) for how this works outside the frame of a microscope. In some cases, this scheme can be made to work also with the objective mounted as usual at the bottom of a microscope tube, but vignetting becomes more of a problem as the objective is moved away from the camera lens. With a compact camera, sometimes vignetting cannot be avoided even when the objective is mounted directly in front of the camera lens -- see HERE for example.

It sounds to me that you are using a variation of method 5, and just barely keeping the vignetting under control by zooming your camera lens full out.

We can provide better advice if you post some pictures of your microscope (one overview plus a couple more showing labels on the objectives), and tell us what model of camera you are using.

--Rik

[GfL]

[GfL]

The Camera is a Cybershot H-1, the cardboard adapter locks onto the camera, I remove the eyepiece when shooting.

Sample shots.

[rjlittlefield]

Ouch. The Sony Cyber-shot DSC H1 does not play nicely with microscopes. It has a fixed lens whose aperture is deep inside the lens so it tends to vignette.

As Pau writes, usually the best way is the afocal setup: shoot through the eyepiece and zoom to reduce or avoid vignetting.

It can help to replace the microscope's eyepiece with one having a "high eyepoint", designed for use by people wearing glasses. The cone of light coming from such an eyepiece will converge to its narrowest point (called the "exit pupil") farther above the scope, where it stands a better chance of getting through the aperture of the camera lens without vignetting.

You can also buy specialized adapters that replace the microscope eyepiece and are designed to play nicely with the H1's lens, but they are expensive. See HERE. I do not know if any cheaper models are available.

--Rik

[GfL]

Snapping things afocally often led to things going kaput when lighting was concerned.

Is there any way I could build an adapter? Are there any plans available for the construction of such a thing?

And will altering the distance between camera lens and microscope tube etc help? what is the optimal distance?

[rjlittlefield]

Snapping things afocally often led to things going kaput when lighting was concerned.

Can you be more explicit than "kaput"? Are you talking about over/under exposure, hot spots, flare, what?

Is there any way I could build an adapter? Are there any plans available for the construction of such a thing?

In principle, an effective though unusual adapter could be constructed fairly easily as follows.

Equip your camera with an ordinary closeup adapter such as the Raynox DCR-250, so that at an appropriate zoom setting your camera will focus and fill the frame with a rectangle inscribed in an 18 mm diameter circle. Remove the microscope eyepiece and mount your camera so that it focuses on the aerial image cast by the objective some 10 mm down inside the eyepiece tube. If you can see the whole field, you're now done. But most likely you will see only the center of the field, surrounded by vignetting. To solve this problem, buy a surplus achromat of diameter 25 mm and focal length equal to 1/(1/150+1/D) mm, where D is the distance from the end of the tube to the middle of your camera lens. For example if D = 180 mm, then you need a focal length of roughly 1/(1/150+1/180) = 80 mm. Place this achromat at the end of the microscope tube to serve as what's called a "field lens". This will fix the vignetting.

I have never seen detailed plans for a setup like this, though I once put together a similar system for my own use (HERE, described mostly in the third post).

Note that if your objectives are designed for use with a "compensating" eyepiece to remove chromatic aberration (CA), then the approach I describe above will leave you with colored fringes because the CA will not be removed. I cannot tell from your current images whether this is the case.

And will altering the distance between camera lens and microscope tube etc help? what is the optimal distance?

With your objective-only setup, you will get less vignetting at shorter distances. What you are essentially doing is treating the objective as if it were an "infinity" design, and using it kinda sorta as described HERE, but with much more separation between objective and telephoto.

--Rik

[GfL]

Wrt things going kaput - no light enters the camera at all if I zoom in to avoid vignetting. It all goes dark, exposure times increase and the quality of the image worsens.

[GfL]

Will go through some of these solutions. Thank you.

[gpmatthews]

You may find some of the ideas on my website at

http://www.gpmatthews.nildram.co.uk/mic ... apter.html

useful

[rjlittlefield]

Wrt things going kaput - no light enters the camera at all if I zoom in to avoid vignetting. It all goes dark, exposure times increase and the quality of the image worsens.

This suggests that the lens on the H1 is designed such that the entrance pupil moves far backward as the lens is zoomed. If so, that's OK for the combination-of-lenses solution I described above, but it will affect the needed strength of the field lens.

In more detail...

First, obtain the macro lens and determine what zoom setting is necessary to focus and fill the frame with a rectangle that is 18 mm diagonal. Set the camera so that you are sure the lens will stop down when a picture is taken. Then, using that determined zoom setting and with the macro lens in place, look into the front of your camera lens while taking a picture. At some place inside the lens, you will see the aperture stop down. That place may appear to be deep inside the lens, or even behind the camera, or you may not even be able to see it clearly because the macro lens has moved it "beyond infinity". In any case, do your best to estimate the apparent position of the aperture, as it is seen through the macro lens.

This apparent position of the aperture is called the "entrance pupil", and this is a very important term to know.

In the description that I gave earlier, I said that "D is the distance from the end of the tube to the middle of your camera lens". But that's not really correct. Actually D is the distance from the end of the tube to the position of the camera's entrance pupil with the macro lens in place. I casually assumed that the entrance pupil for your lens would be somewhere around its middle, but that now sounds unlikely. So you need to figure out where the entrance pupil is, measure from there to the end of the tube, and use that value where D appears in the formula.

If the entrance pupil has been moved "beyond infinity" so that you can't even see the aperture clearly through the macro lens, then effectively the entrance pupil is really in front of the camera. In this case D may be negative. The best of all conceivable outcomes is that the entrance pupil of the macro+H1 combo happens to coincide with the objective, in which case D = -150 and the field lens is not needed at all.

For more information about the entrance pupil as it matters here, study THIS PART of the FAQ: Stopping down a lens combo.

I confess, I'm a bit nervous showing you this path because I have no idea how hard it is to understand. I had to essentially figure it out over a period of years as a side effect of studying other issues. I cannot point you to any descriptions that are more concise than what I've written and linked above. Please go study them carefully, but I suspect that the descriptions will not make complete sense until you have the lenses in hand to play with. Even then it may take a while.

--Rik

[GfL]

Now, in the system I have, which ones would be part of the front lens and which ones the rear?

[rjlittlefield]

"Front" = closer to subject, "rear" = closer to sensor.

But I was not really intending those diagrams to be useful for understanding your current system.

Instead I suggested them to help understand what happens if you add a macro lens to your camera, then use that combination to look at the aerial image cast by the objective. In that case, "front" would be the added macro lens, and "rear" would be the lens built into your camera.

--Rik

[GfL]

"Front" = closer to subject, "rear" = closer to sensor.

But I was not really intending those diagrams to be useful for understanding your current system.

Instead I suggested them to help understand what happens if you add a macro lens to your camera, then use that combination to look at the aerial image cast by the objective. In that case, "front" would be the added macro lens, and "rear" would be the lens built into your camera.

--Rik

[1] Would the eyepiece serve as a macro lens?
[2] I have a 0.45x macro lens, do you suggest I work out details of the entrance pupil et cetera using that in conjunction with the camera?