Three diatoms

Charles Krebs · Post by **Charles Krebs** » Tue Oct 18, 2011 11:18 pm

Mounted in Zrax. Darkfield and circular oblique. Olympus 100/1.40 S PLan Apo and Zeiss Ultracondenser.

Cactusdave · Post by **Cactusdave** » Tue Oct 18, 2011 11:43 pm

Very nice images of a personal favourite subject. I particularly like the first image. It's always interesting to 'push the envelope' with light microscopy, in comparison with Scanning Electron Microscopy (SEM) for example.

Wim van Egmond · Post by **Wim van Egmond** » Wed Oct 19, 2011 12:55 am

Beautiful tranquile images, Charles, a joy to watch! I assume that objective has an aperture? I was a bit puzzled you could create darkfield with an 1.4 NA objective.

I have recently bought a zeiss ultracondenser but have difficulty getting the illumination right. I think it is because my flash illumination is not positioned exact enough. This is not a problem for the lower mags but for higher magnification it does not work well. I'll have to try it without the flash.

Wim

Marek Mis · Post by **Marek Mis** » Wed Oct 19, 2011 1:48 am

Charlie,

Very, very beautiful images ! The first one is simply breathtaking. Your skills are incredible !
Thank you for sharing.

Best regards

Marek

RogelioMoreno · Post by **RogelioMoreno** » Wed Oct 19, 2011 4:59 am

Beautiful! The first one is amazing.

Like Win I would like to know how you did darkfield with the 1.4NA objective.

Rogelio

Chris_M · Post by **Chris_M** » Wed Oct 19, 2011 10:33 am

Awesome images, especially the first one.

Charles Krebs · Post by **Charles Krebs** » Wed Oct 19, 2011 11:24 am

Thanks all for the kind comments!

The Olympus 100/1.4 S Plan Apo does have a built in diaphragm. The Zeiss Ultra condenser is 1.2/1.4 (inner portion of the light "ring" has a NA of 1.2, the outer edge is 1.4). So it is necessary to "close down" the aperture in the objective to just below 1.2 in order to get darkfield as seen in the first shot. But if you play around with the aperture size and the positioning of the condenser you can get some really beautiful lighting effects when the objective aperture is just a slight bit larger than 1.2 (or if it is near 1.2 and you move the condenser so just a "sliver" of light makes it into the objective). Very subject/mount dependent and highly variable. In can be tricky to obtain with live subjects, but with a mounted diatom you have all the time you need to play around and tweak with the lighting. Sometimes just the slightest adjustment makes a huge difference so if (as Wim mentioned) your flash "geometry" is not exactly the same as your viewing light it is probably best to stick with the continuous light source for exposures.

Wim van Egmond · Post by **Wim van Egmond** » Wed Oct 19, 2011 12:24 pm

Thank you for the explanation Charles, so microscopy still works the way I thought it worked.

I did a quick test with a very old 100X plan apo I have that has an aperture which was stuck, with a bit of physical persuasion I could stop it down a bit and I could get darkfield with my darkfield condenser but very little light remained. I have to make 10 a seconds exposure to get an image. And than I use a 100 watt lamp attached to my Zeiss standard the normal way.

Was that limted amount of light remaining also the case with your images, Charles? I hope you can help me out here. The image resolution I get is quite o.k. but I think something is wrong when so much of the light is lost.

all the best from the Netherlands,

Wim

Charles Krebs · Post by **Charles Krebs** » Wed Oct 19, 2011 12:42 pm

Wim,

I have to make 10 a seconds exposure to get an image. And than I use a 100 watt lamp attached to my Zeiss standard the normal way.

Something sounds strange there! That is more than six stops less light than I had!

I just checked the EXIF data on the original files for the above pictures. For the first two images my exposure times were 1/10 second @ ISO 100. On the third it was 1/8 second. (Can't remember if I was using the 1.67X or the 2.5X photoeyepiece in the trinocular tube).

This is with the Olympus BHS stand with the "stock" 100 watt lamphouse. (The condenser does not fit the Olympus fitting... wrong dovetail size and condenser is too short... so I needed to make an "extension" with the Olympus dovetail at the bottom, but that should not make any real difference). What sort of exposure times are you getting with something like a 40X?

Wim van Egmond · Post by **Wim van Egmond** » Wed Oct 19, 2011 12:51 pm

Thank you Charles, yes, than there is indeed something wrong. With other magnifications there is also very little light. It could also be that there is something wrong with the condenser itself.

I will work on it again tomorrow and keep. It is getting late and if I continue working now I can't sleep, I will see nothing but diatoms when I close my eyes.

best regards,

Wim

Mitch640 · Post by **Mitch640** » Thu Oct 20, 2011 4:11 pm

Very beautiful diatoms Charles. The fist one looks like something from the Oort Cloud come to visit.

On another note, have you determined if the T31 has shutter sync to stop vibration, as the T1i has?

Charles Krebs · Post by **Charles Krebs** » Thu Oct 20, 2011 11:32 pm

Mitch,

On another note, have you determined if the T31 has shutter sync to stop vibration, as the T1i has?

Not sure what you are asking here.

The T3i has a similar shutter procedure (and electronic first shutter curtain) as the T1i and T2i if that is what you wanted to know. So vibration has not been a problem. (These shots were taken with an older model, 350D, mounted on a separate stand above the microscope).

Mitch640 · Post by **Mitch640** » Fri Oct 21, 2011 1:56 am

Yup, that's what I wanted to know. I'm about ready to upgrade and the T2i and T3i prices are only $50 apart.