Phase vs. HMC: diatom pics

nanometer · Post by **nanometer** » Sun May 29, 2016 7:35 pm

A friend let me borrow a Hoffman condenser and 20x LWD Hoffman objective--he's too busy setting up his DIC system

I jerry-rigged it onto my Diavert and did some tests on Kemp's 100 form slide.

Here are a few results (phase 25x Fluotar Phaco in the left column). The HMC images were taken with deep extinction in the polarized part of the condenser mask. There was no coloring for less-deep extinctions, but I obtained the strongest effect on the diatoms with the polarizers crossed. No retouching of images except cropping and down-sizing.

I was surprised how well the HMC worked.

zzffnn · Post by **zzffnn** » Mon May 30, 2016 7:46 am

Both sets are very nice!

Was the phase set produced by the Heine condenser? I know it is one of the 3 most resolving phase systems, but am still surprised that it does not lack too much compared to HMC.

That said, comparing HMC and phase is still not quite fair, considering the aperture difference?

May be offset COL with Heine vs HMC would be a more fair and interesting fight? I will get popcorns ready, if you are doing that

nanometer · Post by **nanometer** » Mon May 30, 2016 8:10 am

I used the Heine but with a phaco objective. Might be interesting to image them with the Pv 25x as it's phase ring is at higher NA than the phaco.

Great idea about trying offset COL. Maybe I'll find some time for that and the Pv.

I didn't mean to be comparing apples to apples here. This was my first point of curiosity with HMC. I'm starting to think about setting up HMC on the Diavert, but wanted to make sure I understood how it would perform first.

I have both a flip-top Leitz condenser and a Nikon 1.4 aplanat (with a Leitz dovetail). Either of this might be good options along with homemade condenser HMC masks.

Unfortunately, due to the large 'U' bracket on this particular HMC condenser, there wasn't enough room for my flash beamsplitter. Tried some protozoa, but without flash, the exposure times were too long for almost everything. I did manage to get a couple Dinobryan, but had to bump the iso to 500 at 1/15th sec, so it's not great. Also is a heavy crop.

nanometer · Post by **nanometer** » Mon May 30, 2016 10:01 am

Here's a quick comparison of offset COL at the edge of the 25x Fluotar (NA 0.55) vs. the 20x Hoffman (NA= 0.4). Now it's not fair for HMC. I could have improved the offset COL with some PP for contrast and clarity, but as with the other pics, only LR defaults, cropping and resizing. On the second set, I wonder if I got the best focus for HMC, but since that setup is no longer on the Diavert, I can't go back and check it.

zzffnn · Post by **zzffnn** » Mon May 30, 2016 12:34 pm

Thank you very much! I like those nice photos and the informative comparison.

I agree, not a fair fight, given the NA advantage of Heine/Pv offset COL. Also, it might be difficult to maintain the same point of focus, since objectives have to been changed.

Is the HMC objective an achromat? And PV Fluotar has fluorite correction?

I am saving up to buy a Leitz Heine condenser and will use it with some LOMO objectives (which are very old short Zeiss Jena clones). My 20/0.65, 40/0.95 are dry apo's and my 70/1.23 is a water immersion apo, do you think they will perform about the same as the Leitz Fluotars, in terms of clarity/cleanness?

I also have some LOMO high NA achromats (30/0.9 WI and 10/0.4 dry), which I assume will not produce images that are as clean. All of those are reasonably clean with compensating eyepieces and regular condenser oblique. Though I am not sure about the effect of Heine, since its oblique (offset COL) is at a more extreme angle/edge.

And the slightly yellowish color of the offset COL came from light source, or from Heine?

nanometer · Post by **nanometer** » Mon May 30, 2016 4:04 pm

No problem zzffnn. The Heine is a wonderful condenser. If you get one, make sure they get a macro shot of the output ring (on the last surface near the slide). Make sure it is in excellent shape and not tattered and that the NA adjuster turns freely. They are fricking expensive, so you might as well make sure it's good.

My Heine did not have a Leitz dovetail connection, but one was made out of brass.

Oh yes, the Fluotars have fluorite correction (semi-apos I guess). The HMC objective was a plain-jane LWD achromat with the HMC plate.

zzffnn · Post by **zzffnn** » Mon May 30, 2016 6:00 pm

Thank you!

Were your Heine photos made with halogen light without blue filter? I wonder if that slightly yellow color (at subjects' edge) came from the halogen light source, or was it produced by Heine (a side effect of extreme oblique)?

I found some more Heine photos at a German forum (but I had to rely on Google Translate):
http://www.mikroskopie-forum.de/index.php?topic=13978.0

Those photos have more dramatic colors. It almost looks like those colors there were made deliberately. For photo #1 there, it seems that a yellow filter was used along with darkfield position. That photo#3 puzzled me, as it has gold color at edges and blue color inside the diatom. Were those made by color Heine, side effects of a regular Heine, or digital processing? I personally prefer to turn off those dramatic colors most of the times, but your photos look good to me (your colors are more natural).

Thanks again.

nanometer · Post by **nanometer** » Mon May 30, 2016 7:40 pm

No filters. I had about 1/4 of the phase ring inside the NA of the objective so it's not colored. It looks like the pics in the link were darkfield. Since the Heine ring NA can be chosen outside of the NA of the objective, diatom colors change as that ring changes. Here are a couple of examples at 40x in darkfield where I adjusted the NA darkring to bring out good colors.

zzffnn · Post by **zzffnn** » Mon May 30, 2016 9:08 pm

Thank you! I find your comments very helpful.

When you said "I had about 1/4 of the phase ring inside the NA of the objective so it's not colored",

That " 1/4" is the bright (illuminated) part of the condenser ring, correct? Would you be so kind as to take a back focal plane image of that, or draw an illustration (to show shape, position and bright vs dark)? Thank you very much.

Photo #3 and #4 of the web page that I linked to are COL or offset COl, not darkfield. But It looks like the color effect was produced by changing ring NA of the Heine. I found two videos showing such a color-changing effect.

Also, the output ring that you were referring to, is the lens element immediately below the oil cap (when 1.4 NA oil cap is installed), but not the oil cap itself, correct?

nanometer · Post by **nanometer** » Tue May 31, 2016 5:56 am

right. Not the oil cap itself. At some point, I should look at the effects more quantitatively on one diatom vs. exactly where the ring is relative to the objective edge. All I can say at this point is that there is a range of color effects you can achieve with this condenser. I suspect it also depends on the objective too.

In general, I find strongly offset oblique light to be frustrating for all but the thinnest of subjects as the shadowing effect on thicker things is too strong and confuses the view.

zzffnn · Post by **zzffnn** » Tue May 31, 2016 6:40 am

I assume the Heine can produce gradual and smooth transition from slight offset to strong offset?

The Heine itself has two centering screws, and my scope's condenser (dovetail) mount has two centering screws too. That should help with smooth transition?

I agree, I tend to use less offset for thick subjects too, with my DIY oblique masks.

I also suspect that a phase objective may not produce color/shadow effects as clean as a plain brightfield objective, assuming both having the same fluorite correction and NA.

Transitional colors of Heine has been shown in this thread: http://www.mikroskopie-forum.de/index.php?topic=10186.0
Reply #11 (on page 1) and #17 (on page 2) provided two videos showing color transition too. I saw resolution changes there too.

Please do show us the objective back focal plane (light ring) image and corresponding subject image, when you have a chance. Thank you very much!

92111 · Post by **92111** » Mon Oct 22, 2018 4:32 am

hello nanometer
can i make frends with you?because i have a leitz diacert,and i have many problem,such as how can i add a Hoffman condenser on my microscope