Pond water - Beginner afocal video

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Javier
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Pond water - Beginner afocal video

#1 Post by Javier » Tue Oct 13, 2020 12:52 am

Hi,

I had the chance to observe a few drops of pond water. I made a video with my entry-level monocular scope and an iPhone 5s in afocal technique. I found a very funny bunny-like worm? that I couldn't identify. It was very long and seemed to have feet only at the upper and lower part of its body. I also found many rotifers (a big colony of them), and spent a lot of time observing diatoms at high power.

I had some format issues when gluing the videos, and lost some resolution. But here it goes anyway:

https://www.youtube.com/watch?v=HnWU0sg ... e=youtu.be

And here is the funny one on original resolution (what is it?)

https://www.youtube.com/watch?v=ZKbT4VQctbI

I know the equipment is quite basic, but I think there is a lot of room for improvement. I would really appreciate your advice.

Thanks in advance for watching it!

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Rapidray
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Re: Pond water - Beginner afocal video

#2 Post by Rapidray » Tue Oct 13, 2020 2:51 am

Some great videos and sharp field of view!
OMAX M83

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micro
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Re: Pond water - Beginner afocal video

#3 Post by micro » Tue Oct 13, 2020 6:55 am

chironomidae larvae

Javier
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Re: Pond water - Beginner afocal video

#4 Post by Javier » Tue Oct 13, 2020 12:37 pm

Rapidray wrote:
Tue Oct 13, 2020 2:51 am
Some great videos and sharp field of view!
Thanks!
micro wrote:
Tue Oct 13, 2020 6:55 am
chironomidae larvae
Larvae... of course :oops:


Thank you!

Unseen World
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Re: Pond water - Beginner afocal video

#5 Post by Unseen World » Sat Oct 17, 2020 6:05 am

Some really good shots of the Rotifers!
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Javier
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Re: Pond water - Beginner afocal video

#6 Post by Javier » Sun Oct 18, 2020 2:22 am

Unseen World wrote:
Sat Oct 17, 2020 6:05 am
Some really good shots of the Rotifers!
Thank you!

DonSchaeffer
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Re: Pond water - Beginner afocal video

#7 Post by DonSchaeffer » Sun Oct 18, 2020 9:11 am

What does afocal mean?

Javier
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Re: Pond water - Beginner afocal video

#8 Post by Javier » Mon Oct 19, 2020 12:33 am

DonSchaeffer wrote:
Sun Oct 18, 2020 9:11 am
What does afocal mean?
In the afocal technique, you capture the exit pupil of an eyepiece with a lens mounted device. In other words, the most common practice of afocal photography, in astronomy or microscopy, consists of placing your phone in front of the eyepiece, hopefully with an adapter to get a still image. It's quite a rough, beginner, low budget technique.

On the other hand, when you have a DSRL or a dedicated camera, you can place the sensor at the focal plane to capture the image formed by the objective. This is called prime focus photography, and this is how things should be done to get decent images.

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Re: Pond water - Beginner afocal video

#9 Post by Element 56 » Mon Oct 19, 2020 2:48 am

Nice clean videos.

I'll never understand the thumbs down responses on youtube. Your videos are sharp and clear and you captured some nice little pieces of footage. I guess there's a critic in every crowd. Probably some bumb who's never done anything more than click on a youtube video.

DonSchaeffer
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Re: Pond water - Beginner afocal video

#10 Post by DonSchaeffer » Mon Oct 19, 2020 2:51 am

Javier wrote:
Mon Oct 19, 2020 12:33 am
DonSchaeffer wrote:
Sun Oct 18, 2020 9:11 am
What does afocal mean?
In the afocal technique, you capture the exit pupil of an eyepiece with a lens mounted device. In other words, the most common practice of afocal photography, in astronomy or microscopy, consists of placing your phone in front of the eyepiece, hopefully with an adapter to get a still image. It's quite a rough, beginner, low budget technique.

On the other hand, when you have a DSRL or a dedicated camera, you can place the sensor at the focal plane to capture the image formed by the objective. This is called prime focus photography, and this is how things should be done to get decent images.
Thanks. Someone did explain that once.

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Re: Pond water - Beginner afocal video

#11 Post by hans » Mon Oct 19, 2020 4:41 am

Javier wrote:
Mon Oct 19, 2020 12:33 am
...placing your phone in front of the eyepiece, hopefully with an adapter to get a still image. IIt's quite a rough, beginner, low budget technique.
Javier wrote:
Mon Oct 19, 2020 12:33 am
...you can place the sensor at the focal plane to capture the image formed by the objective. This is called prime focus photography, and this is how things should be done to get decent images.
Often not the case with microscopes:
http://krebsmicro.com/photomic1/photomic1.html

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Re: Pond water - Beginner afocal video

#12 Post by Javier » Mon Oct 19, 2020 2:05 pm

hans wrote:
Mon Oct 19, 2020 4:41 am
Javier wrote:
Mon Oct 19, 2020 12:33 am
...placing your phone in front of the eyepiece, hopefully with an adapter to get a still image. IIt's quite a rough, beginner, low budget technique.
Javier wrote:
Mon Oct 19, 2020 12:33 am
...you can place the sensor at the focal plane to capture the image formed by the objective. This is called prime focus photography, and this is how things should be done to get decent images.
Often not the case with microscopes:
http://krebsmicro.com/photomic1/photomic1.html
Hi,

I read the article. Please help me understand some points of it.

From your quotes I understand that you are arguing that placing a fixed lens camera isn't rough because there is some sort eyepiece compensation that helps with off-axis aberrations? In my experience, the fixed lens camera will introduce its own aberrations and artifacts and it's never a great idea to add more (in some cases much more) elements between the sensor and the focal plane plane image.

Thanks for the article, it was an interesting reading.

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Re: Pond water - Beginner afocal video

#13 Post by BramHuntingNematodes » Mon Oct 19, 2020 4:07 pm

It's kind of hardware specific Javier. In some old microscopes and with certain lenses the objective and eyepiece combine to single optical system. In some cases, the contribution of the eyepiece can be significant and noticeable.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

Javier
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Re: Pond water - Beginner afocal video

#14 Post by Javier » Mon Oct 19, 2020 4:19 pm

BramHuntingNematodes wrote:
Mon Oct 19, 2020 4:07 pm
It's kind of hardware specific Javier. In some old microscopes and with certain lenses the objective and eyepiece combine to single optical system. In some cases, the contribution of the eyepiece can be significant and noticeable.
Interesting, that make sense with older models. I don't totally get if there is a place for afocal high resolution modern micro photography nowadays. That would be something new to me in terms of optics.

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Re: Pond water - Beginner afocal video

#15 Post by BramHuntingNematodes » Mon Oct 19, 2020 4:22 pm

Someone else would have to chime in there-- my newest compound microscope is from the late 60s.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

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Re: Pond water - Beginner afocal video

#16 Post by 75RR » Mon Oct 19, 2020 7:57 pm

Javier wrote:
Mon Oct 19, 2020 2:05 pm
From your quotes I understand that you are arguing that placing a fixed lens camera isn't rough because there is some sort eyepiece compensation that helps with off-axis aberrations?
In good quality finite microscopes, one should think of the objective and the eyepieces as a complete lens system. The eyepieces are generally tasked with correcting the chromatic aberrations.
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Re: Pond water - Beginner afocal video

#17 Post by DonSchaeffer » Thu Oct 22, 2020 7:42 am

I can't access the videos. They are designated as private.

Javier
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Re: Pond water - Beginner afocal video

#18 Post by Javier » Fri Oct 23, 2020 2:21 pm

DonSchaeffer wrote:
Thu Oct 22, 2020 7:42 am
I can't access the videos. They are designated as private.
Fixed!

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