Gloeotrichia (a cyanobacteria)

Charles Krebs · Post by **Charles Krebs** » Wed Sep 02, 2009 11:43 pm

Found these in a a water sample from a nearby lake this afternoon. Very pretty spherical shaped cyanobacteria. I photographed some almost exactly a year ago from the same location. At that time I also took a very tight shot of the ends of the long "filaments".

These were taken in darkfield with Nikon CF N Plan Achromat 4X, 10X and 20X.

Aynia · Post by **Aynia** » Thu Sep 03, 2009 12:49 am

Wow... very nice as usual Charlie.

ChrisR · Post by **ChrisR** » Thu Sep 03, 2009 3:57 am

I had no idea such things existed

!

Cyan, er...?

bernhardinho · Post by **bernhardinho** » Thu Sep 03, 2009 4:50 am

hi Charles

very nice?? I don't think that really hits the nail. These shots are sensationell!! Normally I'm not a great DF fan, 'cause it tends to look a bit fuzzy. But I think now I change my mind and try harder!

I thought you'd have Olympus optics??

Bernhard

BJ · Post by BJ » Thu Sep 03, 2009 9:30 am

Fabulous !

Brian

Charles Krebs · Post by **Charles Krebs** » Thu Sep 03, 2009 10:54 am

Thanks!

Bernhard...yes I primarily use Olympus equipment. Some time ago I picked up a Nikon Labophot for a very good price and it came with a set of CF N Plan Achromats. I thought I would give them a try, particularly for darkfield. My Olympus 20X is a great optic, but it's 0.70 NA can make it "trickier" to use for darkfield... light colored, out-of-focus areas really "expand" against the dark background because the DOF is so shallow. (I think this may be part of the "fuzzy" look you describe). And while it is possible, it's harder to establish nice darkfield with a standard condenser and a simple "stop" placed near the condenser diaphragm when the NA gets that high.

With strongly 3-dimensional subjects it is a bit of a conundrum. With a 20/0.40 (or the 20/0.5 Nikon CFN) it is much easier to deal with the "fuzzies" than with a 20/0.7 Plan Apo. But with all the brightly lit highlights and spots you get in darkfield any chromatic aberration becomes very obvious. So in that respect the Plan Apo's excel.

If I am not feeling too lazy I think the best darkfield I can get is when I put a sort of "funnel stop" at the back of my 20/0.70 (and the 10/0.40 as well) which, in effect, reduces the NA a little. But adding and removing this frequently is a PITA

Charlie

rjlittlefield · Post by **rjlittlefield** » Thu Sep 03, 2009 10:58 am

Awesome images, Charlie, as always!

Are these single shots or stacked? Flash or continuous illumination?

--Rik

Charles Krebs · Post by **Charles Krebs** » Thu Sep 03, 2009 11:25 am

Rik,

All stacks... between 7-10 images. (Some ZS

, some HF

).

No flash (still in box somewhere

). Taken with Canon 50D attached directly to microscope using the "silent mode" in live-view. Shutter speed was about 1/40 second. The "silent mode" appears to be very effective at minimizing vibration problems. In this case the wet mount was pretty "deep", because I did not want to flatten the delicate spheres too much. This can be particularly problematic when any vibration is present. I could actually see a little "jiggle" when the shutter "re-cocked", but this would be after the exposure (no mirror movement at any time). If anyone is looking for a DSLR to mount directly to a microscope (to be used without electronic flash), I would strongly recommend placing the Canon bodies with "slient-mode, live-view" on the short list of candidates.

Charlie

rjlittlefield · Post by **rjlittlefield** » Thu Sep 03, 2009 11:55 am

Wow -- continuous illumination at 1/40 second in a deep wet mount with a hard-mounted DSLR?!

That's a strong argument for those Canon bodies!

--Rik

bernhardinho · Post by **bernhardinho** » Thu Sep 03, 2009 2:07 pm

Charles-- what exactly is this "silent mode" all about? I couldn't find anything about it in the description of the 50D on the Canon website!

Apart from that question: how could there be any vibration at all using the life view? As long as the main sensor is used for life view, mirror should be down and shutter should be open. and this is the case in more humble versions like the 450D already !

Bernhard

Charles Krebs · Post by **Charles Krebs** » Thu Sep 03, 2009 5:07 pm

Bernhard,

how could there be any vibration at all using the life view? As long as the main sensor is used for life view, mirror should be down and shutter should be open. and this is the case in more humble versions like the 450D already !

Not exactly. With most live-view implementations (including 450D Edited: This is not correct. See below!), at the very least, the following occurs when an exposure is initiated...- the mechanical first shutter curtain closes, -the mechanical first shutter curtain then re-opens to begin the exposure. It happens very quickly so it is hard to see. With a camera hard mounted to the scope these two mechanical shutter actuations are enough to cause problems, especially in the 1/4 to 1/60 second shutter speed range. With some DSLRs it is much worse. With these the following takes place when a picture is initiated in "live-view"... -the mirror comes down, -the shutter closes, -then the mirror goes up, -and then the shutter opens to start the exposure! DSLR vibration nightmare.

This was discussed fairly recently on a Yahoo microscope forum. I'll paste in the answers I gave there.

"Silent Mode, Live View" works as follows... When Live View is turned on, the mirror goes up, the shutter opens, and whatever is reaching the sensor is displayed on the camera back (or monitor/TV). When taking a picture is initiated, there is no mechanical motion of either the shutter or mirror. The camera utilizes an "electronic first shutter curtain". So there is no mirror cycling or shutter closing/re-opening to cause any vibration. To complete the exposure, the rear (mechanical) shutter curtain does release. This then becomes the first, and only, camera induced vibration source. (And it would only be the inertial force caused by it's release... any "impact" at the end of it's travel is after the picture is taken). I don't know the travel time for the rear shutter curtain (and thus the percentage of time it is in motion for a given exposure time), but camera induced vibration is very noticeable less in (at least) the 1/2 to 1/60 shutter speed range (and probably a wider range, haven't tested fully yet). And it is noticeably less than using mirror lock-up with normal shutter action.

Once the exposure is completed, the shutter will recycle, the first shutter curtain will open again, and you return to "live view" mode. At no time does the mirror go up or down. There are actually two "silent modes". In one the shutter will automatically recycle at the end of the exposure. In the second the shutter will recycle only after the shutter release is completely unpressed. For our purposes I see no advantage of one over the other. Again, you can't use electronic flash with the "silent mode".

Canon promotes this feature as a low noise capability, but for some
purposes the elimination of vibration is a bigger benefit. I'm not savvy as to what is actually going on electronically so I'll just quote a relevant section from the Canon 40D "White Paper" (page 14):
-----------------------------
With Live View Function image displayed, the 40D can shift seamlessly to slit exposures with the electronic 1st-curtain shutter, enabling silent shooting which is not possible with a mechanical 1st-curtain shutter. This electronic 1st-curtain shutter uses a unique high-speed scanning and electronic reset system that accurately mimics the EOS 40D's high-speed mechanical shutter operation. It synchronizes with the mechanical 2nd-curtain shutter to obtain a slit exposure. (Note that with CMOS, it is difficult to have an electronic 2nd-curtain shutter. Therefore, only the 1st-curtain shutter is electronic.)
-----------------------------

The key thing is the "electronic first shutter curtain". The Canon cameras that have this "live-view, silent-mode" are the 40D, 50D and the 5D II. (I don't know about the new 7D)
... edit 9/4/09: Note: just looked in 7D manual. It also has "silent-mode".

Some may think that the mirror is the only culprit, and that you can disregard the shutter curtains. But it's easy to see if you have a SLR camera mounted directly on the microscope. Lock up the camera mirror. Use a 20X or higher objective. Put a "deep" wet mount on the microscope, and set a long exposure time (1 second or longer) so that you can observe what happens due only to the action of the first shutter curtain. You can see a slight "jiggle" in the subject when the first shutter curtain opens. This can cause image degradation, especially in the commonly used 1/2 to 1/60 shutter speed range.

Charlie

bernhardinho · Post by **bernhardinho** » Sat Sep 05, 2009 9:11 am

Hi Charles

you really confused me there, cause your arguments really seem to be waterproof!! But I now sorted things out and I think I know the reason for the confusion. At first: my story about the rather cheap EOS 450D based on a set of tests a friend of ours showed in the german forum in a similar discussion

http://www.mikroskopie-forum.de/index.php?topic=2501.30

I recall that you read a bit of german, but I think it's clear what's the issue. The upper diagramm depicts measurement of vibration with only mirror up. You see the expected vibration of the shutter. Second table is Live view, mirror up, shutter open. There is hardly any noticable vibration.

You can check what is going on looking through the camera with no objective attached and shutter at 1s. Nothing happens!! No reopening of the shutter!

NOW the key thing here might be the fact that the confusion about this particular Canon body is due to the strange marketing policy by Canon. For some reason, as far as we know, there is no EOS 450D on the US market. In the US the same camera is called Rebel XSi.

So all I'm saying is that this rather low cost model is very suitable for microphotography and should be added to your short list of candidates

Bye for now

Bernhard

Charles Krebs · Post by **Charles Krebs** » Sat Sep 05, 2009 1:16 pm

Bernhard,

Thanks for making me take a look at this again. I have never used a 450D or 500D. It appears this is very good news. The diagrams on the link you gave show exactly what would be expected with an electronic first shutter curtain. (And the upper one shows that the mechanical first shutter curtain is associated with vibration).

It is interesting that Canon only mentioned the "electronic first shutter curtain" beginning with the 40D (Then 50D and 5d II).

But based on your friend's (and your) observations, it does appear that the 450D (Xsi) and the 500D (T1i) do this as well! This would be great news, since these are (relatively... for DSLR's) inexpensive bodies. If this is so, it's too bad Canon marketing doesn't hype this as a real asset for macro and astro photography... because it really is!

I looked in a 450D instruction book, and there is no mention of this feature, however there were these "cautions" in the "live-view" section:

These are the same "restrictions" mentioned with the 40D/50D when discussing the "electronic" first shutter curtain. So it fits. (BTW...according to the 40D/50D instructions the reason a Canon flash will fire is because it "over-rides" the electronic first shutter curtain operation, and in this case the shutter does close and then re-open for an exposure. I would guess it is the same with the 450D and 500D).

Charlie

rjlittlefield · Post by **rjlittlefield** » Sat Sep 05, 2009 1:25 pm

Fascinating! You don't find many undocumented features that are strong positives. I checked just now, and several vendors are offering the XSi body for $570 USD, new with a regular 1 year warranty. That strikes me as very attractive for a 12 megapixel DSLR with this feature.

--Rik

Charles Krebs · Post by **Charles Krebs** » Sat Sep 05, 2009 5:18 pm

OK, I've looked through a bunch of Canon manuals and documents...

In the Canon 40D White Paper the "electronic first shutter curtain" is discussed in regards to the "silent mode" setting of live-view. At the end of the discussion it gives the following caveats:

In the "live-view, silent mode"section of the 40D instruction book it says:

I've looked through the instruction manuals for all the Canon DSLRs since the 40D. This includes the 40D, 450D (Rebel XSi), 1000D (Rebel XS), 50D, 5DII, 500D (Rebel T1i), and 7D. All of the instruction manuals warn about exposure errors if extension tubes or TS-E lenses are used with live-view. The cameras without the "silent-mode" settings all warn that, when in live view, a non-Canon flash will not fire. Seems to me that it's likely this "electronic first shutter curtain" may be in all of these cameras. It's certainly in the ones that feature "silent modes". Bernhard has confirmed that it is in his 450D (also see Peter Höbel's post in the German forum that Bernhard referenced above).

The TS-E and extension tube exposure warnings are explained in the 40D "White Paper" as a by-product of the electronic first shutter curtain. These warnings, along with the non-Canon flash warnings are consistent with all the cameras.

Too bad Chuck Westfall doesn't lurk around here!