Doli startle reflex and snap turns

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BugEZ
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Doli startle reflex and snap turns

Post by BugEZ »

Dolichopodidae (doli) became famous for their startle reflex. This article

http://journals.fcla.edu/flaent/article ... 6354/74013

suggested that the startle reflex was of the order of 5 milliseconds, faster than the electronic flash of the author’s DSLR camera rig. I have taken hundreds of flash photos of doli and can say with certainty that doli are not faster than a flash. I don’t think the author realized that there was a pre flash in his automated camera to set the exposure. I use the flash in a manual mode so there is no pre flash. If I used an automated pre-flash exposure mode I would take photos of vacant leaves also.

I often use no flash at all as with the photo below, taken with a compact travel camera, Panasonic LUMIX DC-ZS70

When doli launch themselves they often execute “snap turns”. This provides some insight into their flight control and navigation. The you tube videos linked below show doli (and some other insects and a few spiders) taking wing. Interesting to watch.

Keith

You tube video of bug flight

https://youtu.be/_98oTmudl8k

image with Panasonic LUMIX, handheld, no flash, cropped
Image

Beatsy
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Post by Beatsy »

Wow! Fantastic image. Is that a single shot? Great DoF if it is - presume the small sensor provides that.

rjlittlefield
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Post by rjlittlefield »

Oh dear. I suggest emailing the author to let him know of the problem. It will be embarrassing, but I imagine he would rather know than not.

--Rik

rjlittlefield
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Post by rjlittlefield »

Beatsy wrote:Great DoF if it is - presume the small sensor provides that.
Sort of but not really. The small sensor just promotes the use of a short lens, which has a small hole for an aperture. It's that small hole that does the trick. According to the Exif data, this exposure was at f/3.3 on a sensor that is about 1/6 the width of 35mm. So, the equivalent f# on full-frame would be about 6*3.3 = f/19.2.

The effect of sensor size has been discussed many times in this forum, but I see that it's been a couple of years now since the last time I indexed one. See http://www.photomacrography.net/forum/v ... 417#183417 for a quick summary. An early long discussion is from 2008, at http://www.photomacrography.net/forum/v ... 4249#24249 and in the surrounding thread.

--Rik

Beatsy
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Post by Beatsy »

Thanks Rik. That's what I meant (small sensor, small lens, small aperture). Just inappropriate brevity.

BugEZ
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Post by BugEZ »

The sensor size is 1/2.3" (6.17 x 4.55 mm). This is a great travel camera and I love it. I can take bird photos and bug photos. 4X slow motion in high def.

The movie I linked was made with a Sony camera (RX10 M2) that has a higher frame rate than my LUMIX. It goes up to 8X slow motion in high def, and 16X in sort of high def. I am still learning how to use it effectively.

Rik pondered emailing the article’s author. Many years ago I did just that. I explained the pre-flash. His reply was thoughtful.
On Thu, Sep 8, 2011 at 1:42 PM Andrei Sourakov <asourakov@flmnh.ufl.edu> wrote:
Keith:
This is most illuminating! As a person who used manual film cameras and flashes most of my life, I learned new things.

The reason for publishing the article was to attract attention of neuroscientists to the phenomenon, and I am glad to see that someone in the field of insect neuroscience is indeed interested in LLF. I hope they can figure out the mechanism and, in the process, will undoubtedly calculate more precisely how fast LLF reflexes actually are. Somehow, I think it will not be much more than 10ms, even if preflash is the startling factor. This hunch is based on all the literature on startle reflexes that I looked at when writing the article combined with the fact that I encountered no other insect this fast.

Thank you very much for the link and suggestions. Just for fun, I am attaching a couple of my recent photos of dragonfly eyes taken in the field (though they are probably no match for the images of ommatidia you produce, they too show interesting pattern).


Andrei
Aloha

rjlittlefield
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Post by rjlittlefield »

Excellent. No surprise -- Sourakov seems like a good guy. (I've encountered him a few times at Lep Soc meetings.)

--Rik

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