Digiscoping Project - Beginner Questions (1 Viewer)

[beardedbeard]

Hi there folks. I myself am not a nature photographer, though I must admit that going through some of the posts in your forum I might just as well start such a hobby. I came here for a specific reason which I'll describe in a moment, but I'll admit that I found myself for quite some time just hopping between posts enjoying the scenery

I was looking for some digiscoping resources, and I think that here I'd find some experienced answers for some basic questions. I have a project I'm doing for long-distance digital real-time monitoring.

The setup is pretty straight forward. Raspberry pi (running on battery), inside a 3D printed custom housing which also houses a USB camera (based on IMX291 sensor). The 3d printer housing has threads around the lens mount - so I could attach adapters to it so it fits either a monocular or a spotting scope. An example of the rig is in the next picture (in which the pi is disengaged from the camera house as these are two separate pieces).



I am reading / learning about optics, and I enrich my understanding by trail and error. At the moment, there are several issues I can't really understand and I would appreciate if your experience could help me with understanding the science behind it.


Issue #1 - Non-Uniform focus across an image
Since the images I take are going through several optical devices, I understand I can't get a win-win situation and there is somewhat compromises on quality. Also, I understand that the quality of the monocular is of high importance.

However, while using any type of lens on the pi (6mm, 8mm, 12mm and 16mm of either M12, M16 or CS-MOUNT) - the images I get on this monocular (or a "bresser" one) have a non uni-form focus across the image. At first I thought its due to some distortions - hence I tried all sort of combinations (lens type, lens focal point and two monoculars). Althought the focus non-uniformity effects are changing - they are still very much there - and I think its safe to say 25-40 % of the image (in different places) isn't properly focused. Here is just one example of such an outcome (circled in red are the most focused areas):




I think that in this example - what is "somewhat obvious" - is that the non-uniformity is symmetrical. So I think it has something to do with the fact that I'm using a camera lens (this time, 12mm M12) to grab an already optically "enhanced" image from the monocular lenses. Can anyone help me with:

1) Identify this optical behavior. Does it have a name? (non-uniform focus is just a brainf*rt I had)

2) How can I identify this behavior ground rules. That is, how can I know its limits (so I have it effecting me less by choosing the right combination of lens type, focal length [and of course if needed, camera sensor size]? I tried to get my way around with optical calculators (and visualizers) but I'm not sure I'm heading the right way.

My aim is to limit this effect to the maximum. By the way, with other focal lengths (8mm for example) I obviously get less zoom - but the boundaries of effect are pretty much the same.


Issue 2 - Getting most of such a rig for Digital Scoping

1) The camera is manually focused. So, are there any specific "guidelines" on what focus should be set on the camera lens before attaching it to the monocular/spotting scope? I'm not sure I found any rules of thumbs here. Focus the lens at distance of the monocular eyepiece? or focus the lens on the horizon? It does make me change the focus on the monocular to adapt, of course, but I was wonder if aside from that, will it impact quality / the non-uniform focus issue listed above?


2) In case I'm limited to the rig setup above - are there any optical guidelines regarding the camera lens focal length choices? (again, assuming im already losing quality because of all the optics involved). Would it be wiser to choose specific focal length (6mm, 8mm) due to particular optical effect (such as less possible distortion), or am I not even in the right direction asking such a question?



In fact I got other issues - but to be honest, I barged in here with no beautiful animals with awesome blurry field of view effect - so I'll cut short my questions hoping you guys would take the time to read through it all

Thanks in advance..

 

[Hauksen]

Hi!

The setup is pretty straight forward. Raspberry pi (running on battery), inside a 3D printed custom housing which also houses a USB camera (based on IMX291 sensor). The 3d printer housing has threads around the lens mount - so I could attach adapters to it so it fits either a monocular or a spotting scope. An example of the rig is in the next picture (in which the pi is disengaged from the camera house as these are two separate pieces).

View attachment 1463114 View attachment 1463115

While I'm unable to add useful advice on your original question, I do like your modular 3D design quite a lot! I wonder if you have already made it availabe on Thingiverse or Printables, or perhaps plan to do so in the future?

Personally, I have dabbled in designing phonescoping adapters, without really getting to a fully satisfactory long-term solution. Accordingly, I'm always looking for inspiration from related designs!

Regards,

Henning

 

[KC Foggin]

Hi there and a warm welcome to you from those of us on staff here at BirdForum
We're glad you found us and please join in wherever you like.

 

[beardedbeard]

Hi!



While I'm unable to add useful advice on your original question, I do like your modular 3D design quite a lot! I wonder if you have already made it availabe on Thingiverse or Printables, or perhaps plan to do so in the future?

Personally, I have dabbled in designing phonescoping adapters, without really getting to a fully satisfactory long-term solution. Accordingly, I'm always looking for inspiration from related designs!

Regards,

Henning

Why, thank you sir! I appreciate your kind words.

Regarding your question - everything is still in POC (including the 3d designs made for this). Until the models are production grade (even minimally) I have decided to not share functional-limited, mediocre-quality or below results. Since this is an adaptive design (hence, it can accommodate most aliexpress-shipped USB/SDI/AVHD cams with board sizes of 38mm to 34mm [hole-to-hole 36mm to 32mm], including threaded adapters to extend camera from scope [as seen in pictures]) I'd prefer to hand away something of value (rather than just to hand out something).

However, if I can help you in anyway (including privately provide you with STL's or OBJ's), even regarding some of the data I did manage to gather so far, feel free to contact me

Some of the efforts put in here required me to be thoroughly creative if I wanted to keep my bank account stable and my brain saner. Just as a reference, Chinese manufacturers aren't very keen on preserving "standardization" (I can only assume it is in a somewhat irrational economical short thinking). Some of the USB boards they make (particularly for the imx291 sony sensor) support 4 lens holders mounting alternatives. Hole-to-Hole 18mm, 20mm, 22mm and "custom" (which is 'whats your lucky number today? lets print that PCB!'). So Printing a 3d mount for various sizing was a must.



Not to mention learning optics from scratch and constantly playing with various 3d prints of 1.25" extenders when not using eyepiece (and dont get me started on learning by doing the difference a sensor size can make - sorry, the n00b is strong in me there).

Hope you get the results you expected from the designs/planning you've made and let me know if I can be of any help. Not sure the n00bness will contribute much but should it be able to - I'd love to.



@KC Foggin thank you for the welcoming message Like I said, I might just turn this "real time monitoring" project into a "real time long distance nature photography" project Just need to get my optics & sensors right!

 

[Jefrs]

Interesting project
I think you would be perhaps well to look at astronomy astrophotography which uses this sort of set up a lot, with many ready-made parts to do the job.
And methods.
Even the best spotting scopes do not make the best lens-systems for camera work, but they are very long and relatively cheaper than a dedicated ultra-long camera lens - Canon do make a 1200mm f/8 for a mere £22,000 quid. Actually we can go a lot longer for a lot less with MFT, like a 800mm f/8 reflex, (1600mm equivalent), about 16x mag (doubled on MFT). We can probably add a 2x TC to that, 3,200mm equivalent, at the cost of two stops, f/16, doable but dim.
You might look at an astronomical telescope, right-corrected for terrestrial, or simply turn the camera upside down.
And a very, very rigid tripod (those Manfrotto Pixies are cool, but not sturdy).

I can put a helical focuser on the back of an old (bought for next to nothing) Tokina 400mm prime f/6.3 and then mount an astro eyepiece, digital camera on adapter, or an astro-camera. My T7C astro camera has 1/3" sensor 4.8x3.6 thus 6.0mm diagonal i.e crop factor 7.5 and the 400mm lens becomes 3,000mm equivalent, at f/6.3. This is easily doable when a lens has a T-thread, and most all astro scopes do.