Brightfield Practice

[rnabholz]

For the lighting method that is considered the most basic, I find it very challenging to image well.

Managing Kohler, condenser settings for depth of focus vs diffraction and spurious color, compromises at every turn.

I finally have come up with what I believe is a workable camera adapter for my AO4, so tonight I set out to test it and my brightfield skills.

AO4 Apostar, 90x Apo, Phototube with 10x Compens in line as a projection lens to a Canon 70D.

Navicula

Mecan River Navicula 4338.JPG (60.92 KiB) Viewed 5803 times

Cymbella

Mecan River Cymbella 4333.JPG (59.79 KiB) Viewed 5803 times

Girdle View

Mecan River Girdle View Diatom 4346.JPG (51.82 KiB) Viewed 5803 times

Mecan River Surirella 4361.JPG (76.65 KiB) Viewed 5803 times

[apochronaut]

Not too shabby, Rod.

[rnabholz]

Not too shabby, Rod.

Thanks Apo, I'll take it!

[mrsonchus]

Well Rod, these look pretty darn fine to me old chap!
Lovely clean and well-exposed set. If these are your first try we're all in for a treat I think.
Whatever set-up you've used I think it's working (in your capable hands) really well.
Keep up the good work Rod.

[75RR]

Nice and flat! ;)
Actually they look very nice.
As the default/start-out mode, brightfield is mostly seen as a way-point on the path to more rewarding illumination methods.
It does however on occasion provide a view-point that works very well on its own.
This is a good example of the rewards of taking a moment to really look at the brightfield image before we rush on.

I finally have come up with what I believe is a workable camera adapter for my AO4 ...

That bodes well for the other illumination techniques as well - so what did you come up with?

[rnabholz]

Well Rod, these look pretty darn fine to me old chap!
Lovely clean and well-exposed set. If these are your first try we're all in for a treat I think.
Whatever set-up you've used I think it's working (in your capable hands) really well.
Keep up the good work Rod.

Thank you John, glad you like them and I appreciate the feedback!

It seems each stand has its idiosyncrasies, it is always a "journey".

[rnabholz]

Nice and flat!
Actually they look very nice.
As the default/start-out mode, brightfield is mostly seen as a way-point on the path to more rewarding illumination methods.
It does however on occasion provide a view-point that works very well on its own.
This is a good example of the rewards of taking a moment to really look at the brightfield image before we rush on.

I finally have come up with what I believe is a workable camera adapter for my AO4 ...

That bodes well for the other illumination techniques as well - so what did you come up with?

Thank you 75. I think there can be a certain elegance to good brightfield images. My interest has been rekindled a bit with the arrival of the new Apo stand. The clean view at the eyepieces is a new experience for me.

The photo set up is a bit of a tinker toy project. The first attempt was to use components from an AO film camera set up, removing the film body, and using the collar and projection lens. The results were not good. Apo offered the theory that the lens did not provide the correction necessary for the Apo objectives normally addressed by the compens eyepieces.

So the next approach was to put together a set up that would use a compens eyepiece as a projection lens. AO offered another camera adapter back in the day that used a set up like that. The hard part was finding that tube.... To get one I had to buy an Ebay parts stand that happened to have one included.

From there, it was a mix of hardware store parts, photo parts and glue. Here is the kit

IMG_20170207_182302-600x808.jpg (137.94 KiB) Viewed 5745 times

I used a set screw lock collar on the tube to provide adjustability of the camera position. I epoxied a 1" washer to that collar, and epoxied a camera T-mount to the washer.

The compens rides in the tube.

IMG_20170209_182426-600x800.jpg (115.28 KiB) Viewed 5745 times

Extension tubes on the camera attach to the t-mount and provide additional flexibility in camera position.

IMG_20170211_134659-600x808.jpg (122.26 KiB) Viewed 5745 times

Not pretty, but seems to be working.

[75RR]

Not pretty, but seems to be working.

Can't disagree - still as long as it works and we can see that it does - that is all that matters.
Do you fine tune focus to achieve parfocality by turning the set screw lock collar ?

[rnabholz]

Not pretty, but seems to be working.

Can't disagree - still as long as it works and we can see that it does - that is all that matters.
Do you fine tune focus to achieve parfocality by turning the set screw lock collar ?

No, the lock collar only provides some adjustment of the image size, as it moves the camera position relative to the projection lens.

I believe to fine tune the parfocality, I will need to either shim the eyepiece in the tube, or shorten the tube. It is close now, and I am able to tweak it by monitoring the image on an external screen, but I would like to dial it in. Please let me know if I have that wrong.

Here is another image from the same set up. One of John B's lovely sections.

IMG_4317.JPG (214.65 KiB) Viewed 5724 times

[Crater Eddie]

I like your solution. Nothing wrong with a bit of basement engineering if it achieves your goal. The proof is in the result.

CE

[mrsonchus]

Nice, coming along well. That's a typical Canon/brightfield image - the colours are spot-on and your exposure looks perfect too! Those cells look familiar....

Great to see your solution developing, really an interesting exercise - thanks for sharing it with us my friend.

[KurtM]

WOW - that last image really has a 3-D effect on my monitor!

I love the hardware store bits approach to photomicography too, very nicely done! As I always say, you can have my J-B Weld when you pry my cold dead fingers off the tubes.

[75RR]

I believe to fine tune the parfocality, I will need to either shim the eyepiece in the tube, or shorten the tube. It is close now, and I am able to tweak it by monitoring the image on an external screen, but I would like to dial it in.

I used the method Charles Krebs outlines when using a 'normal' eyepiece as a 'projection' eyepiece:

http://krebsmicro.com/pdf/parfocal.pdf

See step 1-B

I used eyepiece shoulder shims cut from PVC electrical wall pipe conduits cut to allow 2.5mm increments.
The initial elevation of about 5mm + provides the 'Real image' needed, additional height is solely to provide the magnification wanted.
By the way, they are impossible to cut straight with a hacksaw.

Camera is held over the phototube on a focusing rail attached to a tripod to allow vertical adjustment and also to limit vibration. I use a black plastic sheet taped into a tube shape to bridge the distance between the eyepiece and the camera to cut out light and dust.

[rnabholz]

I like your solution. Nothing wrong with a bit of basement engineering if it achieves your goal. The proof is in the result.

CE

Thanks CE.

A bit of tinkering kind of adds to the fun too.

[rnabholz]

Nice, coming along well. That's a typical Canon/brightfield image - the colours are spot-on and your exposure looks perfect too! Those cells look familiar....

Great to see your solution developing, really an interesting exercise - thanks for sharing it with us my friend.

I bet they do look familiar!

Thanks for the interest.

Rod

[rnabholz]

WOW - that last image really has a 3-D effect on my monitor!

I love the hardware store bits approach to photomicography too, very nicely done! As I always say, you can have my J-B Weld when you pry my cold dead fingers off the tubes.

Yep, JB Kwik, for us impatient types....

Always fun to walk into a hardware store, and when the clerk asks if they can help you, reply "Yes, where do you keep your Photomicrography parts?"

[rnabholz]

http://krebsmicro.com/pdf/parfocal.pdf

See step 1-B

I used eyepiece shoulder shims cut from PVC electrical wall pipe conduits cut to allow 2.5mm increments.
The initial elevation of about 5mm + provides the 'Real image' needed, additional height is solely to provide the magnification wanted.
By the way, they are impossible to cut straight with a hacksaw.

Camera is held over the phototube on a focusing rail attached to a tripod to allow vertical adjustment and also to limit vibration. I use a black plastic sheet taped into a tube shape to bridge the distance between the eyepiece and the camera to cut out light and dust.

Thanks 75, I have that guide saved.

I was thinking that rubber O Rings might be just the ticket instead of cutting shims, I know that I would also never get them cut straight.

Thanks

Rod

[75RR]

Thanks 75, I have that guide saved.

Good, I find it explains things very well.
One of the main points is that parfocality is first achieved with the 'projection' eyepiece (by raising or lowering it in fine increments as it would be normally) - only then is the eyepiece lifted by 'x' amount to get both a 'real image' and the magnification wanted - finally the camera is then placed and hence focused at this exact point.

I was thinking that rubber O Rings might be just the ticket instead of cutting shims, I know that I would also never get them cut straight.

I was ankle deep in unevenly cut pipe rings before I gave up and had someone with a fine toothed table-saw do it for me. :)
O Rings should be fine.