1st ants, at 7x and 5x

Just bought that first macro lens? Post here to get helpful feedback and answers to any questions you might have.

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Pau
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Post by Pau »

Carmen, I have little experience with Canon flashguns, the EX 600 will be very nice, but for macro you can do about the same with less expensive units like the 430EX or full compatible third party units like the Yongnuo YN560EX I use.

The Yongnuo is inexpensive, fully compatible and works very well, although its color temperature is less constant and not controlled by the camera like in modern Canon units, but for me it's OK.
Pau

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Post by rjlittlefield »

Carmen wrote:
rjlittlefield wrote:...Camera is a Canon T1i, 15.1 megapixels APS-C. Optical chain was a Kenko 1.5X teleconverter, 12 mm empty tube, Canon EF 200mm f/2.8 L IS USM macro lens set at 1m, Nikon CFI Plan Achromat 10X NA 0.25. --Rik
Thank you Rik! To summarize this test:

same Nikon CFI 10x micro' objective
tube lens 300mm (200mm + ext. tube + 1.5x teleconverter)
relevantly similar small APS-C sensor
relevantly similar mount, hanging perpendicularly from amateur tripod
electronic flash, with very brief pulse (perhap 1 milisecond resolution? does that sound correct?)
Sorry, there was a typo in my posting. It should have said 100mm f/2.8.

Here is the setup that produced the test image shown above.

Image

The second flash unit is optically slaved to the in-camera flash.

I just now ran another test, eliminating the second flash unit, shifting the diffuser so as to utilize only the in-camera flash, and also setting the focus ring on the 100mm f/2.8 to be infinity instead of 1 meter. Here is that setup:

Image

Here is the result of that setup.

Whole frame:
Image

Center actual pixels:
Image

Corner actual pixels:
Image

Link to camera-resolution image:
http://janrik.net/MiscSubj/2015/topic27 ... lution.jpg

I notice that this stack shows much less false color than the previous one did. I speculate that this is a result of reduced LCA (longitudinal chromatic aberration) because of running the objective closer to its design point (12mm tube plus infinity focus, versus 12mm tube plus 1m focus). But possibly also it's due to some difference in the illumination.

In this setup I'm not sure what power the camera's flash was running at, except that it was obviously less than full power because the camera's recycle time stayed short for several times longer than when forced to run at full power.

I think you can do this same sort of experiment yourself, right now, using the flash unit built into your camera.

It's interesting to note that in this setup there's a lot of mechanical action just before the exposure is taken. I have to run in Live View in order to focus-stack with CamRanger. But because of some apparently silly constraint inside the camera, flash exposures can only happen outside Live View. The system knows this and automatically applies the workaround: close the shutter, drop the mirror, raise the mirror, open the shutter, and only then -- after thoroughly banging things around -- fire the flash to capture the image. But obviously the flash is fast enough to freeze out most of whatever motion is induced by all that mechanical action.
Correct me if I am in error: the magnification is about 15x?
15X would have been a good estimate given my typo about the lens length. However, the magnification is actually about 7.3X, measured by photographing a stage micrometer.

--Rik

Carmen
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Post by Carmen »

Hello NU!
NikonUser wrote:... the 1st species looks like an Atta; spines on head and spines on thorax fits some species in this genus.
Thank you for the lead: I will investigate. What most fascinates me about ants, and other colony type insects, is the collective "intelligence", and other properties that appear to arise from the group.
NikonUser wrote:...Looking forward to seeing more images as your technique improves (which it will do).
Thank you for the kind encouragement! :D In my view, there are many fascinating arthropods in argentina. But generally not much interest in them.

Carmen
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Post by Carmen »

Hello Rik

Thank you for the clarifications, and variation of test. I interpret it is as indicative of the effectiveness of super brief electronic flash pulse to freeze trembly image.

The mount reminds me of a negative enlarger - is it? It appears to be prone to vibration, perhaps even more than my amateur tripod.

And the clarity is encouraging. To be honest, that's the type of result that I would like to acheive with my micro' objective, which is presumably identical. :wink:

Again, thank you for your work on these tests. For now, I will experiment with the camera's incorporated mini-flash, until a proper flash unit can be had. Additionally, it occurs to me that a provisional configuration of inexpensive mirrors, or other inexpensive reflective surfaces may be effective to improve ilumination of specimen.

Carmen
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Post by Carmen »

Pau wrote:...but for macro you can do about the same with less expensive units like the 430EX or full compatible third party units like the Yongnuo YN560EX I use...
Thank you pau for the thoughtful suggestion. I agree with you -at least in manual mode for photomicrography, macro photography, etc... But my husband wants it for his foto-safaris. He considers the canon original better suited to this end. Additionally, he has reason to believe that the yongnuo flashes have a considerably higher return rate for defective units, which is suggestive of poor process control, poor quality control, lack of rigorous inspections before leaving the factory.

rjlittlefield
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Post by rjlittlefield »

Carmen wrote:The mount reminds me of a negative enlarger - is it? It appears to be prone to vibration, perhaps even more than my amateur tripod.
Yes, it's an enlarger stand that I modified many years ago to include a thumbscrew for fine vertical positioning. I'm using it here unlocked (big handle on the right side), so yes, it's pretty unstable. There are links to more discussion and details about the stand HERE.

--Rik

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