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Photography with a monocular scope - possible focus issues?

 
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dragonblade



Joined: 18 Oct 2014
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PostPosted: Sun Nov 05, 2017 8:41 pm    Post subject: Photography with a monocular scope - possible focus issues? Reply with quote

As much as I'd like a trinocular microscope for my first forays into scope photography, I'll have to settle for a monocular model due to my tiny, restrained budget. The plan is to focus the microscope objective first (using a combination of coarse and fine focus) and then attach the camera in an afocal configuation and focus the camera lens to around infinity. Then proceed to use the microscope's focus controls for the rest of the scope session while viewing through the camera's EVF or alternatively LCD screen.

Am I likely to experience any difficulties using this method to focus? I will be using a Micro 4/3 camera with live view and I have a choice for viewing through the EVF or LCD screen. And generally, I digitally zoom in to the picture when manually focusing to get more accurate focus. Apparently, there's also the option of viewing the onscreen content on a tablet with wifi connection but I haven't succeeded in doing that yet. So hopefully, one of these options will make manual focusing a relatively straight forward task without too much strain or frustration. Though I could be proven wrong!

By the way, I'll mainly be viewing microscopic organisms in fresh water and seawater with 4x, 10x and occasionally 40x objectives with a 10x eyepiece. I hope to get hold of a 30mm lens for the afocal set up. I was considering using the 30mm setting of my 14-45mm zoom but was told earlier on this forum that such a lens might vignette unfortunately. The Sigma 30mm would be ideal as that was recommended to me but that's out of my price range. If I was really desperate, I could get the ultra cheap Chinese-made Fujion 35mm CCTV lens but according to reports, it has pretty average optics and flares easily.
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rjlittlefield
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PostPosted: Sun Nov 05, 2017 10:03 pm    Post subject: Re: Photography with a monocular scope - possible focus issu Reply with quote

dragonblade wrote:
Am I likely to experience any difficulties using this method to focus?

This should work well. In fact I don't know any way to beat focusing a live view image, for precision.

--Rik
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dragonblade



Joined: 18 Oct 2014
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PostPosted: Sun Nov 05, 2017 10:36 pm    Post subject: Re: Photography with a monocular scope - possible focus issu Reply with quote

rjlittlefield wrote:
dragonblade wrote:
Am I likely to experience any difficulties using this method to focus?

This should work well. In fact I don't know any way to beat focusing a live view image, for precision.

--Rik


Ah great to know! I was actually told previously on this forum that focusing this way would be considerably harder / more challenging compared to using the microscope's own viewing optics.
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Pau
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PostPosted: Mon Nov 06, 2017 1:26 am    Post subject: Reply with quote

Do you already have the microscope? If so, it would be nice to know it.

Quote:
I was considering using the 30mm setting of my 14-45mm zoom but was told earlier on this forum that such a lens might vignette unfortunately.


Some short zooms can do pretty well. First test it.

An alternative to a 30mm lens with a 10X is to use a lower magnification eyepiece, in some cases you can find 8X or 6.3X eyepieces adequate for your objectives and you can pair them with much easier to source old manual 40mm or 50mm lenses.

Maybe you've seen my thread http://www.photomacrography.net/forum/viewtopic.php?p=99265
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dragonblade



Joined: 18 Oct 2014
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PostPosted: Mon Nov 06, 2017 1:44 am    Post subject: Reply with quote

Pau wrote:


Some short zooms can do pretty well. First test it.


Yea good idea to test mine first before buying a new lens.

Pau wrote:
An alternative to a 30mm lens with a 10X is to use a lower magnification eyepiece, in some cases you can find 8X or 6.3X eyepieces adequate for your objectives and you can pair them with much easier to source old manual 40mm or 50mm lenses.



Yea I considered the option of using a different magnification eyepiece with a different focal length lens. I don't have the microscope yet but the one I have my eye on comes with 10x and 25x eyepieces. There's also an optional 15x eyepiece available as an accessory. So they're all relatively high magnification eyepieces more or less. I guess if I was to hunt around for a lower magnification eyepiece, it would have to match the objectives? Supposedly, the microscope that I'm interested in has Semi-Plan objectives.

If I ever come across such eye pieces, I do have some old, manual film lenses I can use - notably the Canon FD 50mm f1.8 and Pentax Takumar 55mm M42 mount.

By the way, that's a great, informative post you made about afocal photography.
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zzffnn



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PostPosted: Mon Nov 06, 2017 6:00 am    Post subject: Reply with quote

Almost all eyepieces at 20x or more powerful are difficult to use, due to lower eyepoint and smaller view field. You can kind of judge by looking at top lens diameter (bigger is better). 15x may be ok, if you really need it.

Many Chinese scopes only offer 5x, 10x, 15x, 20x and 25x eyepieces. Their 5x is not easy to use either, again due to small view field and low eyepoint.
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dragonblade



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PostPosted: Mon Nov 06, 2017 9:37 am    Post subject: Reply with quote

Zzffnn, that's good to know. Perhaps I'll stick with the 10x eyepiece if it will make my viewing experience easier. I recall from your earlier thread that your M4/3 zoom lens worked quite well in an afocal setup. So there's a fair chance that my zoom might do a decent job too.
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Pau
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PostPosted: Mon Nov 06, 2017 11:14 am    Post subject: Reply with quote

I agree, 25X eyepieces are in most cases pretty useless: uncomfortable and easily providing empty magnification. I only use 10X, some people prefer 15X. I have the nice 25X ones for my stereo resting in a box.

For afocal (and also better for viewing) you want high eyepoint eyepieces, the ones designed to look with eyeglasses. In many chinese microscopes they are labeled (erroneously) "WF" from Wide Field

Lower than 10X good quality eyepieces are rare in recent microscopes (they were pretty common for classic Zeiss or Leitz like the ones I use).
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rjlittlefield
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PostPosted: Mon Nov 06, 2017 12:18 pm    Post subject: Re: Photography with a monocular scope - possible focus issu Reply with quote

dragonblade wrote:
I was actually told previously on this forum that focusing this way would be considerably harder / more challenging compared to using the microscope's own viewing optics.

There are devils in the details of what the words mean.

I think it's true that focusing through a camera can be more challenging than focusing with direct eye view through the eyepieces. I speculate that has something to do with the accommodation of your eye giving some clue about which way you need to shift focus.

However, if what you ultimately care about is the camera image, then roughly speaking the choice is between A) focusing through the camera's optical eyepiece, B) focusing the image as displayed on the camera's LCD panel, C) focusing the image as displayed on a computer monitor via tethering or wireless, or on a monitor connected directly to the camera say by HDMI, or D) carefully setting up your camera coupler so as to be exactly parfocal with the eyepieces, then focusing with the eyepieces.

Given those choices, I'll pick option C -- a big monitor displaying a live view image. In my setups options A and B always have lousy ergonomics. Option D is attractive in some situations, but there's always the risk that due to accommodation of your eyes, an image that looks great through the eyepieces may not be optimally focused for the camera.

--Rik
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zzffnn



Joined: 22 May 2014
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PostPosted: Mon Nov 06, 2017 2:32 pm    Post subject: Reply with quote

dragonblade wrote:
I recall from your earlier thread that your M4/3 zoom lens worked quite well in an afocal setup. So there's a fair chance that my zoom might do a decent job too.


I don't remember I said that before, so I tested a 10x visual eyepiece with 18mm field number just now, with my Olympus kit zoom M. Zuiko Digital 14-42mm F/3.5-5.6 lens (on micro 4/3).

When zoomed to 30 mm or higher, there is no vignetting at all. Starting from about 28mm or lower, I could see vignetting, which gets pretty bad at 25mm or lower.

I agree with Pau and Rik. I focus with Rik's option D, because with Option C and my camera rig, there is a very slight delay of imaging (with HDMI) and I don't like the mess of wires on my already messy table. My eyes are pretty decent too and I like to video-tape very fast protists, so I prefer option D over C.
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Last edited by zzffnn on Mon Nov 06, 2017 7:59 pm; edited 1 time in total
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dragonblade



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PostPosted: Mon Nov 06, 2017 7:51 pm    Post subject: Reply with quote

That's interesting. I didn't realise there was a delay with a HDMI connection. Even if only slight, that would be a hindrance to accurate focusing. I mentioned before that there is an option to display the Panasonic camera's live view on a tablet with wifi. I don't know if there's a delay with Panasonic's wifi system (haven't been able to test it out yet.) Ive seen GoPro's wifi in action and there is a huge delay there.
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zzffnn



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PostPosted: Mon Nov 06, 2017 8:02 pm    Post subject: Reply with quote

My camera (Olympus E-PM2) and HDMI TV are both a bit dated. Maybe newer systems would have faster data transmission? Rik would know better.
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rjlittlefield
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PostPosted: Mon Nov 06, 2017 11:54 pm    Post subject: Reply with quote

zzffnn wrote:
My camera (Olympus E-PM2) and HDMI TV are both a bit dated. Maybe newer systems would have faster data transmission? Rik would know better.

In this case I don't know much. I have no experience with the cameras in question. In general there's usually a few frame times delay between optical image going into the camera and optical image coming out of the monitor. Some details can be read at my old posting http://www.photomacrography.net/forum/viewtopic.php?t=17939 . That is titled "Live View delay through computer = 0.25 seconds" and also says "The same experiment with analog video and HDMI showed that those were faster, both around 0.12-0.13 seconds."

The delay has not been a problem with the little work that I've done, even for active protists. But that experience is quite limited and I would look to other people for information.

I would expect the delay with wifi to be quite a bit longer than HDMI or direct tethering, since there are more levels of the software stack to traverse.

--Rik
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neurodoc



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PostPosted: Thu Nov 09, 2017 12:49 pm    Post subject: Reply with quote

I check focus at the camera's LCD screen after initial viewing through the eyepieces before taking pictures. Even though the camera and viewing eyepieces are "parfocal" as Rik has said there are issues with individual visual accommodation which can produce focusing discrepancies. What you see on the screen is what your camera will take. Because these screens are not big I use a loupe (like what I use to check focus on my view cameras) to get precise focus. If you have a direct link to a larger computer screen, that's even better, but if you don't then using your camera's screen with a loupe is the most accurate way to focus.
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